tris(n-heptoxy) silane, vinyl-tris(n-octoxy) silane, vinyl-tris(n-dodecyloxy) silane, vinyl-bis(n-butoxy)methyl silane, vinyl-bis(n-pentoxy)methyl silane, vinyl-bis(n-hexoxy)methyl silane, vinyl-(n-butoxy)dimethyl silane, vinyl(n-pentoxy)dimethyl silane and the like; unsaturated silanes having the formula: ##STR5## wherein R7 is an unsaturated hydrocarbon radical such as an alkylene radical having