Cycloaddition reactions of heterocumulenes. Part 8. Crystal structure and valence tautomerism of 5-dimethyliminio-4,4-dimethyl-Δ2-thiazoline-2-thiolate

Abstract

The crystal structure of the title compound has been determined by X-ray diffraction. Crystals are monoclinic, space group P2₁/c, with Z= 4 in a unit cell of dimensions: a= 7.07₇, b= 11.64₄, c= 11.95₅Å, β= 106.7₄°. The structure was solved by direct phase-determining methods and refined to R 0.030 for 1 860 reflections. Except for the C-methyl groups all non-hydrogen atoms are in a single plane. The positive charge is centred essentially at the N(2) atom and the negative charge at the exocyclic S(2) atom. Solution i.r.measurements and temperature-dependent n.m.r. spectra gave no indication of a dipolar species, but revealed the presence of a 2-isothiocyanato-thiocarboxamide, which is formed from the original dipole by ring-opening; this reaction is reversible.