What makes the huge 31P-31P coupling constants in S(PF2)2 and Se(PF2)2 vary so much with temperature?
The enormous temperature dependence of the (2)J(PP) coupling constants in S(PF(2))(2) and Se(PF(2))(2) has been explained by a theoretical investigation of their conformations and NMR coupling constants. In contrast, the coupling in O(PF(2))(2) is almost invariant. Gas electron diffraction data for S(PF(2))(2) have been reinterpreted. The results show that two conformers, with C(s) and C(2v) symmetry, exist for the S and Se compounds. The C(s) and C(2v) conformers have very different (2)J(PP) coupling constants (-12.6 and 395.2 Hz for S(PF(2))(2) at B3LYP/aug-cc-pVQZ) and thermal interconversion of these conformers explains the experimental behavior.
Reilly
Anthony M
AM
School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK.
Wann
Derek A
DA
Rankin
David W H
DW