MAl2Ta35O70 (M = Na,K, Rb), niedervalente Oxotantalate mit isolierten kuboktaedrischen Ta6O12-Clustern

MAl₂Ta₃₅O₇₀ (M = Na, K, Rb), Low-Valent Oxotantalates with Discrete Cuboctahedral Ta₆O₁₂ Clusters The title compounds were prepared by reducing Ta₂O₅ with tantalum and aluminium in the presence of alkali metal carbonates at 1650 K. NaAl₂Ta₃₅O₇₀ was characterized by means of a single crystal X-ray structure determination: space group P 3, lattice parameters a = 780.15(7) pm, c = 2621.7(8) pm, Z = 1, 167 variables, R_F = 0.048. The structure can be described in terms of a close packing of oxide ions with specific defects. The sequence of the layers is hhcchchcchh. The characteristic structural units are Ta₆O₁₂ clusters being substantially stabilized by Ta–Ta bonding (d_Ta–Ta = 279.3–283.3 pm, 14 electrons per cluster). The sodium cations occupy acentrically and statistically half of the anti-cuboctahedral sites. The compounds are semiconductors with band gaps E_a of 0.2 to 0.3 eV.     

Verbrückende Koordination von Gallium–Gallium‐Bindungen durch Chelatliganden – Grenzen der Beständigkeit von Digallium‐Verbindungen

Bridging Coordination of Gallium–Gallium Bonds by Chelating Ligands – Limitations of the Stability of Digallium Derivatives The reactions of bis[bis(trimethylsilyl)methyl]‐di(μ‐acetato)digallium(Ga–Ga) ( 2 ) with lithium‐2‐amido‐1‐methylbenzimidazole in the molar ratios of 1 to 1 or 1 to 2 yielded by the precipitation of lithium aceatate new digallium compounds, in which the intact Ga–Ga bonds were bridged by two chelating ligands. The replacement of only one acetato group gave compound 5 , that possesses two different bridging ligands with the benzimidazole group coordinated by its terminal amido function and that nitrogen atom of the heterocycle which is not attached to a methyl group. If both acetato groups were replaced by imdazole ligands, two products were obtained, in which the chelates are transferred in each other either by a mirror plane parallel to the Ga–Ga bond (cis, 6 ) or by a twofold rotational axis perpendicular to the element–element bond (trans, 7 ). 7 is thermodynamically favored and was irreversibly formed by heating of the mixture. 5 and 7 were characterized by crystal structure determinations and have Ga atoms in a chiral environment. Weaker donor ligands such as diphenyl(lithiomethyl)(piperidinomethyl)silane, which in principal is able to coordinate via its carbanionic carbon atom and more weakly via its sterically shielded piperidino nitrogen atom, led to the cleavage of the Ga–Ga bond. The mononuclear compound 8 was isolated, in which the Ga atom is attached to one bis(trimethylsilyl)methyl group and two (piperidinomethyl)silyl substituents. Furthermore, the synthesis of a dialkyl‐bis(1,3‐dionato)digallium derivative ( 9 ) is reported, in which the chelating 1,3‐dionato groups are terminally coordinated to the Ga atoms of the unsupported Ga–Ga bond.     

Darstellung und Struktur von Th2Ta6O19, dem ersten Beispiel einer „Jahnberg-Struktur”︁ mit M = M4+ (M = Th4+); mit einer Anmerkung zu LaNb7O19

Synthesis and Crystal Structure of Th₂Ta₆O₁₉, the First Example of a “Jahnberg-Structure” with M = M⁴⁺ (M = Th⁴⁺); with a Note to LaNb₇O₁₉ Colorless, hexagonal crystals of Th₂Ta₆O₁₉ were obtained by chemical transport in the temperature gradient 1000°C → 980°C using a mixture of ThO₂, ZrO₂ (or HfO₂) and Ta₂O₅ (1 : 2 : 2) as starting material and Cl₂, ZrCl₄ or HfCl₄ as transport agents. The lattice constants are a = 6.275(1) Å, c = 19.968(6) Å and Z = 2. Structure determination in the space group P6₃/mcm (no. 193) let to R₁ = 0.032 (wR₂ = 0.074). Thorium is surrounded by oxygen like an transbis-capped octahedron (CN = 8) and tantalum like a pentagonal bipyramid (CN = 7). Both coordination polyhedra are for themself arranged to layers (Th to o-, Ta to p-layers) so that in the direction of the c-axes a sequence of layers like p-p-o-p-p-o appears. Therefore the compound is a new representative of the structures described by Jahnberg.     

Na10Zn4O9 – ein neues Oxozinkat mit trigonal-planar koordiniertem Zink

Na₁₀Zn₄O₉, a Novel Oxozincate with Trigonal Planar Coordinated Zinc Using a new preparation method for sodium oxometallates we have succeeded in the synthesis of the new ternary oxide Na₁₀Zn₄O₉. Active ZnO reacted with Na₂O generated in situ from NaN₃ and NaNO₂. The compound consists of ZnO₄ tetrahedra which are connected via edges and corners to form layers of the composition ZnO₂. Furthermore, the structure was found to contain isolated, trigonal planar ZnO₃ units. 21 of 60 Na⁺ ions within the unit cell are disordered. Na₁₀Zn₄O₉ crystallizes in the space group R3 m (Nr. 166). The lattice constants are: a = 10.815(3), c = 17.930(7) Å; Z = 6; 8056 reflections; R = 0.062. The sodium ion conductivity at 400°C is 6 × 10^?3 Ω^?1 cm^?1.     

Ag25Bi3O18, ein gemischtvalentes Bismutat

Ag₂₅Bi₃O₁₈, a Mixed Valent Bismuthate Applying oxygen pressures of 10 MPa black crystals of Ag₂₅Bi₃O₁₈ are prepared for the first time by solid state reaction of Ag₂O and ‘Bi₂O₅’. The crystal structure determination (P3 , a = 11.5887(2), c = 6,2386(1) å, Z = 1, 1369 diffractometer data, R_w = 0.034) proves the presence of trivalent (d(Bi-O) = 2.21, and 2.51 å (3×)) and pentavalent bismuth (d(Bi-O) = 2.13 å (6×)). The structure allows a change in the oxidation states (Bi³⁺ → Bi⁵⁺) by pressure induced shift of the oxygen atoms leading to a delocalisation of the 6s² valence electrons. First evidence for this phenomenon is given by the pressure dependence of the NIR reflectivity. The thermal decomposition was recorded by DTA/TG and measurements of the resistivity were performed.     

ChemInform Abstract: [Ta3O3]A (A: Li,Na, K) and [Ta3O3]B[Ta3O3] (B: Ca,Sr, Ba): Sandwich‐Type Complexes Containing Ta3O3‐ δ and π Double Aromatic Ligands.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Tetrathiafulvalene‐Based Mixed‐Valence Acceptor–Donor–Acceptor Triads: A Joint Theoretical and Experimental Approach

This work presents a joint theoretical and experimental characterisation of the structural and electronic properties of two tetrathiafulvalene (TTF)‐based acceptor–donor–acceptor triads (BQ–TTF–BQ and BTCNQ–TTF—BTCNQ; BQ is naphthoquinone and BTCNQ is benzotetracyano‐p‐quinodimethane) in their neutral and reduced states. The study is performed with the use of electrochemical, electron paramagnetic resonance (EPR), and UV/Vis/NIR spectroelectrochemical techniques guided by quantum‐chemical calculations. Emphasis is placed on the mixed‐valence properties of both triads in their radical anion states. The electrochemical and EPR results reveal that both BQ–TTF–BQ and BTCNQ–TTF–BTCNQ triads in their radical anion states behave as class‐II mixed‐valence compounds with significant electronic communication between the acceptor moieties. Density functional theory calculations (BLYP35/cc‐pVTZ), taking into account the solvent effects, predict charge‐localised species (BQ ^{. ?}–TTF–BQ and BTCNQ ^{. ?}–TTF–BTCNQ) as the most stable structures for the radical anion states of both triads. A stronger localisation is found both experimentally and theoretically for the BTCNQ–TTF–BTCNQ anion, in accordance with the more electron‐withdrawing character of the BTCNQ acceptor. CASSCF/CASPT2 calculations suggest that the low‐energy, broad absorption bands observed experimentally for the BQ–TTF–BQ and BTCNQ–TTF–BTCNQ radical anions are associated with the intervalence charge transfer (IV‐CT) electronic transition and two nearby donor‐to‐acceptor CT excitations. The study highlights the molecular efficiency of the electron‐donor TTF unit as a molecular wire connecting two acceptor redox centres.     

Ein neuartiger Zugang zu reduzierten Polyoxomolybdaten mit komplexen Gegenionen – Synthese und Struktur von [Mn(CH3OH)6][Mo8O16(OCH3)8(C2O4)]

The tetranuclear compound [Mo₂(O₂C‐tBu)₃]₂(μ‐C₂O₄) ( 1 ) that is prepared from [Mo₂(O₂C‐tBu)₃]₄ and oxalic acid, was reacted with MnI₂ · 2THF to form the polyoxomolybdate compound [Mn(CH₃OH)₆] [Mo₈O₁₆(OCH₃)₈(C₂O₄)] ( 2 ) in a complex redox reaction. Crystals of 2 were analyzed by single‐crystal X‐ray diffraction showing a octanuclear polyoxomolybdate dianion in which the Mo=O moieties are alternately connected through μ‐oxo and μ‐methoxo units. Charge balance in 2 is realized by a manganese(II) cation that is octahedrally coordinated by methanol ligands. The crystal structure is dominated by strong hydrogen bond interactions of the O–H ··· O type of methanol molecules coordinated to manganese as well as additional methanol molecules in the crystal lattice.     

catena‐Poly[bis(μ‐2,2′‐bipyridin‐6‐olato)‐κ3N,N′:O;O:N,N′‐dicopper(I,II) [[tetrafluoridoniobium(V)]‐μ‐oxido]]

A novel copper–niobium oxyfluoride, {[Cu₂(C₁₀H₇N₂O)₂][NbOF₄]}_n, has been synthesized by a hydrothermal method and characterized by elemental analysis, EDS, IR, XPS and single‐crystal X‐ray diffraction. The structural unit consists of one C₂‐symmetric [NbOF₄]⁻ anion and one centrosymmetric coordinated [Cu₂(obpy)₂]⁺ cation (obpy is 2,2′‐bipyridin‐6‐olate). In the [NbOF₄]⁻ anion, each Nb^V metal centre is five‐coordinated by four F atoms and one O atom in the first coordination shell, forming a square‐pyramidal coordination geometry. These square pyramids are then further connected to each other via trans O atoms [Nb—O = 2.187 (3) Å], forming an infinite linear {[NbOF₄]⁻}_n polyanion. In the coordinated [Cu₂(obpy)₂]⁺ cation, the oxidation state of each Cu site is disordered, which is confirmed by the XPS results. The disordered Cu sites are coordinated by two N atoms and one O atom from two different obpy ligands. The [NbOF₄]⁻ and [Cu₂(obpy)₂]⁺ units are assembled via weak C—H...F hydrogen bonds, resulting in the formation of a three‐dimensional supramolecular structure. π–π stacking interactions between the pyridine rings [centroid–centroid distance = 3.610 (2) Å] may further stabilize the crystal structure.     

Reaktionen der Digalliumverbindung R2Ga–GaR2 [R = CH(SiMe3)2] mit Wasser und Carbonsäuren – Synthese von μ‐Hydroxo‐μ‐carboxylatodigallium‐Verbindungen unter Erhalt der Ga–Ga‐Bindungen

Treatment of the digallium compound R₂Ga–GaR₂ [ 1 , R = CH(SiMe₃)₂] with a broad variety of functionalized carboxylic acids in the presence of water yielded μ‐hydroxo‐μ‐carboxylatodigallium compounds ( 2 – 10 ) containing intact Ga–Ga bonds in high to moderate yields. The compounds form dimeric formula units in which the unsupported Ga–Ga bonds are bridged by two hydroxo and two carboxylato ligands. Each gallium atom is terminally coordinated by a bulky alkyl group. NMR spectroscopy revealed mixtures of two isomeric compounds in solution in all cases. The second component may show a different bridging mode with each Ga–Ga bond bridged by a bidentate carboxylato ligand to form Ga₂O₂C five‐membered heterocycles.     

New rac‐XP(O)(OC6H5)(NHC6H4‐p‐CH3) [X = N(CH3)(cyclo‐C6H11) and NH(C3H5)] and rac‐(C6H5CH2NH)P(O)(OC6H5)(NH‐cyclo‐C6H11) mixed‐amide phosphinates

The mixed‐amide phosphinates, rac‐phenyl (N‐methylcyclohexylamido)(p‐tolylamido)phosphinate, C₂₀H₂₇N₂O₂P, (I), and rac‐phenyl (allylamido)(p‐tolylamido)phosphinate, C₁₆H₁₉N₂O₂P, (II), were synthesized from the racemic phosphorus–chlorine compound (R,S)‐(Cl)P(O)(OC₆H₅)(NHC₆H₄‐p‐CH₃). Furthermore, the phosphorus–chlorine compound ClP(O)(OC₆H₅)(NH‐cyclo‐C₆H₁₁) was synthesized for the first time and used for the synthesis of rac‐phenyl (benzylamido)(cyclohexylamido)phosphinate, C₁₉H₂₅N₂O₂P, (III). The strategies for the synthesis of racemic mixed‐amide phosphinates are discussed. The P atom in each compound is in a distorted tetrahedral (N¹)P(=O)(O)(N²) environment. In (I) and (II), the p‐tolylamido substituent makes a longer P—N bond than those involving the N‐methylcyclohexylamido and allylamido substituents. In (III), the differences between the P—N bond lengths involving the cyclohexylamido and benzylamido substituents are not significant. In all three structures, the phosphoryl O atom takes part with the N—H unit in hydrogen‐bonding interactions, viz. an N—H...O=P hydrogen bond for (I) and (N—H)(N—H)...O=P hydrogen bonds for (II) and (III), building linear arrangements along [001] for (I) and along [010] for (III), and a ladder arrangement along [100] for (II).     

[Cd(STrt)3]–, ein homoleptischer Cadmiumkomplex mit dem sterisch anspruchsvollen Triphenylmethanthiolat‐Liganden

[Cd(STrt)₃]^–, a Homoleptic Cadmium Complex with the Sterically Demanding Triphenylmethanethiolate Ligand Crystalline [K(18‐crown‐6)(THF)₂][Cd(STrt)₃] · 2 THF ( 1 ) has been isolated in 77% yield from the reaction of CdCl₂, KSTrt and 18‐crown‐6 in tetrahydrofuran (THF; Trt = triphenylmethyl). The Cd^II ion of 1 exhibits a distorted trigonal coordination by three thiolate ligands (Cd–S 2.461(2)–2.518(2) Å, S–Cd–S 106.87(5)–135.20(5)°, Cd atom 0.24 Å above the S₃ plane).     

Zr6STe2 – ein zirconiumreiches Sulfidtellurid mit einer Zr3Te‐Teilstruktur vom Re3B‐Typ

Zr₆STe₂ – a Zirconium‐rich Sulfide Telluride with a Zr₃Te Partial Structure of the Re₃B Type Zr₆STe₂ is accessible through the reduction of a mixture of ZrTe₂ and ZrS₂ with zirconium in fused tantalum tubes at 1520 K. The spatially averaged crystal structure of Zr₆STe₂ is described in the space group Cmcm, a = 377.81(4), b = 1156.4(1), c = 887.96(8), Z = 2, Pearson symbol oC18, 320 reflexions (I > 2σ(I)), 22 variables, R_w(I) = 0.088. Zr₆STe₂ crystallizes in a unique structure type, which can be seen as a filled Re₃B type structure. The tellurium atoms are surrounded by nine zirconium atoms situated at the vertices of a distorted, tricapped trigonal prism. The Zr₉Te tetrakaidecahedra are connected by common triangular prism faces parallel [100], edges approximately along [001] and common vertices along [010], thus forming a three‐dimensional tetrakaidecahedral network [Zr_9/3Te], which is decisively stabilized by homonuclear Zr–Zr‐interactions. The tetrakaidecahedra are arranged in such a way, that Zr₆ octahedra occur. The octahedra are arranged into layers by sharing edges parallel [100] and vertices along [001]. As a result of a distortion of the structure, every second octahedron is expanded to such an extent as to be able to smoothly accommodate sulfur atoms. According to the modulation of the diffraction intensities, the vacancy ordering in adjacent layers of octahedra occurs independently of each other.     

Reductive Coupling Reaction of Aryliminomethylferrocenes with Triethyl Orthoformate Induced by Low‐valent Titanium

Reductive coupling reaction of aryliminomethylferrocenes FcCH = NAr[(1, Ar=QHs (a), p‐ClC₆H₄ (b), p‐BrC₆H₄ (c), p‐CH₃C₆H₄ (d), m‐ClC₆H₄ (e)] with triethyl orthoformate (2) in Zn‐TiCl₄ system gave three kinds of products: 1, 3‐diaryl‐4, 5‐diferrocenyl imidazolidines (3), N, N‐disubstituted formamides (4), and 1, 2‐diferrocenyl ethylene (5). ¹H NMR spectra proved that all the compounds 3 obtained were dl‐isomers. All the new compounds 3 and 4 were characterized by elemental analysis, ¹H NMR, ¹³C NMR (for 3) and IR spectra. The molecular structure of 3c was determined by X‐ray diffraction.     

A novel dinuclear bismuth(III) coordination compound: bis(μ‐pyridine‐2,6‐dicarboxylato)‐κ4O2,N,O6:O6′;κ4O2:O2′,N,O6‐bis[(azido‐κN)(1,10‐phenanthroline‐κ2N,N′)bismuth(III)] tetrahydrate

A novel dinuclear bismuth(III) coordination compound, [Bi₂(C₇H₃NO₄)₂(N₃)₂(C₁₂H₈N₂)₂]·4H₂O, has been synthesized by an ionothermal method and characterized by elemental analysis, energy‐dispersive X‐ray spectroscopy, IR, X‐ray photoelectron spectroscopy and single‐crystal X‐ray diffraction. The molecular structure consists of one centrosymmetric dinuclear neutral fragment and four water molecules. Within the dinuclear fragment, each Bi^III centre is seven‐coordinated by three O atoms and four N atoms. The coordination geometry of each Bi^III atom is distorted pentagonal–bipyramidal (BiO₃N₄), with one azide N atom and one bridging carboxylate O atom located in axial positions. The carboxylate O atoms and water molecules are assembled via O—H...O hydrogen bonds, resulting in the formation of a three‐dimensional supramolecular structure. Two types of π–π stacking interactions are found, with centroid‐to‐centroid distances of 3.461 (4) and 3.641 (4) Å.     

The inorganic–organic hybrid zinc phosphite poly[(μ3‐hydrogen phosphito‐κ3O:O′:O′′)(piperidin‐1‐ium‐4‐carboxylate‐κO)zinc(II)]

A new inorganic–organic hybrid zinc phosphite, [Zn(HPO₃)(C₆H₁₁NO₂)]_n, has been synthesized hydrothermally. Protonated piperidin‐1‐ium‐4‐carboxylate (PDCA) was generated in situ by hydrolysis of the piperidine‐4‐carboxamide precursor. The P atom possesses a typical PO₃H pseudo‐pyramidal geometry. The crystal structure features an unusual (3,4)‐connected two‐dimensional inorganic zinc–phosphite layer, with organic PDCA ligands appended to the sheets and protruding into the interlayer region. Helical chains of opposite chirality are involved in the construction of a puckered sheet structure.     

The heterometallic cadmium–silver complex cis‐bis[dicyanidoargentato(I)‐κN]bis(5,5′‐dimethyl‐2,2′‐bipyridyl‐κ2N,N′)cadmium(II) monohydrate

In the title complex, [Ag₂Cd(CN)₄(C₁₂H₁₂N₂)₂]·H₂O or cis‐[Cd{Ag(CN)₂}₂(5,5′‐dmbpy)₂]·H₂O, where 5,5′‐dmbpy is 5,5′‐dimethyl‐2,2′‐bipyridyl, the asymmetric unit consists of a discrete neutral [Cd{Ag(CN)₂}₂(5,5′‐dmbpy)₂] unit and a solvent water molecule. The Cd^II cation is coordinated by two bidentate chelate 5,5′‐dmbpy ligands and two monodentate [Ag^I(CN)₂]⁻ anions, which are in a cis arrangement around the Cd^II cation, leading to an octahedral CdN₆ geometry. The overall structure is stabilized by a combination of intermolecular hydrogen bonding, and Ag^I...Ag^I and π–π interactions, forming a three‐dimensional supramolecular network.