Synthesis and characterization of complexes containing Ti-O-Si moieties. : Catalytic activity in olefin epoxidation

Reaction of [Cp*TiMe3] with O(SiPh2OH)(2) yields the titanium siloxide derivative [Cp*TiMe-{(OSiPh2)(2)O}] (1). Complex 1 reacts with H,O to yield the corresponding oxo-titanium derivative [(Cp*Ti{(OSiPh2)(2)O})(2)(mu-O)] (2). The molecular structure of complex 2 has been established by X-ray diffraction. Complex I reacts with triphenylsilanol to give the asymmetric titanium siloxide [Cp*Ti(OSiPh3){(OSiPh2)(2)O}] (3). Treatment of the dinuclear titanium compound [(Cp*TiCl2)(2){mu-(OSiPh2)(2)O}(mu-O)] (4) in with an equimolar amount of O(SiPh2OH)(2) yields complex [(Cp*TiCl)(2){mu-(OSiPh2)(2)O}(mu-O)] (4) in which the disiloxide moiety is bridging two titanium atoms. The structure of 4 has been determined by X-ray diffraction. Reaction of [Cp*TiMe3] With HOSiPh3 yields the titanium triphenylsiloxide [Cp*TiMe2 (OSiPh3)] (5). Complex 5 reacts with water to yield [{Cp*TiMe(OSiPh3)}(2)(mu-O)] (6). The triflate compound [Cp*Ti(OSiPh3)(2)(OTf)] (7) can be prepared by reaction of 5 with HOTf and triphenylsilanol. We have tested the catalytic activity of some of the complexes in the epoxidation of cyclohexene.