Bromination and iodination of hydrosilanes and germanes were studied. Treatment of hydrosilanes with an excess of ethyl, propyl, or allyl bromide in the presence of a catalytic amount of PdCl2 or NiCl2 gave bromosilanes in good to high yield by hydrogen–halogen exchange. By using methyl, propyl, or allyl iodide as the iodine source, similar iodination of hydrosilanes was readily performed. Halogenation
Siloxane bond formation by heterofunctional condensation of alkoxysilane and halogenosilane. Application to the preparation of copoly(tetramethyl-p-silphenylenesiloxane-dimethylsiloxane)
Siloxane linkages are formed non-hydrolytically by the reaction of dihalogenosilanes with either dibenzylether, or dibenzyloxysilanes and dibenzhydryloxysilanes. The heterocondensation reaction is activated in the presence of NaI (in acetonitrile) or fluoride anions. This offers an alternative copolymerization route to the usual dehydrocondensation of SiOH-terminated species. Thus, the title copolymer was prepared by reaction of equimolar amounts of Me(2)Si(OCHPh(2))(2) and 1,4-bis(chlorodimelhylsilyl)benzene at 100 degrees C. The Si-29 NMR spectrum supports a quasi-random sequence in the copolymer. Thermal stability is similar to that reported for an alternating microstructure, as inferred from thermogravimetric analysis.