Interstitial carbon molecules, metal-metal bonds, and chemical binding in Gd10C4Cl18.

Satpathy S., Andersen O. K.

Max-Planck-Inst. Festkoerperforsch., Stuttgart , 7000/80, Fed. Rep. Ger.

By means of electronic structure calcns., the chem. binding was studied in the cluster Gd10C4Cl18 (I) that consists of a Gd edge-sharing double octahedron with Cl atoms bridging the remaining edges and with C2 mols. occurring at the octahedral centers. This type of cluster is the basic unit of 3 compds., I, Gd10C4Cl17, and Gd12C6I17. In I, the Cl-like and the C2 .pi.p*-like levels are occupied while the C2 .sigma.p*-like and all Gd-like levels are empty. The cluster has no metal-metal bonds in the sense that there are no occupied MO's that are primarily metal-metal bonding in character. However, 1.7 electrons are contributed to each Gd atom through back-bonding from the occupied Cl-like (1.0 electron/Gd) and C2-like (0.7 electron/Gd) states. The LUMO is a Gd MO in the basal plane - and concd. along the shared edge - of the double octahedron. The binding in I is like that in the isolated cluster and hence is predominantly ionic. For the cluster compds. Gd10C4Cl17 and Gd12C6I17, the MO schemes are essentially the same as in I; however, now an extra electron occupies the metal-metal bond concd. along shared edges in the compd.

Inorganic Chemistry, 24 2604-8, 1985.

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