The syntheses and chemical properties of some 54 compounds are described, all having structural units including rSiCCCN= with either methyl, phenyl, siloxg, alkoxy, or amino groups on silicon and H, alkyl, or phenyl groups on nitrogen. Thirteen of the compounds are novel substituted heterocyclic I-aza-2-silacyclopentanes and one is a 1-aza-2- silacyclohexane.