The polymerization of conjugated dienes by Ziegler - Natta catalysts is studied. It is believed that the active centers of the catalysts are the bimetallic complexes composed of transition metal and organo - aluminum compounds

through lonic chlorine and alkyl or allyl chain endings Controlling the conformation of monomer inserting to the chain ending is of great importance: by chelation of both the double bonds of the monomer with cisoid of conformation on transition metal ions of low ligand field stabilization energy (LFSE)

cisl

4 polymers are obtained

and by coordination of only one double bond with transoid conformation

on transition metal irons of higher LFSE

trans 1

4 or 1

2 polymers will be prepared