Surface chemistry of dimethylamine on Pt(1 1 1): formation of methylaminocarbyne and its decomposition products

Reflection absorption infrared spectroscopy and temperature programmed desorption have been used to study the reactive surface chemistry of dimethylamine (DMA) on the Pt(1 1 1) surface over the temperature range of 85–550 K. DMA adsorbs molecularly at 85 K through the nitrogen lone pair and is stable up to 350 K where it dehydrogenates to form methylaminocarbyne (CNHCH3), a species that was found in an earlier study to also form from the N-protonation of methyl isocyanide (CNCH3) on Pt(1 1 1). Upon annealing to 400 and 450 K, methylaminocarbyne decomposes to several different surface intermediates, including methyl isocyanide, as indicated by a ν(CN) peak at 2238 cm−1. Spectroscopic characterization of a surface intermediate that appears to retain a CNC unit and is stable up to 450 K is presented. This intermediate is formed from several precursors, including DMA, methyl isocyanide, and trimethylamine. At temperatures over 500 K, H2 and HCN desorb by the decomposition of the surface intermediates leaving CN and C on the surface.