Six-, Five-, and Four-Coordinate Ruthenium(II) Hydride Complexes Supported by N-Heterocyclic Carbene Ligands: Synthesis, Characterization, Fundamental Reactivity, and Catalytic Hydrogenation of

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• 作者：John P. Lee^† ; ; Zhuofeng Ke^‡ ; ^§ ; ; Magaly A. Ramrez^† ; ; T. Brent Gunnoe* ; Thomas R. Cundari*^‡ ; ; Paul D. Boyle
• 刊名：Organometallics
• 出版年：2009
• 出版时间：March 23, 2009
• 年：2009
• 卷：28
• 期：6
• 页码：1758-1775
• 全文大小：498K
• 年卷期：v.28,no.6(March 23, 2009)
• ISSN：1520-6041

文摘

The Ru(II) hydride complex (IMes)₂Ru(Cl)(H)(CO) (1) {IMes = 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene} was synthesized from [Ru(CO)₂Cl₂]_n and free IMes. Complex 1 rapidly reacts with CO to produce the cis-dicarbonyl Ru(II) complex (IMes)₂Ru(Cl)(H)(CO)₂ (2). The reaction of 1 with NaBAr′₄ {Ar′ = 3,5-(CF₃)C₆H₃} produces the four-coordinate Ru(II) cationic complex [(IMes)₂Ru(H)(CO)][BAr′₄] (4), which can be trapped by two equivalents of tert-butylisonitrile to produce [(IMes)₂Ru(H)(CO)(CN^tBu)₂][BAr′₄] (5). Experimental and computational studies suggest that complex 4 is a diamagnetic system that adopts a sawhorse structure. The hydride ligand of complex 2 is readily displaced as dihydrogen upon reaction with HCl to produce (IMes)₂Ru(Cl)₂(CO)₂ (3). Both complex 1 and 4 were found to react with D₂ (30 psi) at room temperature to produce the isotopomers (IMes)₂Ru(Cl)(D)(CO) (1-d₁) and [(IMes)₂Ru(D)(CO)][BAr′₄] (4-d₁), respectively, with the rate of formation of 4-d₁ at least 28 times faster than the conversion of 1/D₂ to 1-d₁. In the presence of excess D₂ complex 4 reversibly incorporates deuterium into the ortho methyl groups of the IMes ligands, whereas complex 1 does not show evidence of H/D exchange with the IMes ligands. Both 1 and 4 were found to catalyze the hydrogenation of olefins, ketones, and aldehydes.