Cerium mediated siloxane formation

The formation of the Si-O-Si linkage is a fundamental step in the manufacturing of silicones. Silanol functionalities are generally involved in the build up of such units which may proceed either by homo- (≡Si-OH + ≡Si-OH → ≡Si-O-Si ≡ + H2O) or hetero-functional condensation (≡Si-OH + ≡Si-X → ≡Si-O-Si ≡ + HX (X = halide, alkoxide, etc.)). Usually these competing processes as well as hydrolytic steps to generate the silanol functions in situ occur simultaneously.1 We were interested to investigate the possibility to induce homofunctional condensation of silanetriols with lanthanide cations. We employed the easily accessible (CH3)3CSi(OH)32,3, 1, as the starting monomer. Usually, this compound undergoes condensation reactions only in the presence of a strong base or acid to give the tetrahydroxydisiloxane, [(CH3)3CSi(OH)2]2O, 2.4,