Tetrahedral clusters of GaMo{sub 4}S{sub 8-} type compounds: A metal bonding analysis
- Universite de Rennes (France)
Extended Hueckel tight binding calculations have been performed on ligated as well as on ligand-free Mo{sub 4} and Mo{sub 6} extended frames, in order to analyze the metal-metal bonding within the clusters and particularly the appreciable changes of the metal-metal bond lengths through the M{sub 4} tetrahedral units contained in GaM{sub 4}X{sub 8} (M = Mo, Nb, V, Ta; X = S, Se, Te), units of the MMo{sub 6}S{sub 4}Y{sub 4} (Y = Cl, Br, I). A comparison with the M{sub 6} octahedral units of the MMo{sub 6}X{sub 8} (M = Pb, Ag, La; X = S, Se) series is made. By means of DOS, COOP curves, and overlap populations, results clearly display the strong reorganization of the electronic structure of the bare metal clusters network while the ligand interactions occur, inducing a strong reduction of the strength of the metal-metal bonds. We outline the relationship between the metal-metal bond lengths and various parameters such as the valence electron count (VEC) per cluster and the nature of the ligands. Our results indicate that the two series M{sub 4} and M{sub 6} differ: M-M bond lengths are unaffected by the VEC in the regular M{sub 4} cluster; whereas some M-M bond lengths undergo a significant change when the VEC increases in the distorded M{sub 6} clusters. Likewise, it is worthy to note that metal d orbitals have a more significant effect in M{sub 4} cluster series. In contrast, the metal-ligand covalency induces similar enlongations of metal-metal bonds in the two series.
- OSTI ID:
- 430261
- Journal Information:
- Journal of Solid State Chemistry, Vol. 120, Issue 1; Other Information: PBD: 15 Nov 1995
- Country of Publication:
- United States
- Language:
- English
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