Divergent Reactivity of CO2 and CO and Related Substrates at the Nickel Carbon Double Bond of (PCcarbeneP)Ni(II) Pincer Complexes

The addition of carbon monoxide (CO), carbon dioxide (CO<sub>2</sub>) and isoelectronic isocyanide and isocyanates to the nickel carbene bond in PC<sub>carbene</sub>P pincer complexes is reported. For CO and CNR, irreversible group transfer reactions are observed, while for CO<sub>2</sub>, a reversible 2+2 addition to the carbene moiety occurs. The course of the CO and CO<sub>2</sub> reactions are strongly affected by the nature of the PC<sub>carbene</sub>P pincer ligand framework and a new more rigid ligand based on a 10,10-dimethyl-9,10-dihydroanthracene core was designed in order to study these reactions, illustrating the profound effect of small changes in ligand structure on reaction outcomes.