The non-selective toxicity associated with Pt(II) complexes used in today's cancer therapy has stimulated research for alternative metal complexes. Ru(II) complexes may possess more selective toxicity and experience less tumor resistance than Pt(II) complexes. Co(III) complexes with cytotoxic ligands, can act as bioreductive prodrugs that can be selectively reduced under hypoxic conditions of tumors and release the cytotoxin within solid tumors. A novel ambidentate ligand called H(L5) has a suitable chelating property for the syntheses of potential dual-action (Ru(II)/Co(III)) heterobimetallic complexes. In this work, two Co(III) complexes with the general formula Co(4N)(L5)2, where 4N = tris(2-aminoethyl)amine (tren) or tris(2-pyridylmethyl)amine (tpa), and two corresponding (half-sandwich-Ru(II),Co(III)) heterobimetallic complexes were successfully synthesized with acceptable purity based on 1H-NMR, ESI-MS, and elemental analysis. Electrochemical studies showed that the tpa complexes are more easily reducible than the tren complexes. Cytotoxicity studies on MCF-7 human breast cancer cell line revealed the moderate cytotoxicity of H(L5) and the hypoxia activation of the tpa complexes, demonstrating the action of Co(tpa)(L5)2 as a hypoxia-activated anticancer prodrug. Gene expression analysis further revealed that H(L5) acts as an iron-chelating anticancer agent, and chelation with Co(III) produced an inactive prodrug.