Abstract A Ti III Si active species, Cp 2 TiSiMe 2 Ph, is formed either by the reaction of Cp 2 TiCl 2 with two equivalents of PhMe 2 SiLi or by the reaction of Cp 2 TiCl with one equivalent of PhMe 2 SiLi. Highly regio-and stereo-selective silyltitanation by this species has been observed with acetylenes and 1, 3-dienes.
