EFFECT OF THE SPINNING MOTION OF THE DIHYDROGEN LIGAND ON THE PROPERTIES OF AN ELONGATED DIHYDROGEN COMPLEX - A THEORETICAL-STUDY OF THE OT-CENTER-DOT-CENTER-DOT-H)C1(H2PCH2CH2PH2)(2)](+) COMPLEX

We present in this paper an electronic structure and quantum nuclear d ynamics study of a modeled version of trans-[Os(H ... H)Cl(dppe)(2)](), an elongated dihydrogen complex classified as being between the Fas t and slow Ha spinning limits and whose J(H,D) coupling constant incre ases on increasing temperature. We have found that the librational pot ential energy barrier for the motion of the H-2 unit is quite low, in agreement with the spinning regime of the H-2 unit reported from exper iment. Additionally, while the electronic structure study does not man age to describe the experimentally reported geometry obtained through neutron diffraction experiments, the quantum nuclear motion study repr oduces the experimental findings very satisfactorily. Finally it is se en that only when the librational motion of the H-2 Unit is taken into account in an explicit way in the quantum nuclear motion calculations the temperature dependence of the J(H,D) H-1 NMR coupling constant is also correctly accounted for.