CO2 hydrogenation by phosphorus-nitrogen PN3P-pincer iridium hydride complexes: elucidation of the deactivation pathway

(PNP)-P-3-Ir pincer hydride complexes were synthesized and characterized as catalysts and key intermediates in the direct hydrogenation of CO2 to formate under mild conditions. The formation of a dearomatized (PNP)-P-3*-Ir(i)-CO species was identified as a plausible key process accountable for the loss of catalytic activity in the CO2 hydrogenation.