Spatial Structure Heterocyclic Organoelement Compounds Determined by X-Ray Diffraction. Interpretation Model Based on Hyperconjugative Interactions

Abstract

The interpretation model of the molecular geometry derived from X-ray diffraction data, which gives good results in the structures of symmetric 1,3,2-dioxa- and diaza-phosphacyclanes, is extended on the new classes of non-symmetric sterically hindered structures of 5,6-benzo-1,2-oxaphosphorines, 6,7-benzo-1,3,2- and 1,4,2-dioxa- and oxaza-phosphepines. It is shown, that steric ineractions may invert the anomeric effect of substituents. The observed changes of bond lengths are explained by electron density transfer as a result of hyperconjugative electronic interactions. The interpretation model is supported by the results of analysis of more than 30 structures.

Keywords::

• Stereoelectron interactions
• anomeric effect
• phosphaheterocycles; X-ray diffraction