ansa-Metallocenes Bearing 4-(N-Azolyl)-2-methylindenyl and Related Ligands: Development of Highly Isoselective Catalysts for Propene Polymerization at Higher Temperatures

Abstract

A series of Me2Si-bridged bis(2-Me-indenyl) ansa-zirconocenes containing N-pyrrolyl, N-indolyl, N-carbazolyl, and P-dibenzophospholyl substituents in position 4 of the indenyl moieties has been synthesized. Pd-catalyzed arylation of the azoles with 4-Br-2-Me-indene was used to synthesize the respective 4-(N-azolyl)indenes. 4-(P-Dibenzophospholyl)indene was obtained in high yield by reaction of 5-Cl-dibenzophosphole with (2-Me-inden-4-yl)MgBr. Some of the synthesized zirconocenes were characterized by X-ray crystallography. The rac-zirconocenes were tested in propylene polymerization in the presence of MAO or perfluoroarylborate activators. At 100 °C, the zirconocene rac-Me2Si[2-Me-4-(N-carbazolyl)indenyl]2ZrCl2/MAO afforded highly crystalline isotactic polypropylene with reasonable molecular weight (318 kDa) and a Tm value of 157 °C determined by a remarkably low total number of stereo- and regioerrors, which makes it one of the most isoselective catalysts for high-temperature propylene polymerization.