THE THERMAL-DECOMPOSITION OF AZOMETHANE ON PT(111)

The thermal decomposition of azomethane, CH3N=NCH3, and methylamine, CH3NH2, on Pt(111) has been investigated by reflection absorption infrared spectroscopy (RAIRS) and temperature programmed reaction spectroscopy (TPRS). Using the surface dipole selection rule of RAIRS and comparing with the IR and Raman spectra of solid trans-and cis-azomethane, we find that trans-azomethane converts to cis-azomethane upon adsorbing onto the Pt(111) surface at 84 K. Additionally, we propose that the cis-azomethane tautomerizes to formaldehyde methylhydrazone, CH3NHN=CH2, which subsequently undergoes N-N bond cleavage between 200 and 275 K. Above 300 K aminomethylidyne, CNH2, is formed. Aminomethylidyne is also formed on the methylamine dosed surface. Cyanogen, C2N2(g), formed from the combination of CNads was also observed by TPRS as a minor reaction product. A comparison of the IR spectra of azomethane and methylamine dosed surfaces indicates the formation of chemisorbed methylamine as one intermediate in the decomposition of azomethane.