Olefin Polymerization by Early Transition Metal Catalysts

Abstract

In this contribution we report about the computer modeling of the elementary steps of the propagation reaction for the polymerization of olefins with homogeneous catalysts based on early transition metals. Particular attention will be devoted to biscyclopentadienyl and monocyclopentadienylamido-based catalysts. Beside the coverage of literature data, the performances of various pure and hybrid density functional theory (DFT) approaches, and of classical ab initio Hartree-Fock (HF) and Møller-Plesset perturbative theory up to the second order (MP2) will be discussed through a systematic study of ethene insertion into the Zr-CH3 $σ$-bond of the H2Si(Cp)2ZrCH3+ system. A comparison with singly and doubly excited coupled clusters single point calculations with a perturbative inclusion of triple excitations [CCSD(T)] will be also presented. The effects of the basis set on the insertion barrier will be discussed with a series of single point MP2 calculations. In the final sections we report about the origin of the regio- and stereoselectivity in the propene insertion with biscyclopentadienyl-based catalysts.