Aqueous phase carbon dioxide and bicarbonate hydrogenation catalyzed by cyclopentadienyl ruthenium complexes

The water-soluble ruthenium(II) complexes [Cp'RuX(PTA)(2)]Y and [CpRuCl(PPh3)(mPTA)]OTf (Cp'= Cp, Cp*, X = Cl and Y = nil; or X = MeCN and Y = PF6; PTA = 1,3,5-triaza-7-phosphaadamantane; mPTA = 1-methyl-1,3,5-triaza-7-phosphaadamantane) were used as catalyst precursors for the hydrogenation Of CO2 and bicarbonate in aqueous solutions, in the absence of amines or other additives, under relatively mild conditions (100 bar H-2, 30-80 degrees C), with moderate activities. Kinetic studies showed that the hydrogenation of HCO3- proceeds without an induction period, and that the rate strongly depends on the pH of the reaction medium. High-pressure multinuclear NMR spectroscopy revealed that the ruthenium(II) chloride precursors are quantitatively converted into the corresponding hydrides under H-2 pressure. Copyright (c) 2007 John Wiley & Sons, Ltd.