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Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is used to examine the adsorption of phenyl isocyanide (PhNC), tert-butyl isocyanide (Bu*NC), and 1,4-phenylene diisocyanide (1,4-DINC) from methanol solution on gold powder. These studies indicate that the isocyanides bond end-on to a single gold atom through the terminal carbon atom of the isocyanide group. This structural assignment is based on a comparison of the v(NC) values of the isocyanides adsorbed on gold with those in (PhNC)-AuCl, (BtfNQAuCl, and isocyanide gold cluster compounds. The r(NC) frequencies of the isocyanides typically shift 50-70 cm-1 higher upon adsorption to the gold powder when compared to the uncoordinated isocyanides. The spectra indicate that only one isocyanide group of 1,4-DINC coordinates to the gold; the other one remains uncoordinated. When the concentration of the isocyanide in the methanol is increased, the amount of isocyanide adsorbed increases up to a limiting value. At all loadings, the isocyanides bind to only one Au atom; there is no evidence for bridging RNC groups.

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Bulk gold powder (approximately 10(3) nm particle size) is a highly active catalyst for the oxidative dehydrogenation of secondary amines to imines under the mild conditions of 1 atm O2 and 60-100 degrees C.

Thiophenes, including benzothiophenes and dibenzothiophenes, undergo a variety of reactions with transition metal complexes that lead to products in which the thiophene is partially reduced or cleaved at a C−S bond. The specific types of reactivity depend on the modes of thiophene coordination to the metal, which in turn depend on the particular metal and its associated ligands. It is the intent of this review to organize these numerous reactions of thiophenes into categories that illustrate distinct patterns of reactivity. It is hoped that an understanding of such patterns will stimulate the use of thiophene−organotransition metal chemistry in synthetic organic chemistry.

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