Synthesis and X-Ray structure of CoCl2(PiPrPh2)2. A new highly active and stereospecific catalyst for 1,2 polymerization of conjugated dienes when used associated with MAO

The new cobalt (II) phosphine complex CoCl2(PiPrPh2)2 was synthesized by reacting CoCl2
with isopropyldiphenylphosphine in ethyl alcohol as solvent. The molecular structure of the complex was
determined by the X-ray diffraction method. CoCl2(PiPrPh2)2 was then used in combination with
methylaluminoxane for the polymerization of 1,3-butadiene: it was found to be highly active and
stereospecific for the preparation of 1,2 syndiotactic polybutadiene. The same system was also able to
polymerize substituted butadienes giving highly stereoregular 1,2 polymers from E-1,3-pentadiene, 1,3-
hexadiene, and 3-methyl-1,3-pentadiene. Some of these polymers are completely new and were never
prepared before.