Exploring the Origin of the Anomeric Effects in 2,3-Dihalo-1,4-Diphosphinane-1,4-Diium

To explore the origin of the anomeric relationships, we assessed the roles and contributions of the effective factors on the conformational properties in two types of 2,3-dihalo-1,4-diphosphinane-1,4-diium (halogens are: F, Cl and Br), compounds 1 – 3 , respectively, by means of the B3LYP, M06-2X, and LC-ωPBE methods and NBO interpretations. The results showed that the axial–axial conformations of compounds 1 – 3 are more stable than their corresponding equatorial–equatorial conformations. The NBO analysis showed that the hyperconjugative exo anomeric effects (HCAE- exo -SE) is in favor of compound 1 to 3 . The calculated dipole moment (μ) values for axial–axial conformations of compounds 1 – 3 are lower than their corresponding equatorial–equatorial conformations. The Pauli exchange type repulsions (PETR) are in favors of the axial–axial conformations, revealing that the anomeric relationships in compounds 1 – 3 have also the Pauli exchange-type repulsions origin.