Catalyst systems for rubber polymerizations

The invention provides a catalyst system comprising: (A) cobalt II carboxylate, and (B) at least one co-catalyst of the following structure A: wherein n is from 1 to 10, preferably from 1 to 6, and more preferably from 1 to 4; each R is independently an alkyl. The invention also provides a catalyst system comprising: (A) cobalt II carboxylate; and (B) the reaction product of at least the following components: (i) trialkyl aluminum, (ii) dialkyl aluminum chloride, (iii) water, and wherein the molar ratio of aluminum to chloride (Al: Cl) is less than 1 (preferably 0.7 to 0.2), the molar ratio of water to aluminum (H2O: Al) is from 0.5 to 0.92 (preferably from 0.55 to 0.75), and the molar ratio of trialkyl aluminum to dialkyl aluminum chloride from 0.5 to 5 (preferably from 1 to 5). The invention also provides a catalyst complex comprising the following: (a) CoR'(2-x) Cl(x), wherein x is from 0.01 to 1, preferably from 0.1 to 1; and R' is a carboxylate; (b) (n-m)R2R3AlCl.mRl3Al, wherein n is from 1 to 12, prefer