Complexes of transition metals with Lewis bases as precursors of olefin polymerization catalysts.
Part I. Advance in computer-assisted modeling of polymerization catalyst structure
Polimery 2001, No 5, 368
SummaryA review with 35 references covering molecular modeling in coordination polymerization over homogeneous and heterogeneous Ziegler-Natta catalysts. The study includes supports, cocatalysts, Lewis bases and solvents. Recent progress in elucidating the mechanisrn of elementary polymerization steps is presented against the background of rapidly deveIoping computational methods and available computational power. Theoretical studies on polymerization mcchanisms and structure of active centers are described (egns. 1-4). Authors own calculations are used to compare [MtC14(THF)2] complex-based (Mt = Ti, Hf or Zr) heterogeneous catalysts. The geometrical characteristics of precursors is presented (Table 1), structure of active centers is suggested (egn. 5), charge variations on transitlon metal atoms are analyzed (Table 2), and polymerization enthalpics are evaluated (Table 3). These data are used to infer about activity differences between the catalysts investigated. Tiraniurn is shown to yield the most active catalysts.