Theoretical studies on the structure and aromaticity of Ti2P6+

Cationic cluster Ti 2 P 6 + has been studied within density functional theory. The structure of this cluster is predicted to be a slightly distorted tetragonal prism. The dissociation energy of this cationic cluster is higher than that of the known sandwich compound, [(P 5 ) 2 Ti] 2 - , because of the different bonding in these two compounds. In Ti 2 P 6 + , the hybridization of P atoms of the ring is sp 3 . The bonding between the metal atoms and the P ring is mainly σ-π. While in [(P 5 ) 2 Ti] 2 - , the P atoms take sp 2 hybridization, the bonding between the metal atom and the rings is the typical π-π interaction. The electronic delocalization is another stabilizing factor for Ti 2 P 6 + . The nuclear independent chemical shift indicates that Ti 2 P 6 + is a three-dimensional aromatic molecule. The predicted infrared and NMR help to identify the Ti 2 P 6 + conformations in experiment.