Theoretical study of M+-CO2 and OM+CO systems for first transition row metal atoms

The coordination of carbon dioxide to first transition row metal cations and the insertion reaction of the metal into one CO bond of carbon dioxide have been studied theoretically. The geometry and the vibrational frequencies of the M+-CO2 and OM+CO structures have been determined using the hybrid three-parameter B3LYP density functional approach. Binding energies have also been determined at the CCSD(T) level using large basis sets. The linear end-on M+-OCO structure is the most favorable coordination for CO2, due to the electrostatic nature of the bonding, in the inserted OM+CO structures, the bonding arises from the electrostatic interaction between the ground state of OM+ and CO. For the early transition metals (Sc+, Ti+, and V+), the insertion reaction is exothermic and the inserted OM+CO structure is more stable than the Linear M+-OCO isomer, because of the very strong MO+ bond that is formed.