X-ray studies on anti-tumour triazenes. Structures of 1-(4-carbamoylphenyl)-3,3-dimethyltriazene 1-oxide and 3,3-dimethyl-1-(4-nitrophenyl)triazene

The molecular structures of the title compounds have been determined by X-ray crystallographic methods. The analyses revealed differences in the geometry, and by inference the bond delocalization in these two triazenes owing to the presence in the 1-oxide structure of an N-O bond. The geometries are compared to the crystal structures of the isomeric 3-oxides [Kuroda & Wilman (1985). Acta Cryst. C41, 1543-1545; Neidle, Webster, Kuroda & Wilman (1987). Acta Cryst. C43, 674-676] which shows the dominance of an alternative tautomeric equilibrium for the triazene groups.