FORMATION OF AMINOMETHYLIDYNE FROM HYDROGEN-CYANIDE ON PT(111)

The thermal chemistry of HCN has been investigated from 85 to 450 K by Fourier transform-infrared absorption spectroscopy (FT-IRAS) and thermal desorption spectroscopy (TDS). The adsorption of HCN at 85 K yields an infrared spectrum consisting of an intense band at 3298 cm(-1) due to the CH stretch and a weak band at 1311 cm(-1) that is assigned to the overtone of the HCN bend. The close resemblance between the IR spectrum of HCN absorbed on Pt(111) at 85 K and the IR spectrum of HCN in the gas phase and trapped in an argon matrix suggests that HCN is adsorbed molecularly at 85 K and is only weakly perturbed by the surface. Upon warming to 300 K, the (HCN)-C-12-N-14 is transformed to a new molecular species with bands at 3363, 1567, and 1323 cm(-1). From the shifts of these bands following initial adsorption of the (HCN)-C-13-N-14 and (HCN)-C-12-N-15 isotopes, they are assigned to an NH stretch (3363 cm(-1)), NH2 bend (1567 cm(-1)), and CN stretch (1323 cm(-1)). Comparison with the IR spectrum of an Os3H(mu-CNH2)CO10 complex indicates that the 300 K species is aminomethylidyne, CNH2.