DFT Study on the Copolymerization Mechanism of Ethylene with Cyclopentadiene by the Titanium Complexes Bearing Two β-Enaminoketonato Ligands

We employed DFT calculations for copolymerization mechanism of ethylene (E) with cyclopentadiene (CPD) catalyzed by [PhNC(CH3)CHC(CF3)O](2)TiCl2. Our calculations show that the CPD can incorporate into polymer chain via both 1,2 and 2,1-insertion, and it is predicted that 1,2-insertion might be a preferred pathway due to the lower barrier. And in the copolymerization process, reaction barriers of ethylene insertion into both Metal-E and Metal-CPD bonds are lower than the barriers of CPD insertion, consequently, there might be more E sequences in the growing polymer chain. The CPD insertion into Metal-E bond can occur a certain extent due to the relative low insertion barrier, while for the process of CPD insertion into Metal-CPD chain, its insertion barrier is too high to make this reaction occur. The present conclusion is in line with the experimental fact that no consecutive sequence of CPD has been observed in the polymer product.