Syntheses of transition metal methoxysiloxides
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.