A new reactivity pattern of heterodinuclear complexes [MnRe(CO)6(μ-S2CPR3)] with nBuLi/protonation and its electrochemistry properties investigation as structure and function models for the Fe-only hydrogenase active site

A novel reaction pattern of heterodinuclear complexes was reported. Namely, nucleophilic attack of nBuLi/protonation of complexes [MnRe(CO)6(μ-S2CPR3)] occurs with the cleavage of the Mn–Re, (P)C–S bond and formation of new (Bu)C–S bond, to afford the novel complexes [MnRe(CO)6(μ-SnBu)(μ-S-C(H)PR3)] (L) (L = PR3, C5H5N) 3 and 4 which are different from previous complexes (1 and 2 or other complexes) obtained by the reduction with Na[Hg] or superhydride reagent. Additionally, in order to develop these complexes application, several similar structure Mn–Re binuclear complexes, MnRe(CO)6(μ-H)[μ-S(SnBu)Cdouble bond; length as m-dashC(PiPr3)S] (1), MnRe(CO)6(μ-H)[μ-S(SCH3)Cdouble bond; length as m-dashC(PiPr3)S] (2), MnRe(CO)6(μ-SnBu)[μ-SC(H)PCy3PPh3] (3), MnRe(CO)6(μ-SnBu)[μ-SC(H)PCy3Py] (4), which serve as structural models for the active site of Fe-hydrogenase, were chosen to investigate their possible electrochemical properties. Consequently, they are indeed shown to be electrocatalysts for H2 production in the presence of acetic acid in acetonitrile. The electrocatalysis is initiated by electrochemical reduction of these Mn–Re complexes, which subsequently, under weak acid conditions, undergo protonation of the reduced rhenium center to produce H2. And two probable electrochemical mechanisms (EECC and ECCE) are also proposed.