Transmission mechanisms of four-bond 19F19F coupling constants in fluoropropenes: A theoritical and experimental study

Indirect Nonbonded Nuclear Spin–Spin Coupling: A Guide for the Recognition and Understanding of “Through-Space” NMR J Constants in Small Organic, Organometallic, and Coordination Compounds

“…This is a theoretical formulation still based on the semiempirical INDO method . Using the IPPP method, nonbonded contributions to J FF TS-SSCCs were then calculated. , Although some experimental trends could be consistently calculated, the INDO approach was found not to be reliable enough for this kind of spin–spin coupling constants calculations. Nonetheless, IPPP-INDO calculations supported the assumptions concerning the efficient TS coupling pathway defined by the overlap of two proximate lone pairs .…”

“…In fluoropropenes, the four-bond 4 J FF couplings have been analyzed theoretically. In particular, the angular dependence of the FC, SO, and SD terms was taken into account. , These couplings were found to be critically dependent on the F···F distances and are larger wherever there are more electronegative fluorine atoms on the α-carbon (CF 3 groups). In extended unsaturated molecules such as polyene (Scheme ) and polyyne derivatives, both experimental and theoretical results suggest that the delocalized π-electron system may provide measurable SSCCs over nine bonds .…”

A polarization propagator analysis of through-space spin-spin coupling constants:19F-19F couplings

“…On the other hand, the IPPP method was recently extended to include noncontact contributions [13]. In this new version it was applied to study different transmission mechanisms of F-F couplings in fluoropropenes [14]. In such a case, although general experimental trends could be properly described, a direct comparison with experimental data of the TS component was not possible since in such compounds different transmission mechanisms contribute significantly to the total couplings.…”