THEORETICAL-STUDY ON THE METAL NMR CHEMICAL-SHIFT - MOLYBDENUM COMPLEXES

The 95Mo NMR chemical shift of the molybdenum complexes MoO4−nXn 2− (X = S, Se; n = 0−4) is studied theoretically with the ab initio molecular orbital method. The calculated results are in quite good agreement with experiments, showing the reliability of the method used in this series of studies. The Mo chemical shift mainly reflects the change in the valence 4d orbitals of molybdenum caused by ligand substitution. A perturbation theoretical analysis reveals that this change is dictated by the stabilization of the unoccupied 4dσ* and 4dπ* orbitals by the participation of the ligand orbitals. We then predict that the Mo chemical shift will increase as the softness of the ligand increases. This trend is somewhat similar to that of the Mn chemical shift studied previously. We further predict inverse proportionality between the magnetically allowed d-d transition energy and the Mo chemical shift. © 1990, American Chemical Society. All rights reserved.