Direct observation of a carbonylation reaction relevant to CO/alkene copolymerization in a methylpalladium carbonyl complex containing a bis(N-heterocyclic carbene) ligand.

Use of a bulky bidentate bis(NHC) ligand allows isolation of a stable cationic methylpalladium carbonyl complex that undergoes clean carbonylation to an acyl complex under excess CO, modeling a key step in CO/alkene copolymerization.