Dynamics on an ab-initio surface for calculating J(HH) NMR exchange coupling: the case of OsH₃X(PH₃)₂

Eric Clot (1) , Claude Leforestier (1) , Odile Eisenstein (1) , Michel Pélissier (1)

1 Laboratoire Chimie Théorique

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 to 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 calculated 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 ratio 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.

Mots clés: QUANTUM-MECHANICAL EXCHANGE; TRANSITION-METAL POLYHYDRIDES; TRIHYDRIDE COMPLEXES; EFFECTIVE POTENTIALS; BASIS-SETS

Domaines: Chimie-Physique [physics.chem-ph]

Eric Clot, Claude Leforestier, Odile Eisenstein, Michel Pélissier. Dynamics on an ab-initio surface for calculating J(HH) NMR exchange coupling: the case of OsH₃X(PH₃)₂. Journal of the American Chemical Society, 1995, 117, pp.1797-1799. ⟨10.1021/ja00111a018⟩. ⟨hal-00429124⟩