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.