Weak η2-olefin bonding in palladium and platinum allyl cationic complexes containing chiral monodentate ligands with α-phenyl methyl amine side chains

Detailed NMR studies on a series of Pd and Pt allyl complexes containing phosphoramidite ligands with NCH(CH3)Ph side chains are reported. When a coordination position becomes available, e.g., via abstraction of a chloride ligand, one double bond of the phenyl group of the side chain complexes to the metal, affording an eta(2)-olefin structure. These allyl complexes exhibit a number of dynamic processes, and these have been elucidated via low-temperature NMR studies combined with 2D NOESY methods. DFT calculations confirm the ability of the amine side chain to coordinate to the metal almost without distortion, leading to a weak eta(2)-arene-Pd bonding interaction (similar to 13 kcal mol(-1)). The latter result is supported by the NMR studies.