Synthesis and characterization of complexes containing Ti–O–Si moieties. Catalytic activity in olefinepoxidation

Abstract

Reaction of [Cp*TiMe₃] with O(SiPh₂OH)₂ yields the titanium siloxide derivative [Cp*TiMe{(OSiPh₂)₂O}] (1). Complex 1 reacts with H₂O to yield the corresponding oxo-titanium derivative [(Cp*Ti{(OSiPh₂)₂O})₂(µ-O)] (2). The molecular structure of complex 2 has been established by X-ray diffraction. Complex 1 reacts with triphenylsilanol to give the asymmetric titanium siloxide [Cp*Ti(OSiPh₃){(OSiPh₂)₂O}] (3). Treatment of the dinuclear titanium compound [(Cp*TiCl₂)₂(µ-O)] with an equimolar amount of O(SiPh₂OH)₂ yields complex [(Cp*TiCl)₂{µ-(OSiPh₂)₂O}(µ-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(µ-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.