Syntheses of transition metal methoxysiloxides

Abstract

The paper describes three methods for the preparation of methoxysiloxide complexes, a rare class of complexes of relevance to room temperature vulcanization (RTV) of polysiloxanes. The salt metathesis reaction involves the use of the recently described reagent NaOSi(OMe)₂Me with various metal chlorides to give Cp*₂Ti[OSi(OMe)₂Me](OMe), (^Me,MeN₂N)NiOSi(OMe)₂Me, (IPr)CuOSi(OMe)₂Me, and (triphos)CoOSi(OMe)₂Me (Cp* = C₅Me₅, triphos = Me(CH₂PPh₂)₃). Several attempted reactions gave methoxide complexes instead, a pathway that is attributed to the intermediacy of κ²-OSi(OMe)₂Me species. The diol Cp*₂Zr(OH)₂ reacts with excess (MeO)₃SiMe to give Cp*₂Zr[OSi(OMe)₂Me]₂. In contrast the less nucleophilic Cp*₂Ti(OH)₂ was unreactive. The third route to methoxysiloxide complexes involves the reaction of Cp*₂M(O)(py) with (MeO)₃SiMe to give Cp*₂M[OSi(OMe)₂Me](OMe) in nearly quantitative yield (M = Ti, Zr). The structures of Cp*₂Ti[OSi(OMe)₂Me](OMe), Cp*₂Zr[OSi(OMe)₂Me](OMe), (IPr)CuOSi(OMe)₂Me, and (triphos)CoOSi(OMe)₂Me were confirmed by single crystal X-ray diffraction.