Structural characterization and proton reduction electrocatalysis of thiolate-bridged bimetallic (CoCo and CoFe) complexes

Abstract

Using an assembly method, dinuclear CoCo and CoFe complexes supported by a bdt ligand, [Cp*Co(μ–η²:η²-bdt)(μ-I)CoCp*][PF₆] (1[PF₆], Cp* = η⁵-C₅Me₅, bdt = benzene-1,2-dithiolate), and [Cp*Co(μ–η²:η⁴-bdt)FeCp′][PF₆] (3[PF₆], Cp′ = η⁵-C₅Me₄H) were synthesized in high yields. Upon chemical reduction with CoCp₂, complexes 1[PF₆] and 3[PF₆] were converted to [Cp*Co(μ-η²:η²-bdt)CoCp*] (2) and [Cp*Co(μ–η²:η⁴-bdt)FeCp′][PF₆] (3), respectively. Treatment of 2 with HBF₄ resulted in the protonation of two cobalt centers to generate a hydride bridged complex, [Cp*Co(μ–η²:η²-bdt)(μ-H)CoCp*][BF₄] (4[BF₄]), which was identified by spectroscopy and X-ray crystallography. When treating 3 with HBF₄, a one-electron oxidation occurred to afford complex 3[BF₄] along with the formation of H₂. Importantly, heterodinuclear complex 3[PF₆] and hydride bridged complex 4[BF₄] can serve as effective catalysts to promote proton reduction for hydrogen evolution, as evidenced by cyclic voltammetry.