Geometric and Electronic Structures of VB40/+ Clusters and Reactivity of the Cationic Cluster with Methane from Quantum Chemical Calculations.

Quantum chemical methods have been employed to study the geometric and electronic structures of VB40/+ clusters and the mechanism of the reaction of the cationic clusters with methane. It was found that the ground states of the neutral and cationic clusters were 4A' and 3A' of a planar isomer in Cs symmetry in which vanadium atom side-on binds to the rhombic B4 moiety. The ionization energy of the neutral cluster was calculated to be 7.13 eV at the CCSD(T) level. The reaction pathways on the triplet and quintet potential energy profiles of the dehydrogenation and elimination of V+ in the reaction of VB4+ cluster with methane were established based on the BPW91 functional calculations. Both of the dehydrogenation and elimination of V+ in the reaction of VB4+ cluster with methane were initiated by the B4 moiety of the VB4+ cluster, and these two reaction channels were thermodynamically and kinetically favorable. The dehydrogenation and elimination of V+ in the reaction of VB4+ cluster with methane were exothermic processes.