Synthesis, spectroscopic and electrochemical characterization of water soluble [(η5-C5H5)2Mo(thionucleobase/thionucleoside)]Cl2 complexes

A series of water soluble molybdenocene complexes of general formula [(η5-C5H5)2Mo(L)]Cl2 (L=6-mercaptopurine (2), 6-mercaptopurine ribose (3), 2-amino-6-mercaptopurine (4), 2-amino-6-mercaptopurine ribose (5)) have been prepared by reacting Cp2MoCl2 (1) with the corresponding thionucleobase/thionucleoside in a (2:1) THF/MeOH solvent mixture. The complexes have been characterized by spectroscopic methods (NMR, UV–Vis, IR and MS). 1H NMR spectroscopic data (DMSO-d6) on the complexes suggest a S–Mo–N(7) coordination by the thionucleobase/thionucleoside. In buffer solution NMR data suggest that the thionucleobase/thionucleoside remains coordinated to molybdenum probably through S(6) and assisted by either N(7) or N(1) atoms. Intermediate species such as [Cp2Mo(η1-L)(H2O)]2+/1+ where the L is acting as monodentate ligand are possible in solution. Electrochemical characterization has also been pursued by cyclic voltammetry in DMSO and buffer solution. In DMSO, the complexes including the molybdenocene dichloride exhibit reversible redox behavior. On the other hand, in buffer solution, the oxidation process is irreversible for all the species.