Thiolate-Bridged Nickel–Iron and Nickel–Ruthenium Complexes Relevant to the CO-Inhibited State of [NiFe]-Hydrogenase

Abstract

By employing S(CH 2 CH 2 S – ) 2 (tpdt) and O(CH 2 CH 2 S – ) 2 (opdt) as bridging ligands, two nickel–iron and two nickel–ruthenium heterodimetallic complexes, [Cp*M(μ-1κ 3 SSS ′:2κ 2 SS -tpdt)Ni(dppe)][PF 6 ] ( 1, M = Fe; 3, M = Ru) and [Cp*M(μ-1κ 3 SSO:2κ 2 SS -opdt)Ni(dppe)][PF 6 ] ( 2, M = Fe; 4, M = Ru) (Cp* = η 5 -C 5 Me 5; dppe = Ph 2 P(CH 2 ) 2 PPh 2 ), were obtained by a one-pot synthetic method and were identified by spectroscopy and X-ray crystallography. At 1 atm of CO, the pendant oxygen atom dissociated from the iron or ruthenium center and rapidly transferred to the nickel center when a CO molecule attacked the iron or ruthenium center in 2 and 4 . However, there was no similar reaction occurring in 1 and 3 with the pendant sulfur atom. We confirmed the solid-state structure of the CO complex [Cp*Fe( t -CO)(μ-1κ 2 SS:2κ 3 SSO -opdt)Ni(dppe)][PF 6 ] ( 5 ), which represents a possible configuration in the CO-inhibited state of [NiFe]-hydrogenase and exhibits no catalytic activity in electrochemical proton reduction.