Pressure Modulates Stereoregularities in the Polymerization of Propylene Promoted by rac -Octahedral Heteroallylic Complexes

This communication reports the synthesis and activity of four racemic mixtures of bis(benzamidinate) group-4 complexes, cis -[ p -R‘C 6 H 4 C(NR) 2 ] 2 MX 2 (R‘ = CH 3, R = SiMe 3, M = Ti, X = Cl ( 1 ); R‘ = CH 3, R = SiMe 3, M = Zr, X = Cl ( 2 ); R‘ = H, R = i -pr, M = Zr, X = Cl ( 3 ); R‘ = CH 3, R = SiMe 3, M = Zr, X = CH 3 ( 4 )) as precatalysts for the stereoregular polymerization of propylene. These complexes catalyze the stereoregular polymerization of propylene only under pressure in CH 2 Cl 2, producing polypropylene with very large isotacticities (mmmm % = ∼95−98), high melting points (140−154 °C).