Endohedral (interstitial) atoms are essential for almost all of the rare-earth halide cluster complexes. Most of these contain octahedral clusters, some are isolated, but the majority exhibits condensation by common edges to structures of higher dimensionality. Higher coordination numbers of the endohedral atoms are rare. Four examples of extended cluster complexes with eight-coordinate endohedral atoms of sixth-period elements (Re, Os, Ir) are presented. In the quasi-isostructural, non-isotypic halides {ReGd(4)}Br(4) and (OsSc(4))Cl(4), square antiprisms of gadolinium and scandium atoms, respectively, are connected by two common faces to chains, surrounded and loosely connected by halogenido ligands. The Re and Os atoms build a slightly bent chain with only little bonding interactions. Chemical bonding is dominated by endohedral atom-cluster atom and cluster atom-halide interactions. The same is true for the two scandium bromides and {Os(3)Sc(12)}Br(16)Sc, which contain chains of face-sharing square antiprisms and cubes in a ratio of 2:1. Metal metal bonding is attested by short distances between those endohedral Ir and Os atoms, respectively, which center the square antiprisms (283 pm and 290 pm, respectively). Magnetic and conductivity measurements on {Ir(3)Sc(12)}Br(16) reveal paramagnetism and a small-band-gap semiconductor. This is in accord with electronic structure calculations

Comproportionation reactions of rare-earth metal trihalides, RX 3 , with the respective R metal in the presence of a transition metal Z, preferably from group 8 through 10, yielded single crystals of 31 {ZR 6 }X 12 R and 22 {ZR 6 }X 10 type compounds, in most cases for the first time, especially with R = Tb, Dy, Ho, and Er. These are compared with literature entries. The crystal structures are discussed for the equal-atom pair {IrEr 6 }I 12 Er and {IrEr 6 }I 10 . In both cases,

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Keywords:Cluster compounds / Synthetic methods / Rare earths / Lutetium / Osmium / Electronic structure / Magnetic properties / Endohedral atoms {Os 5 Lu 20 }I 24 was obtained from a conproportionation reaction of lutetium and lutetium triiodide in the presence of osmium in an arc-welded tantalum container at 850-1200°C. The crystal structure has been determined by single-crystal X-ray diffraction analysis. Square antiprisms and cubes of lutetium atoms in a 4:1 ratio share common square faces in a chain; they encapsulate osmium atoms and are surrounded by iodide ions. Os-Os distances within the cluster chains (299, 303, and 325 pm) imply only little if no bonding between neighbouring osmium atoms. The cluster complex chains are packed in the fashion of a hexagonal closest packing of rods.

The oligomeric cluster complex {Ir3Gd11}Br15 was first obtained from a reaction of Gd, GdBr3 and Ir in a 3:4:1 molar ratio at 1123 K. The crystals belong to the hexagonal space group P63/m with lattice parameters a = 1276.79(14) pm and c = 1286.92(16) pm. The structure features isolated {Ir3Gd11} cluster trimers, which are built up by three face‐sharing gadolinium octahedra each centered by an iridium atom. The endohedral iridium atoms form a triangle with Ir–Ir distances of 295.51(11) pm. Thus, the {Ir3Gd11} cluster is topologically equivalent to the suboxide {O3Cs11}. The {Ir3Gd11} clusters are encapsulated in a coordination sphere of 30 bromide ions, which act as bridging ligands according to the formulation {Ir3Gd11}Bri–i12/2Bri–a9/2Bra–i9/2. In {Ir3Gd11}Br15 there are 45 electrons present for intracluster bonding.