Tridentate NNN Ligand Associating Amidoquinoline and Iminophosphorane: Synthesis and Coordination to Pd and Ni Centers

The synthesis of a tridentate NNN ligand incorporating an amidoquinoline and an iminophosphorane (L R H; R = Ph, Cy) was carried out. Coordination to PdII and NiII precursors gave, as expected, square-planar complexes of the general formula [L R MCl]. The most surprising result came from the reaction of L Ph H with [Ni­(COD)2], which gave a NiII phenyl complex bearing a tridentate amidoquinoline-aminophosphine ligand. This rearrangement would result from a proton transfer assisted by the Ni0 on stabilization by a phenyl substituent at the phosphorus, as suggested by DFT calculations and complementary experiments. This nickel phenyl complex formed the corresponding benzoyl complex under a CO atmosphere.