Editor's Page Cite This: Organometallics 2018, 37, 625−627
Organometallic Chemistry in Europe n 1757, Louis Claude Cadet de Gassicourt (*1731−†1799), a Parisian apothecary (French: apothicaire), studied the formulation of a cobalt-based secret ink. Heating arseniccontaining cobalt ores, CoAs2 and CoAsS2, sources of arsenic trioxide, with potassium acetate, Cadet noticed the obnoxious smell of the resulting solution. This liquid, first called “Cadet’s smoking liquid” (French: liqueur fumante de Cadet) and termed “kakodyl” (German: stinking) by the Swede Jöns Jakob Berzelius (*1779−†1848), eventually attracted Robert Bunsen’s (*1836−†1839) attention during his early academic career in Kassel and Marburg, where “kakodyl” and its derivatives were identified as tetramethyldiarsane (CH3)2As−As(CH3)2 and its μ-oxo bridged derivative, the kakodyloxide.1,2 It should be noted that Bunsen nearly lost his life as a result of his studies of the arsine radical precursor and its cyano product (CH3)2As(CN), resulting from kakodyl trapping reactions using Hg(CN)2. Like Cadet, Danish William Christopher Zeise (*1789−†1847) started his early “chemistry” career as a pharmacist. Zeise was an assistant to Oersted in Copenhagen and spent time in Göttingen and Paris, where he became acquainted with Berzelius. Having been influenced by Berzelius, Zeise returned back to Copenhagen, first as an assistant to Oersted, and later as the first Professor of Chemistry at the University of Copenhagen, where he began his early studies of the chemistry of platinum. He continued his studies at the Royal Polytechnic Institute of Copenhagen (founded by Oersted in 1929, today Technical University of Denmark). Zeise’s first article on the reaction of platinum with alcohol (in German language) dates back to 1827,3 and relates to studies carried out by Edmund Davy (*1785−†1857) and Johann Wolfgang Döbereiner (*1780−†1849). This work started a fierce controversy with Justus von Liebig, who believed that the material was nothing else but finely powdered metallic platinum; “platinum black” as we would know it today. In 1830, Zeise followed up on his earlier studies and reported−now in Latin in the university’s Festschrift: “De chlorido platinae et acohole vini sese invicem permutantibus nec non de novis substantiis inde oriundis” (The reaction between platinum chloride and wine alcohol and the new substances arising therefrom). In the German translation,4 a meticulous 45 page publication, Zeise’s salt was described as beautiful lemon-yellow, transparent crystals of half an inch and larger, obtained by reaction of potassium tetrachloridoplatinate with boiling ethanol and, importantly, addition of KCl. In this reaction, acid is lost whereas water is eliminated from ethanol to form of ethene, which, in turn, coordinates to the platinum(II) ion; thus, forming K[PtCl3(C2H4)]·H2O.5,6 At the time, Zeise correctly determined the complex’s composition (including the single, co-crystallized molecule of water) and stoichiometry between carbon, hydrogen, chlorine, and platinum. Only later, in 1861, J. P. Griess and C. A. Martius at the Royal College of Chemistry in London showed that ethylene was liberated when Zeise’s salt was thermally
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decomposed.7 Finally, in 1868, K. Birnbaum developed a new synthetic route to Zeise’s salt employing ethylene gas.8 Although Zeise’s salt is often referred to as “the first organometallic compound of any metal”;9 this account is incorrect and ignores the studies of Cadet, Berzelius, and Bunsen on the chemistry of metalloid arsenic, and likely many more. Regardless, it is rather unimportant and almost irrelevant who or which compound was “the first”. Instead, it is impressive to realize that, in 19th century Europe, a new discipline of chemistry was born; namely, organometallic chemistry. Apparently, a significant number of scientists were fascinated by the newly discovered metal−carbon bond and felt that it was remarkably unusual, worth studying, reporting, and discussing or arguing about. Following the studies of Zeise, and while working on the synthesis of methyl and ethyl radicals in the laboratories of Bunsen in Marburg, Englishman Edward Frankland (*1825−†1899) reported the first metal alkyl species of tin and zinc in the 1850s.10 In 1863, C. Friedel and J. M. Crafts began to employ metal alkyls, such as R2Zn, as alkyl transfer reagents, leading to the development of organochlorsilanes RnSiCl4−n, the foundation of industrial silicon chemistry (Müller and Rochow, 1943). The end of the 19th century is marked by Frenchman Phillipe Barbier’s (*1848−†1922) studies toward the synthesis of organomagnesium compounds, which ultimately led his Ph.D. student Victor Grignard (*1871−†1935) to discover the famous “Grignard reagents”, RMgX, to promote C−C bond formation with carbonyl containing groups.11 In 1912, the Nobel Prize in Chemistry was awarded to Victor Grignard and Paul Sabatier for the discovery of the so-called Grignard reagents, which have greatly advanced the progress of organic chemistry, and for Sabatier’s catalytic hydrogenation of organic compounds in the presence of finely dispersed metals. This Nobel Prize marks a special year for organometallic chemistry, and although awarded to only two living individuals, it is in fact honoring the work of an entire generation of organometallic pioneers for their groundbreaking works and mutual accomplishments. Just like the work of Victor Grignard can be traced back to a number of preceding scientists, Paul Sabatier’s (*1854−†1941) work was likely also influenced by his past peers, such as Ludwig Mond (*1839−†1909), a student of Bunsen, who synthesized the first homoleptic nickel carbonyl, Ni(CO)4, from the reaction of carbon monoxide with finely powdered nickel. Mond’s nickel tetracarbonyl (1890s) set the stage for Job and Cassal’s Cr(CO)6 (1927), and the synthesis of the first organometallic hydride complex [Fe(CO)4H2] by W. Hieber (1931) via reaction of iron pentacarbonyl with bases, according to Fe(CO)5 + 2OH− → Fe(CO)4H2 + CO32−. F. Heins reaction of phenylmagnesium bromide with chromium trichloride did not lead to the intended Special Issue: Organometallic Chemistry in Europe Published: March 12, 2018 625
DOI: 10.1021/acs.organomet.8b00012 Organometallics 2018, 37, 625−627
Organometallics
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contributions from Belgium, France, Germany, The Netherlands, Russia, Spain, Sweden, and the United Kingdom. The chemistry presented in this volume showcases current trends and recent highlights of metalorganic chemistry in Europe and covers the fields of catalysis, main group and transition metal coordination chemistry as well as reports on bond activation chemistry and the synthesis of new ligands. A few examples of this issues’ content are summarized below: Among the many excellent contributions, the Spanish− German team around Markus Hölscher, Walter Leitner, and Jesús Pérez-Torrente report catalytic hydrogenation of CO2 to formate employing a carboxylate-functionalized bis-NHC ligand bound to iridium (DOI: 10.1021/acs.organomet.7b00509). Reactivity studies and theoretical investigations of this catalysis, which proceeds in water with NEt3 base, complement this excellent work and elucidate the crucial role of the base in this system. Also in this issue, Belen Martin-Matute and co-workers from Stockholm University propose an interesting cooperative effect for the acceptorless dehydrogenation of alcohols mediated by bifunctional iridium catalysts coordinated to OH- and NH-functionalized N-heterocyclic carbene ligands (DOI: 10.1021/acs.organomet.7b00220). Clearly, the organometallic chemistry of NHC-supported compounds continues to flourish, while the development of efficient, earth-abundant transition metal catalysts has emerged as a topical and important field of research in recent years. ̈ Lazreg and Catherine Cazin from St. In this context, Faima Andrews, United Kingdom, present the first efficient synthesis of sulfonyl-substituted triazoles that had been difficult to access but were successfully obtained with their novel copper(I)-NHC catalysts (DOI: 10.1021/acs.organomet.7b00506). The French multigroup collaboration led by Louis Fensterbank, Anny Jutand, Guillaume Lefèvre, and Cyril Ollivier elucidates the ligand effects on iron-catalyzed radical cyclization of unsaturated organic halides (DOI: 10.1021/acs.organomet.7b00603). A combination of electrochemical, Mössbauer spectroscopic, and DFT computational analyses provides new perspectives into the reactivity of iron(I) hydride and borohydride species and implications for single electron transfer processes. Alois Fürstner and co-workers from Mülheim/Ruhr, Germany, report an in-depth study on iron π-complex formation and resulting low-valent iron species that readily engage in C−H activation chemistry (DOI: 10.1021/acs.organomet.7b00571). Their structural, spectroscopic, and mechanistic studies offer comprehensive understanding of cycloisomerization and cycloaddition reactions catalyzed by electron-rich iron complexes. In the field of main group chemistry, the French team of Ghenwa Boudir, Karinne Miqueu, and Didier Bourissou communicates a thorough study on the boron-centered reactivity of a phosphorus-stabilized boryl radical that was obtained by reduction of the corresponding phosphino bromoborane (DOI: 10.1021/acs.organomet.7b00598). Ingo Krossing et al. from Freiburg, Germany, also report new group 13 chemistry by describing the synthesis and characterization of the first neutral adduct of R3SiCl, namely, R3SiCl−Al(ORF)3 (DOI: 10.1021/acs.organomet.7b00557). Addition of substoichiometric amounts of HORF to AlEt3 also allows for the isolation and characterization of a variety of ethyl aluminum sesquialkoxides, of which [(RFO)(Et)Al(μ-ORF)2Al(Et)2] was structurally characterized; thus, representing the first crystallographic evidence for this compound class. The reactivity of a lithiated N-heterocyclic carbene with two-coordinate amides of group 14 elements tin and lead is reported by José Goicoechea
triphenylchromium (“polyphenylchromium”, 1919) but was intricately related to E.O. Fischer’s bis(benzene) chromium complex (1955). By the mid 20th century, Dewar, Chatt, and Duncanson developed the concept of “bond strengthening thru backbonding” (1953), and the race to elucidate the structure and bonding situation of FeC10H10, started by Peter L. Pauson and Samuel A. Miller in 1951, ultimately led to the birth of an entirely new class of so-called sandwich complexes and the 1973 Nobel Prize to E. O. Fischer and G. Wilkinson. The historical overview “Ferrocene−how it all began” by P. L. Pauson is a must-read item.12 By then, the field of organometallic chemistry had matured and developed into a fountain of synthetic creativity and curiosities, such as metal carbene as well as carbyne species and metal (carbonyl) clusters with M−M (multiple) bonds. In 1976, John Ellis and Roald Hoffman treated us to the simple but ingenious concept of the isolobal analogy, which not only provides a comprehensive picture of the bonding situation in these organometallic compounds but also allows for the prediction of the bonding properties and the relation between inorganic and organic fragments.13,14 At the beginning of the 1980s, however, the focus of organometallic chemistry shifted from the art of synthesis for art’s sake to interest in finding applications. Chemists now profited from the wealth of known organometallic compounds synthesized in the past; laboratory curiosities were turned into catalysts and even found industrial applications. Accordingly, the 21st century witnessed a hat trick of Nobel Prizes awarded to numerous “Organometalliker” from all over the world: W. S. Knowles, R. Noyori, and K. B. Sharpless (2001), Y. Chauvin, R. H. Grubbs, R. R. Schrock (2005), and most recently to R. F. Heck, E. Negishi, and A. Suzuki (2010). Tracing back the first organometallic compound to the first organometallic chemist and the birthdate of its discipline is difficult, if not impossible. That said, the father of the ACS journal Organometallics unquestionably is Dietmar Seyferth. The founding editor served “his” journal for almost 30 years (1982−2010). In 2001, Dietmar started the tradition of featuring a landmark molecule or reaction on the “The Editor’s Page” and the journal’s cover (DOI: 10.1021/om000992h). He also wrote numerous editorials and meticulously researched historical essays, highlighting many of the organometallic compounds and their discoverer briefly mentioned above. Among many others, Dietmar wrote about Cadet’s fuming arsenical liquid and the cacodyl compounds of Bunsen (DOI: 10.1021/om0101947), Zeise’s salt, the dispute with Liebig, and its unambiguous characterization after his death (DOI: 10.1021/om000993+). Dietmar also featured the discovery of Frankland’s metal alkyls (DOI: 10.1021/om010439f), Grignard’s regents (DOI: 10.1021/om900088z), and the history of bis(benzene) chromium and its identification (DOI: 10.1021/om0201056 and DOI: 10.1021/om020362a). Last but not least, I wish to mention a Special Issue of Organometallics entirely dedicated to the “one-and-only” organometallic compound: “Ferrocene − Beauty and Function”, assembled by guest-editors Katja Heinze and Heinrich Lang (DOI: 10.1021/om400962w). Looking back, Europe has to be recognized as the cradle of organometallic chemistry, and its worldwide popularity took nearly 200 years to develop and grow to its current status of significance. After our more recent Special Issue “Organometallic Chemistry in Asia”, Organometallics is returning to its birthplace, the peninsula of Eurasia. This issue features 26 626
DOI: 10.1021/acs.organomet.8b00012 Organometallics 2018, 37, 625−627
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Notes
and co-workers from the University of Oxford (DOI: 10.1021/ acs.organomet.7b00352), and the group of Alexander Filippou, based in Bonn, Germany, developed a new synthesis approach to silylidyne complexes employing silyliumylidenes (DOI: 10.1021/acs.organomet.7b00665), an approach that relies on an improved and convenient preparation of SiCp*2; thus, offering facile access to multigram quantities of the [Si(η5Cp*)]+ cation, isolated as the [B(C6F5)4]− salt. Work by Rebecca Melen from Cardiff, United Kingdom, showcases the synthesis and reactivity of phosphenium and arsenium species (DOI: 10.1021/acs.organomet.7b00564). Employing a variety of spectroscopic techniques, supplemented by computational analyses, the photophysical and electronic properties of the pnictoles and pnictenium compounds were investigated. Further news involving group 15 chemistry is reported by Jan Weigand from TU Dresden (DOI: 10.1021/acs.organomet.7b00597). Weigand et al. demonstrate that the reduction of the cyclo-tris(phosphonio)methanide dication yields quite an interesting phosphanyl-functionalized carbodiphosphorane ligand with three donor functions, which they utilized to synthesize gold complexes with one-, two-, and threecoordinated AuCl fragments. Their remarkable careful spectroelectrochemical study provides insights into the mechanism of the unusual and reversible ring opening/closing reaction of the cyclo-tris(phosphonio)methanide dication. Sofia Ferrer and Antonio Echavarren from Tarragona, Spain, reported experimental and computational studies of σ−πdigold(I) alkyne complexes and their proposed role in gold(I)catalyzed cycloisomerization reactions (DOI: 10.1021/acs.organomet.7b00668). A thought-provoking contribution comes from the Russian group of Valentine Ananikov, our recent Organometallics Distinguished Author Award Lectureship winner, who reports a comparative theoretical study on the influence of NHC−R coupling on the outcome of R−X oxidative addition to NHC−palladium complexes (DOI: 10.1021/acs.organomet.7b00669). In analogy to Harry Gray’s “oxo wall”, Sven Schneider and his research team at the University of Göttingen challenge the “nitrido wall” and disclose molecular design strategies how to circumvent the π-bonding conflict in electron-rich, mid-valent osmium complexes with strong π-donating ligands, such as terminal nitridos or imidos (DOI: 10.1021/acs.organomet.7b00707). Employing the fully oxidized pincer-type PNP chelate, which features the lowest degree of chelate → metal πdonation, allowed for the unprecedented isolation of four and five-coordinated osmium(IV) nitrido complexes; hence, taking down “the wall”. And yes, Schneider’s manuscript does not report a single metal−carbon bond! However, we the Editors of Organometallics still consider these compounds relevant to the field of organometallic chemistry and generally appreciate inorganic “synaptic transmission”!
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Views expressed in this editorial are those of the authors and not necessarily the views of the ACS.
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REFERENCES
(1) Carrière, J. Berzellius und Liebig, Ihre Briefe von 1831−1845, 2nd ed.; Kgl. Bayer. Akademie der Wissenschaften, Dr. Martin Sändig oHG: Wiesbaden, 1967. (2) Hjelt, E. Geschichte der Organischen Chemie von ältester Zeit bis zur Gegenwart; Springer Fachmedien: Wiesbaden, 1916. (3) By reproduction of Berzelius’ Jahresbericht: Zeise, W. C. Ann. Phys. Chem. (Poggendorff) 1827, 9, 632. (4) Zeise, W. C. Ann. Phys. (Berlin, Ger.) 1831, 21, 497−541. (5) Black, M.; Mais, R. H. B.; Owston, P. G. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1969, 25, 1753−1759. (6) Love, R. A.; Koetzle, T. F.; Williams, G. J. B.; Andrews, L. C.; Bau, R. Inorg. Chem. 1975, 14, 2653−2657. (7) Griefs, P.; Martius, C. A. Ann. Chem. (Liebig) 1861, 120, 324− 327. (8) Birnbaum, K. Ann. Chemie (Liebig) 1868, 145, 67−77. (9) Hunt, L. B. Platinum Metals Rev. 1984, 28, 76−83. (10) von Frankland, E. Ann. Chem. Pharm. 1849, 71, 171−213. (11) Grignard, V. Comptes Rendus Hebd. Séances Acad. Sci., Ser. C 1900, 130, 1322−1324. (12) Pauson, P. L. J. Organomet. Chem. 2001, 637−639, 3−6 and references therein. (13) Ellis, J. E. J. Chem. Educ. 1976, 53, 2−6. (14) Elian, M.; Chen, M.M.-L.; Mingos, D. M. P.; Hoffmann, R. Inorg. Chem. 1976, 15, 1148−1155.
Karsten Meyer* Holger Braunschweig
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Karsten Meyer: 0000-0002-7844-2998 Holger Braunschweig: 0000-0001-9264-1726 627
DOI: 10.1021/acs.organomet.8b00012 Organometallics 2018, 37, 625−627
