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
(LRH; R = Ph, Cy)
was carried out. Coordination to PdII and NiII precursors gave, as expected, square-planar complexes of the general
formula [LRMCl]. The most surprising
result came from the reaction of LPhH 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.