Organometallic chemistry and catalysis on gold metal surfaces

As in transition metal complexes, C N-R ligands adsorbed on powdered gold undergo attack by amines to give putative diamino-carbene groups on the gold surface. This reaction forms the basis for the discovery of a gold metal-catalyzed reaction of C N-R, primary amines (R'NH2) and O-2 to give carbodiimides (R'-N=C=N-R). An analogous reaction of C O, RNH2, and O-2 gives isocyanates (R-N=C=O), which react with additional amine to give urea (RNH)(2)C=O products. The gold-catalyzed reaction of C N-R with secondary amines (HNR'(2)) and O-2 gives mixed ureas RNH(C O)NR'(2). In another type of gold-catalyzed reaction, secondary amines HN(CH2R)(2) react with O-2 to undergo dehydrogenation to the imine product, RCH=N(CH2R). Of special interest is the high catalytic activity of gold powder, which is otherwise well-known for its poor catalytic properties. (C) 2007 Elsevier B.V. All rights reserved.