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Monoclinic CeRuSn with its own structure type transforms to a high-pressure modification at 11.5 GPa and 1470 K (1000 t press, Walker type module). The structure of the high-pressure phase was refined from X-ray single crystal diffractometer data at room temperature. The HP-CeRuSn subcell structure adopts the ZrNiAl type: P6[combining macron]2m, a = 751.4(3) and c = 394.6(2) pm, wR2 = 0.0787, 310 F(2) values and 15 variables. The Ru2 atoms within the Sn6 trigonal prisms show a strongly enhanced U33 parameter. Weak satellite reflections indicate a commensurate modulation: (3 + 1)D superspace group P31m(1/3,1/3,γ)000, a = 751.4(3) and c = 394.6(2) pm, γ = -1/3, wR2 = 0.0786, 1584 F(2) values, 32 variables for the main reflections and wR2 = 0.3757 for the satellites of 1(st) order. A description of this new superstructure variant of the ZrNiAl type is possible in a transformed 3D supercell with the space group R3m and Z = 9. The driving force for formation of the modulation is strengthening of Ru-Sn bonding within the comparatively large Ru@Sn6 trigonal prisms. Electronic structure calculations point to an almost depleted Ce 4f shell. This is substantiated by temperature-dependent magnetic susceptibility data. Fitting of the data within the interconfiguration fluctuation model (ICF) resulted in cerium valences of 3.41 at 10 K and 3.31 at 350 K. Temperature dependent specific heat data underline the absence of magnetic ordering.

The quaternary gold(I) arsenide oxides Nd10Au3As8O10 and Sm10Au3As8O10 were synthesized in sealed quartz ampoules from the rare earth (RE) elements, their appropriate sesquioxides, arsenic, arsenic(III) oxide and finely dispersed gold at maximum annealing temperatures of 1223 K. Both structures were refined from X-ray single crystal diffractometer data at room temperature and at 90 K. Nd10Au3As8O10 and Sm10Au3As8O10 crystallize with a new structure type that derives from the BaAl4 structure through distortions and formation of ordered vacancies. The structures consist of stacked polycationic [RE10O10](10+) layers with oxygen in tetrahedral rare earth coordination and polyanionic [Au(I)3(As2)4](10-) layers with gold in square planar or rectangular planar coordination of four arsenic dumbbells (255 pm As1-As2). In contrast to the well known ionic rare earth oxide layers, the gold arsenide layers rather show covalent bonding and account for the metallic nature of these two new arsenide oxides. This is confirmed by electronic structure calculations and resistivity measurements. The oxidation state of gold was investigated by (197)Au Mössbauer, X-ray absorption near edge structure (XANES) and photoelectron (XPS) spectroscopy. Due to missing comparative gold arsenide compounds, the monovalent gold phosphide oxides RE2AuP2O were measured for comparison. The XANES measurements additionally comprise monovalent gold arsenides REAuAs2. The XPS study contains BaAuAs as reference compound instead. Combination of all data clearly indicates Au(I), which was not observed in square planar coordination up to now. Temperature dependent magnetic susceptibility data show Curie-Weiss paramagnetism for Nd10Au3As8O10 and no magnetic ordering down to 2.5 K. Sm10Au3As8O10 shows the typical Van Vleck type paramagnetism for samarium compounds along with a transition to an antiferromagnetically ordered state at TN = 8.6 K.

Crystals of Bi(4)Ir, a new intermetallic compound, were obtained by the reaction of an iridium-containing intermetallic precursor with liquid bismuth. X-ray diffraction on a single crystal revealed a rhombohedral structure [R3̅m, a = 2656.7(2) pm, and c = 701.6(4) pm]. Bi(4)Ir is not isostructural to Bi(4)Rh but combines motifs of the metastable superconductor Bi1(4)Rh(3) with those found in the weak topological insulator Bi1(4)Rh(3)I(9). The two crystallographically independent iridium sites in Bi(4)Ir have square-prismatic and skewed-square-antiprismatic bismuth coordination with Bi-Ir distances of 283-287 pm. By sharing common edges, the two types of [IrBi(8)] units constitute a complex three-dimensional network of rings and helices. The bonding in the heterometallic framework is dominated by pairwise Bi-Ir interactions. In addition, three-center bonds are found in the bismuth triangles formed by adjacent [IrBi(8)] polyhedra. Density functional theory based band-structure calculations suggest metallic properties.

Members of the solid solution series of CeRu(1-x)Ni(x)Al can be obtained directly by arc melting of the elements. The presented compounds with 0.1 ≤ x ≤ 0.85 crystallize in the orthorhombic space group Pnma (No. 62) in the LaNiAl structure type, while for 0.9 ≤ x ≤ 1, the hexagonal ZrNiAl-type structure is found. The orthorhombic members exhibit an anomaly in the trend of the lattice parameters as well as an interesting behavior of the magnetic susceptibility, suggesting that the cerium cations exhibit no local moment. Besides the mixed-valent nature of the cerium cations, valence fluctuations along with a change in the cerium oxidation state depending on the nickel content have been found. The oxidation state has been determined from the magnetic data and additionally by XANES. Density functional theory calculations have identified the shortest Ce-Ru interaction as decisive for the stability of the orthorhombic solid solution.

Sc(3)RuC(4) and Sc(3)OsC(4) were synthesized by arc-melting and subsequent annealing. At room temperature, they crystallize with the Sc(3)CoC(4) structure, space group Immm. At 223 and 255 K, Sc(3)RuC(4) and Sc(3)OsC(4), respectively, show a monoclinic distortion caused by a pair-wise displacement of the one-dimensional [Ru(C(2))(2)](delta-) and [Os(C(2))(2)](delta-) polyanions, which are embedded in a scandium matrix. Superstructure formation leads to shorter Ru-Ru and Os-Os distances of 316 pm between adjacent [Ru(C(2))(2)](delta-) and [Os(C(2))(2)](delta-) polyanions. Each ruthenium (osmium) atom is covalently bonded to four C(2) pairs with Ru-C (Os-C) distances of 220-222 pm. A comparison of the C-C bond distances at room temperature in Sc(3)TC(4) with T representing a group 8 transition metal (Fe, Ru, Os) reveals a minimum in the case of the 4d metal Ru: 144.98(11) pm (Fe), 142.8(7) pm (Ru), and 144.6(4) pm (Os). Analysis of the local electronic structure of the [T(C(2))(2)] moieties hints at a complex interplay between chemical bonding and relativistic effects, which is responsible for the V-shaped pattern of the C-C bond distances (long, short, and long for T = Fe, Ru, and Os, respectively). Relativistic effects lead to a strengthening of covalent T-C bonding. This is shown on the basis of periodic DFT calculations by a significant increase of the charge density at the T-C bond critical points (0.55 < 0.57 < 0.64 eA(-3)) down the row of group 8 elements. These structural characteristics and topological features do not change in the corresponding low-temperature phases of Sc(3)RuC(4) and Sc(3)OsC(4). However, topological analyses of theoretical charge density distributions reveal distinct changes of the valence shell charge concentrations at the transition metal centers due to the monoclinic distortions. Presumably, the local electronic situation at the transition metals reflects the origin and extent of these monoclinic distortions.

The reaction of the benzannulated bisstannylene ligand 2 with Sn O or Pb O generated in situ gave the pincer complexes 3 and 4. Both complexes have been characterized by X-ray diffraction and multinuclear NMR spectroscopy. A divalent state has been found by Mössbauer spectroscopy for the tin atoms in complexes 3 and 4.

The nature of chemical bonding in the complex carbides Sc3[Fe(C2)2] (1) and Sc3[Co(C2)2] (2) has been explored by combined experimental and theoretical charge density studies. The structures of these organometallic carbides contain one-dimensional infinite TC4 (T = Fe, Co) ribbons embedded in a scandium matrix. Bonding in 1 and 2 was studied experimentally by multipolar refinements based on high-resolution X-ray data and compared to scalar-relativistic electronic structure calculations using the augmented spherical wave method. Besides substantial covalent T-C bonding within the TC4 ribbons, one also observes discrete Sc-C bonds of noticeable covalent character. Furthermore, our study highlights that even tiny differences in the electronic band structure of solids might be faithfully recovered in the properties of the Laplacian of the experimental electron density. In our case, the increase of the Fermi level in the organometallic Co(d9) carbide 2 relative to its isotypic Fe(d8) species 1 is reflected in the charge density picture by a significant change in the polarization pattern displayed by valence shell charge concentrations of the transition metal centers in the TC4 units. Hence, precise high-resolution X-ray diffraction data provide a reliable tool to discriminate and analyze the local electronic structures of isotypic solids, even in the presence of a severe coloring problem (Z(Fe)/Z(Co) = 26/27).