The Chemistry of Yellow Arsenic - Chemical Reviews (ACS Publications)

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Cite This: Chem. Rev. XXXX, XXX, XXX−XXX

The Chemistry of Yellow Arsenic Michael Seidl, Gábor Balázs, and Manfred Scheer*

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Institut für Anorganische Chemie, Universität Regensburg, 93043 Regensburg, Germany ABSTRACT: The generation and handling of the light-sensitive and metastable yellow arsenic (As4) is extremely challenging. In view of recent breakthroughs in synthesizing As4 storage materials and transfer reagents, the more intensive use of yellow arsenic as a source for further reactions can be expected. Given these aspects, the current stage of knowledge of the direct use of As4 is comprehensively summarized in the present review, which lists the activation of As4 by main group elements as well as transition metal compounds (including the f-block elements). Moreover, it also partly compares the reaction outcomes in relation to the corresponding reactions of P4. The possibility of using alternative sources for generating arsenic moieties and compounds is also discussed. The release of As4 molecules from precursor compounds and the use of transfer reagents for polyarsenic entities open up new synthetic pathways to avoid the direct generation of yellow arsenic solutions and to ensure its smooth usage for subsequent reactions.

CONTENTS 1. 2. 3. 4. 5.

Introduction Arsenic: History and Significance Stability of As4 with Respect to Its Allotropes Synthesis of As4 Reactivity of As4 toward Main Group Compounds 6. Reactivity of As 4 toward Transition Metal Complexes 6.1. Activation of As4 by Early Transition Metals 6.1.1. Activation by Transition Metal Complexes of Group 4 Elements 6.1.2. Activation by Transition Metal Complexes of Group 5 Elements 6.1.3. Activation by Transition Metal Complexes of Group 6 Elements 6.2. Activation of As4 by Late Transition Metals 6.2.1. Activation by Transition Metal Complexes of Group 8 Elements 6.2.2. Activation by Transition Metal Complexes of Group 9 Elements 6.2.3. Activation by Transition Metal Complexes of Group 10 Elements 6.2.4. Reactivity with Transition Metal Complexes of Group 11 Elements 6.3. Activation of As 4 by f-Block Element Complexes 7. Alternative Arsenic Sources for Chemical Reactions 7.1. Solid-State Sources 7.1.1. Gray Arsenic 7.1.2. As4 Encapsulated in Supramolecular Cages 7.1.3. Carbon-Based Storage Materials 7.2. Soluble Sources and Transfer Reagents 7.2.1. cyclo-(AsR)n © XXXX American Chemical Society

7.2.2. Release of As4 from Molecular Compounds 7.2.3. Transfer of Polyarsenic Units through the Use of Asn Transfer Reagents 8. Conclusions Author Information Corresponding Author ORCID Notes Biographies Acknowledgments Abbreviations References

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1. INTRODUCTION Arsenic is an interesting element, which has retained its fascination both as an element and in the form of its compounds over the centuries. The following review deals with the reactivity of its most unstable modification, yellow arsenic, which is composed of tetrahedral As4 molecules and therefore comparable with its lighter homologue, white phosphorus, P4. In contrast to P4, which is stable under normal conditions, As4 is largely unstable, gradually transforming into gray arsenic at ambient temperatures. Exposure to light or the presence of seeds of gray arsenic accelerates this process, with the latter being autocatalytic. Due to this instability, the long-term storage of As4 is almost impossible. Therefore, it is only very rarely used as a source of arsenic for chemical reactions, even though it represents its only soluble form. Interestingly, that is where there also is a big difference with regard to white

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Special Issue: Frontiers in Main Group Chemistry Received: November 23, 2018

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DOI: 10.1021/acs.chemrev.8b00713 Chem. Rev. XXXX, XXX, XXX−XXX

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trioxide (As2O3) with charcoal in ca. 1250, is usually accredited with the discovery of elemental arsenic. It is, however, also possible that arsenic had been discovered prior to this. Arsenic has not always had a bad reputation in human history due to its toxicity.5 It was recognized very early that arsenic compounds have certain effects on both humans and animals. Therapeutic preparations made of realgar or orpiment, respectively, have been used in traditional Chinese medicine for at least 2400 years, as, for example, antiparasitic agents or treatments for neurodermatitis. There are also accounts from Ancient Greece and Rome of arsenic-based therapies for asthma and skin diseases. The physician and alchemist Paracelsus, too, recommended a number of arsenic compounds to treat certain diseases. He also realized that the dosage of the arsenic preparations is absolutely crucial, due to the high toxicity of most arsenical substances. While metallic arsenic is not toxic, its compounds are indeed extremely toxic. In this context, As(III) compounds generally have a higher toxicity than As(V) derivatives. Furthermore, inorganic arsenic compounds are generally less toxic than organoarsenic compounds. Thus, when used medicinally, the toxicity toward the pathogen is always a trade-off with the toxicity toward the human recipient. Toward the end of the 18th century, Thomas Fowler developed a tincture (Fowler’s solution) from potassium arsenite (KAsO2) and lavender water, which was used for roughly 150 years as a cure-all. This tincture was used against fevers, headaches, rheumatism, anemia, asthma, syphilis, and leukemia, to name but a few. One of the best-known arsenic-based medications is arsphenamine, which was launched by Hoechst in 1910 under the brand name Salvarsan.6−8 Discovered by Paul Ehrlich, it had initially been postulated to be a diarsene, but only recently, it was found by electrospray ionization mass spectrometry to be a mixture of a cyclotrimer and a cyclopentamer (Scheme 1a).9 It had been especially developed to treat the sexually transmitted disease syphilis. Salvarsan and its enhanced derivatives were replaced by penicillin in the 1940s. Tryparsamide (Scheme 1b) was used since 1922 as a clinically proven remedy against the parasitic African sleeping sickness (African trypanosomiasis). Tryparsamide was later

phosphorus, which shows good solubility in almost all common solvents even at lower temperatures. Although it is isostructural with P4, surprisingly, yellow arsenic shows a very poor solubility even at ambient temperatures, a property that is even more pronounced at low temperatures. Thus, at −30 °C, except in CS2, almost no As4 is dissolved in any solvent. This property, and also its light-sensitivity in solution, can be partly overcome by releasing As4 from a carrier compound,1 leading to five times more concentrated solutions of As4 in CH2Cl2 that are now light-stable for more than 5 h.2 Moreover, very recently, the storage of yellow arsenic in a porous carbon-based material as As4@C was achieved for the first time,3 which will lead to a more extensive use of this modification in preparative chemistry. These groundbreaking changes in the practical usage of yellow arsenic will prospectively increase the value of this highly reactive molecule in synthesis. Therefore, it is vitally important to summarize the current stage of our knowledge in this field to stimulate the inorganic, organic, catalytic, and material-science-oriented chemical community to use As4 much more in the future. This review will give a comprehensive overview of the reactions reported so far starting from As4, will draw comparisons to the reactivity of white phosphorus, and will discuss the use of alternative sources of arsenic instead of As4 for syntheses. Additionally, whereas in phosphorus chemistry 31P NMR spectroscopy is a very powerful tool in the characterization of P-containing products as well as for monitoring reaction pathways, this possibility does not exist in arsenic chemistry. Even though 75As is the only natural isotope of arsenic, its NMR detection presents a challenge. It is well-known that nuclei with I > 1/2 show very short spin−lattice relaxation times that are governed primarily via the quadrupolar relaxation mechanism.4 This effect leads to extreme line broadening and makes nuclei with large quadrupole moments hard to observe in NMR spectra. Owing to the quadrupolar 75 As nucleus (75As (I = 3/2)), an 75As NMR signal is only obtained for highly symmetrical molecules. Otherwise, extremely broad resonances, barely distinguishable from the background noise, are found. Observation of a broad signal is only possible for very symmetrical molecules such as As4. We discovered that freshly prepared solutions of As4 in toluene/ CD2Cl2 give a broad signal at −892 ppm (ω1/2 = 2060 Hz).2

Scheme 1. Structure of (a) Salvarsan/Arsphenamine, (b) Tryparsamide, and (c) Melarsoprol

2. ARSENIC: HISTORY AND SIGNIFICANCE Arsenic is the 33rd element in the periodic table of the elements and is exclusively found as the monoisotopic nuclide 75 As. The element’s name goes back to the Greek name arseniós for the arsenical mineral orpiment (As2S3), which roughly means “virile”, “audacious”, or “brave”. Deposits of elemental arsenic in nature are known as chard cobalt or flaky arsenic, respectively, but are very rare. Arsenic often occurs in sulfidic ores such as realgar (As4S4), also known as “ruby sulfur” or “ruby of arsenic”, and orpiment (As2S3). There are also intermetallic phases, such as allemontite (AsSb) and arsenides such as löllingite (FeAs2) or skutterudite (CoAs3), the latter revealing aromatic As42− units. Even in antiquity, several arsenical minerals were known, such as orpiment and arsenic trioxide (As2O3), also referred to as “white arsenic”. Arsenic is also found in the form of arsenite ions, As(III), and arsenate ions, As(V), in potable waters, with its overall concentration mostly being very low and nonhazardous. Bishop Albertus Magnus of Regensburg, who reduced arsenic B


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accumulators, but also for lead ammunition.14 Perhaps one of the most important applications of arsenic is its use in the semiconductor industry. By n-type doping of group 14 semiconductor materials (mostly silicon) with group 15 atoms (P, As, Sb), their properties are selectively modulated, above all their electrical conductivity. Only this, together with p-type doping, makes the production of semiconductors possible; larger quantities of arsenic are required for the production of III−V semiconductors, because here arsenic not only is a doping component (at the ppm level) but also is needed in stoichiometric quantities. III−V semiconductors have the advantage that they often possess a defined band gap, thus being better suited for use in light-emitting diodes. The latter holds true for GaAs, which is why it is often used in LEDs and lasers. Arsenic is introduced into the environment in a number of different ways, thus contaminating both groundwater and potable water in many parts of the world. Sources of manmade pollution include not only the mining industry, smelting, and the usage of arsenical animal feeds15 and pesticides, but also the use of arsenic in the glass and electrical industries. Natural causes of local arsenic contamination are volcanic activity and the leaching of arsenic minerals. This central problem is currently a focus of research, on one hand, to be able to better detect arsenic and, on the other hand, to separate it from potable water or prevent its contamination, respectively.16,17 Some time ago, arsenic was again the focus of public attention. Under the supervision of NASA, a group of researchers studied extremophilic bacteria (GFAJ-1; halomonadaceae) found in Mono Lake in California, USA. On the basis of their findings, they concluded that the bacteria had incorporated arsenate (AsO43−) instead of phosphates in biomolecules, especially in the DNA,18 which attracted the attention of the general public far beyond scientific circles. However, just a year later, another group disproved this theory after conducting numerous studies.19

replaced by melarsoprol (Scheme 1c), another arsenic compound, in the 1940s and 1950s. Despite its high toxicity and severe, sometimes lethal, side effects (5−10%), melarsoprol is still used today to treat trypanosomiasis, due to the lack of alternatives. Since 2003, trisenox (a medication containing arsenic trioxide, As2O3) has been used against promyelocytic leukemia in the US and in a number of European countries.7,8,10 In the past, the above-mentioned toxicity of arsenic compounds was not only used to treat diseases. As arsenic compounds generally have a toxic effect on all living beings, arsenic chemicals have been and are still used as herbicides and pesticides.11,12 This usage, however, is not without problems, since arsenic may leach into the groundwater, thereby intoxicating both humans and animals. On a smaller scale, arsenic is also used against pests such as flies and rats.5,7 To the general public, however, arsenic is not known for its positive properties. As arsenic compounds have been used for criminal poisoning for centuries, this is what is engraved in our collective memories. To this end, arsenic trioxide was generally used, since it is odorless and tasteless, and water-soluble, and death is not instantaneous; it takes some time for the poisoned person to die. One of the first documented arsenic poisonings is said to have taken place in 55 A.D. when Nero allegedly had his rival Britannicus killed to underpin his rule.6 Particularly since the 17th century, arsenic has been used in many assassinations, among them being some very interesting criminal cases, leading to its nickname of “inheritance powder”. For a comprehensive compilation of these, see ref 5. After James Marsh developed his “Marsh test” for arsenic as a quantitative arsenic detection method in 1836 (Scheme 2), the number of “arsenic murders” dropped. Marsh’s test was the first method to detect arsenic in soft tissue with pinpoint accuracy to identify and convict the culprit. Scheme 2. Identification of Arsenic by Marsh’s Test

3. STABILITY OF As4 WITH RESPECT TO ITS ALLOTROPES In the solid state, arsenic possesses four allotropic modifications: gray or metallic arsenic, two different phases of black arsenic, and yellow arsenic.20 The thermodynamically most stable allotrope at room temperature is gray or metallic arsenic (Scheme 3). It forms a rhombohedral structure (αform) built up from densely packed, puckered arsenic layers consisting of condensed As6 rings in chair conformations (Figure 1).21 The layers are perpendicular to the crystallographic c axis. Its structure is analogous to rhombohedral black

In the past, another illegal use of arsenic preparations was in horse trading (the German expression is “Rosstäuscherei”).13 Feeding arsenic to horses was thought to make the horses’ coats shine and increase their appetite, which made them eat more, and look healthier and well-fed shortly before being sold. In Styria, Austria, in particular in the 19th century, people were in the habit of eating arsenic trioxide to improve their general well-being, increase their physical stamina, and facilitate their respiration.5−7 Initially, they ate small portions, which they gradually increased over time. Arsenic eaters were thus able to tolerate an otherwise lethal dose without showing any detectable symptoms of poisoning. Reports to this effect continued until the middle of the 20th century. In addition, prostitutes are said to have drunk and applied Fowler’s solution to acquire a fresh complexion and look rosy-cheeked. Apart from the above usage in pharmaceutical products and pesticides, arsenic has been and still is used on a large scale in technical applications. Arsenic is a component of a range of different alloys, for instance as a component in lead alloys, because it improves their fluidity, with the material being harder and more corrosion-resistant. This is not only very important for the production of lead-based batteries and

Scheme 3. Selected Phases of Arsenic

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and show that As4 and P4 have a very similar spherical aromaticity according to the calculated nucleus-independent chemical shift values.37 The Raman spectrum of As4 in noble gas matrices38,39 and in the gas phase40−44 has been reported, while the heat of dissociation of As4 into As2 was determined by a mass spectrometric Knudsen effusion technique and amounts to 54.26 kcal mol−1.45 The condensation of arsenic vapor onto heated surfaces results in the formation of amorphous black arsenic (Scheme 3),20 which is speculated to resemble red phosphorus in its amorphous structure.46 By annealing, amorphous black arsenic transforms into rhombohedral gray arsenic. A crystalline phase of orthorhombic black arsenic, which is isostructural to black phosphorus, has been reported and can be obtained by heating amorphous black arsenic with mercury47 or by exposure to vapors of AsX3 (X = Cl, Br, and I).33 It forms a double-layer structure built from strongly corrugated As6 rings (Figure 1) and was exclusively observed in the presence of “impurities”, such as mercury,48 phosphorus (up to 73% As atoms),49 or oxygen.50 It has been supposed that pure orthorhombic arsenic is metastable, and it has not yet be synthesized.49 It has been reported, however, that the natural mineral arsenolamprite found in a mine in the Copiapó area in Chile contains pure black arsenic.51 Very recently, it has been shown that the impurities of a sample of this mineral lie below the detection limits of powder X-ray diffraction, Auger electron spectroscopy, and energy-dispersive X-ray spectroscopy.52 Additionally, it has been shown that thin layers of black arsenic, obtained by mechanical exfoliation of arsenolamprite, possess a very high in-phase anisotropy.52 Both the amorphous and orthorhombic black allotropes convert to gray arsenic at elevated temperatures. At high pressure, a tetragonal phase of black arsenic has also been reported.53 Very recently, two new one-dimensional allotropes of arsenic, i.e., a single-stranded zigzag chain and a doublestranded zigzag ladder incorporated inside single-walled carbon nanotubes (SWCNTs), have been reported (vide infra Figure 37).54 These materials were synthesized by filling SWCNTs with As4 from the gas phase. The occurrence of the various 1D arsenic allotropes depends on the diameter of the SWCNT. Single zigzag chains and individual As4 molecules are preferentially formed when SWCNTs with diameters of 0.8− 0.9 and 0.7−0.8 nm were used, respectively, while zigzag ladders are formed with SWCNTs in the diameter range of 0.8 and 1.2 nm.54 A mixed phosphorus−arsenic one-dimensional chain was synthesized by removing CuI from Cu2P1.8As1.2I2 with aqueous KCN.55 The black solid P−As phase is amorphous, and it was suggested that it preserves the linear 1∞{]E8[E4(4)]} (E = P/ As) chain structure found in the starting material Cu2P1.8As1.2I2.56 The mixed tetrahedral species AsP3 was recently synthesized by the reaction of [P3Nb(ODipp)3]− (Dipp = 2,6-iPr2C6H3) with AsCl3.57 AsP3 is thermally stable for over a week in toluene at 120 °C and can be handled in ambient light. A higher-scale synthetic procedure has very recently been reported.58 Electronically, AsP3 and P4 are very similar, as demonstrated by gas-phase electron diffraction studies and DFT calculations.59 When a mixture of red phosphorus and gray arsenic is heated (up to 1000 °C), the mixed species PnAs4−n (n = 0−4) were detected in the gas phase. These molecules were characterized by gas-phase laser Raman spectroscopy. The

Figure 1. Structure of selected allotropes of arsenic. (a) Rhombohedral, gray arsenic (α-As). Figure created by authors from data in ref 25. (b) Orthorhombic, black arsenic (β-As). Figure created by authors from data in ref 47. (c) Perpendicular view of the arsenic layers in the rhombohedral arsenic. (d) Structure of As4 as found in [Cu2Cl2{Cp*Fe(η5-P5)}2]∞·(0.75As4)n. The polymeric host is omitted for clarity. Figure created by authors from data in ref 2.

phosphorus.22 Each arsenic atom is surrounded by three vicinal arsenic atoms of the same layer (As−As distance of 2.517 Å) and three atoms of the next layer (As−As distance 3.120 Å), leading to a distorted octahedral environment.23−25 This arrangement is reminiscent of a cubic packing, and is in line with the metallic character of gray arsenic. Gray arsenic sublimes at 616 °C.26 In the gas phase, a mixture of the molecular species As4, As2, and As atoms is present, although the content of yellow arsenic (As4) is greater than 99% (Scheme 3).27,28 Sudden condensation of the vapors on a cold surface below 200 K leads to solid yellow arsenic. Depending on the surface temperature, an amorphous as well as several crystalline29 phases can be obtained. They can be transformed into a plastic phase.30 All forms of yellow arsenic transform at temperatures above 20 °C (or by irradiation even at −180 °C) to gray arsenic.31 The condensation of As4 vapors at low temperature leads to the metastable yellow arsenic rather than the more stable rhombohedral gray arsenic, since, at low temperature, the adsorbed molecules of As4 do not have sufficient energy to re-evaporate or to be incorporated into the equilibrium lattice.32 The irradiation of a solution of As4 in CS2 or the addition of small amounts of I2 or Br2 lead to the formation of a brown precipitate, which was postulated to be the arsenic analogue of the amorphous red phosphorus and a mixed polymer containing oxygen and hydroxy groups.33 However, it was not further characterized. Yellow arsenic is the only soluble allotrope of arsenic, consisting of tetrahedral As4 molecules.31 The structure of yellow arsenic in the gas phase has been determined by electron diffraction experiments, with As−As distances of 2.44 Å34 and 2.435(4) Å within the As4 unit.35 Due to the very high light-sensitivity of yellow arsenic, the crystal structure of the crystalline phases of As4 could not be determined. Recently, however, incorporating As4 molecules within polymeric strands built from CuCl and [Cp*Fe(η5-P5)] units enabled the determination of the structure of As4 molecules by singlecrystal X-ray diffraction, leading to average As−As distances within the As4 unit of 2.396(5) Å (Figure 1).2 DFT calculations predict As−As distances of 2.4372 Å (OLYP ZORA/QZ4P level of theory; no symmetry constraints)36 and 2.465 Å (B3LYP/6-311+G** level of theory; Td symmetry) D


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almost any other organic solvent in which As4 is soluble can be used. For the synthesis of yellow arsenic solutions, the setup shown in Figure 2 is used by our research group. In order to

computed frequencies for As3P and AsP3 proved useful in the assignment of bands to the different molecular species.60 Some years later, the mixed tetrahedral species AsP3, As2P2, and As3P were generated in situ in solution and characterized by 31P NMR spectroscopy and GC−MS spectrometry by the reaction of AsP3 with [Cl2Nb(ODipp)3] in the presence of Na/Hg amalgam followed by the treatment of the reaction mixture with AsCl3. The experimental 31P NMR chemical shifts of −484, −452, and −432 ppm for AsP3, As2P2, and As3P, respectively, are in good agreement with the calculated values. In this reaction, As4 was also formed.61 With the discovery of the two-dimensional materials, numerous publications appeared describing studies of the structure, electronic properties, and band structure of thin layers of arsenic (arsarene), which are comparable to phosphorenes 62 or P/As mixed phases by theoretical methods.63−69 The stability, structure, ionization potential, and electron affinities of neutral, cationic, and anionic molecular Asn rings and cages were investigated by theoretical methods.70 It was predicted that the most stable neutral species contain an even number of arsenic atoms, with As2, As4, and As14 being the most stable.71 The most stable cationic species are As3+, As5+, and As7+, and the most stable anionic arsenic species are As2−, As5−, and As15−, with both types preferring an odd number of arsenic atoms.72 A series of new AsmPn± clusters have been generated via laser ablation on phosphorus−arsenic mixtures. Quadrupole ion trap time-of-flight mass spectrometry, coupled with laser desorption ionization methods, was used to determine their mass spectra. The likely structures of several randomly selected representatives were computed by DFT methods.73 The stability of large icosahedral cages and ring-shaped arsenic chains was investigated by theoretical methods. The icosahedral allotropes have puckered cages in order to minimize the lone-pair repulsion, leading to geometries that resemble rhombohedral gray arsenic. The geometries of the ring-shaped modifications are similar to that of red phosphorus.74 According to quantum-chemical calculations, the Asn cages should be stable with respect to yellow arsenic. The maximum stability of the Asn rings is predicted for As200, beyond which the stability decreases and tends toward a linear 74 1 Single-walled group 15 element ∞ {]As2[As8]} chain. nanotubes were also investigated by DFT methods, indicating that, as the diameter of the nanotube increases, the nanotubes approach the respective monolayer structure. In general, orthorhombic tubes are clearly less favorable than rhombohedral tubes of a similar size.75,76

Figure 2. Apparatus used for the synthesis of solutions of yellow arsenic: (a) heat gun or Bunsen burner, (b) quartz tube (length 500 mm, diameter 29 mm, joint NS 29/32), (c) intermediate sealing glass from quartz to borosilicate glass, (d) 500 mL flask, and (e) reflux condenser with cooling coil and cooling jacket.

prevent trace amounts of arsenic vapors reaching the atmosphere/exhaust with the argon stream after the reflux condenser, several washing flasks containing paraffin oil as well as concentrated sulfuric acid are installed. In the central quartz tube, gray arsenic (∼5 g) is placed in a ceramic vessel. The round-bottomed flask is filled with the desired solvent (e.g., toluene) up to a height such that the argon stream bubbles through the solvent, and this mixture is heated to reflux. A heating source (Bunsen burner or heat gun, ∼450 °C) is placed below the glass coil to preheat the carrier gas (argon), and the furnace is heated to 650 °C for 30 min. After this time, all gray arsenic should have evaporated. The still-warm yellow arsenic solution is quickly filtered and can be used for further reactions. In order to remove trace impurities, i.e., traces of moisture, As4 can be purified by precipitating the material from freshly prepared solutions at −80 °C, decanting the solvent, and briefly evacuating the vessel. All manipulations have to be performed under the rigorous exclusion of light.

5. REACTIVITY OF As4 TOWARD MAIN GROUP COMPOUNDS The activation of small molecules such as H2, CO2, N2, or P4 by main group compounds has attracted much interest in recent years. A goal of this chemistry is the use of main group compounds as mimics of transition metals.79−83 In the case of P4 activation, the substitution of transition metal complexes by main group compounds has been examined extensively.84−86 Selected examples are shown in Scheme 4. H. W. Roesky and co-workers reported the formation of [(L2Al)2(P4)] ((L2 = HC(CMeNDipp) 2, Dipp = 2,6iPr2C6H3)) (A) through the reaction of 2 equiv of the aluminum species [L2Al] with P4.87 In 2007, Driess et al. reported the reaction of a silylene with P4 in a 1:1 ratio, which resulted, by insertion of the silylene into the P−P bond, in compound B. The addition of a further equivalent of the silylene resulted in the formation of a compound similar to A. However, this second insertion is kinetically hampered by steric hindrance.88 Also in 2007, Bertrand et al. demonstrated an NHC-mediated aggregation of

4. SYNTHESIS OF As4 As described in the previous section, gray arsenic sublimes at 616 °C. In the gas phase, As4 molecules are present. Condensation of As4 vapors on cold surfaces leads to solid yellow arsenic. However, in the solid state, yellow arsenic is very prone to polymerization, transforming into gray arsenic, especially in the presence of light. Because of this, the isolation of solid yellow arsenic, and especially its storage, is practically impossible. Instead, solutions of yellow arsenic are more stable, rendering the synthesis of solutions of As4 comparatively easy. The condensation of As4 vapors in CS2 was first described in 1867 by Bettendorff.77 Later, O. J. Scherer replaced CS2 with xylene since the former was not inert enough.78 As4 is slightly soluble in common organic solvents, and other than CS2, E


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Scheme 4. Selected Examples of the Activation of P4 by Main Group Compounds

Scheme 6. Synthesis of the Organo-Substituted As4 Butterfly CpPEt2As4 (5-3) and the Release of As4 in Solution

3).94 When exposed to light or heat in solution, the butterfly compound dissociates into the CpPEt radical and As4. This

P4. The reaction of P4 with an NHC at room temperature resulted in the formation of both the (Z)- and (E)tetraphosphatriene isomers (C). Heating of C at 70 °C for 16 h yielded a P12 cluster capped by two NHCs (D).89 Bertrand also showed that cyclic (alkyl)(amino)carbenes (CAACs) can activate P4. Depending on the bulkiness of the CAAC, compounds similar to C are obtained.90 The use of a less sterically hindered CAAC resulted in the fragmentation of P4 into compounds E and F.91 Phosphenium cations are another example of main group compounds capable of activating P4. Weigand et al. reported a solvent-free reaction of P4, GaCl3, and Ph2PCl, as a melt, resulting in the formation of [P5Ph2][GaCl4] (G).92 The reactivity of As4, a higher homologue of P4, has received comparatively less attention, and only a few examples of such reactions are known in the literature. The first example of the activation of yellow arsenic by a main group compound was reported by West et al. in 1992 who reacted the tetramesityldisilene (Mes2SiSiMes2) (Mes = 2,4,6-trimethylphenyl) with As4 resulting in a mixture of 5-1, a 1-arsa-2,3disilacyclopropyl-1,4,5-triarsa-2,3,-disilabicyclo[2.1.0]pentane, and 5-2, a 1,3-diarsa-2,4-disilabicyclobutane with a butterfly structural motif (Scheme 5). By heating this mixture to 95 °C,

Figure 3. Molecular structure of CpPEt2As4 (5-3). Figure created by authors from data in ref 94. In all figures showing crystal structures, the hydrogen atoms and solvent molecules are omitted for clarity.

property can be used to easily release As4 from 5-3 in solution under thermal or photochemical conditions. However, compound 5-3 can be isolated and stored in the solid state without decomposition. Remarkably, yellow arsenic can be sublimed from powder samples of CpPEt2As4 under rather mild conditions (125 °C), making compound 5-3 a promising As4 storage material. The reaction of the CpBIG radical with P4 resulted in the analogous organo-substituted P4 butterfly compound CpBIG2P4, which shows similar properties regarding the release of P4.94,95 In 2011, H. W. Roesky reported on the reaction of P4 with the silylene [PhC(NtBu)2SiN(SiMe3) 2] leading to the formation of compound H, which features a P4 chain stabilized by two silylene units (Scheme 7).96 They also reported the reaction of P4 with the disilene [(Me3Si)2NCp*SiSiCp*N(SiMe3)2] (Cp* = C5Me5), which resulted in the activation of both P4 and a Si−C bond leading to the silicon−phosphorus cage compound (I).96 These results led to our investigation of the reactivities of these two silylene compounds with yellow arsenic;97 however, as shown in Scheme 8, an entirely different set of structures were obtained. The reaction of the silylene [PhC(NtBu)2SiN(SiMe3)2] with As4 led to an aggregation of As4 resulting in the unprecedented As10 cage compound 5-4 with a heptaarsanortricyclane unit as central structural motif (Figure 4). To understand the formation of 5-4, a possible reaction pathway was investigated computationally that predicted an As4 chain compound, similar to H, as a key intermediate. In the case of reaction with the

Scheme 5. Reaction of Tetramesityldisilene with As4

a slow conversion of 5-1 to 5-2 was observed (80% conversion after 30 days heating).93 Comparable reactions of P4 with different disilenes only resulted in products similar to compound 5-2. These results emphasize the differences in the reactivities of As4 and P4. In 2016, the Scheer group showed that it was possible to activate yellow arsenic with main group radicals such as the CpPEt radical. This radical was generated by the reaction of CpPEtNa (CpPEt = C5(4-EtC6H4)5) with CuBr, which was further reacted with As4 to form the first organo-substituted As4 butterfly compound CpPEt2As4 (5-3) (Scheme 6, Figure F


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Scheme 7. Reaction of P4 with the Silylene [PhC(NtBu)2SiN(SiMe3)2] and the Disilene [(Me3Si)2NCp*Si]2

Figure 5. Molecular structure of 5-5. Figure created by authors from data in ref 97.

Scheme 8. Reaction of As4 with the Silylene [PhC(NtBu)2SiN(SiMe3)2] and the Disilene [(Me3Si)2NCp*Si]2

6. REACTIVITY OF As4 TOWARD TRANSITION METAL COMPLEXES The activation of white phosphorus by transition metals and its transformation to different fragmented or substituted phosphorus units represent a very active field of research yielding a range of significant developments in recent years.98−106 In comparison to the activation of white phosphorus, much less is known about the reactivity of yellow arsenic with transition metals. This fact may be attributed to a number of attributes of yellow arsenic including its toxicity, the difficulties involved with its time-consuming preparation, and problems with its handling as a solid or in solution, due to its air- and lightsensitivity (formation of gray arsenic). Furthermore, it is almost impossible to carry out precisely stoichiometric reactions with yellow arsenic as the concentration of As4 in solution can only be estimated at any particular time due to its decomposition to gray arsenic during handling. 6.1. Activation of As4 by Early Transition Metals

6.1.1. Activation by Transition Metal Complexes of Group 4 Elements. Only one example of the activation of yellow arsenic by complexes of the early transition metals of group 4 is known in the literature.107 The reaction of [Cp″2Zr(CO)2] (Cp″ = η5-C5H3tBu2) with As4 in boiling xylene resulted in the formation of the complex [Cp″2Zr(η1:1As4)] (6.1-1) as the main product in 84% yield along with traces of the unprecedented complex [(Cp″2Zr)(Cp″Zr)(μ,η2:2:1-As5)] (6.1-2) (Scheme 9). Scheme 9. Synthesis of [Cp″2Zr(η1:1-As4)] (Cp″ = η5C5H3tBu2) (6.1-1)

Figure 4. Molecular structure of 5-4. Figure created by authors from data in ref 97.

Complex 6.1-1 can be prepared on the gram scale. It is lightstable and can be stored under inert conditions without decomposition for months, making it a potentially interesting reagent for use in As4 transfer reactions. The molecular structures of 6.1-1 and 6.1-2 are depicted in Figure 6. Complex 6.1-1 consists of a [Cp″2Zr] fragment that is inserted into an As−As edge of the As 4 tetrahedron resulting in a tetraarsabicyclo-[1.1.0]-butane framework with As−As dis-

disilene, only compound 5-5, with a butterfly structural motif (similar to 5-2), could be isolated in low yields (Figure 5). However, the LIFDI mass spectrum of the crude reaction mixture indicated the additional formation of a compound with the chemical composition [Cp*2(Me3SiN)2Si2As4], indicative of the formation of an As−Si cage compound similar to I. G


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Figure 6. Molecular structures of the complexes 6.1-1 (left) and 6.1-2 (right). Figure created by authors from data in ref 107.

Figure 7. Molecular structure of [Cp*Nb(CO)2(η4-As4)] (6.1-3). Figure created by authors from data in ref 108.

tances in the range 2.4154(4)−2.4650(4) Å. Complex 6.1-2 consists of [Cp″2Zr] and [Cp″Zr] fragments coordinated to an As5 moiety with As−As bond lengths between 2.4511(8) and 2.4797(9) Å. 6.1.2. Activation by Transition Metal Complexes of Group 5 Elements. In 1989, Scherer et al. published the reaction of yellow arsenic with a group 5 transition metal complex. The photolysis of [Cp*Nb(CO)4] in the presence of yellow arsenic gave the complex [Cp*Nb(CO)2(η4-As4)] (6.13) as the main product (Scheme 10), which was

(Figure 8). The As−As distances in both compounds (6.1-4, 6.1-5) vary between 2.355(3) and 2.530(6) Å (6.1-4) and

Scheme 10. Reactions of As4 with Transition Metal Complexes of Group 5 Elements Figure 8. Molecular structures of 6.1-5 (left) and 6.1-7 (right). Figure created by authors from data in refs 109 and 110.

between 2.360(7) and 2.546(6) Å (6.1-5). The Nb···Nb distances in 6.1-4 and 6.1-5 (3.326(2)/3.311(5) Å) fall at the upper limit of bonding interactions. A compound similar to 6.1-4 was obtained from the reaction of yellow arsenic with the complex [Cp″Ta(CO)4] in decalin at 190 °C. The resulting complex, [(Cp″Ta)2(μ,η4:4-As8)] (6.1-6), also contains a cyclic As8 ligand, which can again be viewed as a heavily distorted analogue of cyclooctatetraene (Scheme 10). The reaction of 6.1-6 with [Cp*Fe(CO)2]2 in decalin at 190 °C led to the heteronuclear complex [{Cp*Fe}{Cp″Ta}(μ,η4:3-As5)] (6.1-7). This compound features an open As5 chain between the two metals with two short (2.380(2)/ 2.375(2) Å) and two long (2.4956(4)/2.489(2) Å) As−As distances (Figure 8, right). The distance between the two As atoms at respective ends of the chain is 3.745 Å, outside of the accepted range of As···As interactions. Complex 6.1-7 can also be obtained by the reaction of [Cp*Fe(η5-As5)] with [Cp″Ta(CO)4] in decalin at 190 °C.110 Cummins et al. showed that the niobaziridine-hydride complex [(H)Nb(η2-tBuHCNAr)(N[Np]Ar)2] (Np = CH2tBu; Ar = 3,5-C6H3Me2) activates As4 under mild conditions (−30 °C to room temperature; in the dark) forming the complex [{Nb{N(Np)Ar}3}2(μ,η2:2-As2)] (6.1-8) (Scheme 10). Complex 6.1-8 features an Nb2As2 butterfly core shown by DFT optimization along with a low-quality X-ray structure that did not allow for the discussion of bond distances, yet confirmed the connectivity of the heavier atoms. The reduction of complex 6.1-8 with excess Na/Hg in THF led to the anionic arsenide complex [AsNb{N(Np)Ar}3]− (6.1-9).36 The Nb−As distance in 6.1-9 of 2.3078(5) Å falls between the sum of the triple- and double-bond covalent radii

unambiguously characterized by X-ray crystallography, elemental analysis, and IR and 1H NMR spectroscopy. A second product was also obtained, which was postulated to be [{Cp*Nb(CO)}2(As2)2]; however, the actual structure could not be proven.108 Complex 6.1-3 features a slightly distorted square-planar cyclo-As4 unit with As−As distances between 2.345(4) and 2.409(4) Å (Figure 7). A similar reaction of As4 with the [Cp″Nb(CO)4] performed at thermolytic conditions (decalin 170 °C) gave the complex [(Cp″Nb)2(μ,η4:4-As8)] (6.1-4).109 This compound features a distorted As8 ring coordinated to two NbCp″ fragments, representing the arsenic analogue of cyclooctatetraene. The reaction with [Cr(CO)5(thf)] resulted in compound 6.1-5 wherein a Cr(CO)5 fragment is coordinated by one As atom of the As8 ring H


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of As and Nb, 2.24 and 2.34 Å, respectively, indicating significant triple bond character. 6.1.3. Activation by Transition Metal Complexes of Group 6 Elements. The activation of yellow arsenic by group 6 complexes is commonly attempted via the thermolytic elimination of CO from carbonyl complexes, resulting in highly reactive transition metal fragments capable of activating As4. An overview of such reactions is given in Scheme 11. The Scheme 11. Activation of Yellow Arsenic by Group 6 Transition Metal Complexes under Thermolytic Conditions

Figure 9. Molecular structures of 6.1-13 (left), 6.1-15 (middle), and 6.1-16 (right). Figure created by authors from data in refs 111 (left) and 115 (middle and right).

[CpRCr(CO)2]2 (CpR = Cp*, C5Me4Et), containing a Cr− Cr triple bond and a sterically more demanding CpR ligand, is reacted with As4 in boiling xylene, complexes [CpRCr(CO)2(η3-As3)] (6.1-15) can be isolated, which are isostructural to complex 6.1-10 (Figure 9). Ultraviolet irradiation of these complexes led to additional CO elimination and the formation of the triple-decker complex [{CpRCr}2(μ,η5-As5)] (6.1-16) (Scheme 11, Figure 9).115 In recent years, it has been shown that harsh reaction conditions, such as boiling xylene, are not needed for the activation of As4 if suitable group 6 complexes are employed. One example, initially reported by Cummins et al., is the reaction of As4 with the three-coordinate compound [Mo{N(tBu)Ar}3] (Ar = 3,5-dimethylphenyl), a reagent known to display remarkable versatility with regard to the formation of terminal Mo−E (E = C−, N, P, O, S, Se, Te) multiple bonds. This reaction proceeds at room temperature in toluene, resulting in the complex [AsMo{N(tBu)Ar}3] (6.1-17) in 67% yield (Scheme 12). The complex 6.1-17 features a Mo− As triple bond and is one of the few known examples of a reaction of [Cp*Mo(CO)2]2 with As4 in refluxing xylene for 30 h resulted in the complexes [Cp*Mo(CO)2(η3-As3)] (6.1-10), [{Cp*Mo(CO)2}2(μ,η2-As2)] (6.1-11), and [Cp*Mo(CO)(μ,η2-As2)]2 (6.1-12).78 Longer reaction times (∼60 h) with a similarly bulky CpR ligand (Cp*/C5Me4Et) led to the formation of the triple-decker complex [(CpRMo)2(μ,η6As6)] (6.1-13) (CpR = Cp*, C5Me4Et), featuring an As6 middle deck, as well as complex 6.1-10.111 It should also be mentioned that the UV irradiation of complex 6.1-10 gave both the triple-decker complex 6.1-13 and the As2−ligand complex 6.1-11. Similarly, upon irradiation, [Cp*Mo(CO)2(η3-P3)] reacted to give the triple-decker complex [{Cp*Mo}2(μ,η6-P6)].112 A crystal structure analysis of 6.113 showed that both five-membered organic rings and the As6 ring are planar and parallel. The As−As distances within the cyclo-As6 unit range from 2.337(3) to 2.365(3) Å, between distances typical for As−As single and double bonds (Figure 9). Moreover, it was also shown that complex 6.1-13 was able to be oxidized with [Cu(MeCN)4][BF4].113 The triple-decker geometry of 6.1-13 persisted after the one-electron oxidation. In the oxidized structure the Mo−Mo distance is retained, but the As−As bond lengths are altered. Two of the As−As bonds are elongated (2.4389(13) Å) while four are shortened (2.3236(8) Å) as compared to the bonds in the neutral compound (As−Asav 2.349 Å), indicative of a bisallylic system. If similar reactions are performed with the Cr compounds [CpRCr(CO)3]2 (CpR = Cp*; C5H4Me) and As4, only the triple-decker complex [{CpRCr}2(μ,η5-As5)] (6.1-14) can be isolated (Scheme 11).114 However, if the Cr complex

Scheme 12. Overview of the Reactivities of Yellow Arsenic with Transition Metal Complexes of Group 6 Elements under Mild Reaction Conditions

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shorter than the other As−As bonds, which range from 2.425(1) to 2.454(1) Å.

complex containing a terminally coordinated As atom (Figure 10).116,117 Low-temperature (−80 °C) reactions with an

Figure 12. Molecular structure of 6.1-19. Figure created by authors from data in ref 120. Figure 10. Molecular structure of 6.1-17. Figure created by authors from data in ref 116.

Complex 6.1-19 cocrystallizes with the As8 realgar-type complex [{Cp*Cr(CO)3}4(μ4,η1:1:1:1-As8)] (6.1-20). This As8 complex is not initially formed during the reaction but instead forms during crystallization by the dimerization of two butterfly complexes (6.1-19). This complex can also be achieved by stirring a solution of 6.1-19 in toluene at ambient conditions, leading to a complete conversion to the complex 6.1-20. The central structural motif of 6.1-20 is an As8 realgarlike unit, best described as an As84− ligand (Figure 13). The As−As bond lengths vary between 2.4229(8) and 2.4600(8) Å, which are in the normal range of As−As single bonds.

equimolar amount of [Mo{N(tBu)Ar}3] gave the complex [(μ-As){Mo{N(tBu)Ar}3}2], in which a color change from yellow-brown to bright-purple can be observed. This color change is reversible and can be replicated by repeated cooling and heating cycles. Another way to activate As4 under mild conditions is the use of transition metal complexes containing metal−metal multiple bonds. One such complex is the Cr−Cr quintuply bonded species reported by Kempe at al.118 This complex reacts with As4 at room temperature and yields 6.1-18 in good yield (69%) within 16 h (Scheme 12).119 The crystal structure of this compound, depicted in Figure 11, shows a nearly square-

Figure 11. Molecular structure of 6.1-18. Figure created by authors from data in ref 119.


planar geometry of the As4 unit with As−As bond lengths varying between 2.388(1) and 2.406(1) Å, shorter than an As− As single bond. As such, the As4 unit can be viewed as a cycloAs42− ligand. This reactivity is not limited to As4, as the use of P4 or AsP3 gave similar products with cyclo-P42− or cyclo-AsP32− units, respectively. An additional strategy for the activation of As4 under mild conditions is via a radical species, as previously discussed for reactions with the CpPEt radical (section 5). For example, the chromium carbonyl complex [{Cp*Cr(CO)3}2] is known to dissociate in solution, to a small extent, forming the radical species [Cp*Cr(CO)3]•. The reaction of [{Cp*Cr(CO)3}2] with yellow arsenic in toluene at room temperature afforded the formation of the complex [{Cp*Cr(CO)3}2(μ,η1:1-As4)] (6.1-19) in good yields (75%).120 Complex 6.1-19 features a structural motif of an As4 butterfly ligand bridging the two [Cp*Cr(CO)3] fragments (Figure 12). The bridgehead As−As bond (2.367(3) Å) is

6.2. Activation of As4 by Late Transition Metals

6.2.1. Activation by Transition Metal Complexes of Group 8 Elements. There are two possible pathways to As4 activation with the metals of group 8. One approach is to start with carbonyl complexes, from which one or more CO ligands are eliminated at harsh reaction conditions (photolysis or thermolysis), resulting in intermediates with unsaturated transition metal centers, which are necessary for the activation. The other approach is the mild activation with metal-centered radicals. The reaction of the complex [CpRFe(CO)2]2 (CpR = Cp*; C5Me4Et) with yellow arsenic in decalin at 190 °C for 1−2 h leads only to the formation of the complex [CpRFe(η5-As5)] (6.2-1) with a pentaarsacyclopentadienyl ligand (cyclo-As5−) (Scheme 13).121 The pentaarsaferrocene 6.2-1 is isolobal to ferrocene, for which only one Cp ligand is replaced by a cycloAs5 ligand (Figure 14). Within the five-membered ring, the J


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Scheme 13. Activation of Yellow Arsenic by Transition Metal Complexes of Group 8 at Harsh Reaction Conditions


Further examples of the size-dependency of the activation of yellow arsenic by different carbonyl metal complexes containing a CpR ligand are the reactions with the complexes [CpRFe(CO)2]2 (CpR = Cp‴, CpBIG) featuring the bulky Cp‴ and CpBIG ligands. These reactions take place at room temperature and proceed via homolytic cleavage of the Fe− Fe bond, resulting in a 17-valence-electron, metal-centered radical, which reacts with As4 through cleavage of one As−As bond to afford a As42− butterfly structure stabilized by two [CpRFe(CO)2] fragments (Scheme 14, Figure 16).120,125 These reactions are straightforward, and the products, [{CpRFe}2(μ,η1:1-As4)] (6.2-7), can be isolated in good to excellent yields (Cp‴, 77%; CpBIG, 84%).

As−As distances are between 2.312 (2) and 2.319(2) Å, thus in the expected range of delocalized As−As double bonds.

Scheme 14. Activation of Yellow Arsenic at Room Temperature through the Complex [CpRFe(CO)2]2 (CpR = Cp‴; CpBIG)


The treatment of the sandwich complex 6.2-1 with the salt [CpFe(C6H6)][PF6] under UV radiation leads to the tripledecker sandwich complex [CpFe(μ,η5-As5)Cp*Fe][PF6] (6.22) (Scheme 13). The formation of such triple-decker complexes is not limited to homometallic complexes as heterometallic complexes have also been realized. One example are the reactions of 6.2-1 with the complex [M(CO)3(NCMe)3] (M = Cr, Mo, W), which lead to the heterometallic triple-decker complexes [CpRFe(μ,η5:5-As5)M(CO)3] (M = Cr, Mo, W) (6.2-3).122 Changing the transition metal in the starting compound [CpRFe(CO)2]2 from Fe to Ru also results in a sandwich complex with a cyclo-As5 ligand [CpRRu(η5-As5)] (6.2-4). However, as opposed to the discussed reaction with Fe, a new complex (6.2-5) containing 9 arsenic and 4 ruthenium atoms was isolated (Scheme 13).123 In addition to the identity of the transition metal, the size of the CpR substituent has a huge influence on the nature of the formed products. For example, the reaction of yellow arsenic with the less bulky complex [CpFe(CO)2]2 led, under similar conditions (decalin 190 °C), to a cluster compound [{CpFe}4(μ4,η2:2:1:1-As2)2] (6.2-6) (Scheme 13, Figure 15).124

Irradiation of the complex [{Cp‴Fe(CO)2}2(μ,η1:1-As4)] (6.2-7) with UV light resulted in the elimination of a CO

Figure 16. Molecular structure of 6.2-7. Figure created by authors from data in ref 120. K


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The E4 butterfly complexes (E = P, As) show interesting reactivities not only if they are irradiated with UV light, but also if they are reacted with As4 in high-boiling solvents. For example, the butterfly complex [{CpBIGFe(CO)2}2(μ,η1:1-As4)] (6.2-7) reacts with As4 to form three products (Scheme 15).

ligand and a shift of the [Cp‴Fe(CO)] fragment to form a bridged butterfly complex (6.2-8). Because of this shift, the steric shielding of the As4 unit is no longer sufficient and dimerization of two complexes [{Cp‴Fe(CO)2}{Cp‴Fe(CO)}(μ,η1:2-As4)] (6.2-8) leads to the formation of the complex [{Cp‴Fe(CO)2}2{Cp‴Fe(CO)}2(μ4,η1:1:2:2-As8)] (6.2-9). The molecular structure of 6.2-9, depicted in Figure 17, shows an As8 realgar-like unit as a main structural motif,

Scheme 15. Reaction of the Butterfly Complex [{CpBIGFe(CO)2}2(μ,η1:1-As4)] (6.2-7) with As4


which can be described as an As84− ligand. The As−As bond lengths (2.4317(5)−2.4607(4) Å) compare well to As−As single bonds, and the Fe−As bond lengths for the terminally coordinated Fe fragments (2.4675(6)−2.4692(6) Å) resemble those found in the starting material (6.2-7).120,125 If the butterfly complex [{CpBIGFe(CO)2}2(μ,η1:1-As4)] (6.2-7) is irradiated with UV light, only [{CpBIGFe}2(μ,η4:4-As4)] (6.210) is obtained as the product of complete decarbonylation.126 Compound 6.2-10 is a triple-decker compound with an aromatic cyclo-As4 ligand showing As−As bond lengths ranging from 2.3909(7) to 2.4558(7) Å and Fe−As bond lengths ranging from 2.4144(7) to 2.5130(7) Å (Figure 18). The complex core can be described as an Fe2As4 octahedron. The two Cp ligands and the As4 plane are nearly parallel (Figure 18).

One is the aforementioned triple-decker complex 6.2-10. Another is the CpBIG-substituted pentaarsaferrocene (6.2-11), and the last is the cluster [{CpBIGFe}3(μ3,η4:4:4-As6)] (6.212).126 The molecular structure of complex 6.2-12 is depicted in Figure 19. Its central structural motif is an As6 prism in which each of the three square faces is capped with a [CpBIGFe] fragment. A further interesting example for the reaction of an E4 butterfly complex (E = P, As) with yellow arsenic is the reaction of [{Cp‴Fe(CO)2}2(μ,η1:1-P4)] in boiling decalin, which results in the complexes [{Cp‴Fe}2(μ,η4:4-PnAs4−n)] (n

Figure 18. Molecular structure of 6.2-10. The nBu groups of the CpBIG ligand are illustrated by only one C atom. Figure created by authors from data in ref 126.

Figure 19. Molecular structure of 6.2-12. The nBu groups of the CpBIG ligand are illustrated by one C atom. Figure created by authors from data in ref 126. L


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= 2−4) (6.2-13) and [(Cp‴Fe)(η5-PnAs5−n)] (n = 2−5) (6.214), rare examples of mixed PnAsm ligands (Scheme 16).127

phos) to give the complex [{(triphos)Co}2(μ,η3:3-As3)][BF4]2 (6.2-19) (Scheme 18).131,132 The cyclo-As3 unit acts as a 3πelectron system, which connects the two Co centers (Figure 20).

Scheme 16. Reaction of [{Cp‴Fe(CO)2}2(μ,η1:1-P4)] with As4

Scheme 18. Reaction of As4 with Cobalt Tetrafluoroborate in the Presence of Triphos

One of the products of the reaction of the As4 butterfly complex 6.2-7 with yellow arsenic is the pentaarsaferrocene [CpBIGFe(η5-As5)] (6.2-11), which can likewise be synthesized by the reaction of [CpRFe(CO)2]2 with As4. This reactivity is amenable to a large variety of CpR ligands. The pentaarsaferrocene 6.2-1, similar to its lighter homologue pentaphosphaferrocene, shows a very versatile reactivity, making it an important starting reagent for the syntheses of different Asn ligand complexes. The cothermolysis of [Cp*Fe(η5-As5)] with [Cp*Co(μ-CO)]2 in decalin led to the complexes [(Cp*Fe)2(Cp*Co)(μ3,η2:2:2-As3)2] and [Cp*Co(μ,η2:2-As2)]2.128 The reaction of [Cp*Fe(η5-As5)] with the rare-earth complex [Cp″2Sm(thf)] (Cp″ = 1,3-tBu2C5H3) resulted in a reduction and rearrangement of the cyclo-As5 ligand. Depending on the reaction conditions, either the triple-decker complex [(Cp″2Sm)(μ,η4:4-As4)(Cp*Fe)], containing a 6π-aromatic As42− ligand, or the As-rich complex [(Cp″2Sm)2As7(Cp*Fe)] can be obtained.129 The reduction of [Cp*Fe(η5-As5)] (6.2-1) with KH gives different arsenic-rich polyarsenide complexes, such as [K(dme)2]2[(Cp*Fe)2(μ,η2:2:2:2-As14)] (6.2-17) or [K(dme)3]2[(Cp*Fe)4(μ4,η4:3:3:2:2:1:1-As18)] (6.2-18), containing up to 18 arsenic atoms (Scheme 17).130 6.2.2. Activation by Transition Metal Complexes of Group 9 Elements. In 1978, Sacconi et al. reported the first polyarsenic complex of Co formed by the activation of yellow arsenic. Freshly prepared As4 was reacted with cobalt tetraflu orobo ra te in t h e pre s ence of 1 ,1 ,1 -t ri s(diphenylphosphinomethyl)ethane ({CH3C(CH2PPh2)3}/tri-

Figure 20. Molecular structure of 6.2-19. Figure created by authors from data in refs 131 and 132. The counterions are omitted for clarity.

In 1992, O. J. Scherer et al. reported the reaction of yellow arsenic with the Co complex [(Cp*Co(μ-CO)]2 in boiling toluene. By column chromatographic workup, the four complexes [{Cp*Co(CO)} 2 (μ,η 1:1:1:1 -As 4 )] (6.2-20), [Cp*Co(CO)(η1:1-As4)] (6.2-21), [Cp*Co(μ,η4:1:1-As4)Cp*Co(CO)] (6.2-22), and [{Cp*Co}(μ,η2:2-As2)]2 (6.2-23) were isolated (Scheme 19).133 The researchers not only succeeded in the isolation and characterization of these complexes, but also in finding strategies to accomplish direct syntheses of the different complexes. The short thermolysis (10 min) of [Cp*Co(CO)]2 in the presence of yellow arsenic resulted in the formation of 6.2-20. Heating pure 6.2-20 in xylene for 1 h at 140 °C led, by

Scheme 17. Reaction of [Cp*Fe(η5-As5)] (6.2-1) with KH

Scheme 19. Pathway for the Reaction of As4 with [Cp*Co(CO)]2.

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CO elimination, to the sole formation of 6.2-22. Heating 6.222 in xylene at 140 °C for 5 h resulted after another CO elimination in the formation of complex 6.2-23 with two As2 units bridging the Cp*Co fragments. The reaction of 6.2-20 with an additional equivalent of As4 led to the formation of [Cp*Co(CO)(η1:1-As4)] (6.2-21) wherein one Co fragment is coordinated by the wingtip As atoms of an As4 butterfly ligand. The molecular structures of 6.2-20, 6.2-21, and 6.2-22 are depicted in Figures 21 and 22.

Figure 23. Molecular structure of 6.2-24 (left) and 6.2-25 (right). Figure created by authors from data in ref 134.

Figure 21. Molecular structures of 6.2-20 (left) and 6.2-21 (right). Figure created by authors from data in ref 133.



Scherer and co-workers also showed that the reaction of yellow arsenic and the dicarbonyl cobalt complex [CpRCo(CO)2] (CpR = Cp*, C5Me4Et), performed with a longer reaction time (4 h) and at a higher temperature (190 °C in decalin), led to the complexes [CpRCo(μ,η2:2-As2)]2 (6.2-24), [{CpRCo}2(μ,η4:2:2-As6)] (6.2-25), and [{CpRCo}3(μ,η2:2As2)(μ3,η4:2:2-As4)] (6.2-26) (Scheme 20).134 These products could be isolated through a chromatographic workup and characterized. The researchers also succeeded in obtaining single crystals for a X-ray structural analysis. The molecular structures of these complexes are shown in Figures 23 and 24.

Complex 6.2-24 consists of two CpRCo fragments connected by two As2 units. The As−As bond lengths (2.272(1) Å) are within the typical range of μ,η2:2-As2 units.135 Complex 6.2-25 features an As6 Dewar benzene structural motif coordinated to two [CpRCo] fragments, with an opened As−As bond. Compound 6.2-26 also contains six As atoms but features one μ,η2:2-As2 unit coordinated to two [CpRCo] fragments and a cyclo-As4 unit coordinated to three [CpRCo] fragments in μ3,η4:2:2 fashion. A similar reaction of As4 with the Rh complex [Cp″Rh(CO)2] (Cp″ = 1,3-tBu2C5H3) in decalin at 190 °C (Scheme 21) was reported by Scherer et al. This reaction resulted in the formation of complex [Cp″Rh(μ,η2:2-As2)]2 (6.2-28), displaying a structural motif similar to 6.2-24. However, in addition to complex 6.2-28, complex [(Cp″Rh)4(μ4,η4:4:2:2:1:1-As10)] (6.227) was also obtained, which was characterized by NMR

Scheme 20. Reaction of As4 with [CpRCo(CO)2]

Scheme 21. Reaction of As4 with [Cp″Rh(CO)2]

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spectroscopy and mass spectrometry. However, no unambiguous X-ray structural analysis could be carried out.136 A mild activation of As4 at room temperature can be initiated by the complex [{Cp‴Co}2(μ,η4:4-toluene)]. In addition to [(Cp‴Co)2(μ,η2:2-As2)2] (6.2-29), which is the main product (54%), this method gives also the two arsenicrich complexes [(Cp‴Co)4(μ4,η4:4:2:2:1:1-As10)] (6.2-30) and [{Cp‴Co}3(μ3,η4:4:2:1-As12)] (6.2-31) containing an As10 and As12 ligand, respectively, representing the largest neutral substituent-free polyarsenic ligands yet characterized by X-ray crystallography (Scheme 22).137

Scheme 23. Reaction of 6.2-29 with [Cp*2Sm(thf)2]

combinations of substituents at the β-diketiminato ligand had a sizable influence on the reaction products.139,140 Yellow arsenic was likewise reacted with different β-diketiminato (L) Co I complexes [LCo(η 6-tol)], and depending on the substituents on the β-diketiminato ligand (L = L0, L1, L2), the complexes [(L0Co)2(μ,η4:4-As4)] (6.2-33), [(L1Co)2(μ,η3:3-As4)] (6.2-34), and [(L2Co)2(μ,η1:1:1:1-As4)] (6.2-35) were obtained (Scheme 24).141 The molecular

Scheme 22. Reaction of As4 with the Triple-Decker Complex [{Cp‴Co}2(μ-tol)]

Scheme 24. Reactions of As4 with Different [LxCo(η6-tol)] (Lx = L0, L1, L2) Complexes The main structural feature of compound 6.2-30 is an As10 ligand consisting of two As5 units connected by an As−As bond. Within each As5 unit, a single [Cp‴Co] fragment coordinates four As atoms, while another [Cp‴Co] fragment is coordinated by only two arsenic atoms of the unit and one arsenic atom of the second As5 ring. The molecular structure of 6.2-31 is depicted in Figure 25. The main structural motif can


structures of these three complexes are depicted in Figures 26 and 27, each displaying significant differences as compared to the corresponding reactions with P4.142 Complex 6.2-33 consists of two [L0Co] fragments bridged by a rectangularshaped cyclo-As4 ligand. The As4 unit features two short (2.3299(5) Å) and two long (2.4638(5)/2.4816(5) Å) As−As distances. Complex 6.2-34 has a central [Co2As4] core, which is best described as a distorted mixture of trigonal prism and antiprism with each Co atom η3-coordinated by three arsenic atoms. The As−As distances are between 2.4064(11) Å and 2.5266(10) Å, in the range of As−As single bonds. The molecular structure of 6.2-35 consists of two [L2Co] fragments bridged by a 2-fold edge-opened As4 tetrahedron. The As−As bond lengths fall between 2.4466(2) and 2.4616(12) Å, again in the range of As−As single bonds. Interestingly, at high temperatures 6.2-35 underwent an extrusion of one As atom, which was monitored by 1H NMR spectroscopy in toluene-d8.

be derived from complex 6.2-30 by replacing one As5{Cp‴Co}2 fragment with a norbornane-like As7CoCp‴ unit. All of the As−As bond lengths are in the range of single bonds with the exception of the As−As bond between the arsenic atoms coordinated to two [Cp‴Co] units, which, at 2.6684(5) Å, is elongated possibly resulting in only weak interactions between these arsenic atoms. By this mild activation method, it was possible to obtain the complex [(Cp‴Co)2(μ,η2:2-As2)2] (6.2-29) in relatively high yields (54%), which enabled an investigation of its reactivity with decamethylsamarocene [Cp*2Sm(thf)2], resulting in the formation of [{Cp‴Co}2(μ3,η3:3:2-As4){Cp*2Sm}] (6.2-32) (Scheme 23).138 By activation of P4 with different β-diketiminato (L) FeI complexes ([LFe(η6-tol)]), it was shown that different O


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Figure 26. Molecular structures of 6.2-33 (left) and 6.2-34 (right). Figure created by authors from data in ref 141. Figure 28. Molecular structure of 6.2-36. Figure created by authors from data in ref 141.

Scheme 26. Reaction of As4 with Nickel Tetrafluoroborate in the Presence of Triphos

Figure 27. Molecular structures of 6.2-35. Figure created by authors from data in ref 141.

27). The reaction of [Cp*Ni(CO)]2 with yellow arsenic in boiling toluene resulted in the cluster compound [{Cp*Ni}3As5] (6.2-38).143 Its molecular structure (Figure 29) shows a Ni3As5 cubane structure constructed of an As4 and an As1 ligand with an average As−As bond length of 2.440 Å and an average Ni−As bond length of 2.323 Å.

A selective transformation to the paramagnetic complex [(L2Co)2(μ,η3:3-As3)] (6.2-36) (Scheme 25) occurred by the Scheme 25. Thermolytic Extrusion of One As Atom from [(L2Co)2(μ,η1:1:1:1-As4)] (6.2-35) and Formation of [(L2Co)2(μ,η3:3-As3)] (6.2-36)

Scheme 27. Reactivities of Yellow Arsenic with Different [CpRNi(CO)]2 Complexes under Thermolytic Conditions

formal elimination of an arsenic atom, resulting in the formation of an arsenic mirror. Compound 6.2-36 was isolated and characterized, including through X-ray analysis which yielded the molecular structure depicted in Figure 28. It confirms the formation of a dinuclear complex consisting of two [L2Co] fragments bridged by a cyclo-As3 middle deck, similar to that of the charged complex 6.2-19. 6.2.3. Activation by Transition Metal Complexes of Group 10 Elements. The reaction of [Ni(H2O)6][BF4]2 with As4 in the presence of the triphos ligand led to the complex [{triphosNi}2(μ,η3:3-As3)][BF4]2 (6.2-37) (Scheme 26); however, it was not possible to obtain single crystals suitable for Xray structural analysis. Nevertheless, 6.2-37 was characterized by IR and elemental analyses. The compound was predicted to be isostructural to 6.2-19 and the phosphorus analogue [{triphosNi}2(μ,η3:3-P3)][BF4]2, which were characterized by X-ray crystallography.132 The thermolytic reactivities of yellow arsenic with complexes of the form [CpRNi(CO)]2 (CpR = Cp*, Cp′, Cp4) bearing CpR ligands of different sizes were also investigated (Scheme P


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[Ag(η2-As4)2][pftb] (6.2-42) in excellent yields of 80−90% (Scheme 28).1 This complex is light-stable and can be stored Scheme 28. Reaction of Yellow Arsenic with [Ag(CH2Cl2)][pftb] (pftb = [Al{OC(CF3)3}4])

under inert conditions without decomposition. Furthermore, the original As4 tetrahedra remain intact and can be released, for example, by the addition of LiCl.2 The molecular structure of complex 6.2-42 is depicted in Figure 31. It shows a rare side-on coordination mode of two


The steric decrease from Cp* to the Cp′ ligand (Cp′ = C5H4Me) resulted, under the same reaction conditions, in the new complex [{Cp′Ni}4As4] (6.2-39), with a Ni4As4 cubane unit, which was characterized by 1H NMR spectroscopy, mass spectrometry, and elemental analysis. The molecular structure of 6.2-39 was predicted to be similar to that of 6.2-38 with the difference being that the As atom previously bound to three As atoms was replaced by an isolobal [Cp′Ni] fragment, which is only possible because of the less bulky Cp′ ligand. Increasing the bulkiness of the CpR ligand from Cp* to Cp4 (Cp4 = C5H(iPr)4), while also increasing the reaction temperature and time, led to the formation of two products, [Cp4Ni(η3-As3)] (6.2-40) and [{Cp4Ni}2(μ,η3:3-As4)] (6.241), with 6.2-40 being the main product (84% yield) (Scheme 27).144 Both complexes were characterized by NMR spectroscopy, mass spectrometry, and elemental analysis, while 6.2-41 was additionally characterized by X-ray structural analysis (Figure 30). The main structural motif present is a distorted

Figure 31. Molecular structure of 6.2-42. Figure created by authors from data in ref 1. The pftb anion is omitted for clarity.

intact As4 tetrahedra to the Ag(I) cation in an almost coplanar fashion with As−Ag distances falling between 2.611(1) and 2.626(2) Å. The As−As bonds between atoms coordinated to Ag measure 2.585(2) and 2.569(2) Å, slightly elongated as compared to the shorter As−As bonds away from the Ag atom (2.423(2) and 2.419(2) Å). Raman spectroscopy and extended DFT investigations indicate that the two As4 tetrahedra are still intact. The structure of 6.2-42 resembles that of the corresponding P4 analogue.145,146 A further example of the coordination of an intact As4 tetrahedron by a coinage metal complex is the reaction of yellow arsenic with [L2Cu(NCMe)] (L2 = [{N(C6H3iPr22,6)C(Me)}2CH]), which results in the complex [{L2Cu}2(μ,η2:2-As4)] (6.2-43) in good yields (74%) (Scheme 29).147 Scheme 29. Reaction of [L2Cu(MeCN)] with Yellow Arsenic


Complex 6.2-43 is the first example of a neutral complex containing a bridging, intact As4 ligand in an η2:2-coordination mode. In the solid state, this compound is stable at ambient conditions and can be stored under argon for months. However, in solution complex 6.2-43 slowly decomposes within days as indicated by a color change and the formation of a black precipitate. The molecular structure of 6.2-43 (Figure 32) shows the side-on coordination of the bridging As4 tetrahedron by the two opposing CuL2 fragments. The As− As distances of the two bonds coordinated to the Cu atoms are both 2.6491(8) Å. Detailed DFT calculations confirmed the

hexagonal prism consisting of two [Cp4Ni] fragments and four arsenic atoms. The As−As bond distances, between 2.374(3) and 2.435(3) Å, are in the range of As−As single bonds. The Ni−As bond distances are, with 2.329(3)−2.360(3) Å, comparable to the Ni−As bond distances of the cubane complex 6.2-38. 6.2.4. Reactivity with Transition Metal Complexes of Group 11 Elements. The reaction of the weakly coordinated silver(I) salt [Ag(CH2Cl2)][pftb] (pftb = [Al{OC(CF3)3}4]) with yellow arsenic led to the formation of the complex Q


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(H)}2Sm}2(μ2,η4:4-As4)] (6.3-2) with a planar As42− middle deck (Scheme 31, Figure 34).149 Scheme 31. Reaction of Yellow Arsenic with [{(DippN)2C(H)}2Sm(thf)2]


As4 tetrahedra to be intact, which was further confirmed experimentally by the release of free As4 in the reaction of 6.243 with an excess of the strong Lewis base pyridine (Py), resulting in the formation of complex [L2CuPy] and free As4. 6.3. Activation of As4 by f-Block Element Complexes

Only two examples of the activation of As4 with f-block elements are known. One is the activation of As4 by [Cp″2Th(η4-C4H6)] (Cp″ = 1,3-(tBu)2C5H3) under thermolytic conditions (xylene; 150 °C), as was reported by Scherer et al. in 1994 (Scheme 30).148 Scheme 30. Activation of Yellow Arsenic with [Cp″2Th(η4C4H6)]


They obtained the dinuclear complex [Cp″2Th(μ,η2:1:2:1As6)ThCp″2] (6.3-1) containing a bicyclic As6 ligand with each five-membered ring being capped by a Cp″2Th fragment (Figure 33). Alternatively, the As6 ligand may also be described as an As6-benzvalene derivative with an open As−As edge. Recently, P. Roesky et al. showed that it is possible to activate small molecules such as P4, As4, and As4S4 (realgar) by their reduction with the sterically encumbered complex [{(DippN)2C(H)}2Sm(thf)2]. In the case of yellow arsenic, they obtained the triple-decker complex [{{(DippN)2C-

Compound 6.3-2 was formed by a 2-fold reduction of the As4-tetrahedra, which proceeded by two single electron transfers leading to a formally π-aromatic cyclotetraarsenide anion. The As−As distances in 6.3-2 are in the range 2.3652(14)−2.3887(13) Å, in good agreement with the structural parameters found for a [{K(18-crown-6)}2(As4)] (av As−As 2.39 Å) species reported in 2006 by Korber et al. to be formed in the reaction of potassium arsenide, triphenylbismuth, and 18-crown-6 in liquid ammonia solution.150 The Sm−As distances range between 3.1430(19) and 3.2481(10) Å.

7. ALTERNATIVE ARSENIC SOURCES FOR CHEMICAL REACTIONS Since the handling of yellow arsenic is not easy, and its synthesis is time-consuming and has to be performed prior to each reaction, alternative arsenic sources have been investigated intensively. To replace yellow arsenic successfully, eligible alternative arsenic sources have to fulfill the following requirements. They should be storable, be easy to handle, and should not decompose at room temperature or when exposed to light. Furthermore, candidates should show good solubilities in common solvents. The capacity for alternatives to enable stoichiometric reactions is also desirable. To date, few alternative sources for arsenic are known that fulfill some or all of the mentioned requirements. The alternative sources

Figure 33. Molecular structure of 6.3-1. Figure created by authors from data in ref 148. R


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described herein will be divided in two groups: insoluble solidstate sources and soluble sources or transfer reagents. 7.1. Solid-State Sources

7.1.1. Gray Arsenic. The simplest alternative source for arsenic is gray arsenic; however, only few reactions are known where gray arsenic is directly activated by transition metal complexes. One is the reaction with the complexes of the type [Cp2M2(CO)6] (M = Mo, W) in boiling xylene that result in complexes [{CpM(CO)2}2(μ,η2-As2)] (M = Mo, W) (7.1-1) and [{CpM(CO)2}3(As)] (7.1-2) in good yields (7.1-1, 35/ 25%; 7.1-2, 40/45%) (Scheme 32).151 Scheme 32. Reaction of [{CpM(CO)3}2] (M = Mo, W) with Gray Arsenic

The Cr complex [{CpCr(CO)3}2] was likewise reacted with gray arsenic in boiling toluene (1.5 h). After column chromatography, the complexes [{CpCr(CO)2}2(μ,η2-As2)] (7.1-3) (21%) and [CpCr(CO)2(η3-As3)] (7.1-4) (14%) were isolated as the main products, with [CpCr(CO) 2 ] 2 , [Cp2Cr2AsO5], and two uncharacterizable compounds also obtained.152 7.1.2. As4 Encapsulated in Supramolecular Cages. A second alternative is not to replace As4 with a different allotrope, as for instance gray arsenic, but rather to store As4 in the pores, canals, or spheres of a material and release it when needed. While inside these storage materials, As4 has to be stable at room temperature, when exposed to light and possibly even to air. Further, it should be easily released from these storage materials. Examples of such storage materials have recently been reported. Yang, Zhao, and co-workers, for example, reported an air- and light-stable form of As4 held within an anioncoordination-based tetrahedral cage [K(18-crown-6)] 12[(PO4)4(L)4⊃As4] (L = tris(bisurea) ligand).153 A freshly prepared As4 solution (in toluene) was added to an acetonitrile solution of the preformed supramolecular cage,154 and after workup, yellow crystals of the cage with encapsulated As4 were obtained. The encapsulation of P4 in a similar reaction was also successful. In the case of P4, release of the encapsulated white phosphorus was demonstrated by the addition of 1.5 equiv of a tetramethylammonium salt. However, the release of yellow arsenic was not tested. Moreover, the reaction of [Cp*Fe(η5-P5)] with CuCl in the presence of E 4 (E = P, As) gave the 1D polymer [Cu2Cl2{Cp*Fe(η5-P5)}2]·(E4)x (E = P, x = 1; E = As, x = 0.75), in which the E4 tetrahedra were incorporated in the tetrahedral voids of the polymer (Figure 35a).2 Crystals of these polymers are light- and air-stable for days, but they are insoluble in common solvents. The reaction of [Cp*Fe(η5-P5)] with CuI in the presence of As4 released from [Ag(η2-As4)2][pftb] (6.2-42) resulted in the formation of the supramolecular species As4@[{Cp*Fe(η5P5)}10Cu30I30(MeCN)6] (7.1-5) containing encapsulated As4 moieties (Figure 35b).

Figure 35. Molecular structure of (a) [Cu2Cl2{Cp*Fe(η5-P5)}2]∞· (0.75As4)n and (b) As4@[{Cp*Fe(η5-P5)}10Cu30I30(MeCN)6] (7.15). Figure created by authors from data in ref 2.

7.1.3. Carbon-Based Storage Materials. A very promising storage material for E4 compounds is an activated microporous carbon material (C) with a defined pore size distribution. The material E4@C (E = P, As) can easily be prepared by stirring freshly prepared E4 solutions in THF in the presence of the activated carbon material (C), yielding an air- and lightstable black solid (E4@C) after workup (Figure 36; for

Figure 36. Loaded storage material (E4@C) at air on a paper tissue. Adapted from the supplementary material for ref 3. (To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.)

synthetic details see ref 3).3,155 The maximum loading of P4 or As4 possible is approximately 36% or 10%, respectively. The E4 molecules can also be easily released either by sublimation in vacuo or by extraction with suitable solvents. The releases of both P4 and As4 were monitored by 31P and 75As NMR spectroscopy, respectively. Beyond the simple release of E4, the use of E4@C for subsequent chemical reactions was tested.3 In such experiments, E4@C was stirred in toluene at room temperature in the presence of [CpBIGFe(CO)2]2 resulting in the quantitative synthesis of the butterfly complex [(CpBIGFe(CO)2)2(μ,η1:1-E4)] (E = As (6.2-7), see section 6.2) (Scheme 33). The empty carbon material C was filtered from the S


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Scheme 34. Examples of Reactions of cyclo-(AsR)n (R = Me, Ph; n = 5, 6) with Different Transition Metal Complexes

reaction solution and recycled by heating for a number of hours under high-vacuum. Scheme 33. Reaction of As4@C with [CpBIGFe(CO)2]2

Additional carbon-based storage materials are single-wall carbon nanotubes (SWCNTs). Salzmann et al. recently reported the successful filling of SWCNTs with about 20 wt % elemental arsenic. This was achieved by exposing SWCNTs with a diameter range of about 0.8−1.2 nm to arsenic vapor at 615 °C in an evacuated quartz-glass ampule. The obtained As@SWCNT were treated with dilute nitric acid and washed with water. The encapsulation of discrete As4 molecules was monitored by HRTEM (high-resolution transmission electron microscopy). It was shown that the encapsulated As4 could be removed from the SWCNTs by thermal annealing at 615 °C under high-vacuum conditions.54 In addition to intact As4 molecules inside the SWCNT, the authors observed two new 1D allotropes of arsenic. One was a single-stranded zigzag chain and the other a double-stranded zigzag ladder (Figure 37). Both represent missing links between small arsenic

wherein one of the As atoms has been substituted by an isolobal [Co(CO)3] fragment (Scheme 34a).157 Rheingold et al. reported the reactions of [CpMo(CO)3]2 and [CpW(CO)3H] with cyclo-(AsPh)6 in toluene in a sealed tube at 180 °C for 24 h, leading to the complexes [{CpM(CO)2}2(μ,η2-As2)] (M = Mo, W) (7.2-2) (Scheme 34b).158 Rheingold also showed that different results were obtained with slightly altered reaction conditions (190 °C, 48 h) in the reaction of cyclo-(AsMe)5 with [CpMo(CO)3]2 rather than cyclo-(AsPh)6 (Scheme 34c).159 This reaction resulted in the triple-decker complex [{CpMo}2(η5-As5)] (7.2-3) with an As5 middle deck. Furthermore, the formation of the complex [{Cp′Mo(CO)}2(μ2,η2-As2)2] (Cp′ = C5H4Me) (7.2-4) was reported to occur when [Cp′Mo(CO)3]2 was reacted with cyclo-(AsMe)5 at 130 °C (toluene, sealed tube) for 48 h (Scheme 34d).160 7.2.2. Release of As4 from Molecular Compounds. Since the harsh conditions employed in reactions with cyclo(AsR)n compounds normally led to the most thermodynamically stable products, alternative As4 sources that release As4 or related As4 moieties at much milder conditions were required in order to open up new pathways to novel kinetically controlled products. One such compound is the complex [Ag(η2-As4)2][pftb] (6.2-42). The reaction of [Ag(η2-As4)2][pftb] (6.2-42) with LiCl (dissolved in a small amount of THF) in CH2Cl2 or toluene led to the formation of AgCl and Li[pftb]. Both compounds are nearly insoluble and precipitate almost completely from the reaction mixture. The released As4 can be monitored by 75As NMR spectroscopy. As4 solutions obtained by this method are more stable when exposed to light (>5 h) and about five times more concentrated than solutions of As4 obtained from high-temperature syntheses. The use of such stable As4 solutions in the reaction of CuI with [Cp*Fe(η5-P5)] resulted in the formation of the supramolecular species {As4@[{Cp*Fe(η5-P5)}10Cu30I30(MeCN)6]} (7.1-5) featuring an encapsulated As4 molecule (Figure 35b).2

Figure 37. DFT-optimized structure of (a) single-stranded zigzag chain and (b) double-stranded zigzag ladder of arsenic in SWCNTs. Figure created by authors from data in ref 54.

clusters and the 2D sheets of gray or black arsenic. The nature of the incorporated arsenic species depended on the diameter of the nanotube. 7.2. Soluble Sources and Transfer Reagents

7.2.1. cyclo-(AsR)n. In the past, cyclo-(AsR)n compounds, such as cyclo-(AsMe)5 or cyclo-(AsPh)6, have often been used in thermolysis reactions with transition metal carbonyl complexes as soluble alternative sources for As4.156 Some examples of such reactions are shown in Scheme 34. In 1969, Dahl et al. reported the reaction of [Co2(CO)8] with cyclo(AsMe)5, which resulted in the formation of [Co(CO)3(η3As3)] (7.2-1). This complex can be viewed as an As4 analogue T


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Scheme 37. Reactions of [Ag(η2-As4)2][pftb] (6.2-42) with [(Ph3P)AuCl] and [Cp*Ru(Cl)(dppe)]

Another compound capable of releasing As4 is the complex 6.2-43. As mentioned in section 6.2, this compound releases As4 when treated with the much stronger Lewis base pyridine (Scheme 35). Again, the formation of As4 was monitored by 75 As{1H} NMR spectroscopy.147 Scheme 35. Release of As4 from Complex 6.2-43

The As butterfly compound 5-3 is also able to release As4 (section 5). In this case, however, the addition of a Lewis base or other supporting reagents is not necessary, since, in solution, 5-3 releases As4 upon exposure to light or heating (Scheme 36).94 Further it was found to be possible to sublime As4 from powdery samples of 5-3.

Scheme 38. Reaction of 6.1-1 with [CpRFeBr]2 (CpR = Cp‴, CpBn)

Scheme 36. Release of As4 from Compound 5-3 upon Heating or Exposure to Light

7.2.3. Transfer of Polyarsenic Units through the Use of Asn Transfer Reagents. Another approach to the use of alternative arsenic sources does not rely on the release of As4, but rather the transfer of polyarsenic units from one compound to another. By reacting [Ag(η2-As4)2][pftb] 6.2-42 with [(Ph3P)AuCl], an intact As4 unit is transferred to the Au atom forming the complex [(Ph3P)Au(η2-As4)] (7.2-5), which features a linearly coordinated Au(I) cation with one coordination site occupied by a PPh3 ligand and the other by a side-on coordinated As4 tetrahedron (Scheme 37).1 The reaction of the complex [Ag(η2-As4)2][pftb] (6.2-42) with [Cp*Ru(Cl)(dppe)] (dppe = 1,2-bis(diphenylphosphino)ethane) generated the unprecedented complex [Cp*Ru(dppe)(η1-As4)][pftb] (7.2-6) bearing the first example of a As4 tetrahedron coordinated end-on to the Ru atom at the complex moiety. The subsequent reaction of 7.2-6 with [CpRu(PPh3)2][pftb] resulted in the complex [Cp*Ru(dppe)(μ-As4)RuCp(PPh3)][pftb]2 (7.27).161 An additional example of such a transfer reagent is [Cp″2Zr(η1:1-As4)] (6.1-1).107 Its suitability as a transfer reagent was demonstrated by its reaction with [CpRFeBr]2 (R = Cp‴ = 1,2,4-tBu3C5H2; CpBn = C5(CH2C6H5)5) under mild conditions, which resulted in the formation of complexes 7.2-8 to 7.2-10 (Scheme 38), revealing the complete transfer of the As4 moiety from the educt. All three complexes are tripledecker sandwich complexes with an As4 middle deck. In the case of the Cp‴Fe fragment, a cisoid acyclic As4 and a cyclic As4 middle deck are formed. Both compounds represent bonding isomers having either three As−As bonds and one Fe−Fe bond (7.2-8) or four As−As bonds and no Fe−Fe bond

(7.2-9). In the case of the CpBnFe fragment, only an acyclic middle deck is found in 7.2-10.107 The use of this transfer reagent is not limited to reactions with transition metal complexes as shown by the reaction of [Cp″2Zr(η1:1-As4)] (6.1-1) with the monochlorosilylene [PhC(NtBu)2SiCl] (Scheme 39), which resulted in the Scheme 39. Reaction of [Cp″2Zr(η1:1-As4)] (6.1-1) with [PhC(NtBu)2SiCl]

formation of [{PhC(NtBu)2}3Si3As3] (7.2-11) and [{PhC(NtBu)2}2Si2As2] (7.2-12), each containing cyclic (SiAs)n moieties.162 Compound 7.2-11 can be regarded as a triarsatrisilabenzene and is therefore a rare example of an “inorganic” heteroatomic benzene. The aromatic character of this compound was verified by computational studies. Also, the molecular structure, determined by X-ray structure analysis (Figure 38), displayed an only slightly distorted six-membered Si3As3 ring system with Si−As distances falling between a single and a double bond as expected for the conjugated aromatic ring system predicted by computations. U


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Figure 40. Molecular structure of 7.2-13. Figure created by authors from data in ref 166. The counterion is omitted for clarity.


ethylenediamine resulting in the dianionic complex [Co(η3As3){η4-As4(Mes)2}][K(2,2,2-crypt)]2 (7.2-14) (Scheme 41, Figure 41).168

The molecular structure of 7.2-12 is depicted in Figure 39. The central structural motif of 7.2-12 is a planar four-

Scheme 41. Examples for Reactions of K3As7


membered As2Si2 ring with Si−As distances in-between a single and double bond, again indicating a conjugated 4πelectron system formally required for antiaromaticity. Indeed, the antiaromatic character of this cyclobutadiene derivative was proven by DFT computations. Both aromaticity and antiaromaticity in inorganic chemistry have been recently reviewed.163,164 Another source for As units is MAsH2 (M = Na, K),165 which can be used for the transfer of one arsenic atom, as shown in the reaction of the Th complex [Th{N(CH2CH2NSiiPr3)2(CH2CH2NSiiPr2C(H)MeCH2)}] with 0.5 equiv of KAsH2 (Scheme 40).166 This reaction results in the formation of the complex [{Th(N[CH2CH2NSiiPr3]3)}2(μ-As)][K(15crown-5)2] (7.2-13) with an arsenic atom linearly bridging two Th complex fragments (Figure 40). The Zintl anion [As7]3− was also reported to be useful as an alternative arsenic source.167 In one example, Goicoechea et al. reported the reaction of K3As7 with [Co(Mes)2(PEt2Ph)2] in

Figure 41. Molecular structure of 7.2-14. Figure created by authors from data in ref 168. Counter ions are omitted for clarity.

Goicoechea et al. also reported the reaction of K3As7 with acetylene resulting in the 1,2,3-triarsolide ion (7.2-15), which could be then reacted with [Ru(COD){η3-CH3C(CH2)2}2] to yield the complex [Ru(η5-As3C2H2){CH3C(CH2)2}2][K(2,2,2-crypt)] (7.2-16) (Figure 42).169 Recently, M(AsCO) (M = Na, K) has begun to attract a great deal of interest as a promising transfer reagent of As1 units. Many reactions with both main group compounds and

Scheme 40. Formation of [{Th(N[CH2CH2NSiiPr3]3)}2(μAs)][K(15-crown-5)2] (7.2-13)

Figure 42. Molecular structure of (a) 7.2-15 and (b) 7.2-16. Figure created by authors from data in ref 169. Counter ions are omitted for clarity. V


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transition metal complexes have been reported. An overview of some of the reactions of Na(AsCO) with main group compounds is given in Scheme 42. Goicoechea et al. reported

Scheme 43. Reactions of Na(AsCO) with Transition Metal Complexes

Scheme 42. Examples for the Reaction of Na(AsCO) with Main Group Compounds

(iPrNHC′)] (iPrNHC′ = [{C(Me)N(iPr)}2C]) reacted with Na(AsCO) to form the NHC-stabilized zincoarsaketene complex [L2Zn(iPrNHC′)(AsCO)] (7.2-24). The addition of the donor ligand tBuNHSi (tBuNHSi = [{C(H)N(tBu)}2Si]) to a solution of 7.2-24 resulted in the formation of the compound [iPrNHC′ → tBuNHSi → AsZnL2], in which the iPrNHC′ ligand migrated, accompanied by CO elimination, from zinc to silicon.175

8. CONCLUSIONS The compiled state-of-the-art regarding the use of yellow arsenic for preparative chemistry clearly shows the difficulties in the generation and use of As4 solutions, due to their instability. Problems also exist in the detection of As-rich products by spectroscopic methods. Therefore, their identification is generally only possible through the chemical isolation of the products and structural characterization by X-ray crystallography. Handling problems, however, can clearly be overcome through recent developments in this field such as the use of either materials capable of storing As4 molecules (As4@C) themselves3,155 or transfer reagents. The latter exists for intact As4 moieties1,147 as well as for (As4)2− moieties107 and As1172,176 entities. Increasing use of such alternative reagents will surely lead to a revitalization of As chemistry, and the creation of new As-containing molecules, clusters, and materials, and will stimulate this area in regard to the search for more useful applications. Moreover, As4 activation has, to this point, mainly been done by transition metal compounds. Rather less work has been carried out in f-block chemistry and in the activation of As4 by main group compounds, a fact which ought to drive the community to increase their activities in these fields. Particularly when considering the enormous diversity in P4 activation chemistry,84−86,98−100 there is clearly a need for additional efforts in As4 activation to enable a comparison of the two in order to assess the differences and advantages in either field. With the relatively small number of results available, the reactivities of these compounds show many similarities with only few alterations described to date. This points to the fact that in As4 activations principally only the most stable products are isolatable; however, in some cases, interesting transient species have been formed and characterized. This suggests the importance of investigating this behavior more comprehensively and in much more detail. In these future studies, the use of the alternative arsenic sources will enable the formation and isolation of unprecedented kinetically controlled products generated in smoother reactions, which is why such reagents are extremely important for

the reaction of the 2-arsaethynolate anion (AsCO)− with the bulky stannylene Ter2Sn (Ter = 2,6-bis[2,4,6trimethylphenyl]phenyl) leading to the formation of the cluster compound [Ter3Sn2As2][Na(18-crown-6)] (7.217).170 The Goicoechea group also described the reaction of Na(AsCO) with the chlorostannylene (TerSnCl). This reaction proceeded at ambient temperatures, and after workup, red crystals of the heterocubane [TerSnAs]4 (7.2-18) were isolated in moderate yields.171 Grützmacher and Driess showed that the reaction of the chlorogermylene [L2GeCl] with Na(AsCO) led to the corresponding arsaketenyl germylene [L2GeAsCO] (7.2-19). However, at ambient temperatures, 7.2-19 tends to decompose to the 1.3-digerma2,4-diarsacyclobutadiene [L2GeAs]2 (7.2-20), supposedly formed by a head-to-tail dimerization of two arsagermyne intermediates [L2GeAs]. To trap this intermediate, iPrNHC was added to the reaction mixture of [L2GeCl] and Na(AsCO) at low temperature, which resulted in the expected NHCsupported arsinidene complex [L2GeAs(iPrNHC)] (7.2-21).172 When attempting to synthesize the first stable free arsinidene, Bertrand and Goicoechea reported inter alia the reaction of Na(AsCO) with the phosphenium salt [{Ar**NCH2}2P][BArF4] (Ar** = 2,6-bis[(4-tert-butylphenyl)methyl]-4-methylphenyl), which led to the formation of a bicyclic tetraarsine (7.2-22).173 Reactions of AsCO− with transition metal moieties have also been reported. The reaction of the Ni complex [CpNi(RNHC)] (RNHC = MesNHC, iPrNHC) with Na(AsCO) gave, by NaCp elimination, the complex [{(RNHC)Ni(CO)}2(μ,η2:2-As2)] (7.2-23) constructed around a Ni2As2 butterfly structural motif (Scheme 43).174 The Zn complex [L2Zn(Cl)W


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the completion of comparative studies. The identification of intermediates and kinetically controlled products is also of seminal importance for understanding the mechanism of the As4 activation and the nature of the formed Asn units. The absence of suitable analytical tools to this effect makes the prediction and understanding of the resulting variety of structural types of Asn units, as well as of the conditions in which they are formed, exceedingly difficult. Finally, completing our knowledge of arsenic chemistry will be extremely useful not only for our fundamental understanding of this field of chemistry, but even more so as a contribution to increasing its use in all parts of society.

of unsubstituted main group element ligands with a focus on the heavier group 15 elements and their use in supramolecular chemistry to construct nanosized spherical aggregates and clusters. A further focus of his research is the stabilization and reactivity of main group compounds consisting of combinations of different elements with the target of generating inorganic oligomers and polymers. Finally, the chemistry of highly reactive molecules such as P4, As4, or compounds containing multiple bonds between transition metals and group 15 elements is of further interest.

ACKNOWLEDGMENTS This work was comprehensively supported by the German Research Council (DFG).

AUTHOR INFORMATION Corresponding Author

ABBREVIATIONS 15-crown-5 [−CH2CH2−O−]5 18-crown-6 [−CH2CH2−O−]6 2,2,2-crypt 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane Ar 3,5-Me2C6H3 Ar** 2,6-[{4-tBuPh}2CH]2-4-MePh CAAC cyclic (alkyl)(amino)carbene Cp* C5Me5 Cp′ C5H4Me Cp″ 1,3-tBu2C5H3 Cp‴ 1,2,4-tBu3C5H2 Cp4 1,2,3,4-iPr4C5H CpBn {CH2(C6H5)}5C5 CpBIG {4-nBu(C6H4)}5C5 CpPEt {4-Et(C6H4)}5C5 dipp 2,6-iPr2C6H3 DFT density functional theory dme 1,2-dimethoxyethane dmf N,N-dimethylformamide dmp 2,6-Me2C6H3 dppe 1,2-(PPh2)2(C2H4) HRTEM high-resolution transmission electron microscopy L0 [CH{C(H)N(dipp)}2] L1 [CH{C(Me)N(dmp)}2] L2 [CH{C(Me)N(dipp)}2] LIFDI liquid injection field desorption/ionization Mes 2,4,6-Me3C6H2 NHC N-heterocyclic carbene iPr NHC [{C(H)N(iPr)}2C] iPr NHC′ [{C(Me)N(iPr)}2C] Mes NHC [{C(H)N(Mes)}2C] tBu NHSi [{C(H)N(tBu)}2Si] NMR nuclear magnetic resonance Np CH2tBu pftb [Al{CO(CF3)3}4] Py C5H5N (pyridine) SWCNTs single-wall carbon nanotubes Ter 2,6-(Mes)2C6H3 thf C4H8O (tetrahydrofuran) tol C7H8 (toluene) triphos [1,1,1-{P(Ph)2CH2}3(C2H3)]

*E-mail: [email protected]. ORCID

Manfred Scheer: 0000-0003-2182-5020 Notes

The authors declare no competing financial interest. Biographies Michael Seidl started his undergraduate studies in chemistry at the University Regensburg (Germany) in 2004. He received his Ph.D. in 2014 under the supervision of Prof. M. Scheer at the University Regensburg. Since January 2015, he has been a postdoctoral associate of Prof. M. Scheer at the University Regensburg. His current area of research focuses on the synthesis of transition-metal-stabilized lowvalent antimony compounds (stibinidene complexes) as well as on the study of the reactivity of bridged pentelidene complexes. Gábor Balázs was born in Branistea, Romania. After undergraduate studies at the Babes-Bolyai University (Cluj-Napoca, Romania), he received his Ph.D. in 2002 under the supervision of Prof. H. J. Breunig at the University of Bremen (Germany). From March 2003 to October 2005, he was a postdoctoral associate of Prof. M. Scheer in Karlsruhe and then in Regensburg (Germany). In October 2005, he joined Professors D. M. P. Mingos and J. C. Green at Oxford University for a postdoctoral stay as a scholar of the Alexander von Humboldt Foundation, which was followed by a postdoctoral stay in the group of Prof. M. Driess in Berlin (Germany). In April 2008, he joined Prof. M. Scheer’s group in Regensburg, where he has been working ever since. His research interests include the field of organometallic chemistry of heavier group 15 elements. Manfred Scheer studied chemistry at the University of HalleWittenberg (Germany), where he received his Diploma in 1980 and his Ph.D. in 1983, both in organometallic tin(II) chemistry. After postdoctoral research in the fields of solid-state chemistry at the Institute of Inorganic Chemistry of the Russian Academy of Sciences in Novosibirsk and of main-group-centered multinuclear metalpromoted catalysis at the Max-Planck-Institut für Kohlenforschung in Mülheim/Ruhr with Gerhard Wilke, he finished his habilitation in the area of phosphorus chemistry in Halle/S. in 1992. Supported by a Feodor Lynen Fellowship of the Alexander von Humboldt Foundation, he spent a research stay as guest professor with Malcolm Chisholm at Indiana University, Bloomington, Indiana, in 1992/93. In 1993, he returned to Germany to join the Institute of Inorganic Chemistry of Karlsruhe as a Heisenberg Fellow of the Deutsche Forschungsgemeinschaft where he was appointed Associated Professor of Chemistry (C3) in 1996. In 2004, he accepted the chair of Inorganic Chemistry at the University of Regensburg (Germany). His research interests include the synthesis and reactivity

REFERENCES (1) Schwarzmaier, C.; Sierka, M.; Scheer, M. Intact As4 Tetrahedra Coordinated Side-On to Metal Cations. Angew. Chem., Int. Ed. 2013, 52, 858−861. (2) Schwarzmaier, C.; Schindler, A.; Heindl, C.; Scheuermayer, S.; Peresypkina, E. V.; Virovets, A. V.; Neumeier, M.; Gschwind, R.; X


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Review

(27) Krebs, H.; Schultze-Gebhardt, F. Ü ber die Struktur und die Eigenschaften der Halbmetalle. X. Die Allotropie des Arsens. Z. Anorg. Allg. Chem. 1956, 283, 263−276. (28) Gokcen, N. A. The As (Arsenic) System. Bull. Alloy Phase Diagrams 1989, 10, 11−22. (29) Kalendarev, R. I.; Sazonov, A. I.; Rodionov, A. N.; Chikvaidze, G. V.; Eiduss, J. Properties of Vapor-Deposited Yellow Arsenic Films at Various Condensation Conditions. Mater. Res. Bull. 1984, 19, 11− 15. (30) Eiduss, J.; Kalendarev, R.; Rodionov, A.; Sazonov, A.; Chikvaidze, G. Some Aspects of the Solid State Physics of Yellow Arsenic. Phys. Status Solidi B 1996, 193, 3−23. (31) Erdmann, H.; Unruh, M. V. VI. Ü ber gelbes Arsen. Z. Anorg. Chem. 1902, 32, 437−452. (32) Rosenblatt, G. M.; Lee, P. K. Rate of Vaporization of Arsenic Single Crystals and the Vaporization Coefficient of Arsenic. J. Chem. Phys. 1968, 49, 2995−3006. (33) Krebs, H. Allotropy of Semimetals. Angew. Chem. 1953, 65, 293−299. (34) Maxwell, L. R.; Hendricks, S. B.; Mosley, V. M. Electron Diffraction by Gases. J. Chem. Phys. 1935, 3, 699−709. (35) Morino, Y.; Ukaji, T.; Ito, T. Molecular Structure Determination by Gas Electron Diffraction at High Temperatures. I. Arsenic. Bull. Chem. Soc. Jpn. 1966, 39, 64−71. (36) Spinney, H. A.; Piro, N. A.; Cummins, C. C. Triple-Bond Reactivity of an AsP Complex Intermediate: Synthesis Stemming from Molecular arsenic, As4. J. Am. Chem. Soc. 2009, 131, 16233−16243. (37) Hirsch, A.; Chen, Z.; Jiao, H. Spherical Aromaticity of Inorganic Cage Molecules. Angew. Chem., Int. Ed. 2001, 40, 2834− 2838. (38) Kornath, A. J.; Kaufmann, A.; Cappellacci, S. Raman Spectroscopic Studies on Matrix-Isolated Arsenic and Antimony Molecules As4 and Sb4 in Noble Gas Matrices. J. Mol. Spectrosc. 2009, 255, 189−193. (39) Manzel, K.; Schulze, W.; Wölfel, V.; Minkwitz, R. RamanMatrixspektrum von As4. Z. Naturforsch., B: J. Chem. Sci. 1982, 37b, 1127−1128. (40) Ozin, G. A. Gas-Phase Raman Spectroscopy of Phosphorus, Arsenic, and Saturated Sulphur Vapours. J. Chem. Soc. D 1969, 1325− 1327. (41) Beattie, I. R.; Ozin, G. A.; Perry, R. O. The Gas-Phase Raman Spectra of P4, P2, As4, and As2. The Resonance Fluorescence Spectrum of 80Se2. Resonance Fluorescence−Raman Effects in the Gas-Phase Spectra of Sulphur and I2. The Effect of Pressure on the Depolarization Ratios for I2. J. Chem. Soc. A 1970, 0, 2071−2074. (42) Brumbach, S. B.; Rosenblatt, G. M. InCavity Laser Raman Spectroscopy of Vapors at Elevated Temperatures. As4 and As4O6. J. Chem. Phys. 1972, 56, 3110−3117. (43) Bosworth, Y. M.; Clark, R. J. H.; Rippon, D. M. The Vapor Phase Raman Spectra, Raman Band Contour Analyses, and Coriolis Constants of the Spherical Top Molecules MF6 (M = S, Se, Te, Mo, W, or U), M(CH3)4 (M = C, Si, Ge, Sn, or Pb), P4, As4 and OsO4. J. Mol. Spectrosc. 1973, 46, 240−255. (44) Herms, M.; Wunderwald, U.; Irmer, G. High-Temperature Raman Investigations of Arsenic Vapour. Cryst. Res. Technol. 1993, 28, 965−971. (45) Murray, J. J.; Pupp, C.; Pottie, R. F. Heat of Dissociation of As4(g) and the Heat of Formation of As2(g). J. Chem. Phys. 1973, 58, 2569−2578. (46) Greaves, G. N.; Elliott, S. R.; Davis, E. A. Amorphous Arsenic. Adv. Phys. 1979, 28, 49−141. (47) Krebs, H.; Holz, W.; Worms, K. H. Ü ber die Struktur und die Eigenschaften der Halbmetalle, X. Eine Neue Rhombische Arsenmodifikation und Ihre Mischkristallbildung mit Schwarzem Phosphor. Chem. Ber. 1957, 90, 1031−1037. (48) Pušelj, M.; Ban, Z.; Grdenić, D. On the Allotropy of Arsenic. Z. Anorg. Allg. Chem. 1977, 437, 289−292. (49) Osters, O.; Nilges, T.; Bachhuber, F.; Pielnhofer, F.; Weihrich, R.; Schoeneich, M.; Schmidt, P. Synthesis and Identification of

Scheer, M. Stabilization of Tetrahedral P4 and As4 Molecules as Guests in Polymeric and Spherical Environments. Angew. Chem., Int. Ed. 2013, 52, 10896−10899. (3) Seitz, A. E.; Hippauf, F.; Kremer, W.; Kaskel, S.; Scheer, M. Facile Storage and Release of White Phosphorus and Yellow Arsenic. Nat. Commun. 2018, 9, 361. (4) Abragam, A. The Principles of Nuclear Magnetism; Oxford University Press: Oxford, 1961. (5) Sü ss-Fink, G. Arsenvergiftungen: Ein Element schreibt Kriminalgeschichte. Chem. Unserer Zeit 2012, 46, 100−109. (6) Jolliffe, D. M. A History of the Use of Arsenicals in Man. J. R Soc. Med. 1993, 86, 287−289. (7) Bentley, R.; Chasteen, T. G. Arsenic Curiosa and Humanity. Chem. Educ. 2002, 7, 51−60. (8) Gibaud, S.; Jaouen, G. Arsenic-Based Drugs: From Fowler’s Solution to Modern Anticancer Chemotherapy. In Medicinal Organometallic Chemistry; Jaouen, G., Alberto, R., Eds.; Topics in Organometallic Chemistry 32; Springer-Verlag: Berlin, 2010; pp 1− 20. (9) Lloyd, N. C.; Morgan, H. W.; Nicholson, B. K.; Ronimus, R. S. The Composition of Ehrlich’s Salvarsan: Resolution of a Century-Old Debate. Angew. Chem., Int. Ed. 2005, 44, 941−944. (10) Chen, S.-J.; Zhou, G.-B.; Zhang, X.-W.; Mao, J.-H.; de Thé, H.; Chen, Z. From an Old Remedy to a Magic Bullet: Molecular Mechanisms Underlying the Therapeutic Effects of Arsenic in Fighting Leukemia. Blood 2011, 117, 6425−6437. (11) Hughes, M. F.; Beck, B. D.; Chen, Y.; Lewis, A. S.; Thomas, D. J. Arsenic exposure and Toxicology: A Historical Perspective. Toxicol. Sci. 2011, 123, 305−332. (12) Mandal, B. K.; Suzuki, K. T. Arsenic Round the World. Talanta 2002, 58, 201−235. (13) Meyer, H. Roßtäuscherei. Pferdeheilkunde 2002, 18, 377−389. (14) Grund, S. C.; Hanusch, K.; Wolf, H. U. Arsenic and Arsenic Compounds. In Ullmann’s Encyclopedia of Industrial Chemistry; Ed.; Wiley, 2008. DOI: 10.1002/14356007.a03_113.pub2 (15) In the US, arsenical additives in poultry feed are approved for use in poultry feed: http://www.fda.gov/food/ ingredientspackaginglabeling/foodadditivesingredients/ucm091048. htm. (16) Luong, J. H. T.; Lam, E.; Male, K. B. Recent Advances in Electrochemical Detection of Arsenic in Drinking and Ground Waters. Anal. Methods 2014, 6, 6157−6169. (17) van Halem, D.; Bakker, S. A.; Amy, G. L.; van Dijk, J. C. Arsenic in Drinking Water: A Worldwide Water Quality Concern for Water Supply Companies. Drinking Water Eng. Sci. 2009, 2, 29−34. (18) Wolfe-Simon, F.; Blum, J. S.; Kulp, T. R.; Gordon, G. W.; Hoeft, S. E.; Pett-Ridge, J.; Stolz, J. F.; Webb, S. M.; Weber, P. K.; Davies, P. C. W.; et al. A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus. Science 2011, 332, 1163. (19) Reaves, M. L.; Sinha, S.; Rabinowitz, J. D.; Kruglyak, L.; Redfield, R. J. Absence of Detectable Arsenate in DNA from ArsenateGrown GFAJ-1 Cells. Science 2012, 337, 470. (20) Stöhr, H. Beiträge zur Kenntnis der Allotropie des Arsens. Z. Anorg. Allg. Chem. 1939, 242, 138−144. (21) Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements, 2nd ed.; Elsevier, 1998. (22) Holleman-Wiberg, E. Lehrbuch der Anorganischen Chemie, 102nd ed.; Walter de Gruyter: Berlin, 2007. (23) Bradley, A. J. LX. The Crystal Structure of Metallic Arsenic. London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science 1924, 47, 657−671. (24) Schiferl, D.; Barrett, C. S. The Crystal Structure of Arsenic at 4.2, 78 and 299 K. J. Appl. Crystallogr. 1969, 2, 30−36. (25) Taylor, J. B.; Bennett, S. L.; Heyding, A. D. Physical Properties of α and γ Arsenic. J. Phys. Chem. Solids 1965, 26, 69−74. (26) Rosenblatt, G. M.; Lee, P. K. Rate of Vaporization of Arsenic Single Crystals and the Vaporization Coefficient of Arsenic. J. Chem. Phys. 1968, 49, 2995−3006. Y


Chemical Reviews

Review

Metastable Compounds: Black Arsenic-Science or Fiction? Angew. Chem., Int. Ed. 2012, 51, 2994−2997. (50) Smith, P. M.; Leadbetter, A. J.; Apling, A. J. The Structures of Orthorhombic and Vitreous Arsenic. Philos. Mag. 1975, 31, 57−64. (51) Clark, A. H. Arsenolamprite Confirmed from the Copiapó Area, Northern Chile. Mineralogical Magazine 1970, 37, 2. (52) Chen, Y.; Chen, C.; Kealhofer, R.; Liu, H.; Yuan, Z.; Jiang, L.; Suh, J.; Park, J.; Ko, C.; Choe, H. S.; et al. Black Arsenic: A Layered Semiconductor with Extreme In-Plane Anisotropy. Adv. Mater. 2018, 30, 1800754. (53) Duggin, M. J. A High-Pressure Phase in Arsenic and its Relation to Pressure-Induced Phase Changes in Group 5B Elements. J. Phys. Chem. Solids 1972, 33, 1267−1271. (54) Hart, M.; Chen, J.; Michaelides, A.; Sella, A.; Shaffer, M. S. P.; Salzmann, C. G. One-Dimensional Arsenic Allotropes: Polymerization of Yellow Arsenic Inside Single-Wall Carbon Nanotubes. Angew. Chem., Int. Ed. 2018, 57, 11649−11653. (55) Jayasekera, B.; Somaskandan, K.; Brock, S. L. Liberation of Pnicogen Chains from Cu2P1.8As1.2I2: Synthesis and Characterization of a New Allotrope of P-As. Inorg. Chem. 2004, 43, 6902−6904. (56) Jayasekera, B.; Aitken, J. A.; Heeg, M. J.; Brock, S. L. Toward an Arsenic Analogue of Hittorf’s Phosphorus: Mixed Pnicogen Chains in Cu2P1.8As1.2I2. Inorg. Chem. 2003, 42, 658−660. (57) Cossairt, B. M.; Diawara, M.-C.; Cummins, C. C. Facile Synthesis of AsP3. Science 2009, 323, 602−602. (58) Cossairt, B. M.; Cummins, C. C. Synthetic Route to White Phosphorus (P4) and Arsenic Triphosphide (AsP3). In Inorganic Syntheses; Power, P. P., Ed.; John Wiley & Sons, Inc., 2018; Vol. 37, pp 130−134. (59) Cossairt, B. M.; Cummins, C. C.; Head, A. R.; Lichtenberger, D. L.; Berger, R. J. F.; Hayes, S. A.; Mitzel, N. W.; Wu, G. On the Molecular and Electronic Structures of AsP3 and P4. J. Am. Chem. Soc. 2010, 132, 8459−8465. (60) Ozin, G. A. High-Temperature Gas-Phase Laser Raman Spectroscopy: Evidence for the Existence and Molecular Structure of the Interpnictides As3P, As2P2, and AsP3 in Mixtures of Phosphorus and Arsenic Vapours and SbP3 in Mixtures of Phosphorus and Antimony Vapours. J. Chem. Soc. A 1970, 2307−2310. (61) Cossairt, B. M.; Cummins, C. C. Properties and Reactivity Patterns of AsP3: An Experimental and Computational Study of Group 15 Elemental Molecules. J. Am. Chem. Soc. 2009, 131, 15501− 15511. (62) Carvalho, A.; Wang, M.; Zhu, X.; Rodin, A. S.; Su, H.; Castro Neto, A. H. Phosphorene: from Theory to Applications. Nat. Rev. Mater. 2016, 1, 16061. (63) Liu, B.; Köpf, M.; Abbas, A. N.; Wang, X.; Guo, Q.; Jia, Y.; Xia, F.; Weihrich, R.; Bachhuber, F.; Pielnhofer, F.; Wang, H.; et al. Black Arsenic−Phosphorus: Layered Anisotropic Infrared Semiconductors with Highly Tunable Compositions and Properties. Adv. Mater. 2015, 27, 4423−4429. (64) Nahas, S.; Bajaj, A.; Bhowmick, S. Polymorphs of Two Dimensional Phosphorus and Arsenic: Insight From an Evolutionary Search. Phys. Chem. Chem. Phys. 2017, 19, 11282−11288. (65) Mardanya, S.; Thakur, V. K.; Bhowmick, S.; Agarwal, A. Four Allotropes of Semiconducting Layered Arsenic That Switch Into a Topological Insulator Via an Electric Field: Computational Study. Phys. Rev. B: Condens. Matter Mater. Phys. 2016, 94, No. 035423. (66) Li, P.; Luo, W. A new Structure of Two-Dimensional Allotropes of Group V Elements. Sci. Rep. 2016, 6, 25423. (67) Kamal, C.; Ezawa, M. Arsenene: Two-Dimensional Buckled and Puckered Honeycomb Arsenic Systems. Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 91, No. 085423. (68) Zhu, Z.; Guan, J.; Tománek, D. Unusual Electronic Structure of Few-Layer Gray Arsenic: A Computational Study. cond-mat.mes-hall 2014, 1. (69) Gusmão, R.; Sofer, Z.; Bouša, D.; Pumera, M. Pnictogen (As, Sb, Bi) Nanosheets for Electrochemical Applications Are Produced by Shear Exfoliation Using Kitchen Blenders. Angew. Chem., Int. Ed. 2017, 56, 14417−14422.

(70) Zhao, Y.; Xu, W.; Li, Q.; Xie, Y.; Schaefer, H. F. The Arsenic Clusters Asn (n = 1−5) and their Anions: Structures, Thermochemistry, and Electron Affinities. J. Comput. Chem. 2004, 25, 907−920. (71) Guo, L. Evolution of the Electronic Structure and Properties of Neutral and Charged Arsenic Clusters. J. Mater. Sci. 2007, 42, 9154− 9162. (72) Bai, X.; Zhang, Q.; Gao, A.; Yang, J. Arsenic Clusters Asn (n = 6−16) and their Anions: Structures, Thermochemistry, and Electron Affinities. Comput. Theor. Chem. 2013, 1009, 94−102. (73) Kubácě k, P.; Prokeš, L.; Pamreddy, A.; Peña-Méndez, E. M.; Conde, J. E.; Alberti, M.; Havel, J. Laser Ablation Synthesis Of Arsenic−Phosphide AsmPn Clusters from As−P Mixtures. Laser Desorption Ionisation with Quadrupole Ion Trap Time-of-Flight Mass Spectrometry: The Mass Spectrometer as a Synthesizer. Rapid Commun. Mass Spectrom. 2018, 32, 789−800. (74) Karttunen, A. J.; Linnolahti, M.; Pakkanen, T. A. Icosahedral and Ring-Shaped Allotropes of Arsenic. ChemPhysChem 2007, 8, 2373−2378. (75) Karttunen, A. J.; Tanskanen, J. T.; Linnolahti, M.; Pakkanen, T. A. Structural and Electronic Trends among Group 15 Elemental Nanotubes. J. Phys. Chem. C 2009, 113, 12220−12224. (76) Zamfira, S.; Popescu, M.; Sava, F. Fullerene-Like and Nanotubes Based on Arsenic Networks. A Modelling Study. Chalcogenide Lett. 2005, 2, 55−61. (77) Bettendorff, A. Allotropische Zustände des Arsens. Justus Liebigs Ann. Chem. 1867, 144, 110−114. (78) Scherer, O. J.; Sitzmann, H.; Wolmershäuser, G. (E2)2einheiten (E = P, As) als clusterbausteine. J. Organomet. Chem. 1986, 309, 77−86. (79) Power, P. P. Main-Group Elements as Transition Metals. Nature 2010, 463, 171−177. (80) Melaimi, M.; Jazzar, R.; Soleilhavoup, M.; Bertrand, G. Cyclic (Alkyl)(amino)carbenes (CAACs): Recent Developments. Angew. Chem., Int. Ed. 2017, 56, 10046−10068. (81) Wang, Y.; Robinson, G. H. N-Heterocyclic Carbene-MainGroup Chemistry: A Rapidly Evolving Field. Inorg. Chem. 2014, 53, 11815−11832. (82) Stephan, D. W. The Broadening Reach of Frustrated Lewis Pair Chemistry. Science 2016, 354, aaf7229. (83) Martin, D.; Soleilhavoup, M.; Bertrand, G. Stable Singlet Carbenes as Mimics for Transition Metal Centers. Chem. Sci. 2011, 2, 389−399. (84) Scheer, M.; Balázs, G.; Seitz, A. P4 Activation by Main Group Elements and Compounds. Chem. Rev. 2010, 110, 4236−4256. (85) Giffin, N. A.; Masuda, J. D. Reactivity of White Phosphorous with Compounds of the p-Block. Coord. Chem. Rev. 2011, 255, 1342− 1359. (86) Khan, S.; Sen, S. S.; Roesky, H. W. Activation of Phosphorus by Group 14 Elements in Low Oxidation States. Chem. Commun. 2012, 48, 2169−2179. (87) Peng, Y.; Fan, H.; Zhu, H.; Roesky, H. W.; Magull, J.; Hughes, C. E. [{HC(CMeNAr)2}2Al2P4] (Ar = 2,6-iPr2C6H3): A Reduction to a Formal {P4}4‑ Charged Species. Angew. Chem., Int. Ed. 2004, 43, 3443−3445. (88) Xiong, Y.; Yao, S.; Brym, M.; Driess, M. Consecutive Insertion of a Silylene into the P4 Tetrahedron: Facile Access to Strained SiP4 and Si2P4 Cage Compounds. Angew. Chem., Int. Ed. 2007, 46, 4511− 4513. (89) Masuda, J. D.; Schoeller, W. W.; Donnadieu, B.; Bertrand, G. NHC-Mediated Aggregation of P4: Isolation of a P12 Cluster. J. Am. Chem. Soc. 2007, 129, 14180−14181. (90) Masuda, J. D.; Schoeller, W. W.; Donnadieu, B.; Bertrand, G. Carbene Activation of P4 and Subsequent Derivatization. Angew. Chem., Int. Ed. 2007, 46, 7052−7055. (91) Back, O.; Kuchenbeiser, G.; Donnadieu, B.; Bertrand, G. Nonmetal-Mediated Fragmentation of P4: Isolation of P1 and P2 Bis(carbene) Adducts. Angew. Chem., Int. Ed. 2009, 48, 5530−5533. (92) Weigand, J. J.; Holthausen, M.; Fröhlich, R. Formation of [Ph2P5]+, [Ph4P6]2+, and [Ph6P7]3+ Cationic Clusters by Consecutive Z


Chemical Reviews

Review

Insertions of [Ph2P]+ into PP Bonds of the P4 Tetrahedron. Angew. Chem., Int. Ed. 2009, 48, 295−298. (93) Tan, R. P.; Comerlato, N. M.; Powell, D. R.; West, R. The Reaction of Tetramesityldisilene with As4: Synthesis and Structure of a Novel Arsenic-Silicon Tricyclic Ring System. Angew. Chem., Int. Ed. Engl. 1992, 31, 1217−1218. (94) Heinl, S.; Balazs, G.; Stauber, A.; Scheer, M. CpPEt2As4 -An Organic-Substituted As4 Butterfly Compound. Angew. Chem., Int. Ed. 2016, 55, 15524−15527. (95) Heinl, S.; Reisinger, S.; Schwarzmaier, C.; Bodensteiner, M.; Scheer, M. Selective Functionalization of P4 by Metal-Mediated C−P Bond Formation. Angew. Chem., Int. Ed. 2014, 53, 7639−7642. (96) Khan, S.; Michel, R.; Sen, S. S.; Roesky, H. W.; Stalke, D. A P4 Chain and Cage from Silylene-Activated White Phosphorus. Angew. Chem., Int. Ed. 2011, 50, 11786−11789. (97) Seitz, A. E.; Eckhardt, M.; Sen, S. S.; Erlebach, A.; Peresypkina, E. V.; Roesky, H. W.; Sierka, M.; Scheer, M. Different Reactivity of As4 Towards Disilenes and Silylenes. Angew. Chem., Int. Ed. 2017, 56, 6655−6659. (98) Caporali, M.; Gonsalvi, L.; Rossin, A.; Peruzzini, M. P4 Activation by Late-Transition Metal Complexes. Chem. Rev. 2010, 110, 4178−4235. (99) Cossairt, B. M.; Piro, N. A.; Cummins, C. C. Early-TransitionMetal-Mediated Activation and Transformation of White Phosphorus. Chem. Rev. 2010, 110, 4164−4177. (100) Serrano-Ruiz, M.; Romerosa, A.; Lorenzo-Luis, P. Elemental Phosphorus and Electromagnetic Radiation. Eur. J. Inorg. Chem. 2014, 2014, 1587−1598. (101) Dielmann, F.; Timoshkin, A.; Piesch, M.; Balázs, G.; Scheer, M. The Cobalt cyclo-P4 Sandwich Complex and its Role in the Formation of Polyphosphorus Compounds. Angew. Chem., Int. Ed. 2017, 56, 1671−1675. (102) Spitzer, F.; Graßl, C.; Balázs, G.; Mädl, E.; Keilwerth, M.; Zolnhofer, E. M.; Meyer, K.; Scheer, M. Nacnac-Cobalt-Mediated P4 Transformations. Chem. - Eur. J. 2017, 23, 2716−2721. (103) Mokhtarzadeh, C. C.; Rheingold, A. L.; Figueroa, J. S. Dinitrogen Binding, P4-Activation and aza-Büchner Ring Expansions Mediated by an Isocyano Analogue of the CpCo(CO) Fragment. Dalton Trans. 2016, 45, 14561−14569. (104) Huang, W.; Diaconescu, P. L. P4 Activation by Lanthanum and Lutetium Naphthalene Complexes Supported by a Ferrocene Diamide Ligand. Eur. J. Inorg. Chem. 2013, 2013, 4090−4096. (105) Zarzycki, B.; Zell, T.; Schmidt, D.; Radius, U. P4 Activation at Ni0: Selective Formation of an NHC-Stabilized, Dinuclear Nickel Complex [Ni2(iPr2Im)4(μ,η2:2-P2)]. Eur. J. Inorg. Chem. 2013, 2013, 2051−2058. (106) Huang, W.; Diaconescu, P. L. P4 Activation by Group 3 Metal Arene Complexes. Chem. Commun. 2012, 48, 2216−2218. (107) Schmidt, M.; Seitz, A. E.; Eckhardt, M.; Balazs, G.; Peresypkina, E. V.; Virovets, A. V.; Riedlberger, F.; Bodensteiner, M.; Zolnhofer, E. M.; Meyer, K.; Scheer, M. Transfer Reagent for Bonding Isomers of Iron Complexes. J. Am. Chem. Soc. 2017, 139, 13981−13984. (108) Scherer, O. J.; Vondung, J.; Wolmershäuser, G. Tetraarsacyclobutadiene as a Complex Ligand. J. Organomet. Chem. 1989, 376, C35−C38. (109) Scherer, O. J.; Winter, R.; Heckmann, G.; Wolmershäuser, G. cyclo-As8, as Complex Ligand. Angew. Chem., Int. Ed. Engl. 1991, 30, 850−852. (110) Mast, K.; Meiers, J.; Scherer, O. J.; Wolmershäuser, G. Mehrkernige Eisen/Tantal- und Tantal-Komplexe mit Asn -Liganden. Z. Anorg. Allg. Chem. 1999, 625, 70−74. (111) Scherer, O. J.; Sitzmann, H.; Wolmershäuser, G. Hexaarsabenzene as a Complex Ligand. Angew. Chem., Int. Ed. Engl. 1989, 28, 212−213. (112) Jutzi, P.; Kroos, R. Pentamethylcyclopentadienyl-substituierte Cyclophosphane als Quelle für Px-Einheiten in Ü bergangsmetallkomplexen. Chem. Ber. 1988, 121, 1399−1401.

(113) Fleischmann, M.; Dielmann, F.; Balázs, G.; Scheer, M. Oxidation Chemistry of Inorganic Benzene Complexes. Chem. - Eur. J. 2016, 22, 15248−15251. (114) Scherer, O. J.; Wiedemann, W.; Wolmershäuser, G. A TripleDecker Sandwich Complex with an Unstrained Cyclic Pentaarsane Middle Layer. J. Organomet. Chem. 1989, 361, C11−C14. (115) Scherer, O. J.; Wiedemann, W.; Wolmershäuser, G. Chromium Complexes with cyclo-Asx Ligands. Chem. Ber. 1990, 123, 3−6. (116) Curley, J. J.; Piro, N. A.; Cummins, C. C. A Terminal Molybdenum Arsenide Complex Synthesized from Yellow Arsenic. Inorg. Chem. 2009, 48, 9599−9601. (117) Scheer, M.; Müller, J.; Häser, M. Complexes Containing Phosphorus and Arsenic as Terminal Ligands. Angew. Chem., Int. Ed. Engl. 1996, 35, 2492−2496. (118) Noor, A.; Glatz, G.; Müller, R.; Kaupp, M.; Demeshko, S.; Kempe, R. Carboalumination of a Chromium−Chromium Quintuple Bond. Nat. Chem. 2009, 1, 322−325. (119) Schwarzmaier, C.; Noor, A.; Glatz, G.; Zabel, M.; Timoshkin, A. Y.; Cossairt, B. M.; Cummins, C. C.; Kempe, R.; Scheer, M. Formation of cyclo-E42‑ Units (E4 = P4, As4, AsP3) by a Complex with a Cr-Cr Quintuple Bond. Angew. Chem., Int. Ed. 2011, 50, 7283− 7286. (120) Schwarzmaier, C.; Timoshkin, A. Y.; Balazs, G.; Scheer, M. Selective Formation and Unusual Reactivity of Tetraarsabicyclo[1.1.0]butane Complexes. Angew. Chem., Int. Ed. 2014, 53, 9077−9081. (121) Scherer, O. J.; Blath, C.; Wolmershäuser, G. Ferrocene mit einem Pentaarsacyclopentadienyl-Liganden. J. Organomet. Chem. 1990, 387, C21−C24. (122) Rink, B.; Scherer, O. J.; Heckmann, G.; Wolmershäuser, G. Neutrale 30-Valenzelektronen-Tripeldeckerkomplexe mit cyclo-E5Mitteldeck (E = P, As). Chem. Ber. 1992, 125, 1011−1016. (123) Scherer, O. J.; Blath, C.; Heckmann, G.; Wolmershäuser, G. [{(C5Me4R)Ru}3Ru(η3-As3)(μ3,η3-As3)(μ3-As)3], an Arsenic Rich Tetranuclear Cluster. J. Organomet. Chem. 1991, 409, C15−C18. (124) Scherer, O. J.; Kemeny, G.; Wolmershäuser, G. [Cp4Fe4(E2)2] Clusters with Triangulated Dodecahedral Fe4E4 Skeletons (E = P, As). Chem. Ber. 1995, 128, 1145−1148. (125) Heinl, S.; Scheer, M. Activation of Group 15 Based Cage Compounds by [CpBIGFe(CO)2] Radicals. Chem. Sci. 2014, 5, 3221− 3225. (126) Heinl, S.; Timoshkin, A. Y.; Müller, J.; Scheer, M. Unexpected Differences in the Reactivity Between the Phosphorus and Arsenic Derivatives (CpBIGFe)2(μ,η4:4-E4) (E = P and As). Chem. Commun. 2018, 54, 2244−2247. (127) Schwarzmaier, C.; Bodensteiner, M.; Timoshkin, A. Y.; Scheer, M. An Approach to Mixed PnAsm Ligand Complexes. Angew. Chem., Int. Ed. 2014, 53, 290−293. (128) Friedrich, G.; Scherer, O. J.; Wolmershuser, G. HeterometallKomplexe mit E6-Liganden (E = P, As). Z. Anorg. Allg. Chem. 1996, 622, 1478−1486. (129) Arleth, N.; Gamer, M. T.; Köppe, R.; Konchenko, S. N.; Fleischmann, M.; Scheer, M.; Roesky, P. W. Molecular Polyarsenides of the Rare-Earth Elements. Angew. Chem., Int. Ed. 2016, 55, 1557− 1560. (130) Schmidt, M.; Konieczny, D.; Peresypkina, E. V.; Virovets, A. V.; Balázs, G.; Bodensteiner, M.; Riedlberger, F.; Krauss, H.; Scheer, M. Arsenic-Rich Polyarsenides Stabilized by Cp*Fe Fragments. Angew. Chem., Int. Ed. 2017, 56, 7307−7311. (131) Di Vaira, M.; Midollini, S.; Sacconi, L. cyclo-Triphosphorus and cyclo-Triarsenic as Ligands in ″Double Sandwich″ Complexes of Cobalt and Nickel. J. Am. Chem. Soc. 1979, 101, 1757−1763. (132) Di Vaira, M.; Midollini, S.; Sacconi, L.; Zanobini, F. cycloTriarsenic as μ,η-Ligand in Transition-Metal Complexes. Angew. Chem., Int. Ed. Engl. 1978, 17, 676−677. (133) Scherer, O. J.; Pfeiffer, K.; Wolmershaeuser, G. Cobalt Complexes with Tetraarsenic Ligands. Chem. Ber. 1992, 125, 2367− 2372. AA


Chemical Reviews

Review

(155) Scheer, M.; Seitz, A.; Hippauf, F.; Kaskel, S. Storage Material Containing White Phosphorus or Yellow Arsenic. Patent EP 17 163 405.8, 2017. (156) DiMaio, A. J.; Rheingold, A. L. Structural Chemistry of Transition Metal Complexes Containing Arsenic-Arsenic Bonds. Chem. Rev. 1990, 90, 169−190. (157) Foust, A. S.; Foster, M. S.; Dahl, L. RF. Organometallic Pnicogen Complexes. III. Preparation and Structural Characterization of the Triarsenic-Cobalt Atom Cluster System As3Co(CO)3. The First Known X3-Transition Metal Analog of Group V a Tetrahedral X4 Molecules. J. Am. Chem. Soc. 1969, 91, 5631−5633. (158) Sullivan, P. L.; Rheingold, A. L. Group 6B Complexes Containing Arsenic-Arsenic Double Bonds. Synthesis and Crystallographic Characterization of [η5-C5H5M(CO)2]2(μ,η2-As2) (M = Mo or W). Organometallics 1982, 1, 1547−1549. (159) Rheingold, A. L.; Foley, M. J.; Sullivan, P. J. ″Triple-decker sandwich″ with a planar As5 ring. Synthesis and crystal structure of CpMo[μ,η4-As5]MoCp. J. Am. Chem. Soc. 1982, 104, 4727−4729. (160) DiMaio, A.-J.; Rheingold, A. L. A Complex containing Two Side-on (μ2,η2-As2) Ligands. The Synthesis and Structural Characterization of [(η5-MeC5H4)Mo(CO)]2(μ2,η2-As2)2. J. Chem. Soc., Chem. Commun. 1987, 404−405. (161) Schwarzmaier, C.; Timoshkin, A. Y.; Scheer, M. An End-onCoordinated As4 Tetrahedron. Angew. Chem., Int. Ed. 2013, 52, 7600−7603. (162) Seitz, A. E.; Eckhardt, M.; Erlebach, A.; Peresypkina, E. V.; Sierka, M.; Scheer, M. Pnictogen-Silicon Analogues of Benzene. J. Am. Chem. Soc. 2016, 138, 10433−10436. (163) Liu, C.; Popov, I. A.; Chen, Z.; Boldyrev, A. I.; Sun, Z.-M. Aromaticity and Antiaromaticity in Zintl Clusters. Chem. - Eur. J. 2018, 24, 14583−14597. (164) Galeev, T. R.; Boldyrev, A. I. Aromaticity and Antiaromaticity in Inorganic Chemistry. In Comprehensive Inorganic Chemistry II; Reedijk, J., Poeppelmeier, K., Eds.; Elsevier: Amsterdam, 2013. (165) Gardner, B. M.; Balázs, G.; Scheer, M.; Tuna, F.; McInnes, E. J. L.; McMaster, J.; Lewis, W.; Blake, A. J.; Liddle, S. T. Triamidoamine Uranium(IV)-Arsenic Complexes Containing One-, Two- and Threefold U-As Bonding Interactions. Nat. Chem. 2015, 7, 582−590. (166) Wildman, E. P.; Balázs, G.; Wooles, A. J.; Scheer, M.; Liddle, S. T. Triamidoamine Thorium-Arsenic Complexes with Parent Arsenide, Arsinidiide and Arsenido Structural Motifs. Nat. Commun. 2017, 8, 14769. (167) Turbervill, R. S. P.; Goicoechea, J. M. From Clusters to Unorthodox Pnictogen Sources: Solution-Phase Reactivity of [E7]3‑ (E = P-Sb) Anions. Chem. Rev. 2014, 114, 10807−10828. (168) Knapp, C. M.; Westcott, B. H.; Raybould, M. A. C.; McGrady, J. E.; Goicoechea, J. M. Transition-Metal-Mediated Activation of the Heptaarsenide Trianion: Isolation of a Diaryltetraarsenabutadienediide. Chem. Commun. 2012, 48, 12183−12185. (169) Turbervill, R. S. P.; Goicoechea, J. M. Synthesis of 1,2,3Tripnictolide Anions by Reaction of Group 15 Zintl Ions with Acetylene. Isolation of [E3C2H2]− (E = P, As) and Preliminary Reactivity Studies. Chem. Commun. 2012, 48, 6100−6102. (170) Hinz, A.; Goicoechea, J. M. A Monoanionic Arsenide Source: Decarbonylation of the 2-Arsaethynolate Anion upon Reaction with Bulky Stannylenes. Angew. Chem., Int. Ed. 2016, 55, 15515−15519. (171) Hinz, A.; Goicoechea, J. M. The Heterocubane [TerSnAs]4. Dalton Trans. 2018, 47, 8879−8883. (172) Yao, S.; Grossheim, Y.; Kostenko, A.; Ballestero-Martínez, E.; Schutte, S.; Bispinghoff, M.; Grützmacher, H.; Driess, M. Facile Access to NaOC≡As and Its Use as an Arsenic Source to Form Germylidenylarsinidene Complexes. Angew. Chem., Int. Ed. 2017, 56, 7465−7469. (173) Hinz, A.; Hansmann, M. M.; Bertrand, G.; Goicoechea, J. M. Intercepting a Transient Phosphino-Arsinidene. Chem. - Eur. J. 2018, 24, 9514−9519.

(134) Scherer, O. J.; Pfeiffer, K.; Heckmann, G.; Wolmershaeuser, G. [(C5Me4R)Co(As2)] Molecular Building Blocks. J. Organomet. Chem. 1992, 425, 141−149. (135) Scherer, O. J. Complexes with Substituent-free Acyclic and Cyclic Phosphorus, Arsenic, Antimony, and Bismuth Ligands. Angew. Chem., Int. Ed. Engl. 1990, 29, 1104−1122. (136) Scherer, O. J.; Höbel, B.; Wolmershäuser, G. Zweifach kantengeöffnetes P10-Dihydrofulvalen als 16-Elektronendonorligand. Angew. Chem. 1992, 104, 1042−1043. (137) Grassl, C.; Bodensteiner, M.; Zabel, M.; Scheer, M. Synthesis of Arsenic-Rich Asn Ligand Complexes from Yellow Arsenic. Chem. Sci. 2015, 6, 1379−1382. (138) Schoo, C.; Köppe, R.; Piesch, M.; Gamer, M. T.; Konchenko, S. N.; Scheer, M.; Roesky, P. W. Open Chain Polyarsenides of the Lanthanides. Chem. - Eur. J. 2018, 24, 7890−7895. (139) Yao, S.; Szilvási, T.; Lindenmaier, N.; Xiong, Y.; Inoue, S.; Adelhardt, M.; Sutter, J.; Meyer, K.; Driess, M. Reductive Cleavage of P4 by Iron(I) Centres: Synthesis and Structural Characterisation of Fe2(P2)2 Complexes with two Bridging P22‑ Ligands. Chem. Commun. 2015, 51, 6153−6156. (140) Spitzer, F.; Graßl, C.; Balázs, G.; Zolnhofer, E. M.; Meyer, K.; Scheer, M. Influence of the nacnac Ligand in Iron(I)-Mediated P4 Transformations. Angew. Chem., Int. Ed. 2016, 55, 4340−4344. (141) Spitzer, F.; Balázs, G.; Grassl, C.; Keilwerth, M.; Meyer, K.; Scheer, M. The Influence of β-diiminato Ligands on the As4 Activation by Co Complexes. Angew. Chem., Int. Ed. 2018, 57, 8760−8764. (142) Spitzer, F.; Graßl, C.; Balázs, G.; Mädl, E.; Keilwerth, M.; Zolnhofer, E. M.; Meyer, K.; Scheer, M. Nacnac-Cobalt-Mediated P4 Transformations. Chem. - Eur. J. 2017, 23, 2716−2721. (143) Scherer, O. J.; Braun, J.; Wolmershäuser, G. Nickelapnicogencubane. Chem. Ber. 1990, 123, 471−475. (144) Scherer, O. J.; Braun, J.; Walther, P.; Wolmershäuser, G. Dinuclear Nickel Complexes with Ni2E4 Framework (E = P, As). Chem. Ber. 1992, 125, 2661−2665. (145) Krossing, I. Ag(P4)2+: The First Homoleptic Metal− Phosphorus Cation. J. Am. Chem. Soc. 2001, 123, 4603−4604. (146) Krossing, I.; van Wüllen, L. Superweak Complexes of Tetrahedral P4 Molecules with the Silver Cation of Weakly Coordinating Anions. Chem. - Eur. J. 2002, 8, 700−711. (147) Spitzer, F.; Sierka, M.; Latronico, M.; Mastrorilli, P.; Virovets, A. V.; Scheer, M. Fixation and Release of Intact E4 Tetrahedra (E = P, As). Angew. Chem., Int. Ed. 2015, 54, 4392−4396. (148) Scherer, O. J.; Schulze, J.; Wolmershäuser, G. Bicyclisches As6 als Komplexligand. J. Organomet. Chem. 1994, 484, c5−c7. (149) Schoo, C.; Bestgen, S.; Koeppe, R.; Konchenko, S. N.; Roesky, P. W. Reactivity of Bulky Ln(II) Amidinates Towards P4, As4, and As4S4. Chem. Commun. 2018, 54, 4770−4773. (150) Kraus, F.; Hanauer, T.; Korber, N. Nature of the Chemical Bond in Polypnictides: The Lone Pair Aromatic Anions P42‑ and As42‑. Inorg. Chem. 2006, 45, 1117−1123. (151) Ziegler, M. L.; Blechschmitt, K.; Nuber, B.; Zahn, T. Darstellung und Charakterisierung von Tetrahedranen des Typs Cp3M3As(CO)6 und Cp2M2As2(CO)4 (Cp = C5H5, M = Mo, W) sowie von Derivaten dieser Tetrahedrane. Chem. Ber. 1988, 121, 159− 171. (152) Goh, L. Y.; Wong, R. C. S.; Yip, W. H.; Mak, T. C. W. Synthesis and Thermolysis of Di- and Triarsenic Complexes of Chromium. Crystal Structure of [CpCr(CO)2]2As2. Organometallics 1991, 10, 875−879. (153) Yang, D.; Zhao, J.; Yu, L.; Lin, X.; Zhang, W.; Ma, H.; Gogoll, A.; Zhang, Z.; Wang, Y.; Yang, X.-J.; et al. Air- and Light-Stable P4 and As4 within an Anion-Coordination-Based Tetrahedral Cage. J. Am. Chem. Soc. 2017, 139, 5946−5951. (154) Wu, B.; Cui, F.; Lei, Y.; Li, S.; de Sousa Amadeu, N.; Janiak, C.; Lin, Y.-J.; Weng, L.-H.; Wang, Y.-Y.; Yang, X.-J. Tetrahedral Anion Cage: Self-Assembly of a (PO4)4L4 Complex from a Tris(bisurea) Ligand. Angew. Chem., Int. Ed. 2013, 52, 5096−5100. AB


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(174) Hierlmeier, G.; Hinz, A.; Wolf, R.; Goicoechea, J. M. Synthesis and Reactivity of Nickel-Stabilised μ2:η2,η2-P2, As2 and PAs Units. Angew. Chem., Int. Ed. 2018, 57, 431−436. (175) Ballestero-Martínez, E.; Hadlington, T. J.; Szilvási, T.; Yao, S.; Driess, M. From Zinco(II) Arsaketenes to Silylene-Stabilised Zinco Arsinidene Complexes. Chem. Commun. 2018, 54, 6124−6127. (176) Hinz, A.; Goicoechea, J. M. The 2-Arsaethynolate Anion: Synthesis and Reactivity Towards Heteroallenes. Angew. Chem., Int. Ed. 2016, 55, 8536−8541.

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