Non-bridged amido cyclopentadienyl complexes of titanium: synthesis, characterization, and olefin polymerization catalysis

Alkylation of Ti(η5-C5Me5)(NMe2)Cl2 gives thermally stable, crystalline dialkyl complexes Ti(η5-C5Me5)(NMe2)R2 (R=Me, CH2Ph, Ph). The molecular structure of the dibenzyl complex reveals an unprecedented conformation of the doubly bonded NMe2 group which is turned parallel to the η5-C5Me5 ligand, according to single-crystal X-ray diffraction studies. Treatment of the dibenzyl complex with B(C6F5)3 in d5-bromobenzene solution results in the quantitative formation of a thermally (>10°C) unstable monobenzyl cation as solvent-separated ion pair [Ti(η5-C5Me5)(NMe2)CH2Ph]+ [PhCH2B(C6F5)3]− which efficiently polymerizes styrene syndiospecifically at 25°C. Ethylene is polymerized by Ti(η5-C5Me5)(NMe2)Cl2methylalumoxane with low activity.