Iridium(I) Complexes Bearing a Noninnocent PNP‐Pincer‐Type Phosphaalkene ­Ligand: Catalytic Application in the Base‐Free N‐Alkylation of Amines with Alcohols

Abstract

AbstractA series of IrI complexes [Ir(L)(PPEP*)] [L = Cl– (3), CO (4), tBuNC (5), PMe3 (6), PPh3 (7)], coordinated with a PNP‐pincer‐type phosphaalkene ligand bearing a dearomatized pyridine ring (PPEP*), have been prepared and their catalytic properties for the dehydration/condensation of amines with alcohols has been examined. The catalytic reactions successfully proceed under base‐free conditions to give N‐alkylated amines and their dehydrogenation derivatives (imines). The product selectivity is dependent on L coordinated with Ir(PPEP*). Complexes 4 and 5 that contain π‐accepting ligands (CO, tBuNC) form N‐alkylated amines as the major products in a closed system using a nitrogen‐gas‐filled Schlenk tube. In contrast, complex 7 that contain PPh3 as L produces imines as the major products under a nitrogen‐gas flow. The reason for the selectivity change depending on L is discussed based on stoichiometric reactions using model compounds of presumed catalytic intermediates.