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 TiII species by olefin
insertion into a Ti–Me bond, followed by β-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 α-olefins, displaying high selectivity for trimers (>95%),
approximately 85% of which are one regioisomer. This catalyst system
thus shows promise for selectively converting light α-olefins
into transportation fuels and lubricants.