Stereoregular Polymerization of Dienes

Stereoregular Polymerization of Dienes. Coordination polymerization exhibiting high degree of chemo- and stereoselectivity is the method of choice to synthe-size c -1,4-polybutadiene the commercially most important product (see 

Cobalt compounds, - particularly salts of organic acids, such as cobalt(II) octanoate369-371 with aluminum alkyls, are also suitable catalysts in hydrocarbon solvents. An A1 Co ratio higher than 1 and water370-372 are essential to obtain high catalytic activity and high cis selectivity.184,363 Polybutadiene with a high cis content can also be synthesized by nickel-based catalysts. Of the 

The mechanism of coordination polymerization of 1,3-butadiene and, in general, that of conjugated dienes follows the same pathway discussed for alkene polymerization that is, monomer insertion into the transition metal-carbon bond of the growing polymer chain occurs. One important difference, however, was recognized very early.47,378,379 In the polymerization of dienes the growing chain end is tt-allyl complexed to the transition metal  

Insertion involves a transitory a-allyl-bonded chain and -coordinated monomer eventually leading to the re-formation of the rr-allyl chain complex.380-382 

Polyacetylene and poly(p-phenylene) (PPP) are two polymeric hydrocarbons with a unique property both are conducting polymers on doping. Polyacetylene, a 

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