Platinum Metals Review - Volume 56, Issue 2, 2012

Palladium-catalysed cross-couplings, in particular Heck, Suzuki-Miyaura and Negishi reactions developed over three decades ago, are routinely carried out in organic solvents. However, alternative media are currently of considerable interest given an increasing emphasis on making organic processes ‘greener’; for example, by minimising organic waste in the form of organic solvents. Water is the obvious leading candidate in this regard. Hence, this review focuses on the application of micellar catalysis, in which a ‘designer’ surfactant enables these award-winning coupling reactions to be run in water at room temperature.

Palladium nanoparticles are of great importance as catalytic materials, as well as for a number of other applications such as hydrogen storage and sensing. Their synthesis has been wi dely studied and interest in their properties is growing. Here the synthesis of palladium nanoparticles by chemical and electrochemical methods using a variety of stabilisers including organic ligands, salts/surfactants, polymers and dendrimers is reviewed and their potential benefits in catalytic applications are introduced.

Palladium-catalysed cross-coupling has huge importance for the synthesis of many organic molecules at both laboratory and industrial scale. A range of commercially available preformed (R3P)2Pd(0) catalysts have now been developed and are available from Johnson Matthey. Some unique and highly selective applications of these palladium catalysts for various cross-coupling reactions, including novel reactions such as carbohalogenation reactions, Negishi coupling of aryl chlorides and copper-free Sonogashira coupling, are highlighted in this review.