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 th e bonding of the C-3(+) unit to the metal fragments in this complex. A n analysis of the MOs and of the Mulliken populations has been perform ed in order to understand the extent of the relative sigma and pi inte ractions between the C-3(+) and the Fe(CO)(2)Cp fragments. The results show that the iron-cyclopropenyl bond is mainly of sigma character wi th a smaller, but important, pi contribution. DFT calculations were al so performed on the hypothetical mononuclear [Fe(CO)(2)Cp(C3H2)](+) co mplex to study the relative stabilities of the possible orientations o f the Fe(CO)(2)Cp fragments with respect to the C-3(+) ring and to stu dy its rotation about the Fe-C bond.