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-iPr2C6H3N(SiMe3)Li) reacts with MCl4 (M ) Zr, Hf) in a 2:1 molar ratio to give [{2,6-iPr2C6H3N(SiMe3)}2MCl2] (1a, M ) Zr; 1b, M ) Hf) and with (C5Me5)MCl3 (1:1) to give [(C5Me5){2,6-iPr2C6H3N(SiMe3)}MCl2] (2a, M ) Zr; 2b, M ) Hf). Further reaction of the dichlorides (1a,b, 2a,b) with Me3SnF leads to the corresponding difluorides [{2,6-iPr2C6H3N(SiMe3)}2MF2] (3a, M ) Zr; 3b, M ) Hf) and [(C5Me5){2,6-iPr2C6H3N(SiMe3)}MF2] (4a, M ) Zr; 4b, M ) Hf). The compounds 1-4 were investigated as potential catalysts for the polymerization of olefins, in combination with methylaluminoxane (MAO). For the first time the catalytic activities, toward the poly merization of ethylene, of chlorides and the corresponding fluorides are compared under identical conditions. The solid-state structures of 1a,b, 2b, 3a, and 4a were determined by single-crystal X-ray diffraction.