Palladium catalysts bearing imidazo[1,5-a]quinolin-9-olate-1-ylidene (IzQO) ligands polymerize alpha-olefins while incorporating polar monomers. The steric environment provided by N-heterocyclic-carbene (NHC) enables regioselective insertion of alpha-olefins and polar monomers, yielding polypropylene, propylene/allyl carboxylate copolymers, and propylene/methyl acrylate copolymer. Known polymerization catalysts bearing NHC-based ligands decompose rapidly, whereas the present catalyst is durable because of structural confinement, wherein the NHC-plane is coplanar to the metal square plane. The present catalyst system enables facile access to a new class of functionalized polyolefins and helps conceive a new fundamental principle for designing NHC-based ligands.