C- and O-metallation of N-benzylideneamines by palladium .2. Synthesis and X-ray crystal structure of [Pd(2{CH=N-(CH2)(2)-4'-(MeO)C6H4}-4,5-(MeO)(2)C6H2)Br(PPh(3))]

The action of Pd(AcO)(2) on the imines 3,4-(MeO)(2)C6H3CH=N(CH2)(n)C(6)H(4)R has been studied. Five-membered endo metallacycles were obtained from the imines 1a (R = H, n = 0), 1b (R = 2-MeO, n = 0), 1c (R = 4-MeO, n = 1) and 1d (R = 4-MeO, n = 2) by activation of the less hindered C(aromatic)-H bond. A six-membered metallacycle, containing a Pd-O bond, was obtained from the imine 1e, 2,4,6-(MeO)(3)C6H2CH=NC6H5, by activation of one of the ortho O-CH3 bonds. All these results show the strong tendency of imines to form endocyclic compounds and the importance of steric factors in the process. Complexes [PdBr(C-N)(PPh(3))] or even [Pd(AcO)(C-N)PPh(3))], in which the acetate acts as a monodentated ligand, can be obtained by the action of PPh(3) on the new cyclometallated compounds. [Pd(2-(CH=N-(CH2)(2)-4'-(MeO)C6H4]5-(MeO(2))Br(PPh(3))] crystallizes in the triclinic space group P (1) over bar with a = 18.388(3), b = 10.167(2), c = 9.858(2) Angstrom, alpha = 69.00(2), beta = 76.79(2), gamma = 78.80(3)degrees and Z = 2.