Die KristallStrukturen von K6[Ge2Te6] und K6[Sn2Te6] und ihre kristall-chemische Beziehung zum K6[Si2Te6]-Typ

Germanium Antimony Bonding in Ba4Ge2Sb2Te10 with Low Thermal Conductivity

A new quaternary telluride, Ba₄Ge₂Sb₂Te₁₀, was synthesized at high temperature via the reaction of elements. A single-crystal X-ray diffraction study shows that the title compound crystallizes in its own structure type in the monoclinic P2₁/c space group having cell dimensions of a = 13.984(3) Å, b = 13.472(3) Å, c = 13.569(3) Å, and β = 90.16(3)° with four formula units per unit cell (Z = 4). The pseudo-one-dimensional crystal structure of Ba₄Ge₂Sb₂Te₁₀ consists of infinite ₁^∞[Ge₂Sb₂Te₁₀]^8- stripes, which are separated by Ba²⁺ cations. Each of the Ge(1) atoms is covalently bonded to four Te atoms, whereas the Ge(2) atom is covalently bonded with one Sb(2) and three Te atoms in a distorted tetrahedral geometry. The title compound is the first example of a chalcogenide that shows Ge-Sb bonding. The Sb(1) atom is present at the center of the seesaw geometry of four Te atoms. In contrast, the Sb(2) atom forms a seesaw geometry by coordinating with one Ge(2) and three Te atoms. Condensation of these Ge and Sb centered polyhedral units lead to the formation of ₁^∞[Ge₂Sb₂Te₁₀]^8- stripes. The temperature-dependent resistivity study suggests the semimetallic/degenerate semiconducting nature of polycrystalline Ba₄Ge₂Sb₂Te₁₀. The positive sign of Seebeck coefficient values indicates that the predominant charge carriers are holes in Ba₄Ge₂Sb₂Te₁₀. An extremely low lattice thermal conductivity of ∼0.34 W/mK at 773 K was observed for polycrystalline Ba₄Ge₂Sb₂Te₁₀, which is presumably due to the lattice anharmonicity induced by the stereochemically active 5s² lone pair of Sb. The electronic structure of Ba₄Ge₂Sb₂Te₁₀ and the bonding of atom pairs in the structure have been analyzed by means of ELF analysis and crystal orbital Hamilton population (COHP) analysis.

The Reduced Nitridogermanates(III) Ca6 [Ge2 N6 ] and Sr6 [Ge2 N6 ] with Ge-Ge Bonds

The first nitridogermanates(III) Ca₆[Ge₂N₆] and Sr₆[Ge₂N₆] were synthesized from sodium flux and structurally characterized by powder and single crystal X‐ray diffraction, respectively. They crystallize isostructurally to each other and homeotypic to Ca₆[Cr₂N₆]H in space group R3‾ . They feature unprecedented, mutually isolated, ethane‐like [Ge^III₂N₆]¹²⁻ anions in a staggered conformation. The compounds are semiconductors according to resistivity measurements and electronic structure calculations, yielding band gaps of 1.1 eV for Ca₆[Ge₂N₆] and 0.2 eV for Sr₆[Ge₂N₆].

Ba2Ge2Te5: a ternary NLO-active telluride with unusual one-dimensional helical chains and giant second harmonic-generation tensors

The linear-optical and NLO properties of a ternary NLO-active telluride, Ba2Ge2Te5, were investigated systematically at the experimental and theoretical levels for the first time.

Cs2Ge3In6Se14: A Structure Transformation Driven by the Size Preference and Its Properties

The new selenide Cs₂Ge₃In₆Se₁₄, featuring its own structure type with germanium in mixed-valence states, is discovered via a solid-state reaction at 1173 K. The compound crystallizes in the R3̅ m space group with a = 7.9951(6) Å and c = 41.726(4) Å. Two adjacent condensed layers of InSe₄ tetrahedra are linked by a [Ge²⁺Se₆] octahedron into a double slice that is further stacked along the c direction with a packing sequence of ··· abca··· through the [Ge³⁺₂Se₆] dimer via its Ge-Ge metallic bond. The coexistence of Ge²⁺/Ge³⁺ and Ge-Ge metallic bonding has been confirmed by XPS and ELF analyses, respectively. More interestingly, although sharing many structure similarities, Cs₂Ge₃In₆Se₁₄ and our previously reported Cs₂Ge₃In₆Te₁₄ reveal a R3̅ m to P3̅ m1 structure transformation with a tripled c parameter. Single-crystal diffraction data and a thorough structure survey of related compounds point out that such a transformation is driven by the size preference of the [Ge₂Q₆] dimer. The title compound possesses a band gap of 2.08 eV and shows photodegradation of RhB under visible light that is more efficient than that for the commercial P25.

Li3Ge3Se6: the first ternary lithium germanium selenide with interesting∞[Ge6Se12]nchains constructed by ethane-like [Ge2Se6]6−clusters

The first lithium germanium selenide, Li₃Ge₃Se₆with the first discovered chain formed by [Ge₂Se₆]⁶⁻clusters in the [Li₃Se₆] tunnels.

Thiostannate tin-tin bond formation in solution: in situ generation of the mixed-valent, functionalized complex [{(RSn(IV))2(mu-S)2}3Sn(III)2S6]

In broad daylight: The double-decker thiostannate [(RSn(IV))(4)S(6)] (1, R = CMe(2)CH(2)COMe) condenses to form [{(RSn(IV))(2)(mu-S)(2)}(3)Sn(III)(2)S(6)] (2; see picture). This mixed-valent complex, which formally contains both Sn(III) and Sn(IV) atoms as confirmed by Mössbauer spectroscopy and DFT calculations, forms by a complicated, concerted mechanism. Additionally, 2 provides six carbonyl groups for further derivatization.