Aspects of the coordination chemistry of the antimitotics colchicine (Col) and trimethylcolchicinic acid (Tmca) with the metal fragments Pt(bpy)(2+) and Ru(bpy)(2)(2+) are reported. In addition, the coordination chemistry of the tropolone anion (Tp) with the same fragments, which serves as a model for one mode of binding of the antimitotic, is described. The new complexes have been characterized by a variety of spectroscopic techniques. We have tested the in vitro antitumor activity of the new complexes against human chronic myelogenous leukemia, K562, and human colon adenocarcinoma, COLO 205. In these experiments we can demonstrate cytotoxicity comparable to that of cisplatin, and surprisingly, activity of the substitutionally-inert Ru(bpy)(2)(2+) complexes of Tmca and Col is comparable to that of colchicine itself. It is suggested that the antineoplastic activity is predominantly due to the intact complexes since solution studies of all the Ru and Pt complexes at room temperature in 0.1 M saline/5% DMSO show no degradation products over 48 h.