Structural studies of organoboron compounds. XXIV. 5-Methyl-5-nitro-2-phenyl-1,3-dioxa-2-boracyclohexane

Abstract

The title compound was prepared according to the literature in order to determine whether it has a bicyclic cage structure resulting from intramolecular O → B coordination or a monocyclic boronate structure incorporating a trigonal planar boron atom. Crystals of 5-methyl-5-nitro-2-phenyl-1,3-dioxa-2-boracyclohexane are orthorhombic, a = 17.2358(4), b = 6.5007(2), c = 9.9225(3) Å, Z = 4, space group Pnam. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.064 and Rw = 0.070 for 798 reflections with I ≥ 3σ(I). The molecule actually has C1symmetry but, in the solid state, is located at a site of crystallographic Cs symmetry. In order to maintain the apparent mirror symmetry the nitro oxygen atoms are disordered over two mirror-related rotational positions around the C(2)—N bond. The molecule was found to have a monocyclic boronate structure, in agreement with earlier predictions. The six-membered heterocyclic ring has a "semi-planar" conformation. Bond distances and angles are normal.