New multifunctional heterobinuclear palladium (II) complexes based on organometallic dithiocarbazate ligands

Abstract

In the research of new compounds with multifunctional applications, heterobinuclear palladium (II) complexes based on organometallic dithiocarbazates (DTCZs) have been isolated. The organometallic DTCZ ligands of the general formula [{(η5‐C5H4)‐CH=NNHC(S)SCH3}]MLn [MLn = Re (CO)3 (2a); Mn (CO)3 (2b); FeCp (2c)] were prepared by the reaction between formyl organometallic precursors (1a−c) with S‐methyldithiocarbazate. Subsequently, a two‐step reaction of 2a−c with: (i) K2[PdCl4] and (ii) PPh3 yielded heterobinuclear complexes [Pd{MLn(η5‐C5H4)‐CH=NNHC(S)SCH3}–(Cl)(PPh3)] [MLn = Re (CO)3 (3a); Mn (CO)3 (3b); FeCp (3c)]. All compounds were characterized by conventional spectroscopic techniques (infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectrometry and elemental analysis). In addition, the molecular structures of 2a, 2c and 3c were determined by single‐crystal X‐ray diffraction. The new palladium (II) complexes (3a−c) were evaluated as antiproliferative agents against non‐small cell lung cancer cells (H1299 cells). Complexes 3a and 3b containing cyrhetrenyl‐ and cymantrenyl‐DTCZ ligands, respectively, were more active than their ferrocenyl analogue 3c. The activity was associated with the electron‐withdrawing properties of the (η5‐C5H4)M (CO)3 moieties and their better lipophilicity than that of the ferrocenyl analogue. In addition, we studied the capacity of metalloligands (2a−c) and palladium (II) complexes (3a−c) to remove methylene blue in water under UV–visible light irradiation. The results established that the complexes showed moderate efficiency and were less active than their corresponding free ligands.