Organometallic chemistry and catalysis on gold metal surfaces

As in transition metal complexes, CN–R ligands adsorbed on powdered gold undergo attack by amines to give putative diaminocarbene groups on the gold surface. This reaction forms the basis for the discovery of a gold metal-catalyzed reaction of CN–R, primary amines (R′NH2) and O2 to give carbodiimides (R′–NCN–R). An analogous reaction of CO, RNH2, and O2 gives isocyanates (R–NCO), which react with additional amine to give urea (RNH)2CO products. The gold-catalyzed reaction of CN–R with secondary amines (HNR′2) and O2 gives mixed ureas RNH(CO)NR′2. In another type of gold-catalyzed reaction, secondary amines HN(CH2R)2 react with O2 to undergo dehydrogenation to the imine product, RCHN(CH2R). Of special interest is the high catalytic activity of gold powder, which is otherwise well-known for its poor catalytic properties.

In a reaction that mimics reactions of isocyanide ligands in transition metal complexes, amines attack isocyanides adsorbed on gold metal powder. In the presence of O2, ureas or carbodiimides are produced catalytically (see graphic). Also, gold powder catalyzes reactions of CO, primary amines, and O2 to give isocyanates (R–NCO).Figure optionsDownload as PowerPoint slide