Theoretical study on the reaction mechanisms of ethylene with Cp2TiR, Cp2Ti(Cl)R, and Cp2Ti(Cl:AlH2Cl)R (R=H and CH3)

The potential energy surfaces for reactions of ethylene with Cp₂Ti⁺R, Cp₂Ti(Cl)R, and Cp₂Ti(Cl:AlH₂Cl)R (R=H and CH₃) were calculated by ab initio molecular orbital methods. These six reaction mechanisms were compared. Of the two possible reaction paths, attack of ethylene at Ti and the Cl and R ligands (path IN) and that from the opposite side of the Cl ligand (path OUT), the former is found to be more favorable, with a very low activation energy for reaction of ethylene with Cp₂Ti(Cl)H. For reaction of ethylene with Cp₂Ti(Cl)CH₃, the insertion transition states on both paths have almost the same energy barrier height above the reactants. For reaction of ethylene with Cp₂Ti(Cl:AlH₂Cl)R, the bond alternation between Ti–Cl and Cl–Al plays an important role in the mechanisms.