MONONUCLEAR AND BINUCLEAR O-XYLYLENE DERIVATIVES OF PD(II)

The synthesis of binuclear complexes of composition C6H4-o-(CH2PdX(PMe 3)(2))(2) (X = Cl, 4a; Br, 4b) that contain bridging o-xylylene units, can be accomplished by reaction of the corresponding alpha,alpha'-dih aloxylenes with the Pd(0) species [Pd(eta(2)-CH2=CHCO2Me)(PMe3)(2)] (1 ). For X=Cl, partial oxidative addition takes place when the reaction is conducted at room temperature, leading to the mononuclear compound Pd(CH2C6H4-o-CH2Cl)Cl(PMe3)(2) (3a) which undergoes a slow decompositi on process in solution that involves oxidative addition of the chlorom ethyl group to palladium. The binuclear derivative 4a can also be obta ined by reaction of the metallacycle Pd(CH2C6H4-o-CH2)(PMe3)(2) (9) wi th PdCl2(PMe3)(2). Complexes 4a, 4b and 3a react with carbon monoxide and t-butyl isocyanide, giving rise to the corresponding acyl and imid oyl products. However, in the case of the imidoyl complex derived from 3a, (i.e., compound 13), the reactive chloromethyl group experiences a nucleophilic attack either by the metal or by the nitrogen atom of t he imidoyl functionality to give respectively either unstable Pd(IV) s pecies or the cationic amidocarbene complex 15. The structure of the c ation of the 15.BPh4- salt has been determined by X-ray diffraction me thods. Crystal data for 15.BPh4-: orthorhombic, Pna2(1), a = 19.826(5) , b = 11.076(4), c = 19.131(5) Angstrom, Z = 4, R1 = 0.0544 and wR2 = 0.4141. (C) 1998 Elsevier Science S.A.