Insights into the alternating <i>vs.</i> non-alternating copolymerization of ethylene and CO catalyzed by P,O-coordinated nickel and palladium diphosphazane monoxide complexes

Shorter metal–ligand distances and a larger bite angle in Ni-PNPO destabilize the six-membered γ-carbonyl chelate, facilitating alternating path. Pd-PNPO stabilizes this intermediate, raising barriers and enabling a competing non-alternating path.