Investigation of hybridization of oxygen atom in n, v-type complexes by methods of X-ray analysis, nuclear magnetic resonance, and electronic spectroscopy

The 1H NMR and X-ray analysis proved that the space structure and hybridization type (sp 2 or sp 3) of the oxygen atom of N-oxide group in n,v-type molecular complexes of heteroaromatic N-oxides with BF 3 and other Lewis acids depend on electronic factors of the substituents in pyridine ring, solvent type, and space bulks during complexation. For example, in CDCl 3 and DMSO-d 6 in ad-duct of 4-methylpyridine N-oxide with boron trifluoride bond O-B lies in plane of pyridine cycle (sp 2-hybridization), but in crystal dihedral the angle between planes of N-O-B atoms and pyridine ring is 87,81o (sp 3-hybridization). Perhaps hybride state of the oxygen atom in n,v-type complexes of carbonylic compounds (aldehyds, ketones, carboxylic acids and their functional derivatives) depends on the same factors.