Use of an Organometallic Palladium Oxazoline Catalyst for the Hydrolysis of Methylparathion

Reaction of (S)-4-carbomethoxy-2-phenyl-2-oxazoline with Pd(OAc)2 leads to the formation
of the ortho-palladated complex (S,S)-di-μ-(acetate)-bis{2-[2-(4-carbomethoxy)oxazolinyl]phenyl-C,N}dipalladium(II) (1). In the presence of water, this complex reacts with methylparathion to produce p-nitrophenol as well as two oxazoline palladium dimethylthiophosphate complexes (2 and 3), which have been observed in solution by 31P NMR. This reaction
is accompanied by racemization of the oxazoline ligand and ultimately produces the dinuclear
complex (R,S)-di-μ-(dimethylthiophosphate-S,S)-bis{2-[2-(4-carbomethoxy)oxazolinyl]phenyl-C,N}dipal-ladium(II) (4), which features bridging dimethylthiophosphate ligands. At pH
9−10, complex 1 serves as a precatalyst for the hydrolysis of methylparathion. The reaction
rate has a first-order dependence in substrate and palladium catalyst with a second-order
rate constant of 726 (± 30) M-1 s-1 at pH 9.0.