Selective Cytotoxic Ru(II) Arene Cp* Complex Salts [R-PhRuCp*]⁺X⁻ for X = BF₄⁻, PF₆⁻, and BPh₄⁻

A novel series of ionic Ru(II) arene Cp* sandwich complexes has been synthesized and characterized. Screening results for cytotoxicity against a range of human tumor cell lines and normal human cells indicate that the complexes show promising anticancer activity, which varies with changes in the arene ligand and the anionic counterion.