fac-[Fe(II)(CN)(3)(CO)(3)](-) and cis-[Fe(II)(CN)(4)(CO)(2)](2)(-): new members of the class of [Fe(II)(CN)(x)(CO)(y)] compounds.

The reaction of Fe(CO)(4)I(2) with NaCN or KCN in methanol gives M[Fe(II)(CN)(3)(CO)(3)] (M = Na, K), which can be converted to [Ph(4)E][Fe(II)(CN)(3)(CO)(3)] (E = P, As). The structure of the fac-[Fe(II)(CN)(3)(CO)(3)](-) (1) anion was established by the X-ray crystal structures of K-1 and [Ph(4)As]-1.H(2)O. Compound 1 has also been characterized by IR, Raman, and (13)C 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 Na(2) cis-[Fe(II)(CN)(4)(CO)(2)] (Na-2), which has been structurally characterized as [Ph(4)P][Et(4)N]-2. Compounds 1 and 2 are additional members of the series of compounds of general formula [Fe(II)(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.