Comparative Study of Conjugational Effects in 3,4,5-Triaryl-1-R-1,2-Diphospholes and 3,4,5-Triaryl-1,2-Diphosphacyclopentadienide-Anions

GRAPHICAL ABSTRACT

Abstract

The strength of conjugation between the phosphorus ring of 3,4,5-triaryl-1,2-diphosphacyclopentadienide-anion and exocyclic phenyl groups has been quantitatively characterized by the use of Raman activities of the bands of the phenyl substituents and the structural parameters obtained by an X-ray diffraction study. It is shown that conjugation in 1,2-diphospholides is very similar to conjugation of phenyl groups with the diene system of 1-R-1,2-diphospholes. The conjugation produces a dramatic intensification of Raman bands and a simultaneous bathochromic shift of the whole electronic absorption spectra for both types of phosphorus heterocycles.

Keywords:

• 1,2-diphospholes
• phospholides
• aromaticity
• conjugation
• phosphorus heterocycles
• Raman spectra
• DFT calculations