Reactivity and biological activity of N,N,S-Schiff-base rhodium pentamethylcyclopentadienyl complexes

Neutral piano-stool complexes of the general formula [(eta(5)-C5Me5)Rh(L-OR)] (R = Me, 1; R = Et, 2; R = Pe(i), 3) have been prepared in alcohols (methanol, 1; ethanol, 2; isopropanol, 3) from the Schiff-base 5-methyl-4-{(pyridin-2-ylmethylene)amino}-4H-1,2,4-triazole-3-thiol (L-H) and the dinuclear precursor (eta(5)-C5Me5) RhCl2. Concomitant with the coordination of the Schiff-base ligand, an alkoxilation occurs on the imine carbon atom of the ligand, thus forming the corresponding L-OR compounds. In these complexes, the L-OR ligand is N,N,S-coordinated, introducing chirality at the metal center. The antiproliferative activity of the piano-stool complexes 1-3 was evaluated on cancerous (A2780 and A2780cisR) and non-cancerous (HEK293) cell lines, showing no significant activity in vitro (IC50 > 200 mu M), except for the ethanolate derivative 2, which shows an IC50 of 21 mu M on the ovarian cancer cell line A2780.