RING-OPENING POLYMERIZATION OF STRAINED CYCLOTETRASILANES AS A NEW ROUTE TOWARDS WELL-DEFINED POLYSILYLENES

Ring-opening polymerization of cyclic silanes is described as a new synthetic route to well defined high molecular weight polysilylenes (polysilanes). Strained cyclotetrasilanes with phenyl and methyl substituents at each Si atom in the four-membered ring are prepared by partial dephenylation of octaphenylcyclotetrasilane with triflic acid and the subsequent treatment with methylmagnesium bromide. Chemoselectivity, regioselectivity and stereoselectivity of monomer synthesis is discussed in detail. In addition to classic anionic initiators for the ring-opening process, new catalysts and initiators based on transition metals (Cu, Pd, Pt) are described. They provide much better control of the microstructure than systems with Li+ counterion.