The enormous temperature dependence of the 2JPP coupling constants in S(PF2)2 and Se(PF2)2 has been explained by a theoretical investigation of their conformations and NMR coupling constants. In contrast, the coupling in O(PF2)2 is almost invariant. Gas electron diffraction data for S(PF2)2 have been reinterpreted. The results show that two conformers, with Cs and C2v symmetry, exist for the S and Se compounds. The Cs and C2v conformers have very different 2JPP coupling constants (-12.6 and 395.2 Hz for S(PF2)2 at B3LYP/aug-cc-pVQZ) and thermal interconversion of these conformers explains the experimental behavior.
- GENERALIZED GRADIENT APPROXIMATION
- CORRELATED MOLECULAR CALCULATIONS
- PHASE ELECTRON-DIFFRACTION
- DENSITY-FUNCTIONAL THEORY
- GAUSSIAN-BASIS SETS