New Outcomes of Beryllium Chemistry: Lewis Base Adducts for Salt

Article Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

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New Outcomes of Beryllium Chemistry: Lewis Base Adducts for Salt Elimination Reactions Julia K. Schuster,†,‡,§ Dipak Kumar Roy,†,‡,§ Carsten Lenczyk,†,‡ Jan Mies,†,‡ and Holger Braunschweig*,†,‡ †

Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany Institute for Sustainable Chemistry and Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

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S Supporting Information *

ABSTRACT: A range of mono- and bis-adducts of beryllium dichloride with cyclic (alkyl)(amino)carbenes (CAAC), cyclic diamidocarbene (DAC), and carbodiphosphorane (CDP) are prepared, and their reactions with nucleophiles are studied. Salt elimination with Yamashita and Nozaki’s lithium diazaborolide reagent led to the isolation of an unsymmetrical beryllium diazaborolyl complex and a base-stabilized diazaborolyl beryllium chloride. From structural and spectroscopic analyses, the Be−B bonding in these compounds was determined to be polar covalent in character. In addition, the nucleophilic addition of magnesium anthracenediyl to one of the adducts resulted in the isolation of an interesting tetracyclic berylliumbridged molecule.

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donor and strong π-acceptor properties, making them ideal ligands for stabilizing very electron-rich p-block compounds by back-donation into the empty π-type orbital of the CAAC ligand.12b Bertrand and co-workers took advantage of these electronic properties to synthesize the first three-coordinate, bis(CAAC)-stabilized boron(I) derivative,12c as well as a linear two-coordinate aminoborylene,12 whereas our group used CAACs to isolate the first structurally authenticated boryl radicals13a and a highly reactive diboracumulene.13b The progress of novel and transition-metal-inspired reactivity for the main-group elements thus represents an exciting and encouraging possibility for the discovery of synthetic applications of earth-abundant elements. In this context, beryllium chemistry, which is underdeveloped due to the presumed high toxicity of compounds containing this element,14 has received growing interest over the past decade.14b−e This led to the isolation and characterization of diketiminate (nacnac)15a and trispyrazolylborate (Tp)15b complexes of beryllium, the former being found to undergo ether cleavage reactions. The monomeric Be(BH4)2 moiety could be stabilized and structurally characterized with the help of NHCs.16 It was also demonstrated that Be readily inserts into the C−N bond of NHCs when the steric shielding and the electron density at the metal are reduced,17 and that it is able to form dative Pt→Be bonds.18 In a recent article, Schulz and co-workers reported the synthesis of the first homoleptic beryllium azides.19

INTRODUCTION Since the isolation of a stable N-heterocyclic carbene (NHC) by Arduengo1 in the early 1990s, interest in NHCs has been driven by their ease of synthesis and their ability to act as robust two-electron σ-donor ligands.2 This latter attribute has proven to be especially advantageous in many organocatalytic reactions, including the benzoin condensation, Stetter, Diels− Alder, and acyl-transfer reactions.3,4 Although the field of NHC-transition metal complexes is developing rapidly, analogous main-group metal complexes remain a rarity due to the difficulty of stabilizing such highly reactive low-valent species. However, over the past decade, stable, low-valent pblock compounds have evolved from laboratory curiosities to highly coveted synthetic targets and exhibit a rich chemistry reminiscent of that traditionally considered to be the sole domain of transition-metal compounds, as well as some unique bond-activating reactivity.5,6 The use of strongly σ-donating and sterically protecting NHCs has even allowed the isolation of a number of neutral dinuclear Group 13, 14, and 15 complexes in their zero oxidation state.7−9 For its part, our research group has employed IDip (1,3Dip2-imidazol-2-ylidene; Dip = 2,6-iPr2C6H3) and the less sterically demanding IDep (1,3-Dep2-imidazol-2-ylidene; Dep = 2,6-Et2C6H3), as well as the saturated counterparts, SIDipp and SIDep (1,3-Ar2-imidazolin-2-ylidene, Ar = Dip, Dep), to stabilize compounds with BB triple bonds.7b,10 The less sterically demanding IMe (1,3-dimethylimidazol-2-ylidene) ligand has also provided access to a range of electron-rich 1,2-diaryldiborenes from the 2-fold reduction of IMesupported aryldihaloboranes.11 Outside of traditional NHCs, cyclic (alkyl)(amino)carbenes (CAACs)12a offer enhanced σ© XXXX American Chemical Society

Received: November 22, 2018

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DOI: 10.1021/acs.inorgchem.8b03263 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

tetracoordinate beryllium center. The 13C NMR spectra of these species exhibited low-field signals for the carbene carbon atoms (1: δ 213; 2: δ 225; 3: δ 192; 4: δ 198). The solid-state structures obtained of complexes 1−4 further confirm the connectivity of the compounds (Figure 1). As

The limited knowledge regarding the chemistry of beryllium and our general interest in main-group metal chemistry drew our attention to beryllium carbene adducts, leading to the synthesis of doubly CAAC-stabilized Be(0) complexes,20 the first neutral compound with a zerovalent s-block element. Further, using the borolyllithium compound of Yamashita and Nozaki, our group reported a bis(diazaborolyl) beryllium complex21 containing the first example of a noncluster bond between boron and beryllium. In efforts to more fully explore beryllium-carbene chemistry, we targeted a range of single and double carbene adducts of beryllium dichloride, seeking to determine to what extent the nature of the donor affects these adducts. The results of these studies are presented herein, including their reactions with different nucleophiles, leading to a number of beryllium compounds with unprecedented structures, such as an unsymmetrical beryllium diazaborolyl and a base-stabilized beryllium-bridged anthracene.

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RESULTS AND DISCUSSION Single and Double Lewis Base Adducts of BeCl2. Given the limited π-accepting ability of NHCs and the successful use of CAACs for the stabilization of a variety of both low-valent transition-metal and p-block elements, we envisaged that BeCl2 adducts of π-accepting carbenes can be a useful starting point for a range of beryllium compounds. Thereby, BeCl2 was treated in separate experiments with 1 equiv of each of the two cyclic (alkyl)(amino)carbenes ( Et CAAC and Menth CAAC; Scheme 1) and a cyclic Scheme 1. Synthesis of Single and Double Carbene Adducts of BeCl2

Figure 1. Solid-state structures of carbene adducts 1−4. Ellipsoids are shown at the 50% probability level. Some ellipsoids and all hydrogen atoms have been removed for clarity. Selected bond lengths [Å] and angles [deg] for 1: C1−Be1 1.796(3), Cl1−Be1 1.922(2), Cl2−Be1 1.889(3), C1−N1 1.300(2); N1−C1−C2 109.47(15), C1−Be1−Cl1 122.72(14), C1−Be1−Cl2 118.29(14), Cl1−Be1−Cl2 118.72(13). For 2: C1−Be1 1.802(3), Cl1−Be1 1.908(3), Cl2−Be1 1.901(3), C1−N1 1.303(3); N1−C1−C2 109.32(18), C1−Be1−Cl1 126.86(18), C1−Be1−Cl2 114.82(18), Cl1−Be1−Cl2 118.19(15). For 3: C1−Be1 1.806(4), Cl1−Be1 1.8989(17), N1−C1 1.3451(19), O1−C2 1.200(2); N1−C1−N2 118.9(2), C1−Be1−Cl1 117.71(9), Cl2−Be1−Cl1 124.58(17). For 4: C1−Be1 1.839(2), Cl1−Be1 2.0390(18), Cl2−Be1 2.052(2), C1−N1 1.360(2) C1−N2 1.361(2); N1−C1−N2 103.25(11), C1−Be1−C2 106.39(10), C1−Be1−Cl1 109.99(9), C1−Be1−Cl2 113.18(9), C2−Be1−Cl1 114.29(9), C2− Be1−Cl2 106.62(9), Cl1−Be1−Cl2 110.46(8).

expected, the Dip and Mes groups are perpendicular to the respective carbene units and the Ccarbene−Be lengths are in the single bond range for the CAAC (1: 1.796 (3) Å; 2: 1.802 (3) Å) and DAC adducts (3: 1.805(4) Å).20 Compound 3 is the first example of a DAC adduct of beryllium. The carbene ring in 3 is somewhat more planar compared to the common conformation of DAC ligands in DAC-borane adducts22 or in DAC-supported olefin metathesis catalysts,23 wherein the sp3 carbon atom is found significantly above the plane of the remaining ring atoms. In general, the DAC N−Cacyl and O− Cacyl distances are inequivalent in DAC-borane adducts and DAC-supported olefin metathesis catalysts, while, in 3, the C− N and C−O bond lengths on both sides of the ligand are equidistant, and are in the expected range of single and double bonds, respectively. In the double NHC adduct 4, the beryllium atom adopts a distorted tetrahedral coordination and the Ccarbene−Be distances (1.843 (3) Å and 1.847 (3) Å)

diamidocarbene (DAC) at room temperature. After removal of solvent, washing, and recrystallization, colorless crystalline solids of the corresponding adducts 1−3 were obtained in 60− 70% yields (Scheme 1). These isolated adducts showed characteristically broad 9Be NMR chemical shifts for the CAAC (1: δ 12.9; 2: δ 12.8) and DAC (3: δ 11.6) adducts corresponding to the tricoordinate beryllium species. In contrast, the treatment of NHC (2 equiv) with BeCl2 resulted in formation of the double NHC adduct 4, and the 9Be NMR spectrum showed a sharp signal at δ 1.2, consistent with a B


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Inorganic Chemistry

indicating a planar coordination at both atoms. The BeCl2 planes of the complexes are twisted with respect to the CP2 planes by 43° (5) and 60° (6). The methyl groups of 5 are anti with respect to the P−P axis, whereas, in 6, they are syn and both point toward the middle of the ligand. The Be1−C1 distance of 6 (1.743(5) Å) is statistically equivalent to those of 5 (1.720 (3) Å) and [BeCl2(C(PPh3)2)] (1.742(9) Å), while the Be−Cl bond lengths are shorter than those of the [BeCl2(CAAC)] adducts. Nucleophilic Substitution Reactions at [BeCl2(MeCAAC)] and Cp*BeCl. Having in hand the adduct of BeCl2 with MeCAAC (1-(2,6-di-isopropylphenyl)-3,3,5,5-tetramethylpyrrolidine-2-ylidene), we sought to test its salt elimination reactions with an anionic N,N′-chelating ligand, a 1,3,2diazaborolide anion, and magnesium anthracenediyl 30 (Scheme 3). For comparison with donor-free beryllium

are slightly longer than those of the [BeCl2(CAAC)] adducts 1 and 2. Carbodiphosphoranes (CDPs) are powerful Lewis bases, with the donor carbon atom (formally) bearing two lone pairs of electrons, and as such have appeared in a range of adducts with elements throughout the periodic table.24−27 In 2011, Petz, Frenking, and Neumüller reported the synthesis of the monoadduct of carbodiphosphorane [::C(PPh3) 2] with BeCl227b but considered the possibility of binding two BeCl2 units to the donor. Thus, we were interested in combining BeCl2 with more electron-donating (and different-sized) carbodiphosphoranes [::C(PPh2Me)2] and [::C(PCy2Me)2]. Carbodiphosphorane [::C(PCy2Me)2] has been prepared similar to the method applied to [::C(PPh2Me)2].28 Treatment of equimolar amounts of BeCl2 and carbodiphosphoranes [::C(PPh2Me)2] and [::C(PCy2Me)2] in benzene in an ultrasonic bath, followed by removal of solvents and recrystallization from 1,2-difluorobenzene, resulted in the formation of CDP adducts of BeCl2 (5 and 6) (Scheme 2).

Scheme 3. Salt Elimination Reactions with Different Beryllium Precursors

Scheme 2. Synthesis of Carbodiphosphorane Adducts of Beryllium Dichloride

Although our aim was to prepare the double BeCl2 adduct of carbodiphosphoranes, adducts 5 and 6 were determined to be the monoadducts, similar to the results of Petz, Frenking, and Neumüller.27b Further, use of an excess of BeCl2 and more forcing conditions led to the binary salt of the dianion29 [Be2Cl6]2− with the dication [H2C(PCy2Me)2]2+ (Figure S40; see Supporting Information). As shown in Figure 2, the angular sums at Be and at C (1) both amount to 360°,

chlorides, the cyclopentadienyl-stabilized Cp*BeCl (Cp*= η5-C5Me5)31 was chosen as a rare example of a monomeric organylberyllium. As sterically demanding, chelating substituents with strong N-donor centers are known to effectively stabilize reactive metal complexes containing low-valent and/ or cationic metal centers, we treated 1 molar equiv of a lithium amidinato salt with [BeCl2(MeCAAC)] with an eye toward the further reduction of the product. The reaction occurs smoothly at room temperature, and washing with hexane and recrystallization from benzene yielded colorless solid 7 in

Figure 2. Solid-state structures of CDP adducts 5 and 6. Ellipsoids are shown at the 50% probability level. Some ellipsoids and all hydrogen atoms have been removed for clarity. Selected bond lengths [Å] and angles [deg] for 5: C1−Be1 1.720(3), Cl1−Be1 1.931(3), P1−C1 1.701(2); P2−C1−P1 119.71(11), P2−C1−Be1 120.38(14), Cl2− Be1−Cl1 115.29(13). For 6: C1−Be1 1.743(5), Cl1−Be1 1.956(4), P1−C1 1.704(3); P2−C1−P1 125.16(17), P2−C1−Be1 117.1(2), Cl2−Be1−Cl1 112.29(19). C


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Inorganic Chemistry

Figure 3. Solid-state structures of 7−10. Ellipsoids are shown at the 50% probability level. Some ellipsoids and all hydrogen atoms have been removed for clarity. Selected bond lengths [Å] and angles [deg] for 7: C1−Be1 1.880(3), Cl1−Be1 1.995(3), N3−C1 1.303(2), N1−Be1 1.780(3), N1−C21 1.334(3); N1−Be1−N2 75.66(12), N1−Be1−Cl1 114.39(15), C1−Be1−Cl1 117.53(14). For 8, two molecules are present in one unit cell and the bond lengths and angles are from one molecule: C1−Be1 1.807(3), Cl1−Be1 1.942(3), Be1−B1 1.895(3), B1−N2 1.453(2), C1−N3 1.298(2); C1−Be1−B1 138.36(14), C1−Be1−Cl1 102.79(14), B1−Be1−Cl1 118.15(14), N1−B1−N2 101.32(15), N3−C1−C2, 108.42(16). For 9: Be−Cp*Centroid 1.461(1), Be1−B1 1.855(2), B1−N1 1.4502(17), B1−N2 1.4502(17); Cp*Centroid−Be1−B1 179.25 N1−B1−N2 101.95(10). For 10: Be1−C9 1.819(2), Be1−C10 1.837(3), C9−C11 1.485(2), C9−C12 1.490(2), C10−C13 1.491(2), C10−C14 1.478(2); C11−C9−C12 114.0(1), C13−C10−C14 113.5(1), Be1−C9−C12 75.1(1), Be1−C9−C11 101.7(1), C9−Be1−C10 89.9(1). Due to disorder, the bond lengths and angles of the CAAC moiety of 10 are not discussed.

53% yield. The 1H and 13C NMR spectra show the expected resonances for the amidinato and MeCAAC ligands, while a sharp signal was observed at δ 4.1 in the 9Be NMR spectrum. Single crystals of 7 were obtained upon slow evaporation from a benzene solution. As shown in Figure 3, the N1−C21−N2 plane is nearly orthogonal to the C1−Be1−Cl1 plane (dihedral angle 89.7°), leading to a distorted tetragonal coordination sphere of the Be atom. The endocyclic N−Be−N bond angle is significantly smaller than the exocyclic N−Be−C, N−Be−Cl, C−Be−Cl angles (∼75° vs ∼115°); however, this is comparable to that reported previously for four-membered BeN2C rings such as Be{(NSiMe3)2CPh}2 and [PPh4][Be{(NSiMe3)2CPh}Cl2]. The Be1−C1 distance in 7 (1.880 (3) Å) is ∼0.1 Å longer, and the Be−N bond lengths slightly longer (1.780 (3), 1.781 (3) Å), than the corresponding bonds of bisamidinate Be{(NDip)2CEt}2 (1.7544(10), 1.7240(9) Å) and bisdiimidosulfinate complexes Be{(NSiMe 3 ) 2 SEt} 2 (1.750(5), 1.731(5) Å),32 but the differences are only barely statistically significant. After our previous report of a symmetrical beryllium bis(diazaborolyl) complex,21 we sought to synthesize unsymmetrical diazaborolyl compounds from suitable beryllium precursors. In this regard, we chose [BeCl2(MeCAAC)] and Cp*BeCl (Cp* = η5-C5Me5) as our starting points. The reaction of 1 molar equiv of lithium diazaborolide with [BeCl2(MeCAAC)] in benzene resulted in formation of base-

stabilized diazaborolyl beryllium chloride 8 with the concomitant elimination of LiCl. Filtration of the solution, followed by evaporation of the solvent and recrystallization from cold hexane (−30 °C), gave analytically pure 8 in 37% yield. In a similar approach, reaction of Cp*BeCl with lithium diazaborolide in benzene yielded the linear beryllium diazaborolide complex 9. The 9Be NMR spectrum of 8 features a broad peak at δ 20, somewhat shifted downfield compared to the normal range for three-coordinate beryllium. The 11B NMR spectrum shows a broad peak at δ 34, falling in the appropriate range for a 1,3,2-diazaborolyl complex. The 1H NMR spectrum of 8 indicates the presence of both borolyl and CAAC ligands in a 1:1 ratio. For 9, the 9Be NMR spectrum shows a sharp signal at δ −22.2, which fits to the corresponding signals of related Cp/Cp* beryllium compounds.33 The room-temperature 1H NMR spectrum displays two sets of methyl proton signals for the isopropyl groups; however, only one CH proton signal was observed. The solid-state structures of 8 and 9 were determined via single-crystal X-ray crystallography (Figure 3). The structure of 8 is described using data from one of the roughly isostructural molecules. In 8, the Be−B bond length of 1.894 (3) Å is slightly longer than the corresponding Be−B distances of the previously published beryllium bis(diazaborolyl) complex (1.870 (3), 1.873 (3) Å) but shorter than those of the 1,3dimethylimidazol-2-ylidene (IMe) adduct of the aforemenD


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have synthesized and structurally characterized a basestabilized beryllium-bridged anthracene complex, which shows a coordination pattern and folding of the anthracene group reminiscent of Mg-anthracene complexes. General Considerations. Caution! Beryllium and organometallic beryllium compounds have to be handled with appropriate safety precautions since they are regarded as highly toxic and carcinogenic. The reactions for adduct formation are carried out in benzene in which BeCl2 forms suspensions and in few cases the sonication helps in adduct formation. Full experimental details are given in the Supporting Information.

tioned beryllium bis(diazaborolyl) complex (1.944 (3), 1.954 (3) Å).21 Although the Be atoms of the IMe adduct of the beryllium bis(diazaborolyl) and 8 feature trigonal planar geometries with bond angles summing to 360°, the increased Be−B bond distance for the IMe adduct may be due to the increased steric bulk at the beryllium center. The Be1−C1 bond length (1.807 (3) Å) is in the expected range of [BeCl2(CAAC)] adducts.20 Although the B−N distances (1.452 (3), 1.454 (3) Å) are similar in length to those of the triborane species bis(diazaborolyl) chloroborane34a (1.452 Å), they are shorter than the calculated values for the naked diazaborolide anion34b [{HCN(Dip)}2B]− (avg. 1.475 Å). The solid-state structure of 9 as shown in Figure 3 represents an unsymmetrical beryllium diazaborolyl complex. The Be−C5Me5 centroid separation of 1.461 Å is far shorter than the Be−C5Me5 centroid separation of beryllocene [Be(η5C5Me5)2] (1.665 Å), thus revealing a significantly stronger Be−C5Me5 bonding interaction. The Be−C separations of 9 (avg. 1.897 Å) are also shorter than in [Be(η5-C5Me5)2]35 (avg. 2.05 Å). The Be−B distance of 9 (1.855 (2) Å) is marginally shorter than that of 8, whereas the B−N distances (1.4502(17) Å) are identical and similar to those of 8. In the presence of metal halides or organometallic halides, [Mg(anthracenediyl)(thf)3] has the unusual ability to react in three different ways: (i) as a nucleophile, (ii) as a source of zerovalent magnesium, and (iii) as a single-electron reducing agent.31 Keeping in mind that [BeCl2(CAAC)] adducts can be reduced to zerovalent beryllium species, we turned our attention toward [Mg(anthracenediyl)(thf)3], which we combined with [BeCl2(MeCAAC)]. After workup, the reaction mixture afforded a thermally stable red diamagnetic solid (10) in moderate yield. The 1H NMR spectrum of 10 showed a singlet at δ 3.57 with a relative intensity corresponding to two protons, which can be attributed to the 9,10 protons of the anthracenediyl unit. The 9Be NMR spectrum displayed a signal at δ 1.7, shifted upfield compared to [BeCl2(MeCAAC)] (δ 12.9), indicating higher electron density around the Be center. The X-ray crystal structure of 10 was determined, and the molecular structure is depicted in Figure 3. The structure of 10 shows it to be a tetracyclic compound wherein a Be atom bridges the former 9,10 anthracene positions and is in turn bound by a MeCAAC unit, formed via the nucleophilic attack of the [Mg(anthracene)(thf)3] with [BeCl2(MeCAAC)]. The geometry at the beryllium center is planar, with bond angles amounting to 360°, and the angle between the two phenyl planes of each anthracene ligand is 36.6°, making it similar in geometry to [Mg(anthracene)(thf)3] (30.6°).36 The folding of the anthracene ligand and the presence of the covalent bonds involving sp3 carbon centers in 10 differs from almost planar (sp2 carbons) in anthracenelithium complex [{Li(TMEDA)}2(anthracene)]37 where the bonding is primarily ionic.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.8b03263. Experimental and crystallographic details (PDF) Accession Codes

CCDC 1879067−1879079 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Holger Braunschweig: 0000-0001-9264-1726 Author Contributions §

These authors contributed equally.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS D.K.R. thanks the Science and Engineering Research Board (India) for Overseas postdoctoral fellowship. The authors thank Julius-Maximilians-Universität Würzburg for financial support and Dr. Guillaume Bélanger-Chabot for his assistance in X-ray data analysis.

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REFERENCES

(1) Arduengo, J.; Harlow, R. L.; Kline, M. A Stable Crystalline Carbene. J. Am. Chem. Soc. 1991, 113, 361−363. (2) (a) Herrmann, W. A. N-Heterocyclic Carbenes: A New Concept in Organometallic Catalysis. Angew. Chem., Int. Ed. 2002, 41, 1290− 1309. (b) Díez-González, S.; Marion, N.; Nolan, S. P. N-Heterocyclic Carbenes in Late Transition Metal Catalysis. Chem. Rev. 2009, 109, 3612−3676. (3) Recent reviews and book chapters: (a) Flanigan, D. M.; Romanov-Michailidis, F.; White, N. A.; Rovis, T. Organocatalytic Reactions Enabled by N-Heterocyclic Carbenes. Chem. Rev. 2015, 115, 9307−9387. (b) Matsuoka, S. N-Heterocyclic CarbeneCatalyzed Dimerization, Cyclotetramerization and Polymerization of Michael acceptors. Polym. J. 2015, 47, 713−718. (c) Ryan, S. J.; Candish, L.; Lupton, D. W. Acyl Anion Free N-Heterocyclic Carbene Organocatalysis. Chem. Soc. Rev. 2013, 42, 4906−4917. (d) NHeterocyclic Carbenes in Transition Metal Catalysis and Organocatalysis; Cazin, C. S. J., Ed.; Springer: Dordrecht, 2011.

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CONCLUSIONS In conclusion, we report herein the synthesis of various Lewis base adducts of beryllium chloride. Further, we have studied the salt elimination reactions of two beryllium precursors with various nucleophiles, which yielded two beryllium diazaborolyl compounds. Structural and spectroscopic analyses of these compounds indicate that the bonding between the boron and beryllium is polar-covalent in nature, which is in contrast with the more ionic bonding featured in Yamashita and Nozaki’s boryl anion and other s-block elements. Taking advantage of the nucleophilic behavior of magnesium anthracenediyl, we E


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New Outcomes of Beryllium Chemistry: Lewis Base Adducts for Salt

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