Five-membered [C,N] and [N,O] metallocyclic complexes of palladium(II) with monoalkyl [alpha-( 4-benzeneazoanilino)-N-benzyl] phosphonates: synthesis, characterization and antitumour activity

The synthesis, spectroscopic and biological properties of the novel palladi um(II) complexes with monoethyl (HL1) and monobutyl (HL2) eaters of [alpha- (4-benzeneazoanilino)-N-benzyl] phosphonic acid, have been prepared and stu died. These potential polydentate ligands form two types of metallocyclic c ompounds, those with [C,N] and [N,O] five-membered chelate rings. The forme r are cyclopailadated chloro-bridged binuclear complexes, [PdL(mu-Cl)](2), in which the deprotonated ligand undergoes palladation at the azo nitrogen and the ortho-carbon, while the latter mononuclear complexes, PdL2, contain the organophosphorus ligand bonded through the aniline nitrogen and the de protonated phosphonic acid oxygen. The complexes were identified and charac terized by elemental analysis, magnetic and conductance measurements as wel l as by IR,H-1, C-13 and P-31 nuclear magnetic resonance and ESI-mass spect roscopic studies. The in vitro antitumour activity of all the complexes was evaluated against the human KB cell line as a preliminary screening for th eir biological activity. The coordination behaviour of monoalkyl benzeneazo phosphonates as well as the spectral and biological properties of their com plexes were compared with the results reported for the corresponding dialky l phosphonates and their palladium(II) complexes. (C) 2000 Elsevier Science Ltd All rights reserved.