Controllable Electrochemical Synthesis of Mono- and Di-Substituted Diphosphine Complexes Related to [Fe-Fe]-Hydrogenase

Abstract

By the electrocatalytic reactions of [Fe₂(CO)₆(μ-pdt)] (1) (pdt = SCH₂CH₂CH₂S) with bidentate phosphine complexes dppx (dppm = PPh₂CH₂PPh₂, dppe = PPh₂(CH₂)₂PPh₂, dppt = PPh₂(CH₂)₄PPh₂), three mono-substituted diphosphine complexes [Fe₂(CO)₅(μ-pdt)(k¹-dppm)] (2), ([Fe₂(CO)₅(μ-pdt)(k¹-dppe)] (3) and [Fe₂(CO)₅(μ-pdt) (k¹-dppt)] (4) were synthesized by keeping the controlling potential at -1.75 V. Di-substituted phosphine complexes [Fe₂(CO)₄(μ-pdt)(k²-dppe)] (5), [Fe₂(CO)₄(μ-pdt)(μ-dppm)] (6), [Fe₂(CO)₄(μ-pdt)(μ-dppm)] (7), [Fe₂(CO)₄(μ-pdt) (μ-dppt)] (8) were synthesized by holding the potential at -1.85 V. The mono-substituted diphosphine complexes 3 and 4 were characterized by elemental, NMR and IR analysis. We also discuss the catalytic mechanisms of the synthetic process.