Aa. Arestyakubovich, ROLE OF BIMETALLIC ACTIVE-CENTERS IN ANIONIC-POLYMERIZATION OF HYDROCARBON MONOMERS, Macromolecular symposia, 85, 1994, pp. 279-294
Polymerization of hydrocarbon monomers initiated by organometallic com
pounds of alkali and alkaline earth metals modified by derivatives of
other metals of Groups I-III is reviewed. Various mixed initiators, su
ch as RLi-RONa, RLi-RNa, R2Ba-R3Al, RNa-R3Al, are discussed in details
. It is shown that the presence of a second metal greatly affects the
kinetics of elementary steps of chain propagation and chain transfer a
nd also the structure and molecular weight of polymer formed. Active c
entres in all the systems are complexes containing two or more metal a
toms linked by a bridge bond; the addition of a monomer occurs by an i
nsertion either into the ''usual'' metal-carbon bond which is external
with respect to the polymetal nucleus of the complex or directly into
Mt1-R-Mt2 bridge bond.