Synthesis and Reactivity of Methylpalladium Complexes Bearing a Partially Saturated IzQO Ligand

A saturated N-heterocyclic carbene–phenolate bidentate ligand, 3,3a,4,5-tetrahydroimidazo­[1,5-a]­quinolin-9-olate-1-ylidene (SIzQO), was synthesized and characterized. The SIzQO ligand was then treated with PdClMe­(pyridine)2 and [Pd­(μ-Cl)­Me­(2,6-lutidine)]2, which afforded C,C-cis-(SIzQO)­PdMe­(pyridine) and the thermodynamically unstable trans isomer C,C-trans-(SIzQO)­PdMe­(2,6-lutidine), respectively. The latter isomerizes at 40 °C into the corresponding cis isomer via a dissociative mechanism. These palladium/SIzQO complexes catalyze the polymerization of ethylene at 100–120 °C, although the catalytic activity is lower than that of a previously reported palladium/imidazo­[1,5-a]­quinolin-9-olate-1-ylidene (IzQO) system.