Synthesis of Pt(dpk)Cl₄ and the Reversible Hydration to Pt(dpk-O-OH)Cl₃·H-phenCl:  X-ray, Spectroscopic, and Electrochemical Characterization

We report on the synthesis of a platinum(IV) compound containing a di-2-pyridyl ketone (dpk) ligand that is stable both in its anhydrous form [Pt(dpk)Cl₄] (1) and in its hydrated form [Pt(dpk-O-OH)Cl₃]·H-phenCl (2). The crystal structure of the hydrated form shows that one of the hydroxide groups from the resulting gem-diol has undergone a cyclometalation/condensation reaction resulting in an oxygen atom directly coordinated to the Pt(IV) center and the formation of H-phenCl. We correlate our physical data with predictions made by molecular modeling, and we propose an explanation for the unusual activity found for this dpk ketone. Spectroscopic and solubility studies are presented here, as well. Electrochemical studies of 1 indicate that it undergoes a highly irreversible reduction at a potential of about −0.45 V vs Ag⁺/Ag in CH₃CN and that the irreversibility is likely due to an EC mechanism, the nature of which is currently under further investigation. Another distinct redox pair, apparently reversible, appears at a potential of about −1.1 V vs Ag⁺/Ag.