Spectroscopic Identification of Surface Intermediates in the Decomposition of Methylamine on Ru(001)

Abstract

The thermal decomposition of methylamine on Ru(001) was studied with reflection absorption infrared spectroscopy (RAIRS) and temperature programmed reaction spectroscopy (TPRS). After the multilayer methylamine desorbs at 150 K, the RAIR spectra of the remaining monolayer methylamine undergo small changes due to structural rearrangements but do not indicate any chemical changes until 250 K. The results are in agreement with recent theoretical investigations indicating that CH3 dehydrogenation to produce H x CNH2 species occurs before N–H and C–N bond scission. Experimental spectra of 13C- and 15N-substituted methylamine combined with DFT calculations of H x CNH y fragments attached to a Ru19 cluster to simulate the RAIR spectra, including isotopic shifts, clarified the spectral assignments.

Competing Reaction Pathways in Heterogeneously Catalyzed Hydrogenation of Allyl Cyanide: The Chemical Nature of Surface Species

“…Both bands lie in the vibrational region typical for deformation vibration of amino groups δ(NH x ). In previous studies, formation of vibrational bands in the range 1560–1616 cm −1 upon adsorption of simple amines at different transition metal surfaces was reported [9h,m,24] . Interestingly, both bands appear first at 200 K at comparable intensities.…”

“…In previous studies, formation of vibrational bands in the range 1560–1616 cm −1 upon adsorption of simple amines at different transition metal surfaces was reported. [ 9h , 9m , 24 ] Interestingly, both bands appear first at 200 K at comparable intensities. However, the band at 1609 cm −1 decreases in intensity at 250 K, while the band at 1580 cm −1 simultaneously grows (Figure 5 ), suggesting that these bands may be correlated as an intermediate (species related the band at 1609 cm −1 ) and the final product (species related the band at 1580 cm −1 ).…”

“…Previously adsorption behavior of structurally similar molecules – simple nitriles and isocyanides – was addressed by a variety of surface sensitive spectroscopies on pristine transition metal surfaces [9] . Specifically, two possible adsorption configurations – η 1 (N) or η 2 (N,C) – were proposed for acetonitrile, [9d,j] methyl isocyanide, [9g,k] azomethane, [9l] HCNH [10] and HCN [9m] adsorbed on Pt(111), methyl isocyanide and acetonitrile [9f] on Pd(111), acetonitrile on TiO 2 ‐supported Au, [9i] methyl isocyanide on Rh(111) [9e] and HCNH on Ru(001) [9h] . In the η 1 (N) configuration, the N atom directly interacts with the underlying metal, while the nearest C atom is attached only to N. In the η 2 (N,C) configuration, both N and the nearest C establish bonds to the underlying metal surface.…”

“…[9] Specifically, two possible adsorption configurations – η 1 (N) or η 2 (N,C) – were proposed for acetonitrile,[ 9d , 9j ] methyl isocyanide,[ 9g , 9k ] azomethane, [9l] HCNH [10] and HCN [9m] adsorbed on Pt(111), methyl isocyanide and acetonitrile [9f] on Pd(111), acetonitrile on TiO 2 ‐supported Au, [9i] methyl isocyanide on Rh(111) [9e] and HCNH on Ru(001). [9h] In the η 1 (N) configuration, the N atom directly interacts with the underlying metal, while the nearest C atom is attached only to N. In the η 2 (N,C) configuration, both N and the nearest C establish bonds to the underlying metal surface. Adsorption and reactivity behavior of these compounds on H‐containing transition metal surfaces and/or under hydrogenation reaction conditions at elevated temperatures was not yet investigated in surface science studies to the best of our knowledge.…”