First example of 'palladium-nanoparticle'-catalyzed selective alcoholysis of polyhydrosiloxane: a new approach to macromolecular grafting

'Palladium-polysiloxane' nanocomposites were synthesized as stable and isolable powder by reduction of Pd(OAc)(2) with polymethylhydrosiloxane, which functions as a reducing agent and as a capping agent for the generation and stabilization of 'palladium'-nanoclusters. Redispersion of 'palladium-polysiloxane' nanocomposite in common organic solvents, in the presence of polymethylhydrosiloxane, yielded catalytically active polysiloxane-wrapped soluble 'palladium'-nanoclusters. Polysiloxane-encapsulated 'palladium'-nanoclusters were used as recyclable catalyst for macromolecular grafting via alcoholysis of polyhydrosiloxane. Selective alcoholysis of polyhydrosiloxane took place in fair to excellent yields under moderate reaction conditions with a variety of alcohols (primary, secondary, tertiary/sterically bulky and functional alcohols). 'In situ' electron microscopy studies of the reaction mixtures in conjunction with controlled poisoning experiments revealed catalytic participation of 'palladium'-nanoclusters during substitution reactions. Copyright (c) 2005 John Wiley ' Sons, Ltd.