N.m.r. spectroscopic and X-ray crystallographic studies on some o-NO2 substituted aromatic sulphur amides

Abstract

Solid state ¹³C c.p.-m.a.s. and solution ¹³C, ¹⁵N, ¹⁴N, and ¹⁷O n.m.r. spectra have been measured for N,N-dimethyl-o-nitrobenzenesulphenamide, o-nitrobenzenesulphenamide, and N,N-dimethyl-onitrobenzenesulphonamide. The ¹³C c.p.-m.a.s. n.m.r. resonance signals of the methyl carbon atoms bonded to nitrogen show a characteristic doublet pattern. In addition, like the signal of N,N-dimethyltoluene-p-sulphonamide, the N-methyl resonance signal of N,N-dimethyl-o-nitrobenzenesulphenamide shows extra splitting. In the solution spectra the ¹⁵N nuclei of the amide group of the sulphonamides are considerably less shielded than those of the corresponding sulphenamides. The nitro-substituent of the aromatic ring has hardly any effect on the electron density of the nitrogen atom of the sulphonamide group.

The crystal structures of N,N-dimethyl-o-nitrobenzenesulphenamide (1) and N,N-dimethyl-o-nitrobenzenesulphonamide (2) have been determined by the single crystal X-ray diffraction technique and refined to final R values 0.043 and 0.049, respectively. The configurations of these sulphur(II) and sulphur(VI) amides, with respect to the geometry around the sulphur atom and the orientation of the substituents in the phenyl ring, are different. The sulphenamide adopts crystallographic σ symmetry, with all atoms except the methyl groups lying in the crystallographic mirror plane. N,N-Dimethyl-o-nitrobenzenesulphonamide has no high molecular symmetry and there is clear steric repulsion between the NO₂ group and the oxygen atoms of the SO₂N group. The nitro group is rotated 53.5(2)° relative to the plane through the phenyl group. The amide nitrogen displays a pseudo-trigonal arrangement in both compounds.