Preparative and Structural Studies on the Carbonyl Cyanides of Iron, Manganese, and Ruthenium: Fundamentals Relevant to the Hydrogenases

The reaction of cyanide, carbon monoxide, and ferrous derivatives led to the isolation of three products, trans- and
cis-[Fe(CN)4(CO)2]2- and [Fe(CN)5(CO)]3-, the first two of which were characterized by single-crystal X-ray diffraction.
The new compounds show self-consistent IR, 13C NMR, and mass spectroscopic properties. The reaction of trans-[Fe(CN)4(CO)2]2- with Et4NCN gives [Fe(CN)5(CO)]3- via a first-order (dissociative) pathway. The corresponding
cyanation of cis-[Fe(CN)4(CO)2]2-, which is a minor product of the Fe(II)/CN-/CO reaction, does not proceed at
measurable rates. Methylation of [Fe(CN)5(CO)]3- gave exclusively cis-[Fe(CN)4(CNMe)(CO)]2-, demonstrating the
enhanced nucleophilicity of CN- trans to CN- vs CN- trans to CO. Methylation has an electronic effect similar to
that of protonation as determined electrochemically. We also characterized [M(CN)3(CO)3]n- for Ru (n = 1) and
Mn (n = 2) derivatives. The Ru complex, which is new, was prepared by cyanation of a [RuCl2(CO)3]2 solution.