Well-defined transition metal complexes with phosphorus and nitrogen ligands for 1,3-dienes polymerization

This article provides an overview on recent progress in the polymerization of 1,3-dienes catalyzed by transition metal complexes with phosphorus and nitrogen ligands. Polymers having different microstructures (cis-1,4; 1,2; mixed cis-1,4/1,2) and tacticity (iso- or syndiotactic) were obtained from various 1,3-dienes (1,3-butadiene, isoprene, 1,3-pentadienes, 1,3-hexadienes) depending on the catalyst used, clearly suggesting that the catalyst structure (i.e. metal nature, type of ligand) strongly affects the polymerization chemo- and stereoselectivity. However, as indicated by the results obtained in the polymerization of substituted butadienes, a fundamental role in determining the selectivity is also played by the type of monomer: polymers with different structure, some of them completely new, were obtained from different monomers with the same catalyst. All these observations permitted to confirm, and in some cases to improve, the knowledge on the diene polymerization mechanism.