Gold metal-catalyzed reactions of isocyanides with primary amines and oxygen: Analogies with reactions of isocyanides in transition metal complexes

Despite its generally poor catalytic properties, bulk gold metal is observed to catalyze reactions of isocyanides (C equivalent to N-R) with primary amines (H2N-R') and O-2 to give carbodiimides (R-N=C=N-R') at room temperature and above. Detailed infrared reflection absorption spectroscopic (IRRAS) and kinetic studies show that the reaction occurs by initial eta(1)-adsorption of the isocyanide on the Au surface, which activates the isocyanide to attack by the amine. This attack is the rate-determining step in the catalytic cycle and has characteristics very similar to those of amine reactions with coordinated isocyanides in transition metal complexes. However, the metallic Au surface provides a pathway involving O-2 to give the carbodiimide product whereas homogeneous metal ion catalysts give formamidines[HC(dNR)(NHR')].