A comparative study on the reaction mechanisms of Cp2MH2 (M = Cr, Mo, W) with HBF4

The reaction mechanisms of group 6 transition metal dihydride complexes, Cp2MH2 (M = Cr, Mo, and W), and HBF4 were studied using M06-L density functional theory. The chemical bond changes along the reaction pathway are analyzed by the topological analysis of electron density. The calculated results show that the interactions between the H atom of HBF4 and Cp2MH2 are stronger than those between Cp2MH2 and BF3; additionally, due to the low energy barriers in the subsequent reaction, all the title reactions can occur easily, and the yield rates of the Cp2MH2 + HBF4 reactions are high. For M = Cr and Mo, the [Cp2MH3](+) in the product Cp2MH3 center dot BF4 is in the nonclassic dihydrogen-hydride form ([Cp2M(eta(2)-H-2)H](+)). [Cp2CrH3](+) and [Cp2MoH3](+)are unstable, and H-2 can be easily liberated from them. For M = W, the final product is Cp2WH3 center dot BF4, and [Cp2WH3](+) is stable in the classic trihydride form.