The new phosphonium salt, the C,C-chelating phosphorus ylide ligand, (MeOC6H5C(O) CH@PPh2(CH2)2PPh2@CHC(O)C6H5OMe), and its Pd(II) and Pt(II) complexes have been synthesized and the cytotoxic activity of the synthesized complexes against three human cancer cell lines, including HeLa (Human cervix cancer cell line), KB (human oral cancer cell line) and U87 MG (human glioblastoma cell line) were evaluated using an MTT assay. The new compounds were identified and characterized using multinuclear (1H, 13C and 31P) NMR, infrared (IR) spectroscopy, elemental analysis, and through UV absorption and fluorescence emission spectra. Also, the crystal structure of the phosphorus ylide ligand was determined by single-crystal X-ray diffraction analysis. According to the obtained results from the MTT assay, the Pd(II) and Pt(II) complexes demonstrated a higher cytotoxic activity against KB human oral cancer cells in comparison with other cell lines, rendering these compounds into suitable candidates for further anti-oral cancer studies. Furthermore, a theoretical study on structure and nature of the MAC bonding between the Y ligand (ylide) and MCl2 fragment in the [YMCl2] (M = Pd, Pt and Y = (MeOC6H5C(O)CH@PPh2(CH2)2PPh2@CHC(O)C6H5OMe)) complexes have been reported via NBO and energy-decomposition analysis (EDA).
