RESONANCE INTERACTIONS IN THE N-NITRAMINO GROUP - X-RAY STUDY OF ALPHA-NITRAMINOPYRIDINE, BETA-NITRAMINOPYRIDINE AND GAMMA-NITRAMINOPYRIDINE

The crystal and molecular structure of three isomers (alpha, beta and gamma) of nitraminopyridine have been solved by X-ray diffraction at r oom temperature with Cu K alpha radiation, All isomers exist as the im ino tautomeric form with strong resonance interactions in the nitramin o group. NN and NO bond lengths and ONO bond angles are interrelated a s found from consideration of 61 structures taken from the Cambridge S tructural Database (release April 1995). Changes in geometry of the ni tramino group are explained by differences in the s/p-character of the bond. Stabilization of the imino form seems to be due to the I-I-bond ing net in the crystal, a phenomenon not taken into account in the nb initio calculation of alpha-isomers, which favors the amino form.