Nature of the Rh-H(2) Bond in a Dihydrogen Complex Stabilized Only by Nitrogen Donors. Inelastic Neutron Scattering Study of Tp(Me)2RhH(2)(eta(2)-H(2)) (Tp(Me)2 = Hydrotris(3,5-dimethylpyrazolyl)borate).
The tunnel splitting of the librational ground state and the torsional frequencies of the dihydrogen ligand in Tp(Me)()2RhH(2)(eta(2)-H(2)) (Tp(Me)()2 = hydrotris(3,5-dimethylpyrazolyl)borate) were measured using inelastic neutron scattering spectroscopy. The barrier for the rotation of the H(2) ligand and its H-H separation, calculated from these data, are 0.56(2) kcal/mol and 0.94 Å, respectively. These values indicate that pi-back-donation from the Tp(Me)()2RhH(2) fragment to H(2) is relatively weak and/or the interaction between the coordinated dihydrogen molecule and the two cis-hydride ligands significantly lowers the barrier for H(2) rotation.
Eckert
Juergen
J
LANSCE, MS H805, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, Istituto di Chimica Farmaceutica, Universitá di Milano, I-20131 Milano, Italy, and Laboratorium für anorganische Chemie der Eidgenössischen Technischen Hochschule, ETH-Zentrum, Universitätstrasse 6, CH-8092 Zürich, Switzerland.
Albinati
Alberto
A
Bucher
Urs E.
UE
Venanzi
Luigi M.
LM