Theoretical study of the [{Fe(CO)(2)Cp}(3)(mu(3)-C-3)](+) tricarbido cation

Density functional calculations have been carried out on a trinuclear [{Fe(CO)(2)Cp}(3)(mu(3)-C-3)](+) cation, and on related C3H3+ and C-3(NH2)(3)(+) molecules in order to study the electronic structure and the bonding of the C-3(+) unit to the metal fragments in this complex. An analysis of the MOs and of the Mulliken populations has been performed in order to understand the extent of the relative sigma and pi interactions between the C-3(+) and the Fe(CO)(2)Cp fragments. The results show that the iron-cyclopropenyl bond is mainly of sigma character with a smaller, but important, pi contribution. DFT calculations were also performed on the hypothetical mononuclear [Fe(CO)(2)Cp(C3H2)](+) complex to study the relative stabilities of the possible orientations of the Fe(CO)(2)Cp fragments with respect to the C-3(+) ring and to study its rotation about the Fe-C bond.