Organometallic chemistry and catalysis on gold metal surfaces

As in transition metal complexes, Ctriple bond; length of mdashN–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 Ctriple bond; length of mdashN–R, primary amines (R′NH2) and O2 to give carbodiimides (R′–Ndouble bond; length as m-dashCdouble bond; length as m-dashN–R). An analogous reaction of Ctriple bond; length of mdashO, RNH2, and O2 gives isocyanates (R–Ndouble bond; length as m-dashCdouble bond; length as m-dashO), which react with additional amine to give urea (RNH)2Cdouble bond; length as m-dashO products. The gold-catalyzed reaction of Ctriple bond; length of mdashN–R with secondary amines (HNR′2) and O2 gives mixed ureas RNH(Cdouble bond; length as m-dashO)NR′2. In another type of gold-catalyzed reaction, secondary amines HN(CH2R)2 react with O2 to undergo dehydrogenation to the imine product, RCHdouble bond; length as m-dashN(CH2R). Of special interest is the high catalytic activity of gold powder, which is otherwise well-known for its poor catalytic properties.