Palladium(II) Complexes Containing P∼N∼O Donors. Ligand Effect of Tridentate versus Bidentate Coordination on the Oligomerization of Ethylene

Palladium complexes containing the [(RO) n C 6 H 5 - n C ]N(C 6 H 4 PPh 2 - o ) ( P ∼ N ∼ O ) ligand were synthesized, and the hemilability of the coordinating oxygen donors toward the metal center was studied. In the case of oxygen being a ether functionality (R = Me), acetonitrile readily replaces the tridentate ether donor in [Pd( P ∼ N ∼ O )Me]BF 4 ( 1 ) to yield [Pd( P ∼ N ∼ O )(MeCN)Me]BF 4 ( 2 ). The labile nature of the ether donor assists the complex 1 in catalyzing the oligomerization of ethylene. Presumably, the temporary coordination of the ether donor to the vacant site during migratory insertion suppresses the β-elimination, which allows the elongation of the alkyl chain.