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|Section2= |Section3= |Section7= |Section8= }} Dicobalt octacarbonyl is the inorganic compound Co2(CO)8. This metal carbonyl is a reagent and catalyst in organometallic chemistry and organic synthesis.〔Pauson, P. L. “Octacarbonyldicobalt” in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. .〕 It is used as a catalyst for hydroformylation, the conversion of alkenes into aldehydes.〔Elschenbroich, C.; Salzer, A. ”Organometallics : A Concise Introduction” (2nd Ed) (1992) Wiley-VCH: Weinheim. ISBN 3-527-28165-7〕 It is highly reactive towards alkynes, and is sometimes used as an alkyne protecting group. As the cobalt-alkyne complex, it plays a role in promoting both the Nicholas reaction and the Pauson–Khand reaction. ==Synthesis, structure, properties== It is synthesised by the high pressure carbonylation of cobalt(II) salts, often in the presence of cyanide. It is an orange-colored, pyrophoric solid that is thermally unstable. It exists as two isomers in solution〔Ray L. Sweany and Theodore L. Brown "Infrared spectra of matrix-isolated dicobalt octacarbonyl. Evidence for the third isomer" Inorganic Chemistry 1977, 16, pp 415 - 421. 〕 that rapidly interconvert. :350px The major isomer contains two bridging CO ligands linking the Co atoms and six terminal CO ligands, three on each Co atom. It can be described by the formula (CO)3Co(μ-CO)2Co(CO)3 and has C2v symmetry. This structure resembles Fe2(CO)9, but with one fewer bridging CO. The Co---Co distance is 2.52 Å, and the Co–COterminal and Co–CObridge distances are 1.80 and 1.90 Å, respectively.〔G. G. Sumner, H. P. Klug, L. E. Alexander "The crystal structure of dicobalt octacarbonyl" Acta Crystallographica, 1964 Volume 17 Part 6 Pages 732-742. 〕 Analysis of the bonding suggests the absence of a direct Co–Co bond.〔Jennifer C. Green, Malcolm L. H. Green, Gerard Parkin "The occurrence and representation of three-centre two-electron bonds in covalent inorganic compounds" Chem. Commun. 2012, 11481-11503. 〕 The minor isomer has no bridging CO ligands, but instead has a direct Co–Co bond and eight terminal CO ligands, four on each Co atom. It can be described by the formula (CO)4Co-Co(CO)4 and has D3d symmetry. It features an unbridged Co-Co bond that is 2.70 Å in length.〔Thelma Y. Garcia, James C. Fettinger, Marilyn M. Olmstead, Alan L. Balch, "Splendid symmetry: crystallization of an unbridged isomer of Co2(CO)8 in Co2(CO)8·C60" Chem. Commun., 2009, p. 7143-7145. .〕 The minor isomer has been crystallized together with C60. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Dicobalt octacarbonyl」の詳細全文を読む スポンサード リンク
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