Coupling H2 to Electron Transfer with a 17-Electron Heterobimetallic Hydride: A "Redox Switch" Model for the H2-Activating Center of Hydrogenase

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• 作者：Robert T. Hembre ; J. Scott McQueen ; and Victor W. Day
• 刊名：Journal of the American Chemical Society
• 出版年：1996
• 出版时间：January 31, 1996
• 年：1996
• 卷：118
• 期：4
• 页码：798 - 803
• 全文大小：209K
• 年卷期：v.118,no.4(January 31, 1996)
• ISSN：1520-5126

文摘

A meta-stable heterobimetallic mixed-valence ion,[Fe(II),Ru(III)], is formed by the one-electronoxidationof Cp*(dppf)RuH {1, dppf =1,1'-bis(diphenylphosphino)ferrocene, Cp* =pentamethylcyclopentadienide}. Aremarkable stability toward one-electron oxidation is revealed by thecyclic voltammetry of 1 which contains tworeversible oxidations at +0.073 and +0.541 V and a quasireversibleoxidation at +0.975 V (vs NHE) assigned toRu(III/II), Ru(IV/III), and Fe(III/II), respectively.The isolable Ru(III) metal hydride,[Cp*(dppf)RuH]PF₆(1⁺), ischaracterized by a NIR absorption at 912 nm ( = 486M^-1 cm^-1) assigned to an intervalencetransfer band and aseries of atom transfer reactions yielding the even electronderivatives [Cp*(dppf)RuXH]PF₆ (X = H,Cl, Br, I). Acrystallographically determined Fe-Ru distance of 4.383(1) Å in1 is consonant with the classification of1⁺ as aweakly coupled, Type II mixed-valence ion (H_ab= 627 cm^-1, ² = 3.3 ×10^-3). This is the first reportedexampleof a mixed-valence bimetallic complex containing the widely used dppfligand. The ability of 1 to serve as aheterobimetallic catalyst for the reduction of methyl viologen withH₂ makes it a unique functional model of[NiFe]hydrogenase enzymes.