The photoreaction of Fe(CO)(5) and cyanide salts in MeCN solution affords the dianion [Fe(CN)(2)(CO)(3)](2-), conveniently isolated as [K(18-crown-6)](2)[Fe(CN)(2)(CO)(3)]. Solutions of [Fe(CN)(2)(CO)(3)](2-) oxidize irreversibly at -600 mV (vs Ag/ AgCl) to give primarily [Fe(CN)(3)(CO)(3)](-) Protonation of the dianion affords the hydride [K(18-crown-6)][HFe(CN)(2)(CO)(3)] with a pK(a) approximate to 17 (MeCN). The ferrous hydride exhibits enhanced electrophilicity vs its dianionic precursor, which resists substitution. Treatment of [K(18-crown-6)][Fe(CN)(2)(CO)(3)] with tertiary phosphines and phosphites gives isomeric mixtures of [HFe(CN)(2)(CO)(2)L](-) (L = P(OPh)(3) and PPh3). Carbonyl substitution on [1H(CO)(2)](-) by P(OPh)(3) is first-order in both the phosphite and iron (k = 0.18 M-1 s(-1) at 22 degrees C) with Delta H-double dagger = 51.6 kJ mol(-1) and Delta S-double dagger = -83.0 J K-1 mol(-1). These ligands are displaced under an atmosphere of CO. With cis-Ph2PCH=CHPPh2 (dppv), we obtained the monocarbonyl, [HFe(CN)(2)(CO)(dppv)](-), a highly basic hydride (pK(a) > 23.3) that rearranges in solution to a single isomer. Treatment of [K(18-crown-6)][HFe(CN)(2)(CO)(3)] with Et4NCN resulted in rapid deprotonation to give [Fe(CN)(2)(CO)(3)](2-) and HCN. The tricyano hydride [HFe(CN)(3)(CO)(2)](2-) is prepared by the reaction of [HFe(CN)(2)(CO)(2)(PPh3)] and [K(18-crown-6)]CN. Similar to the phosphine and phosphite derivatives, [HFe(CN)(3)(CO)(2)](2-) exists as a mixture of all three possible isomers. Protonation of the hydrides [HFe(CN)(2)(CO)(dppv)](-) and [HFe(CN)(3)(CO)(2)](-) in acetonitrile solutions releases H-2 and gives the corresponding acetonitrile complexes [K(18-crown-6)][Fe(CN)(3)(NCMe)(CO)(2)] and Fe(CN)(2)(NCMe)(CO)(dppv). Alkylation of [K(18crown-6)](2)[Fe(CN)(2)(CO)(3)] with MeOTf gives the thermally unstable [MeFe(CN)(2)(CO)(3)](-), which was characterized spectroscopically at -40 degrees C. Reaction of dppv with (MeFe(CN)(2)(CO)(3)](-) gives the acetyl complex, [Fe(CN)(2)(COMe)(CO)(dppv)](-). Whereas [Fe(CN)(2)(CO)(3)](2-) undergoes protonation and methylation at Fe, acid chlorides give the iron(O) N-acylisocyan ides [Fe(CN)(CO)(3)(CNCOR)](-) (R = Ph, CH3). The solid state structures of [K(18-crown-6)][HFe(CN)(2)(CO)(dppv)], Fe(CN)(2)(NCMe)(CO)(dppv), and [K(18-crown-6)12[HFe(CN)(3)(CO)(2)] were confirmed crystallographically. In all three cases, the cyanide ligands are cis to the hydride or acetonitrile ligands.