E. Clot et al., DYNAMICS ON AN AB-INITIO SURFACE FOR CALCULATING J(HH) NMR EXCHANGE COUPLING - THE CASE OF OSH(3)X(PH3)(2), Journal of the American Chemical Society, 117(6), 1995, pp. 1797-1799
The exchange coupling J(HH) in OsH(3)X(PH3)(2) (X = Cl and I) has been
calculated by determining the eigenstates resulting from the coupling
between the internal rotation and vibration modes, which correspond t
o the painwise hydrogen exchange, The potential has been calculated by
core potential ab initio methods at the RHF/MP2, level. The height of
the barrier for exchange of two adjacent hydrogen atoms has been calc
ulated to be 12.9 kcal.mol(-1) (X = Cl) and 14.6 kcal.mol(-1) (X = I).
The ratio between the calculated exchange coupling constants for X =
Cl and X = I is found to be in good agreement with the experimental ra
tio though shifted up in temperature. The temperature dependence of J(
HH) is calculated to be exponential, which is the typical behavior for
such a coupling constant.