ATTEMPTED OXIDATIVE GENERATION OF A DIHYDROGEN COMPLEX

Cyclic voltammetry of 1, CpRu(P)(H)3 (P = PPh3), in MeCN at a gold el ectrode (20-degrees-C, 1 V/s) is irreversible but produces in high yie ld 2, CpRuP(MeCN)2+, which does show a reversible cyclic voltammogram . The reaction consumes 1 faraday/mol of Ru, and thus all hydride liga nds are converted to H-2. Sweep rate and low-temperature studies, chem ical trapping, and chemical oxidation (with Cp2Fe+) are consistent wit h 1.+ reacting by proton transfer to 1, to form transient 3, CpRuPH4. This species was independently synthesized by protonation of 1 at lo w temperature in CH2Cl2 and was characterized by NMR spectroscopy. It reacts rapidly with MeCN to produce first CpRuPH2(MeCN)+ and H-2 and then 2. Proton T1 relaxation time measurements suggest 3 contains at l east one H-2 molecule. Cyclic voltammetry at a Pt electrode shows curv e crossings whose origin is traced to adsorption and then oxidation of H-2 released from the metal complex(es).