Hydrogenation – Homogeneous

Abstract

Homogeneous hydrogenation constitutes an important synthetic procedure and is one of the most extensively studied reactions of homogeneous catalysis. A very large number of soluble metal complexes, usually derived from transition metals, are active catalyst under very mild conditions. Detailed mechanistic studies have now firmly established reaction pathways for some hydrogenation catalysts such as the Wilkinson's catalyst, RhCl(P(C 6 H 5 ) 3 ) 3 , and rhodium and iridium catalyst precursors of formula [M(diene) 2 L 2 ] + or [Ir(diene)(py)(PCy 3 )] + , usually known as Crabtree's catalyst; other well‐known examples are RuHCl(P(C 6 H 5 ) 3 ) 3 and OsHCl(CO)(P( i ‐C 3 H 7 ) 3 ) 2 complexes. Homogeneous hydrogenation reactions have found important applications. One of the most important developments of homogeneous catalysis is the synthesis of optically active compounds by asymmetric hydrogenation of prochiral substrates. On the other hand, transfer hydrogenation, where the addition of hydrogen to an unsaturated substrate is provided by a donor molecule, can be considered as a viable alternative and complement to the classical reduction reactions with molecular hydrogen. The catalysts are usually late transition metal complexes with bidentate nitrogen ligands or tertiary phosphine ligands.

Hydrogenation Catalysis in Biobased Ionic Liquids

“…Hydrogenation reactions of unsaturated compounds have been among the most extensively studied processes in catalysis for many years [1,2]. To process, generally metallic catalysts are required.…”