Adsorption and decomposition of trimethylamine on Pt(111):: formation of dimethylaminocarbyne (CN(CH3)2)

Reflection absorption infrared spectroscopy (RAIRS), temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) have been used to study the adsorption and decomposition of trimethylamine ((CH3)(3)N) on the Pt(1 1 1) surface. Trimethylamine (TMA) adsorbs molecularly at 85 K and is stable up to 250 K. Based on previous studies showing that methylaminocarbyne (CNHCH3) and aminocarbyne (CNH2) form from the partial dehydrogenation of dimethylamine and methylamine, respectively, dimethylaminocarbyne, CN(CH3)(2) is expected from the analogous reaction of trimethylamine. Spectral changes that occur when adsorbed TMA is heated to 350 K, including the appearance of a CN stretch at 1507 cm(-1), are attributed to formation of CN(CH3)(2). Spectral assignments are supported by shifts observed following initial adsorption of the TMA isotopomers (CH3)(3) N-15 and (CD3)(3)N and by density functional theory calculations based on a Pt2CN(CH3)(2) model. The results provide further evidence that aminocarbyne species are common intermediates in the surface chemistry of molecules containing CN bonds. (C) 2003 Elsevier B.V. All rights reserved.