Mixed Valence Tungsten (IV,V) Compounds with Layered Structures (Part IV): Syntheses,Crystal Structures,and Conductivity of BiX2[W2O2X6] (X = Cl,Br)

The reaction of metallic bismuth with either tungsten tetrachlorideoxide WOCl₄ at 650 K or tungsten tetrabromideoxide WOBr₄ at 670 K, respectively, leads to BiX₂[W₂O₂X₆] (X = Cl, Br) as black, lustrous crystal needles. The crystal structure determinations (triclinic, P$\bar{1}$ ) show the two isotypic structures to be closely related to Hg_0.55[W₂O₂Cl₆] with the presence of 1D‐polymeric W₂O₂X₆ double strands. Dinuclear [Bi₂X₄]²⁺ cations are embedded in the host structure via secondary W–X ··· Bi bonds. Unlike the other members of theM_y[W₂O₂X₆] structure family, which crystallize monoclinic and show crystallographic equivalent tungsten atoms, BiX₂[W₂O₂X₆] has independent tungsten sites. Nevertheless, an assignment of an individual oxidation state to the tungsten atoms within the W₂ group (W–W 2.8321(4) Å for X = Cl, 2.8985(4) Å for X = Br) is not possible and a dynamic intervalent state W(IV, V) is assumed. Electrical conductivity measurements for BiCl₂[W₂O₂Cl₆] show semi‐conductive behavior with a very small band gap of 70 meV and a high conductivity of around 0.5 Ω^–1cm^–1 at temperatures above 220 K. A temperature dependence of the activation energy of charge transport is present and interpreted by the Varshni model.     

Mixed Valence Tungsten(IV,V) Compounds with Layered Structures (Part II)): Synthesis and Crystal Structures of Cu1−x[W2O2Cl6] and Cu1−x[W4O4Cl10]

The reaction of CuCl with WOCl₃ at 400 °C leads to a mixture of Cu_1?x[W₂O₂Cl₆] ( 1 ) and Cu_1?x[W₄O₄Cl₁₀] ( 2 ) in form of black lustrous needles. Both compounds crystallize in space group C2/m with a = 12.7832(5) Å, b = 3.7656(2) Å, c = 10.7362(3) Å, β = 119.169(2)° for 1 and a = 12.8367(19) Å, b = 3.7715(7) Å, c = 15.955(3) Å, β = 102.736(5)° for 2 . The structures are made up of WO₂Cl₄ octahedra. In the case of 1 two octahedra are edge‐sharing via chlorine atoms to form pairs which are linked via the trans‐positioned oxygen atoms to form infinite double strands . In the structure of 2 two of these double strands are condensed via terminal chlorine atoms to form quadruple strands . Like for all members of the M_x[W₂O₂X₆] structure family (X = Cl, Br) nonstochiometry with respect to the cations M was observed. The copper content of 1 and 2 was derived from the site occupation factors of the respective structure refinements. For several crystals examined the copper content varied between x = 0.27 and 0.17 for 1 and x = 0.04 for 2 . In both structures the oxochlorotungstate strands are negatively charged and connected to layers by the monovalent copper ions, which are tetrahedrally coordinated by the non‐bridging chlorine atoms of the strands. The structure models imply disorder of the Cu⁺ ions over closely neighboured sites.     

Constitutional Isomerism of BiW6Cl15: (BiCl)[W6Cl14] and (BiCl2)[W6Cl13]

The compound (BiCl)[W₆Cl₁₄] was previously characterized as a product of the reduction of tungsten hexachloride with elemental bismuth. Another modification of BiW₆Cl₁₅ is now presented as (BiCl₂)[W₆Cl₁₃], based on the results of an X‐ray single crystal structure determination (space group P2₁/c, a = 1354.3(2) pm, b = 1234.4(2) pm, c = 1538.9(2) pm, and β = 118.76(1) °). The structure of (BiCl₂)[W₆Cl₁₃] contains chains of [(W₆Cl₈ⁱ)Cl₄^aCl_2/2^a–a]^– clusters bridged by chlorine atoms. The (BiCl₂)⁺ counterion exhibits two short Bi–Cl distances of 244.1(4) and 245.9(3) pm, respectively.     

Synthesen,Kristallstrukturen und Drillingsbildung der Cluster‐Trimere Bi2[PtBi6Br12]3 und Bi2[PtBi6I12]3

Syntheses, Crystal Structures, and Triple Twinning of the Cluster Trimers Bi₂[PtBi₆Br₁₂]₃ and Bi₂[PtBi₆I₁₂]₃ Melting reactions of Bi with Pt and BiX₃ (X = Br, I) yield shiny black, air insensitive crystals of the subhalides Bi₂[PtBi₆X₁₂]. Bi₂[PtBi₆Br₁₂]₃ crystallizes in the monoclinic space group C2/m with lattice parameters a = 1617.6(2) pm, b = 1488.5(1) pm, c = 1752.4(2) pm, and β = 110.85(4)°. Bi₂[PtBi₆I₁₂]₃ adopts the triclinic space group with pseudo‐monoclinic lattice parameters a = 1711.2(2) pm, b = 1585.1(1) pm, c = 1865.7(2) pm, and α = 90°, β = 111.15(4)°, γ = 90°. The two homoeotypic compounds consist of cuboctahedral [Pt^?IIBi^II₆X^?I₁₂]^2? clusters that are concatenated into linear trimers by Bi^III atoms. The ordered distribution of Bi^III atoms destroys the inherent threefold rotation axes in the packing of cluster anions. As a consequence of the pseudosymmetry the crystals are triple twinned along [201]. Due to different orientations of the cluster trimers there are two Bi^II···X inter‐cluster bridges per Bi^II atom in Bi₂[PtBi₆Br₁₂]₃ but only one bridge in Bi₂[PtBi₆I₁₂]₃. The structure of the iodine compound can be deduced from the NaCl structure type, leaving 37 of 96 atomic positions unoccupied. The arrangement of the cuboctahedral clusters follows the motif of a body‐centered cubic packing.     

Oxo-Phosphaniminato-Komplexe von Molybdän und Wolfram. Die Kristallstrukturen von [Mo(O)2(NPPh3)2] und [WO(NPPh3)3]2[W6O19]

Oxo-phosphoraneiminato Complexes of Molybdenum and Tungsten. Crystal Structures of [Mo(O)₂(NPPh₃)₂] and [WO(NPPh₃)₃]₂[W₆O₁₉] The dioxo-phosphoraneiminato complexes [Mo(O)₂(NPPh₃)₂] ( 1 ) and [W(O)₂(NPPh₃)₂] ( 2 ) originate from hydrolysis of the nitrido complexes [MN(NPPh₃)₃] (M = Mo, W). They form colourless crystals, which are characterized by IR and NMR spectroscopy as well as by mass spectrometry. According to the crystal structure analysis of 1 (space group Fdd2, Z = 8; lattice dimensions at –83 °C: a = 1953.3(1), b = 3275.8(3), c = 953.4(1) pm) there are monomeric molecules with tetrahedrally coordinated molybdenum atoms. The distances MoO of 171.2 pm and MoN of 185.9 pm correspond to double bonds. In dichloromethane solution 2 undergoes further hydrolysis with colourless crystals of [WO(NPPh₃)₃]₂[W₆O₁₉] ( 3 ) originating, which are characterized crystallographically (space group Pbcn, Z = 4; lattice dimensions at –50 °C: a = 3225.1(6), b = 1803.6(3), c = 1811.9(3) pm). 3 consists of cations [WO(NPPh₃)₃]⁺ with tetrahedrally coordinated tungsten atoms and of the known [W₆O₁₉]^2– anions. The tungsten atoms of the cations show distances WO of 171.8 pm and WN of 182 pm which correspond to double bonds as in 1 .     

Alkaline Earth Cluster Compounds AE[W6I14] and the Solvate [Ca(C2H6SO)6][W6I14]

Alkaline earth tungsten iodide clusters AE[W₆I₁₄] with AE = Mg, Ca, Sr, Ba and the solvated compound [Ca(C₂H₆SO)₆][W₆I₁₄] were prepared and structurally characterized. A new synthesis was employed, starting from W₆I₂₂, which is an exceptional compound among binary tungsten iodides because it is soluble in common polar organic solvents. As evidence for the wide range of the applicability of W₆I₂₂, we report the synthesis of the new AE[W₆I₁₄] compounds in comparison to a solid‐state reaction departing from W₃I₁₂.     

Reaction of Selenium with Bromine in the Presence of Methyltriphenylphosphonium Bromide: Syntheses and Crystal Structures of [PMePh3]2[Se2Br6] and [PMePh3]2[SeBr6(SeBr2)2]

The brown crystals of [PMePh₃]₂[Se₂Br₆] ( 1 ) and red crystals of [PMePh₃]₂[SeBr₆(SeBr₂)₂] ( 2 ) were obtained when selenium and bromine reacted in the solution of acetonitrile in the presence of methyltriphenylphosphonium bromide. The crystal structures of 1 and 2 has been determined by the X‐ray methods and refined to R = 0.0373 for 2397 reflections and 0.0397 for 3417 reflections, respectively. The salt 1 crystallizes in the monoclinic space group P2₁/n with the cell dimensions a = 13.202(5) Å, b = 11.954(4) Å, c = 13.418(6) Å, β = 93.08(4)° (193(2)). The crystals of 2 are triclinic, space group with the cell dimensions a = 10.266(3) Å, b = 11.311(3) Å, c = 11.619(2) Å, α = 108.87(2)°, β = 105.72(2)°, γ = 99.40(2)° (193(2) K). In the solid state structure of 1 the dinuclear hexabromo‐diselenate(II) anion is centrosymmetric and consists of two distorted almost square planar SeBr₄ units sharing a common edge through two μ‐bridging Br atoms. The terminal Se^II–Br bonds are 2.3984(11) and 2.4273(11) Å, whereas the bridging μBr–Se^II bonds are 2.7817(11) and 2.9081(12) Å. In the solid state the trinuclear [SeBr₆(SeBr₂)₂]^2? anion of 2 is centrosymmetric too and contains a nearly regular [SeBr₆] octahedron where the four equatorial bromo ligands each have developed bonds to the Se^II atoms of the SeBr₂ molecules. The contacts between the bridging bromo and the Se^II atoms of the SeBr₂ molecules are 3.0603(15) and 3.1043(12) Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr₂ molecules as acceptors. The Se^IV–Br distances are in the range 2.5570(9)–2.5773(11) Å and the Se^II–Br bond lengths in coordinated SeBr₂ molecules – 2.3411(12) and 2.3421(10) Å.     

K2NdP2S7: A Mixed‐Valent Neodymium(III) Thiophosphate According to K4Nd2[PS4]2[P2S6] with Discrete [PS4]3– and [S3P–PS3]4– Anions

Pale blue, lath‐shaped single crystals of K₂NdP₂S₇ (≡ K₄Nd₂[PS₄]₂[P₂S₆]; monoclinic, P2₁/n, a = 904.76(8), b = 677.38(6), c = 1988.7(2) pm, β = 97.295(5)°, Z = 2) are obtained by the reaction of Nd, S and P₂S₅ with an excess of KCl as a flux in evacuated silica tubes at 750 °C (7 d) which should produce Nd[PS₄] instead. Beside isolated [PS₄]^3– tetrahedra, the crystal structure contains discrete ethane‐analogous [P₂S₆]^4– (≡ [S₃P–PS₃]^4–) units in staggered conformation with tetravalent phosphorus cations and a P–P distance of 219 pm. The two crystallographically different potassium cations show coordination numbers of nine and ten in the shape of distorted mono‐ and bicapped square antiprisms. Finally, the Nd³⁺ cations are surrounded by eight sulfur atoms arranged as (uncapped) square antiprisms. The entire structure is dominated by (K1)⁺ containing {(Nd₂[PS₄]₂[P₂S₆])^4–} layers parallel (101) which are three‐dimensionally interconnected by (K2)⁺ cations.     

The Intermetalloid Clusters [Ni2Bi12]4+ and [Rh2Bi12]4+ – Ionothermal Synthesis,Crystal Structures,and Chemical Bonding

The intermetalloid clusters [M₂Bi₁₂]⁴⁺ (M = Ni, Rh) were synthesized as halogenido‐aluminates in Lewis‐acidic ionic liquids. The reaction of bismuth and NiCl₂ in [BMIm]Cl · 5AlCl₃ (BMIm = 1‐butyl‐3‐methylimidazolium) at 180 °C yielded black, triclinic (P1 ) crystals of [Ni₂Bi₁₂][AlCl₄]₃[Al₂Cl₇]. Black, monoclinic (P2₁/m) crystals of [Rh₂Bi₁₂][AlBr₄]₄ precipitated after dissolving the cluster salt Bi_12–xRhX_13–x (X = Cl, Br; 0 < x < 1) in [BMIm]Br·4.1AlBr₃ at 140 °C. In the cationic cluster [Ni₂Bi₁₂]⁴⁺, the nickel atoms center two base‐sharing square antiprisms of bismuth atoms (symmetry close to D_4h). The valence‐electron‐poorer rhodium‐containing cluster is a distorted variant of this motif: the terminating Bi₄ rings are folded to bicyclic “butterflies“ and the central square splits into two dumbbells (symmetry close to D_2h). DFT‐based calculations and real‐space bonding analyses place the intermetalloid units between a triple‐decker complex and a conjoined Wade‐Mingos cluster.     

New Silver Tellurates – The Crystal Structures of a Third Modification of Ag2Te2O6 and of Ag4TeO5

Single crystals of a third modification of Ag₂Te₂O₆ (denoted as Ag₂Te₂O₆–III) and of Ag₄TeO₅ have been obtained as minor by‐products during hydrothermal phase formation experiments in the system Ag‐Hg‐Te‐O. The crystal structure of Ag₂Te₂O₆–III (P2₁/c, Z = 4, a = 6.4255(10), b = 6.9852(11), c = 13.204(2) Å, β = 90.090(3)°, 1885 independent reflections, R[F² > 2σ(F²)] = 0.0334, wR2(F² all) = 0.0817) comprises tellurium in oxidation states +IV and +VI and is topologically related to the structure of the Ag₂Te₂O₆–I modification, which consists of similar layers and interjacent layers of Ag⁺ cations. Ag₄TeO₅ (C2/c, Z = 8, a = 16.271(2), b = 6.0874(10), c = 11.4373(16) Å, β = 106.730(10)°, 2372 independent reflections, R[F² > 2σ(F²)] = 0.0288, wR2(F² all) = 0.0737) is made up of a layer‐like arrangement of isolated [Te^VI₂O₁₀] double octahedra and of Ag⁺ cations situated both in layers parallel and inside the layers of the anionic moieties.     

Syntheses and Crystal Structures of Hydrated Ternary Cerium Sulfates: Mixed‐valence K5Ce2(SO4)6·H2O and K2Ce(SO4)3·H2O

A new chemical and structural interpretation of K₅Ce₂(SO₄)₆·H₂O ( I ) and a redetermination of the structure of K₂Ce(SO₄)₃·H₂O ( II ) is presented. The mixed‐valent compound I crystallizes in the space group C2/c with a = 17.7321(3), b = 7.0599(1), c = 19.4628(4) Å, β = 112.373(1)° and Z = 4. Compound I has been discussed earlier with space group Cc. In the structure of I , there are pairs of edge sharing cerium polyhedra connected by sulfate oxygen atoms in the μ₃ bonding mode. These cerium dimers are linked through edge and corner sharing sulfate bridges, forming layers. The layers are joined by potassium ions which together with the water molecules are placed between the layers. No irregularity in the distribution of the Ce^III and Ce^IV to cause the lost of a crystallographic center of symmetry was detected. We suggest that the charge exerted by the extra f¹ electron for every cerium dimer is delocalized over the Ce1–O₂–Ce2 moiety in a non‐bonding mode. As a result, the oxidations state of each cerium ion is a mean value between III and IV at each atomic position. Compound II crystallizes in the space group C2 with a = 20.6149(2), b = 7.0742(1), c = 17.8570(1) Å, β = 122.720(1)° and Z = 8. The hydrogen atoms have been located and the absolute structure has been established. Neither hydrogen atom positions nor anisotropic displacement parameters were given in the previous reports. In compound II , the cerium polyhedra are connected by edge and corner sharing sulfate groups forming a three‐dimensional network. This network contains Z‐shaped channels hosting the charge compensating potassium ions.     

Synthesis and Crystal Structures of [TeI3][GaI4] and [TeI3][InI4]

The compounds [TeI₃][MI₄] (M = Ga, In) were obtained as air sensitive black crystals by the reactions of Te, I₂ and Ga or In in vacuum sealed ampoules. The gallium compound crystallizes in the structural type of [SCl₃][AlCl₄]: monoclinic system, space group Pc (No. 7), a = 7.211(11), b = 7.2340(9), c = 15.67(2) Å and β = 102.51(6)°. The indium derivative crystallizes in the orthorhombic space group Pna2₁ (No. 33), a = 14.752(2), b = 7.1915(6) and c = 23.391(5) Å, with two crystallographically independent formula units per asymmetric unit. The structures consist of tetrahedral GaI₄^– or InI₄^– and trigonal pyramidal TeI₃⁺ units. Additionally, in both structures the tellurium atoms establish three weak interactions with iodine atoms of the MI₄^– units to form a distorted octahedral Te_{3 + 3} coordination sphere.     

Überschreitungen der konventionellen Zahl von Clusterelektronen in Metallhalogeniden des M6X12‐Typs: W6Cl18, (Me4N)2[W6Cl18] und Cs2[W6Cl18]

Beyond the Conventional Number of Electrons in M₆X₁₂ Type Metal Halide Clusters: W₆Cl₁₈, (Me₄N)₂[W₆Cl₁₈], and Cs₂[W₆Cl₁₈] Black octahedral single crystals of W₆Cl₁₈ were obtained by reducing WCl₄ with graphite in a silica tube at 600 °C. The single crystal structure refinement (space group R 3¯, Z = 3, a = b = 1498.9(1) pm, c = 845.47(5) pm) yielded the W₆Cl₁₈ structure, already reported on the basis of X‐ray powder data. (Me₄N)₂[W₆Cl₁₈] and Cs₂[W₆Cl₁₈] were obtained from methanolic solutions of W₆Cl₁₈ with Me₄NCl and CsCl, respectively. The structure of (Me₄N)₂[W₆Cl₁₈] was refined from X‐ray single crystal data (space group P 3¯m1, Z = 1, a = b = 1079.3(1) pm, c = 857.81(7) pm), and the structure of Cs₂[W₆Cl₁₈] was refined from X‐ray powder data (space group P 3¯, Z = 1, a = b = 932.10(7) pm, c = 853.02(6) pm). The crystal structure of W₆Cl₁₈ contains molecular W₆Cl₁₈ units arranged as in a cubic closest packing. The structures of (Me₄N)₂[W₆Cl₁₈] and Cs₂[W₆Cl₁₈] can be considered as derivatives of the W₆Cl₁₈ structure in which 2/3 of the W₆Cl₁₈ molecules are substituted by Me₄N⁺ ions and Cs⁺ ions, respectively. The conventional number of 16 electrons/cluster is exceeded in these compounds, with 18 electrons for W₆Cl₁₈ and 20 electrons for (Me₄N)₂[W₆Cl₁₈] and Cs₂[W₆Cl₁₈]. Cs₂[W₆Cl₁₈] exhibits temperature independent paramagnetic behaviour.     

Synthese und Kristallstruktur von [(n‐Bu)4N][W6Cl18]

Synthesis and Crystal Structure of [(n‐Bu)₄N][W₆Cl₁₈] Single‐crystals of [(n‐Bu)₄N][W₆Cl₁₈] were obtained as thin needles by adding methanol to a solution of W₆Cl₁₈ and [(n‐Bu)₄N]Cl in tetrahydrofuran. The structure was determined by single‐crystal X‐ray diffraction at 210 K. [(n‐Bu)₄N][W₆Cl₁₈] crystallizes in the monoclinic space group C 2/c with Z = 8 and the lattice parameters a = 2175.6(1) pm, b = 1738.0(1) pm, c = 2160.36(9) pm, and β = 91.680(5) °. The crystal structure contains isolated [(W₆Cl₁₂ⁱ)Cl₆^a]^— clusters and [(n‐Bu)₄N]⁺ ions.     

On the Oxidation of Octamethylenetetrathiafulvalene by CuBr2 – Synthesis,Crystal Structure and Magnetic Properties of (OMTTF)2[Cu4Br10]

The reaction of octamethylenetetrathiafulvalene (OMTTF) with excess CuBr₂ in tetrahydrofurane/acetonitrile yields black (OMTTF)₂[Cu₄Br₁₀] ( 1 ). The crystal structure determination shows the presence of OMTTF cations and tetranuclear bromidocuprate anions. The novel anion consists of four edge and corner sharing CuBr₄ tetrahedra, which are connected to a ring. The assignment of the ionic charges and oxidation states for the copper atoms is supported by the magnetic properties. 1 is antiferromagnetic with T_N ≈ 30 K. The magnetic moment reaches 2.54 B.M., which indicates, together with the Curie–Weiss constant of –35 K, a coupling of the paramagnetic spins over the whole temperature region. The ionic charges of the salt‐like compound 1 are therefore (OMTTF²⁺)₂[(Cu⁺)₂(Cu²⁺)₂Br₁₀]^4–. The antiferromagnetism is explained by the coupling of the spins of two Cu²⁺ ions in the anion with an exchange constant of J = –18 cm^–1. The Cu^I and Cu^II atoms are clearly distinguishable in the mixed valent anion. The OMTTF cation is not planar but exhibits an interplanar angle between the two central C₃S₂ ring moieties of 15.3°, which is in accordance to the dicationic oxidation state.     

The Triclinic Lanthanoid(III) Halide Oxidoarsenates(III) Sm3Cl2[As2O5][AsO3] and Tm3Br2[As2O5][AsO3]

Pale yellow single crystals of the composition Ln₃X₂[As₂O₅][AsO₃] (Ln = Tm for X = Br and Ln = Sm for X = Cl) were obtained via solid-state reactions in the systems Ln₂O₃/As₂O₃ from sealed silica ampoules using different halides as fluxing agents. Sm₃Cl₂[As₂O₅][AsO₃] and Tm₃Br₂[As₂O₅][AsO₃] crystallize isotypically in the triclinic space group P1 with Z = 2 and cell parameters of a = 543.51(4) pm, b = 837.24(6) pm, c = 1113.45(8) pm, α = 90.084(2)°, β = 94.532(2)°, γ = 90.487(2)° for the samarium and a = 534.96(4) pm, b = 869.26(6) pm, c = 1081.84(8) pm, α = 90.723(2)°, β = 94.792(2)° γ = 90.119(2)° for the thulium compound. The isotypic crystal structure of both representatives exhibits three crystallographically different Ln³⁺ cations, each with a coordination number of eight. (Ln1)³⁺ and (Ln2)³⁺ are only coordinated by three oxygen atoms, whereas (Ln3)³⁺ shows additional contacts to halide anions in forming square [LnO₄X₄]^9– antiprisms. All As³⁺ cations are surrounded by three oxygen atoms in the shape of isolated [AsO₃]^3– ψ¹-tetrahedra. They occur either isolated or condensed as pyroanionic [As₂O₅]^4– units with a bridging oxygen atom. In both anions, non-binding lone-pair electrons are present at the As³⁺ cations with a pronounced stereochemically active function.     

The Remarkably Robust,Photoactive Tungsten Iodide Cluster [W6I12(NCC6H5)2]

The new heteroleptic tungsten iodide cluster compound [W₆I₁₂(NCC₆H₅)₂] is presented. The synthesis is carried-out from Cs₂W₆I₁₄ and ZnI₂ under solvothermal conditions in benzonitrile solution, yielding red cube-shaped crystals. [W₆I₁₂(NCC₆H₅)₂] represents a heteroleptic [W₆I₈]-type cluster bearing four apical iodides and two benzonitrile ligands. Molecular [W₆I₁₂(NCC₆H₅)₂] clusters form a robust hydrogen bridged crystal structure with high thermal stability and high resistibility against hydrolysis. The electronic structure is analyzed by quantum chemical methods of the calculated electron localization function (ELF) and the band structure. Photoluminescence measurements are performed to verify and describe the photophysical properties of [W₆I₁₂(NCC₆H₅)₂]. Finally, the photocatalytic properties of [W₆I₁₂(NCC₆H₅)₂] are evaluated as a proof-of-concept.     

Synthesen,Eigenschaften und Kristallstrukturen der Cluster‐Salze Bi6[PtBi6Cl12] und Bi2/3[PtBi6Cl12]

Syntheses, Properties and Crystal Structures of the Cluster Salts Bi₆[PtBi₆Cl₁₂] and Bi_2/3[PtBi₆Cl₁₂] Melting reactions of Bi with Pt and BiCl₃ yield shiny black, air insensitive crystals of the subchlorides Bi₆[PtBi₆Cl₁₂] and Bi_2/3[PtBi₆Cl₁₂]. Despite the substantial difference in the bismuth content the two compounds have almost the same pseudo‐cubic unit cell and follow the structural principle of a CsCl type cluster salt. Bi₆[PtBi₆Cl₁₂] consists of cuboctahedral [PtBi₆Cl₁₂]^2? clusters and Bi₆²⁺ polycations (a = 9.052(2) Å, α = 89.88(2)°, space group P 1, multiple twins). In the electron precise cluster anion, the Pt atom (18 electron count) centers an octahedron of Bi atoms whose edges are bridged by chlorine atoms. The Bi₆²⁺ cation, a nido cluster with 16 skeletal electrons, has the shape of a distorted octahedron with an opened edge. In Bi_2/3[PtBi₆Cl₁₂] the anion charge is compensated by weakly coordinating Bi³⁺ cations which are distributed statistically over two crystallographic positions (a = 9.048(2) Å, α = 90.44(3)°, space group ). Bi₆[PtBi₆Cl₁₂] is a semiconductor with a band gap of about 0.1 eV. The compound is diamagnetic at room temperature though a small paramagnetic contribution appears towards lower temperature.     

Darstellung und Kristallstruktur von K6[Al2O6] und Rb6[Al2O6]

Preparation of Crystal Structure of K₆[Al₂O₆] and Rb₆[Al₂O₆] Colourless single crystals of K₆[Al₂O₆] have been prepared from intimate mixtures of KAlO₂ and K₂O (550°C, 90 d). The structure determination from four-circle diffractometer data (MoKα , 742 I_o(hkl), R = 2.2%, R_w = 2.1%) confirms the space group C2/m with Z = 2; a = 698.25 pm, b = 1 103.54 pm, c = 646.49 pm, β = 102.49°. Colourless single crystals of hitherto unknown Rb₆[Al₂O₆] have been prepared from intimate mixtures of RbAlO₂ and Rb₂O (520°C, 120 d). The structure determination from four-circle diffractometer data (MoKα , 1 240 I_o(hkl)) results in the residual values R = 7.2%, R_w = 4.9%; space group C2/m; a = 725.92 pm, b = 1 143.33 pm, c = 678.06 pm, β = 104.05°; Z = 2. K₆[Al₂O₆] and Rb₆[Al₂O₆] are isostructural with K₆[Fe₂O₆]. A characteristic structure unit is the anion [Al₂O₆]^6? consisting of two edge-sharing [AlO₄] tetrahedra. Effective Coordination Numbers (ECoN), Mean Fictive Ionic Radii (MEFIR), the Madelung Part of Lattice Energy (MAPLE) and the Charge Distribution (CHARDI) are calculated and discussed.