The ligand of antitumor organotitanium or other metallodug complexes plays a pivotal role in determining the mechanism of their cytotoxic action. Although the specific contribution of several ligands is generally well established, our understanding of the overall mechanism of the cytotoxic action of the complexes themselves is limited and incomplete in most cases, except perhaps in the case of cis-platin. A strategy to monitor the mode of cytotoxic action of candidate antitumor complexes requires tagging with bioactive side chains like a diazo group, for in-cell site-specific labelling. In this review we expand on a previous publication  to discuss several new methods for the preparation of potential antitumor organotitanium complexes with a pendant diazo group, aiming at better understanding their mode of cytotoxic action. By introducing this new class of titanium-based potential antitumor agents, we hope to contribute to the world-wide effort in this important area of medicinal chemistry research, for an ultimate usable titanium-based antitumor drug.