The use of Pearlman's catalyst for the oxidation of Si-H bonds. Synthesis, structures and acid-catalysed condensation of novel α, ω-oligosiloxanediols HOSiMe2O(SiPh2O) nSiMe2OH (n = 1-4)

The preparation of α, ω-oligosiloxanediols HOSiMe 2 O(SiPh 2 O) n SiMe 2 OH(5-8; n=1-4) by the mild oxidation of the corresponding organo-H-siloxane HSiMe 2 O(SiPh 2 O) n SiMe 2 H(1-4; n = 1-4) using Pearlman's catalyst, Pd(OH 2 )/C, is reported. Compounds 5-7 possess new hydrogen bonding modes, whose influences on the Si-O chain conformation are discussed and compared with the published analogues HOSiPh 2 OSiPh 2 OSiPh 2 OH (9), HOSit-Bu 2 OSiMe 2 OSit-Bu 2 OH (10) and HOSiPh 2 OSiPh 2 OSiPh 2 OSiPh 2 OH(11), whereas compound 8 appears to be polycrystalline. Preliminary results of the HCl-catalysed condensation of 5-8 are also reported, which provided complex mixtures ofoligomeric products in the case of 5 and 8, and (almost) exclusively cyclo-(Me 2 SiO) 2 (Ph 2 SiO) 2 (12) and cyclo-(Me 2 SiO) 2 (Ph 2 SiO) 3 (13) in the case of 6 and 7, respectively. Compounds 5-7 and 13 were investigated by X-ray crystallography. © Kluwer Academic Publishers 2003.