A compound useful as a cocatalyst or cocatalyst component, especially for use as an addition polymerization catalyst compound, corresponding to the formula: (A*+a)b(Z*J*j)−cd, wherein: A* is a cation of from 1 to 80, preferably 1 to 60 atoms, not counting hydrogen atoms, said A* having a charge +a, Z* is an anion group of from 1 to 50, preferably 1 to 30 atoms, not counting hydrogen atoms, further containing two or more Lewis base sites; J* independently each occurrence is a Lewis acid of from 1 to 80, preferably 1 to 60 atoms, not counting hydrogen atoms, coordinated to at least one Lewis base site of Z*, and optionally two or more such J* groups may be joined together in a moiety having multiple Lewis acidic functionality, j is a number from 2 to 12 and a, b, c, and d are integers from 1 to 3, with the proviso that a×b is equal to c×d, and provided further that one or more of A*, Z* or J* comprises a hydroxyl group or a polar group containing quiescent reactive functionality.