Isolation, characterization, and DNA binding kinetics of three dirhodium(II,II) carboxyamidate complexes: Rh2(µ-L)(HNOCCF3)3 where L= [OOCCH3]-, [OOCCF3]-, or [HNOCCF3]-.

Several transition metal compounds are effective antitumor drugs whose biological activity can be attributed to their ability to bind deoxyribonucleic acid (DNA). In this study, DNA-binding experiments reveal that changing one bridging ligand on compounds with the general formula Rh(2)(µ-L)(HNOCCF(3))(3) alters the rate of DNA-binding by greater than 100-fold with µ-L = trifluoroacetate ≫ acetate > trifluoroacetamidate. These three dirhodium compounds are isolated as the major products of the reaction between Rh(2)(OOCCH(3))(4) and trifluoroacetamide in either refluxing chlorobenzene or molten trifluoroacetamide and have been characterized by NMR and LC/MS. By using (15)N-enriched trifluoroacetamide, NMR spectroscopy was used to assign the cis-(2,1) orientations of Rh(2)(µ-L)(HNOCCF(3))(3) compounds where µ-L = trifluoroacetate or acetate. This is the first report of Rh(2)(OOCCF(3))(HNOCCF(3))(3), a novel compound that may play a significant role in the biological and/or catalytic activity of compound mixtures commonly isolated as "Rh(2)(HNOCCF(3))(4)".