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.
