Molecular mechanics: Extension of the MM2 program to pentacoordinate phosphorus compounds. 1. Conformational study of the bicyclic phosphoranes of the type R-P(H)N(CH2-CH2-O2 (R=H, Me, Ph)

Abstract

Extension of Allinger's program MM2 [21] to pentacoordinate phosphorus compounds has been performed, tested, and used for a conformational study of the bicyclic phosphoranes R-P(H)N(CH2-CH2-O)2 with R = H, Me, and Ph. Conformations of low energy and barriers between them agree well with the interpretation of NMR results in terms of flexibility of the rings with an exception for R = Ph. In that case, one possible explanation could be the lack of modeling of a special stereoelectronic interaction of the oxygen lone pairs with the phenyl ring.