HOST-GUEST CHEMISTRY. THE STRUCTURE AND PROTON DISORDER OF THE THREE-COMPONENT CRYSTAL FORMED BY 3(5)-METHYL-4-NITROPYRAZOLE, (R,R)-(-)-TRANS-4,5- BIS(HYDROXYDIPHENYLMETHYL)-2,2-DIMETHYL-1,3- DIOXOLANE AND TOLUENE

摘要

The crystal structure at 200 K of the complex formed by the optically active host (R,R)-(-)-trans-4,5-bis(hydroxydiphenylmethyl)-2,2-dimethyl-1,3-dioxolane (2) and 4-nitro-5-methylpyrazole (1b) and toluene as guests was determined by x-ray analysis. Although only the NH protons corresponding to tautomer 1b were found in the structure, some anomalies in the bond angles involving the nitrogen atoms of the pyrazole ring suggested the presence of about 25% of a structure containing the 3-methyl-4-nitropyrazole tautomer (1a). This hypothesis was confirmed by ~(13)C cross polarization magic angle spinning NMR spectroscopy.