Reactions of Laser-Ablated Chromium Atoms with Nitric Oxide: Infrared Spectra of NCrO, Cr−(η-NO)X (x = 1, 2, 3, 4), and Cr-η-NO in Solid Argon

Abstract

Laser-ablated chromium atoms have been reacted with NO molecules during condensation in excess argon. Absorptions due to NCrO (976.1, 866.2 cm-1), Cr−η1-NO (1614.3, 541.1 cm-1), and Cr−η2-NO (1108.8, 528.2,478.0 cm-1) are observed and identified via isotopic substitution and DFT frequency calculations. The insertion reaction to give the more stable NCrO product requires activation energy, while the addition products Cr−η1-NO and Cr−η2-NO can be formed on diffusion of cold reagents in solid argon. Higher nitrosyls are also formed on annealing. On the basis of isotopic multiplets, a 1623.3 cm-1 absorption is assigned to Cr−(η1-NO)2, a 1663.5 cm-1 absorption to Cr−(η1-NO)3, and absorptions at 1726.0, 663.0, and 506.1 cm-1 are assigned to Cr−(η1-NO)4. Evidence is also presented for the Cr−(η1-NO)x- anions (x = 1, 2, 3) absorbing 100−160 cm-1 lower than the neutral nitrosyl counterparts. In addition, NO complexes with CrO and CrO2 are also observed.