Non-symmetric CNS-Pt(II) pincer complexes including thioether functionalized iminophosphoranes. Evaluation of their in vitro anticancer activity

Abstract

Iminophosphoranes of general formula Ph3P = NC6H4SR [R = 4-C6H4NO2 (3) and CH2C6H5 (4)], combining the iminophosphorane group with a thioether moiety were synthesized and fully characterized, including the unequivocal determination of the solid state structure of ligand (3) by single crystal X-ray diffraction techniques. These ligands and other related [R = CH3 (1), C6H5 (2)] were further reacted with [Pt(S(CH3)2)2Cl2] to produce, in all cases, the non-symmetric CNS-Pt(II) pincer complexes [PtCl{C6H4(Ph2P = NC6H4SR–κ3–C,N,S)}] [R = CH3 (5), C6H5 (6), 4-C6H4NO2 (7), CH2C6H5 (8)]. All compounds were fully characterized using common analytical techniques and the solid state structures of (5), (6) and (7) were unequivocally determined by single crystal X-ray diffraction experiments. The in vitro antiproliferative activity of these new species was explored against a series of tumoral cell lines [U251 (human glioblastoma), PC-3 (human prostate cancer cell line), K562 (human leukemia), HCT-15 (human colorectal adenocarcinoma), MCF-7 (human breast adenocarcinoma), SKLU (human lung adenocarcinoma) and HeLa (epitheloid cervix carcinoma)] showing compounds 5 (R = CH3) and 8 (R = CH2C6H5) to have better cytotoxic activity than cisplatin against HeLa and K562 tumoral cell lines.