ADSORPTION OF ARYL AND ALKYL ISOCYANIDES ON POWDERED GOLD

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) i s used to examine the adsorption of phenyl isocyanide (PhNC), tert-but yl isocyanide (Bu(t)NC), and 1,4-phenylene diisocyanide (1,4-DINC) fro m methanol solution on gold powder. These studies indicate that the is ocyanides bond end-on to a single gold atom through the terminal carbo n atom of the isocyanide group. This structural assignment is based on a comparison of the nu(NC) values of the isocyanides adsorbed on gold with those in (PhNC)AuCl, (Bu(t)NC)AuCl, and isocyanide gold cluster compounds. The nu(NC) frequencies of the isocyanides typically shift 5 0-70 cm-1 higher upon adsorption to the gold powder when compared to t he uncoordinated isocyanides. The spectra indicate that only one isocy anide group of 1,4-DINC coordinates to the gold; the other one remains uncoordinated. When the concentration of the isocyanide in the methan ol is increased, the amount of isocyanide adsorbed increases up to a l imiting value. At all loadings, the isocyanides bind to only one Au at om; there is no evidence for bridging RNC groups.