Acceptorless and Base-Free Dehydrogenation of Alcohols and Amines using Ruthenium-Hydride Complexes.

An efficient, operatively simple, acceptorless, and base-free dehydrogenation of secondary alcohols and nitrogen-containing heterocyclic compounds was achieved by using readily available ruthenium hydride complexes as precatalysts. The complex RuH2(CO)(PPh3)3 ( 1) and Shvo's complex ( 2) showed excellent activities for the dehydrogenation of secondary alcohols and nitrogen containing heterocycles. In addition to complexes 1 and 2, the complex RuH2(PPh3)4 ( 3) also showed moderate to excellent activity for the acceptorless dehydrogenation of nitrogen-containing heterocyclic compounds. Kinetic studies on the oxidation reaction of 1-phenylethanol using complex 1 were carried out in the presence and the absence of external triphenylphosphine (PPh3). External addition of PPh3 had a negative influence on the rate of the reaction, which suggested that dissociation of PPh3 occurred during the course of the reaction. Hydrogen was evolved from the oxidation reaction of 1-phenylethanol by using 1 mol% of 1 (88%) and 2 (92%), which demonstrated the possible usage of the catalytic systems in hydrogen generation. [ABSTRACT FROM AUTHOR]