The Generalized Valence Bond Description of Titanium Carbonyl

Ab initio calculations using the generalized valence bond (GVB) method are reported for a number of electronic states of TiCO⁺ and TiCO. The nature of the bonding in these compounds is discussed in terms of the GVB orbitals, and the implications for the bonding in other carbonyls are discussed. These results indicate that the TiC bond can be accurately described as a CO nonbonding pair that is slightly shifted onto (donated to) the Ti. In return, the Ti(3dπ) orbitals shift back somewhat onto the CO (into the π* orbital); one might refer to this as π back bonding.