Electronic structure of [M(η-P3C2Bu2t)(CO)3] (M = Mn or Re):: a study by photoelectron spectroscopy and density functional calculations

The compounds [M(eta (5)-P3C2Bu2t)(CO)(3)] (M = Mn 1 or Re 2) are reported and their He I and He II photoelectron spectra assigned. Their electronic structure has been investigated by means of density functional calculations and reasonable agreement between experimental and calculated ionisation energies is achieved. The bonding between the metal and the ring is predominantly donation from the ring to the metal. Back donation into the highest pi orbitals of the ring is minimal. The calculations suggest substantial mixing between the ring sigma and pi orbitals on coordination to the metal. Calculations on [Mn(eta (5)-P3C2Bu2t)(2)] reproduce the unusual (2)A ground state and show that this results from stabilisation of the metal e(2) type orbitals by formation of a delta bond with the unoccupied pi orbitals of the rings.