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New Reactions of Terminal Hydrides on a Diiron Dithiolate

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journal contribution
posted on 16.04.2014, 00:00 by Wenguang Wang, Thomas B. Rauchfuss, Lingyang Zhu, Giuseppe Zampella
Mechanisms for biological and bioinspired dihydrogen activation and production often invoke the intermediacy of diiron dithiolato dihydrides. The first example of such a Fe2(SR)2H2 species is provided by the complex [(term-H)­(μ-H)­Fe2(pdt)­(CO)­(dppv)2] ([H1H]0). Spectroscopic and computational studies indicate that [H1H]0 contains both a bridging hydride and a terminal hydride, which, notably, occupies a basal site. The synthesis begins with [(μ-H)­Fe2(pdt)­(CO)2(dppv)2]+ ([H1(CO)]+), which undergoes substitution to afford [(μ-H)­Fe2(pdt)­(CO)­(NCMe)­(dppv)2]+ ([H1(NCMe)]+). Upon treatment of [H1(NCMe)]+ with borohydride salts, the MeCN ligand is displaced to afford [H1H]0. DNMR (EXSY, SST) experiments on this complex show that the terminal and bridging hydride ligands interchange intramolecularly at a rate of 1 s–1 at −40 °C. The compound reacts with D2 to afford [D1D]0, but not mixed isotopomers such as [H1D]0. The dihydride undergoes oxidation with Fc+ under CO to give [1(CO)]+ and H2. Protonation in MeCN solution gives [H1(NCMe)]+ and H2. Carbonylation converts [H1H]0 into [1(CO)]0.