Facile Decarboxylation of Propiolic Acid on a Ruthenium Center and Related Chemistry

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• 作者：John H. Bowie ; Michael I. Bruce ; Mark A. Buntine ; Alexander S. Gentleman ; David C. Graham ; Paul J. Low ; Gregory F. Metha ; Cassandra Mitchell ; Christian R. Parker ; Brian W. Skelton ; Allan H. White
• 刊名：Organometallics
• 出版年：2012
• 出版时间：August 13, 2012
• 年：2012
• 卷：31
• 期：15
• 页码：5262-5273
• 全文大小：517K
• 年卷期：v.31,no.15(August 13, 2012)
• ISSN：1520-6041

文摘

Spontaneous decarboxylation of RC鈮CO₂H (R = H, Ph) occurs in reactions with RuCl(PP)Cp (PP = (PPh₃)₂, dppe) to give [Ru(鈺怌鈺怌HR)(PP)Cp]⁺. Computational studies (DFT) of possible decarboxylation mechanisms suggest that the reaction that leads to extrusion of CO₂ and formation of [Ru(鈺怌鈺怌H₂)(dppe)Cp]⁺ most likely occurs by initial interaction of the anion HC鈮CO₂^{鈥?/sup> with RuCl(dppe)Cp by coordination of carboxylate to Ru, followed by formation of an 畏2-alkyne intermediate which rearranges to the 畏1-ethynyl species with loss of CO₂. Protonation of the ethynyl group affords the parent vinylidene. In contrast, reactions of HC鈮CO₂R (R = Me, Et) with RuCl(PP)Cp and [NH₄]PF₆ in MeOH have given [Ru{鈺怌(OMe)CH₂(CO₂R)}(PP)Cp]+, formed by attack of MeOH at C_伪 of the intermediate vinylidenes [Ru{鈺怌鈺怌H(CO₂R)}(PP)Cp]+. Deprotonation of the carbenes affords Ru{C(OMe)鈺怌H(CO₂R)}(PP)Cp as mixtures of cis and trans isomers. The vinylidenes, which are obtained directly from RuCl(PP)Cp and HC鈮CO₂R in the presence of [NH₄]PF₆ in ButOH, can be deprotonated (Na/PriOH) to the corresponding alkynyls. Attempted deprotonation of [Ru(鈺怌鈺怌H₂)(dppe)Cp]+ with LiBu gave the binuclear cyclobutenylidinium complex [{Ru(dppe)Cp}₂(渭-C₄H₃)]+. The X-ray diffraction molecular structures of [{Ru(dppe)Cp}₂(渭-C₄H₃)]PF₆ (11), [Ru{鈺怌(OMe)CH₂(CO₂Me)}(dppe)Cp]PF₆ (13), Ru{C(OMe)鈺怌H(CO₂R)}(dppe)Cp (R 鈺?Me (15), Et (16)) and Ru(C鈮CO₂R)(dppe)Cp (R = Me (21), Et (22)) are described.}