A cyclometalated diplatinum complex containing 1,1′-bis(diphenylphosphino)ferrocene as spacer ligand: Antitumor study

Cyclometalated platinum(II) complex [Pt(C^N)Cl(dmso)], 1, in which C^N = N(1),C(2′)-chelated deprotonated 2-phenylpyridine and dmso = dimethylsulfoxide, was reacted with 1 equiv of 1,1′-bis(diphenylphosphino)ferrocene, dppf, to give the cyclometalated diplatinum(II) complex [Pt2(C^N)2Cl2(μ-dppf)], 2, along with 0.5 equiv of unreacted dppf. However, the related reaction with 0.5 equiv of dppf produced complex 2 in pure form. Complex 2 in solution was fully characterized by using multinuclear NMR spectroscopy (1H, 13C, 31P, and 195Pt) and a number of 2D NMR experiments. The structure of complex 2 in solid state was determined by X-ray crystallography showing that the bridging dppf ligand is arranged close to “antiperiplanar staggered” conformation. Cytotoxicity of the complex 2 was studied in three human cancer cell lines derived from ovarian carcinoma(CH1), lung carcinoma(A549), and colon carcinoma (SW480) by means of the MTT assay (MTT = 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide).