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 sy nthetic route to well defined high molecular weight polysilylenes (pol ysilanes). Strained cyclotetrasilanes with phenyl and methyl substitue nts 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, r egioselectivity and stereoselectivity of monomer synthesis is discusse d in detail. In addition to classic anionic initiators for the ring-op ening process, new catalysts and initiators based on transition metals (Cu, Pd, Pt) are described. They provide much better control of the m icrostructure than systems with Li+ counterion.