Copolymerization of Propylene and Polar Monomers Using Pd/IzQO Catalysts

Palladium catalysts bearing imidazo­[1,5-a]­quinolin-9-olate-1-ylidene
(IzQO) ligands polymerize α-olefins while incorporating polar
monomers. The steric environment provided by N-heterocyclic-carbene
(NHC) enables regioselective insertion of α-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.