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 31 P 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.