Metallacyclodisiladiazanes of titanium and zirconium; Synthesis, structure and polymerization studies

A series of metallacyclodisiladiazanes has been prepared. Lithiated (SiMe(2)NHtBu)(2) (1) reacts with TiCI4 . 2 THF to give (SiMe(2)NtBu)(2)TiCl2 (4). Methylation or fluorination of 4 leads to (SiMe(2)NtBu)(2)TiMe(2) (8) and (SiMe(2)NtBu)(2)TiF2 (9), respectively. The reaction of ZrCl4 . 2 THF with lithiated 1 or [SiMe(2)NH(4-FC6H4)](2) (2) yields (SiMe(2)NtBu)(2)ZrCl2 (5) and [SiMe(2)N(4-FC6H4)]2ZrCl2 . THF (7), respectively. The lithiated ligand [SiMe(2)NH(2,6-iPr(2)C(6)H(3))](2) (3) reacts with noncoordinated ZrCl4 to give [SiMe(2)N(2,6-iPr(2)C(6)H(3))]2ZrCl2 (6). X-ray structural analysis of 9 showed it to be a fluorine-bridged dimer in the solid state. Compounds 4, 6, 8 and 9 were found to be catalysts for the polymerization of ethylene.