Theoretical investigation of the electronic structures of the mixed-ring sandwich molecules [M(η7-C7H7)(η5-C5H5)](M = Ti, V, Nb or Ta)

Abstract

Density-functional methods have been used to investigate the valence electronic structures of four mixed-ring transition-metal sandwich molecules, [M(η⁷-C₇H₇)(η⁵-C₅H₅)](M = Ti, V, Nb or Ta). Close agreement with previous experimental data is obtained in all cases for the ionisation energies and localisation properties of the highest occupied molecular orbitals. The metal-cyclopentadienyl ring bonding is predominantly ionic, while the interaction of the metal with the cycloheptatrienyl ring is found to have a significant covalent component. Analysis of the composition of the highest occupied molecular orbital corresponding to the metal–cycloheptatrienyl ring bonding of [Ti(η⁷-C₇H₇)(η⁵-C₅H₅)], for which experimental data are not available, suggests that it is not appreciably different from that in the Group 5 molecules.