Synthesis of C1 symmetrical ansa-cyclopentadienylamidotitanium complexes and their application for living polymerization of propylene

•Synthesis and characterization of C1 symmetrical cyclopentadienylamidotitanium complexes.•Living polymerization of propylene with fast propagation rate.•Mechanistic study for stereospecific propagation of propylene.

Optically active C1 symmetrical [(R)-NCHMe(Naphthyl)SiMe2Flu]TiMe2 (1) and [(R)-NCHMe(Naphthyl)SiMe2(C5Me4)]TiMe2 (2) were synthesized and characterized by elemental analysis, 1H NMR and single crystal X-ray analysis. These complexes were applied for propylene polymerization using dried modified methyaluminoxane (dMMAO) as a cocatalyst at 0 °C in toluene, heptane and chlorobenzene, respectively. All the systems showed steady polymerization rate and gave high molecular weight polypropylene with narrow molecular weight distribution, and the toluene system showed higher activity than the heptane system. The postpolymerization testified that each catalytic system conducted the propylene polymerization in a living manner. The 2-chlorobenzene system showed fastest propagation rate of 437 mol min−1. The polymers produced with the 1-heptane and -toluene systems or 2-heptane system were statistically atactic, while the polymers produced with the 2-toluene system were isotactic-rich PP with isotactic triad (mm) of 0.61.

Graphical abstractOptically active C1 symmetical [(R)-NCHMe(naphthyl)SiMe2Flu]TiMe2 (1) and [(R)-NCHMe(naphthyl)SiMe2(C5Me4)]TiMe2 (2) were synthesized and characterized by elemental analysis, 1H NMR and single crystal X-ray analysis. These complexes are useful for the fast living polymerization of propylene. The 1-heptane, 1-toluene, and 2-heptane systems gave statistically atactic polypropylene, while the 2-toluene system gave isotactic-rich polypropylene with mm value of 0.61.Figure optionsDownload full-size imageDownload as PowerPoint slide