Cationic aluminum alkyl complexes incorporating amidinate ligands as polymerization catalysts

Aluminum amidinate compounds of the formula ##STR1## wherein R, R2, and R3 are selected from the group consisting of C1 to C50 alkyl, aryl, and silyl groups, X is an anionic ligand, preferably a hydrocarbyl, n=0 or 1, L, if present, is a labile Lewis base ligand, preferably having an oxygen, nitrogen, or phosphorus atom donating a lone pair of electrons to the aluminum center, and A- is an anion which balances the charge of the aluminum cation and only weakly if at all coordinates to the aluminum center and preferably contains boron, are disclosed. These compounds are useful as olefin polymerization catalysts without the need for cocatalysts or transition metal species.