Polymerization of conjugated dienes and olefins promoted by cobalt complexes supported by phosphine oxide ligands

Abstract Four cobalt complexes supported by phosphine oxide (P=O) donors (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphine oxide) cobalt dichloride (Co1), (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphine oxide) cobalt bromide (Co2), N, N'-(pyridine-2,6-diyl)bis(P,P-di-tert-butylphosphinic amide) cobalt dichloride (Co3) and N, N'-(pyridine-2,6-diyl)bis(P,P-di-tert-butylphosphinic amide) cobalt dichloride (Co4) were prepared and characterized. Their catalyses performances in polymerization of isoprene, butadiene, myrcene as well as MMA and styrene were examined. In combination with AlEt2Cl, Co1 and Co2 are able to convert isoprene to polyisoprene, whereas the activities of Co3 and Co4 are much low. The resultant polyisoprene are mixture of cis-1,4 and 3,4 isomers, whose ratio are not significantly affected by the type of catalysts and polymerization conditions. Isoprene was found to be more active than myrcene, and butadiene in the case of Co1/AlEt2Cl, suggestive of compromised sterical and electronic effect from the alkyl group at 2-positon of monomers. The Co1/AlEt2Cl system is also moderately active in polymerizations of methyl methacrylate and styrene. Therefore, the current catalysts provided dual polymerization reactivities towards conjugated dienes and olefins that are rare in transition metals catalyzed coordinative polymerization.