Silicon-oxygen bonding on diphenylsilane through palladium(II)-catalysed reactions

The reactions of phenols with diphenylsilane are catalysed by palladium(II) catalysts such as Pd(TMEDA)Cl-2 (TMEDA = tetramethylethylenediamine), Pd(D EED)Cl-2 (DEED = N,N'-diethylethylenediamine), Pd(TEEDA)Cl-2 (TEEDA = N,N'- tetraethylethylenediamine) or PdCl2 to form hydrated silanols with molecula r formula Ph2Si(OR)OH . nH(2)O (when R = C6H5, if = 3; when R = p-CH3C6H4 O r o-CH3C6H4, n = 1), The reaction of hydroquinone with diphenylsilane in th e presence of catalytic amounts of Pd(TMEDA)Cl-2 forms an Si-O-bonded hydra ted aggregate of composition [(C6H5)(2)Si(O-C6H4O).0.5H(2)O]n. p-Benzoquino ne reacted with diphenylsilane in the presence of a catalytic amount of Pd( TMEDA)Cl-2 and the reaction proceeded via a multiple pathway involving quin hydrone as an intermediate charge-transfer complex which reacted further wi th diphenylsilane to give a linear siloxane. Copyright (C) 2000 John Wiley & Sons, Ltd.