Dinuclear bridged biphosphinic and mononuclear cyclopalladated complexes of benzylamines: Synthesis, structural characterization and antitumor activity

Reaction of chloro-bridged dinuclear palladacycles, [Pd2{(C,N)-C6H4CH2NH(R)}2(μ-Cl)2] (R = Et (1a); R = t-Bu (1b)) with pyridine and PPh3 in the 1:2 M ratio at room temperature was used to prepare the mononuclear complexes, [Pd(C,N)-C6H4CH2NH(R)Cl(L)] (R = Et and L = Py (2a); R = t-Bu and L = PPh3 (2b)). Bridged biphosphinic palladacycle, [Pd2(C,N-dmba)2(μ-dppe)(Cl)2] (2c), (where dmba = N,N-dimethylbenzylamine and dppe = 1,2-bis(diphenylphosphino)ethane) has been also synthesized. The complexes were fully characterized by elemental analysis, IR and NMR spectroscopies. In addition, the solid structures of palladacycles 2a and 2c were studied by single-crystal X-ray crystallography. In vitro cytotoxicity assays of the cyclopalladated complexes, (2a−2c) and cisplatin were evaluated against the Hela (human cervix carcinoma), HT-29 (colon cancer cell line), K562 (leukemia cancer cell line) and MDA-MB-468 (human breast carcinoma). The complexes 2a−2c display IC50 values in a μM range better than that of the antitumor drug cisplatin.