The chemistry of htdridocarbonylferrates revisited: syntheses and structures of the new [H2Fe4(CO)12]2– and [HFe5(CO)14]3– amions, and the [Fe(DMF)4][Fe4(CO)12(6-2-CO)(-H)]2 adduct containing an unprecedented isocarbonyl

The di-hydride di-anion [H2Fe4(CO)(12)](2-) has been quantitatively obtained by protonation of the previously reported mono-hydride tri-anion [HFe4(CO)(12)](3-) in DMSO and structurally characterised in its [NEt4](2)[H2Fe4(CO)(12)] salt. It shows some subtle but yet significant differences in the stereochemistry of the ligands in comparison to the heavier Ru-4 and Os-4 congeners. The study of the reactivity of these [H4-nFe4(CO)(12)](n-) (n = 2,3) species allowed the serendipitous isolation and structural characterization of the new pentanuclear [HFe5(CO)(14)](3-) mono-hydride tri-anion. Attempts to obtain the latter in better yields led to the discovery of intermolecular CO/H- mutual exchange reactions and isolation and structural characterization of the [Fe(DMF)(4)][Fe-4(CO)(12)(mu(5)-eta(2)-CO)(mu-H)](2)center dot 0.5CH(2)Cl(2) and [M+][Fe-4(CO)(12)(mu(4)-eta(2)-CO)(mu-H)](-) (M = K, Cs) adducts, the former containing an unprecedented isocarbonyl group. The isolation of new tetranuclear and, above all, pentanuclear hydridocarbonylferrates indicates that it is possible to further expand the chemistry of homoleptic Fe carbonyl species