Protonation Studies of the New Iron Carbonyl Cyanide trans-[Fe(CO)3(CN)2]2-: Implications with Respect to Hydrogenases

The new iron carbonyl cyanide trans-[Fe(CN)2(CO)3]^2-, [2]^2-, forms in high yield via photosubstitution of Fe(CO)5 with 2 equiv of Et4NCN. Protonation of [2]^2- generated [HFe(CN)2(CO)3]^-, [2H]^-, the first H-Fe-CN-CO species. Further protonation gives dihydrogen. This simple system provides insights into hydrogen evolution by the hydrogenase enzymes, which also feature H-Fe-CN-CO centers.