Characterisation of CrO2Br2 and CrO2BrCl by matrix-isolation infrared spectroscopy

Abstract

Chromyl bromide, CrO₂Br₂, has been prepared by the reaction between HBr and CrO₂Cl₂, and its i.r. spectrum recorded in low-temperature matrices. In particular, characteristic ⁵²CrO stretching modes are observed at 995.4 and 982.6 cm^–1(Ar matrix) and analysis of the chromium isotope structure on these bands leads to an estimate of ca. 107° for the OCrO bond angle in the C_2v monomer. The most intense Cr–Br stretching mode lies at 403.5 cm^–1. Similar matrix studies on mixtures of CrO₂Br₂ and CrO₂Cl₂ reveal the existence of molecular CrO₂BrCl, with characteristic absorptions at ca. 996, 985.5 [ν(CrO)], 483 [ν(Cr–Cl)], and 412.5 [ν(Cr–Br)] cm^–1.