Abstract
Fenske-Hall molecular orbital calculations on the metal atom clusters: {Mo(,3)((mu)(,3)-O)(,2)(O(,2)CH)(,6)(H(,2)O)(,3)}('2+), Mo(,3)((mu)(,3)-CH)(,2)(O(,2)CH)(,6)(H(,2)O)(,3), {Mo(,3)((mu)(,3)-O)(O(,2)CH)(,6)(H(,2)O)(,3)}('2+), {Mo(,4)(OH)(,16)}('2-) and Mo(,4)(OH)(,16) have been performed and are presented in detail. Comparison of the results for the {Mo(,3)((mu)(,3)-O)(,2)(O(,2)CH)(,6)(H(,2)O)(,3)}('2+) and Mo(,3)((mu)(,3)-CH)(,2)(O(,2)CH)(,6)(H(,2)O)(,3) clusters shows no significant differences. The calculations confirm the presence of an (e')('4)(a(,1)')('2) configuration which corresponds to a single metal-to-metal bond between each pair of metal atoms. The highest two occupied energy levels are primarily metal in character. The one- or two-electron oxidation of the Mo(,3)((mu)(,3)-CR)(,2)(O(,2)CR)(,6)(H(,2)O)(,3) cluster results in the reduction of the metal-metal bond order without major disturbance of the metal-to-ligand bonding. The electronic structure of the hemibicapped species, {W(,3)((mu)(,3)-O)(O(,2)CR)(,6)(H(,2)O)(,3)}('2+), can be considered similar to that of the bicapped species except that in place of three bonds to a second capping atom there is an empty e orbital and a filled a(,1) orbital that has moderately bonding character with respect to the metal triangle. The bonding in the type of compound exemplified by W(,4)(OC(,2)H(,5))(,16) has been examined. It is shown that the low-symmetry (C(,i)) structure of this molecule can be understood as the result of a second-order Jahn-Teller distortion of a more regular (C(,2h)) structure; the more regular structure would require two more electrons, which would then permit the formation of the entire set of five metal-metal single bonds. Loss of two electrons from such a structure is shown to lead uniquely to the type of distortion observed and the calculations suggest that the molecule is stabilized by about 0.5 eV as a result of the distortion.
Fang, Ann (1982). The electronic structures of metal atom cluster compounds,. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -394850.