Abstract: Palladium compound compositions are provided in accordance with Formulae [((R)3E)aPd(Q)(LB)b]p [WCA]r, where ((R)3E) is a Group 15 electron donor ligand, Q is an anionic ligand, LB is a Lewis base, WCA is a weakly coordinating anion, a is 1, 2 or 3, b is 0, 1 or 2, the sum of a and b is 1, 2 or 3 and each of p and r is an integer such that the molecular charge is zero, or [(E(R)3)(E(R)2R*)Pd(LB)]p[WCA]r where E(R)2R* represents a Group 15 neutral electron donor ligand and where R* is an anionic hydrocarbyl containing moiety, bonded to the Pd and having a ? hydrogen with respect to the Pd center. Such compound composition exhibits latent polymerization activity in the presence of polycyclic olefins.