Synthesis, Structure, and Reactivity of Diazoketiminato Complexes of Platinum(II) and Palladium(II): Cytotoxic Properties of a Platinum Complex

Reaction of the 2‐(arylazo)anilines Ar‐N=N‐C 6 H 4 NH 2 [HL n NH 2 ; Ar = C 6 H 5 (HL 1 ), p ‐CH 3 C 6 H 4 (HL 2 ), p ‐ClC 6 H 4 (HL 3 )] with K 2 PtCl 4 in dmso affords the new Pt II azoimine complexes [(HL n NH)Pt(dmso)Cl] where the chloride and dmso ligands are mutually cis . In contrast, treatment of Na 2 PdCl 4 with HL n NH 2 in dmso gives the chloro‐bridged palladium dimer [{(HL n NH)PdCl} 2 ] as the major product along with [(HL n NH) 2 Pd] as the minor product. Further, the reaction of HL n NHCH 2 Ph with K 2 PtCl 4 in dmso also gives [(HL n NH)Pt(dmso)Cl] whereas Na 2 PdCl 4 affords the orthopalladated complexes [(L n NHCH 2 Ph)PdCl]. This means that the N–C(CH 2 Ph) bond is selectively cleaved by K 2 PtCl 4 . The reaction of [(HL n NH)Pt(dmso)Cl] with acetylacetone (acacH) gives the heteroleptic complex [(HL n NH)Pt(acac)]. [(HL n NH)Pt(dmso)Cl] and [(HL n NH)Pt(acac)] display a reversible reductive response at –1.20 and –1.46 V vs. SCE, respectively, in their cyclic voltammograms. The nature of the redox orbitals has been determined semi‐empirically employing the EHMO method. The cytotoxicity of [(HL 1 NH)Pt(dmso)Cl] has been examined with HeLa cells and the sub‐lethal dose (8 μ M ) determined by dose‐dependence studies. The relative degree of apoptotic and necrotic cell death using a sub‐lethal dose were measured by flow cytometry.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)