Synthesis and Anticancer Properties of Heterobimetallic Fe(II)/Pd(II) Complexes Bearing Different Butadienyl Fragments

In this work, we describe the synthesis of heterobimetallic Fe(II)/Pd(II) complexes bearing different halides and halide-substituted butadienyl ligands. The synthetic approach involves the preparation of suitable Pd(II)-butadienyl precursors containing a thioquinoline moiety, followed by the substitution of this relatively labile ligand with dppf (dppf=1,1′-bis(diphenylphosphino)ferrocene). With the exception of complexes containing at least one iodine atom, all compounds were synthesized in high yields and purity, and thoroughly characterized using spectroscopic and diffractometric methods. The investigation of the antiproliferative activity of the synthesized organometallic complexes against ovarian and breast cancer cell lines revealed that all compounds exhibit noteworthy cytotoxicity, with IC50 values in the micromolar range and generally comparable to those of cisplatin. Interestingly, significant differences of cytotoxicity among the analysed compounds were observed in the case of MRC-5 normal cells. Of particular interest is the dichloride derivative 3 a, which is essentially inactive towards non-cancerous cells (IC50>100 μM), thus demonstrating promising in vitro selectivity that we believe warrants further investigation in the future.