Formation of CNO 2–2 paramagnetic species by the interaction of CO and NO on the surface of MgO

Abstract

CO and NO react on the less exposed ions of the MgO surface to give CO₂ and N₂. On particularly coordinatively unsaturated ions a paramagnetic species CNO^2–₂ is formed. This has been characterized by infrared spectroscopy (CO stretch at 1624 cm^–1, CO bending mode at 800 cm^–1 and C—N—O pseudoantisymmetric stretch at 1091 cm^–1) and by e.s.r. spectroscopy [g₁= 2.014, g₂= 2.007, g₃= 2.003, g^′₃= 2.005; A₁(¹⁴N)= 7 G, A₂(¹⁴N)= 9 G, A₃(¹⁴N)= 21.5 G, A₁(¹³C)= 7 G, A₂(¹³C)= 7.5 G, A₃(¹³C)= 0] using binary and ternary mixtures of N and C isotopes.

The structure proposed is close to an acyl nitroxide and correspondence is found with the e.s.r. parameters of organic analogues. The species is unstable towards outgassing, oxidation (O₂) and reduction and surface isocyanates are found on reaction with H₂.