Crystal and molecular structure of 2-(m-bromophenyl)-3-methyl-4-(trifluoroacetyl)oxazolium 5-oxide, a mesoionic oxazolone

Abstract

Crystals of the title compound (1) are monoclinic, space group B2₁/c, with Z= 8 in a unit cell of dimensions: a= 21.69 ± 0.03, b= 13.32 ± 0.02, c= 8.55 ± 0.01 Å, β= 85.4 ± 0.1°. The structure was determined by Patterson and Fourier methods from photographic data and refined by full-matrix least-squares techniques to R 0.080 for 748 independent reflections. The m-bromophenyl substituent is titled 44° from the planar oxazolone ring, whereas the trifluoroacetyl group is coplanar with it. Bond angles and distances suggest that an aromatic oxazolium oxide structure is not a good representation.