The reaction of multidentate pyrazine based ligands was explored towards Cp*rhodium and Cp*iridium precursors. Mononuclear and dinuclear complexes formed by the ratio-based reaction between ligand and metal precursor. The representative complexes have been determined by single crystal X-ray diffraction studies. Cytotoxicity study of the ligands and their complexes are evaluated against human colorectal cancer cell lines HT-29, HCT-116 p53+/+ and HCT-116 p53−/− and ARPE-19 (non-cancer retinal epithelium) cells. Complexes 2-5 and 7-8 were cytotoxic to cells and although the potency of these complexes was less than cisplatin, selectivity towards cancer cell lines as opposed to non-cancer ARPE-19 cells was comparable to cisplatin. From in-vitro cytotoxicity studies complexes 4 and 5 demonstrated good selectivity towards HCT116 p53−/− cells suggesting that these complexes are promising leads for the treatment of p53 deficient cancers.