Adsorption, decomposition and isomerization of methyl isocyanide and acetonitrile on Pd(111)

The adsorption of methyl isocyanide (CH3NC) and acetonitrile (CH3CN) has been studied on Pd(111). Methyl isocyanide adsorbs on Pd(111) at 80 K at low coverages with the isocyanide functionality oriented close to parallel to the surface; the surface-bound species reorients to a geometry in which the isocyanide group is perpendicular to the surface as the coverage increases. Desorbing the excess isocyanide recovers the parallel geometry. Heating to above ∼300 K forms a third, thermally stable, rehybridized species with its CN axis close to perpendicular to the surface. This thermally decomposes to desorb HCN and hydrogen at above 450 K. Acetonitrile is much less reactive and adsorbs in an η2(C,N) configuration where the adsorbate appears to maintain a reasonably linear CCN geometry on the surface and which desorbs with no thermal decomposition at 225 K.