Water-soluble cyclopalladated aryl oxime: a potent 'green' catalyst

Orthopalladated aryl oxime with a 15-crown-5 motif is prepared in a 72% yield by the exchange of cyclopalladated ligands from oxime of 4'-acetylbenzo-15-crown-5 and orthometalated N,N-dimethylbenzylamine, [Pd(o-C6H4CH2NMe2)Cl](2). Its solubility in water is more than ten times higher than that of the related complex without the crown fragment and increases further in the presence of magnesium(II) salts. Potential applications of the newly synthesized palladacycle in catalysis is demonstrated by the example of biomimetic hydrolysis of 4-nitrophenyl 2,3-dihydroxybenzoate. It has been demonstrated that a 120-fold rate increase is achieved by realization of the intramolecular general base mechanism. (C) 2001 Elsevier Science B.V. All rights reserved.