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We describe the reaction of anion [RhCl 6 ] 3− with a series of hydantoin ligands (HL1, HL2 and HL3 = 5-methyl-5-(2-, 3-and 4-pyridyl)-2,4-imidazolidenedione, respectively). Based on spectroscopic, cyclic voltammetric, elemental and MS analyses, the complexes have the general formula K[RhCl 2 (L1) 2 ] (1), cis-and trans-K[RhCl 4 (HL2) 2 ] (2a and 2b) and cis-and trans-K[RhCl 4 (HL3) 2 ] (3a and 3b). Complexes 2a, 2b, 3a and 3b were characterized successfully using infrared, 1 H NMR and 13 C NMR spectral analyses. Dissolution of complex 1 in dimethylsulfoxide (DMSO) led to elimination of one KL1 ligand and coordination of two DMSO molecules as ligands and transformation of this complex to cis-and trans-[RhCl 2 L1(DMSO) 2 ] (1a and 1b). Recrystallization led to separation and isolation of crystals of 1a from the initial mixture. X-ray analysis results showed that this complex was crystallized as solvated complex cis-[RhCl 2 L1(DMSO) 2 ]DMSO. The catalytic activity of these complexes was then evaluated for the hydrogenation of various ketones.

New Pd(II) and Pt(II) complexes are described in which the multidentate phosphorus ylides [Ph2P(CH2)nPPh2=C(H)C(O)C6H4‐p‐OCH3] (n=1, (Y1); n=2, (Y2)) act as P,C chelating ligands. The chelating ability of these ligands resulted in the formation of [MBr2{K2(P,C)‐Y1}] (M=Pd (1), Pt (2)); [MBr2{K2(P,C)‐Y2}] (M=Pd (3), Pt (4) complexes, which were investigated using physicochemical techniques. X‐ray diffraction studies of a single crystal of complex 2 confirmed the structure of the five‐membered ring. Owing to the redox activity of phosphorus‐ylide complexes, their electrocatalytic activity for the oxidation of methanol has been studied. All compounds were found to possess the anti‐proliferative potency against MCF‐7 (breast carcinoma), A549 (non‐small lung carcinoma) and AGS (gastric carcinoma) cell lines with average IC50 values in the range of 14.53 to 287.92 μM. In general, the compounds Y1, Y2, 2, and 3 displayed high anticancer activities compared to 1 and 4. The antioxidant activity of the compounds, which was estimated by 1, 1‐diphenyl‐2‐picryl‐hydrazyl (DPPH) free radical scavenging, was moderate to strong with IC50 values in the range 0.18 to 0.59 mg mL−1.

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