GROUP-4 METAL AMIDO FLUORIDES AND CHLORIDES - MOLECULAR-STRUCTURES AND THE FIRST COMPARISON IN ETHYLENE POLYMERIZATION CATALYSIS

Lithium (2,6-diisopropylphenyl)(trimethylsilyl)amide (2,6-iPr(2)C(6)H( 3)N(SiMe(3))Li) reacts with MCl(4) (M = Zr, Hf) in a 2:1 molar ratio t o give [{2,6-iPr(2)C(6)H(3)N(SiMe(3))}(2)MCl(2)] (1a, M = Zr; 1b, M = Hf) and with (C(5)Me(5))MCl(3) (1:1) to give [(C(5)Me(5)){2,6-iPr(2)C( 6)H(3)N(SiMe(3))}MCl(2)] (2a, M = Zr; 2b, M = Hf). Further reaction of the dichlorides (1a,b,2a,b) with Me(3)SnF leads to the corresponding difluorides [{2,6-iPr(2)C(6)H(3)N(SiMe(3))}(2)MF(2)] (3a, M = Zr; 3b, M = Hf) and [(C(5)Me(5)){2,6-iPr(2)C(6)H(3)N(SiMe(3))}MF(2)] (4a, M = Zr; 4b, M = Hf). The compounds 1-4 were investigated as potential cata lysts for the polymerization of olefins, in combination with methylalu minoxane (MAO). For the first time the catalytic activities, toward th e polymerization of ethylene, of chlorides and the corresponding fluor ides are compared under identical conditions. The solid-state structur es of 1a,b,2b,3a, and 4a were determined by single-crystal X-ray diffr action.