Activation of Molecular Hydrogen by Homogeneous Catalysts

Abstract

Publisher Summary This chapter describes activation of molecular hydrogen by homogeneous catalysts. Catalytic hydrogenation in homogeneous liquid solutions is significant primarily because of the insight it provides into the mechanism of catalytic activation of molecular hydrogen. The functioning of homogeneous catalysts involves the properties of coordination compounds. In 1938, it was discovered by Calvin that cuprous acetate or salicylaldehyde dissolved in quinoline catalyzed the reduction by molecular hydrogen of (p-benzo-) quinone or of cupric ion. The solution remains optically clear over the course of these reductions. The rate of reduction is rapid at 100°C, being complete in about 1 hr, with convenient pressures and solution concentrations. In addition, the rate of reduction is independent of the substrate concentration. However, it is dependent on the environment surrounding the copper, such as solvent, anions, and complexing compounds. Among the relatively few catalysts known, activity is found for CuI, AgI, and HgII, which form a series of similar electronic arrangements.