Heterogeneously catalyzed hydrogenation and dehydrogenation reactions involving surface C–N bonds have been studied on a variety of single-crystal transition-metal surfaces. Most notably, a class of stable surface intermediates called aminocarbynes with the general formula CNRR′ (R, R′ = H or CH3) has been characterized on Pt(111) using reflection absorption infrared spectroscopy (RAIRS). The simplest aminocarbyne with the formula CNH2 can be formed on Pt(111) through either the hydrogenation of surface CN or the decomposition of azomethane (CH3N═NCH3) and methylamine (CH3NH2).(1-3) Methylaminocarbyne (CNHCH3) is formed through either the hydrogenation of methyl isocyanide (CH3NC) or the partial dehydrogenation of dimethylamine ((CH3)2NH).(4-6) Finally, dimethylaminocarbyne (CN(CH3)2) has been shown to be the product of the partial dehydrogenation of trimethylamine ((CH3)3N).(7) All of these aminocarbyne-type surface species are bonded to the surface through the terminal C atom with the C–N bond perpendicular to the surface, and the C–N bond has an intermediate character between that of a single and a double bond. In contrast, a NH2C═CH intermediate bonded to the surface through the C atoms with the C═C bond parallel to the surface was proposed to form from the reaction between NH3 and surface C2 on Pt(111).(8)