fac-[FeII(CN)3(CO)3]- and cis-[FeII(CN)4(CO)2]2-:: New members of the class of [FeII(CN)x(CO)y] compounds

The reaction of Fe(CO)4I2 with NaCN or KCN in methanol gives M[Fe11(CN)3(CO)3] (M = Na, K), which can be converted to [Ph4E][Fe11(CN)3(CO)3] (E = P, As). The structure of the fac-[Fe11(CN)3(CO)3]- (1) anion was established by the X-ray crystal structures of K-1 and [Ph4As]-1·H2O. Compound 1 has also been characterized by IR, Raman, and 13C NMR. The coupling of the CO and CN stretching modes in the vibrational spectra of 1 have been analyzed. The reaction of Na-1 with NaCN gives Na2 cis-[Fe11(CN)4(CO)2] (Na-2), which has been structurally characterized as [Ph4P][Et4N]-2. Compounds 1 and 2 are additional members of the series of compounds of general formula [Fe11(CN)(6-x)(CO)x](x-4). [Fe(CN)x(CO)y] compounds are of interest due to the occurrence of such coordination modes in hydrogenase enzymes.