Highly Selective Olefin Trimerization Catalysis by a Borane-Activated Titanium Trimethyl Complex

Reaction of a trimethyl titanium complex, (FI)TiMe3 (FI = phenoxy-imine), with 1 equiv of B(C6F5)(3) gives [(FI)TiMe2][MeB(C6F5)(3)], an effective precatalyst for the selective trimerization of ethylene. Mechanistic studies indicate that catalyst initiation involves generation of an active Ti-II species by olefin insertion into a Ti-Me bond, followed by beta-H elimination and reductive elimination of methane, and that initiation is slow relative to trimerization. (FI)TiMe3/B(C6F5)(3) also leads to a competent catalyst for the oligomerization of alpha-olefins, displaying high selectivity for trimers (>95%), approximately 85% of which are one regioisomer. This catalyst system thus shows promise for selectively converting light a-olefins into transportation fuels and lubricants.