##STR1## where at least one R is a methyl or cyclohexyl radical and where the remaining R's are selected from the group consisting of alkyl and cycloalkyl radicals having from 1 to 6 carbon atoms which may be the same or different and where the mol ratio of a to b is from about 99.5:0.5 to 88:12 and (2) R'Li in which R' is selected from the group consisting of normal, secondary and tertiary alkyl