Abstract
Di- and trisilylethenes have been prepared by catalytic hydrosilylation of trimethylsilyl-, bis-(trimethylsilyl)- and bis(trichlorosilyl)ethyne and converted into the hydrogenated derivatives by LiAlH4-reduction. The stereochemistry of the products and the effects of substitution of methyl vs. chlorine ligands on the NMR coupling constants J(29Si/1H) have been investigated by analysis of selectively (Me)-decoupled 29Si NMR spectra. From the results it has been concluded, that the catalytic hydrosilylation of silylated ethynes proceeds in a stereospecific syn fashion yielding trans adducts. Substitution of methyl by chlorine at one or two Si-atoms in tris(trimethylsilyl)ethene leads to an increase of the coupling constant J(29Si/1H vinyl) with the chlorinated Si-atoms and reduces the values for those Si-atoms, where the methyl groups are retained.

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