Discrete Polyanion Research Articles

Na3Ge2P3: A Zintl Phase Featuring [P3Ge-GeP3] Dimers as Building Blocks.

Recently, ternary lithium phosphidotetrelates have attracted interest particularly due to their high ionic conductivities, while corresponding sodium and heavier alkali metal compounds have been less investigated. Hence, we report the synthesis and characterization of the novel ternary sodium phosphidogermanate Na3Ge2P3, which is readily accessible via ball milling of the elements and subsequent annealing. According to single crystal X-ray structure determination, Na3Ge2P3 crystallizes in the monoclinic space group P21/c (no. 14.) with unit cell parameters of a = 7.2894(6) Å, b = 14.7725(8) Å, c = 7.0528(6) Å, β = 106.331(6)° and forms an unprecedented two-dimensional polyanionic network in the b/c plane of interconnected [P3Ge-GeP3] building units. The system can also be interpreted as differently sized ring structures that interconnect and form a two-dimensional network. A comparison with related ternary compounds from the corresponding phase system as well as with the binary compound GeP shows that the polyanionic network of Na3Ge2P3 resembles an intermediate step between highly condensed cages and discrete polyanions, which highlights the structural variety of phosphidogermanates. The structure is confirmed by 23Na- and 31P-MAS NMR measurements and Raman spectroscopy. Computational investigation of the electronic structure reveals that Na3Ge2P3 is an indirect band gap semiconductor with a band gap of 2.9 eV.

AE2[Ni(Te4O10)Cl2] (AE = Ca, Sr, Ba, Pb): A New Type of Inorganic Compound Synthesized through the Recombination of Tellurium(IV) Oxide Anion Fragments by Introducing Post-transition-metal Halide NiCl2

Introduction of divalent metal oxides into the TeO2 matrix can produce the chemical formula Mn[TemO2m+n] ≡ (MO)n(TeO2)m, compounds in which divalent metal oxides provide oxygen ions to the parent compound TeO2, to cleave neutral Te–O net to form various tellurium(IV) oxide anion [TemO2m+n]2n− and divalent metal cations as balanced charges. [TemO2m+n]2n− can form isolated anion, discrete polyanion, one-dimensional chain and ribbon polyanion, two-dimensional (2D) layered polyanion, and 3D tunnel polyanion depending on the ratio of MO/TeO2. In this work, a new type of inorganic compound AE2[Ni(Te4O10)Cl2] ≡ [(AEO)2(TeO2)4](NiCl2) (AE = Ca, Sr, Ba, Pb) can be obtained by introducing NiCl2 into the compound AE2[Te4O10] ≡ (AEO)2(TeO2)4 (AE = Ca, Sr, Ba, Pb). In AE2[Ni(Te4O10)Cl2] ≡ [(AEO)2(TeO2)4](NiCl2), AEO acts as a structural shearing agent to cleave the neutral Te–O layered structures of parent TeO2 into [Te4O10]4– anionic fragments, and the introduced NiCl2 acts as an “adhesive” to recombine [TemO2m+n]2n−...

CeIII-Functionalized Polyoxotungstates: Discrete vs Extended Architectures

Four polyoxotungstate solid state structures comprising discrete and polymeric architectures based on CeIII complexes of monolacunary Wells-Dawson-type anions [α2-PV2WVI17O61]10–, isolated as [NMe4]7Li4K3[{Ce(H2O)3(α2-P2W17O61)}2]·35H2O (KLT-1), [NMe4]8Na2[Ce(H2O)7]2[{Ce(CH3COO)(H2O)4(α2-P2W17O61)}2]·32.5H2O (NT-2), [NMe4]8K0.5Na1.5[Ce(H2O)7]2[{Ce(H2O)1.5(CH3COO)(α2-P2W17O61)}2]·22H2O (KNT-3), and [NMe4]3Li[Ce(H2O)7][Ce(H2O)4(α2-P2W17O61)]·15H2O (LT-4), illustrate the structural flexibility of CeIII ions, here imparted by their variable coordination numbers, with respect to their incorporation into polyoxometalate clusters versus their role in intercluster bridging in the solid state. While KLT-1 comprises discrete dimeric {CeP2W17}2 clusters, NT-2 and KNT-3 represent coordination polymers of linear {(Ce)(CeP2W17)}n strands, every two of which are paired via acetate bridges to yield a ladder-like topology. Finally, LT-4 features the same {(Ce)(CeP2W17)}n strands but in alternating orientation, enabling the formation of a 2D net. The title compounds have been isolated and fully characterized via single-crystal and powder X-ray diffraction, elemental and thermogravimetric analyses, IR spectroscopy, and SQUID magnetometry. The discrete polyanion [{Ce(H2O)3(α2-P2W17O61)}2]14– (1) exhibits considerable stability in aqueous medium and interesting electrochemical behavior associated with redox transitions of its CeIII and WVI centers.

“Zeoball” [Sn36Ge24Se132]24–: A Molecular Anion with Zeolite-Related Composition and Spherical Shape

Ionothermal reactions of [Ge(4)Se(10)](4-) with SnCl(4)·5H(2)O yielded [BMMIm](24)[Sn(36)Ge(24)Se(132)] (ZBT-1) and [BMIm](24)[Sn(32.5)Ge(27.5)Se(132)] [ZBT-2; B(M)MIm = 1-butyl-(2,)3-(di)methylimidazolium]. These contain the largest known discrete polyanion consisting only of main-group elements. In spite of a zeolite-related composition, the 192-atom "zeoball" anion adopts a spherical shape, which has been unprecedented in the chemistry of zeolites and their homologues and relatives. Preliminary studies indicated that ZBT-1 traps I(2) molecules and induces heterolytic I-I bond cleavage.

Investigation of framework and cation substitutions in Keggin-type heteropoly acids probed by scanning tunneling microscopy and tunneling spectroscopy

Scanning tunneling microscopy (STM) and spatially resolved tunneling spectroscopy were used to characterize surface arrays of heteropoly acids (HPAs) of the Keggin structural class. STM images revealed that these discrete oxide anions formed single, ordered monolayers on inert graphite surfaces, with lattice spacings of ∼11 Å, which is the characteristic dimension of the Keggin anion. However, increases in the lattice constants were observed in the STM images upon the substitution of the protons in H3PMo12O40 with larger counter cations such as Cs and K. This finding is consistent with those observed for bulk crystals of these salts. Substitution of metal ions in the Keggin ion framework (such as the replacement of Mo with W, or vice versa), led to insignificant variations in the lattice constants of the surface arrays. Tunneling spectroscopy measurements on discrete polyanions in the STM images revealed that the HPAs (both cation-exchanged and framework-substituted) exhibited current peaks in their respective current-voltage spectra, but at different applied potentials. The location of the current peak, or negative differential resistance (NDR) feature, was characteristic of the reducibility of the Keggin-type HPA in each case—the more reducible the HPA, the smaller the magnitude of the NDR peak voltage.

Über Tetraalkylammonium-polyvanadate.

In the reaction of V2O5 with aqueous or alcoholic solutions of tetraalkylammoniumhydroxide the orange decavanadates (NR4)3H3V10O28, (NR4)4H2V10O28, (NR4)5HV10O28 (NR4)6V10O28 and colourless metavanadates can be obtained. The tetrabutylammoniumsalt [N(C4H9)4]3HV4O12 is the first known metavanadate with discrete polyanion. Its molecular weight was determined by vapor pressure osmometry in chloroform. The Raman spectrum is identical with the spectrum of a sodium metavanadate solution. The vibration spectra of the compounds are discussed and partial assignments were made.

The Crystal Structure of Ammonium Pentamolybdodisulfate(IV) (4-) Trihydrate (NH4)4[SIV2Mo5O2l]·3H2O

Abstract The crystal of (NH4)4S2Mo5O21·3H2O contains a discrete polyanion, S2Mo5O214−, formed by reactions in an aqueous solution: 5Mo7O246−+14SO2+2H+\ightleftarrows7S2Mo5O214−+H2O or 5MoO42−+2SO2+6H+\ightleftarrowsS2Mo5O214−+3H2O It is orthorhombic, with the space group Pbcn and with a=15.096(9), b=13.375(8), c=23.734(7) Å, Dm=2.79, and Dx=2.79g cm−3 for Z=8. The crystal consists of S2Mo5O214− anions connected with each other by hydrogen bonds, with intervening water molecules and ammonium cations. In the polyanion, five MoO6 octahedra are connected by edge sharing, and the two octahedra at the two ends are connected by corner sharing to complete the Mo5O21 ring; the two SO3 trigonal pyramids are attached to the ring from above and below the ring.

THE CRYSTAL STRUCTURE OF AMMONIUM DODECAMOLYBDOTETRAARSENATE(V) TETRAHYDRATE,(NH4)4 H4As4Mo12O50·4H2O

Abstract (NH4)4H4As4Mo12O50·4H2O is tetragonal: space group P42/nnm, Z = 2, a = 11.923 (3), c = 17.564 (2) Å. The crystal contains a discrete polyanion, H4As4Mo12O504− of a Td point symmetry, consisting of four trigonal Mo3O13 groups. They are bound each other at six oxygen atoms, four AsO4 tetrahedra are attached from outside of the Mo12O46 cage. There is an empty cavity of the radius of 1.43 Å at the center of the polyanion.

CRYSTAL STRUCTURE OF K7[NiIVV13O38]·18H2O

Abstract K7[NiIVV13O38]·18H2O is orthorhombic: space group I4⁄mmm, Z=2, a=11.37(1), c=19.56(1) Å. On Fourier projection maps, a discrete polyanion with an apparent point symmetry of D4h was found. But it was realized that this electron density image was yielded by the random orientation of the polyanion NiV13O384− which consists of one NiIVO6 and 13VO6 octahedra sharing edges.

The Structure of Mo7O246− Ion in the Crystal of Ammonium Heptamolybdate Tetrahydrate

Abstract The structure of a discrete polyanion, Mo7O246−, in the crystal of ammonium heptamolybdate tetrahydrate, previously determined by Lindqvist, has been redetermined and refined by a two-dimensional, single crystal X-ray diffraction study. The positional parameters of the oxygen atoms, which were left undetermined in the previous investigation, have been determined. Lindqvist’s description of the structure still applies. However, the distortion of the polyanion has been found to be more pronounced than was previously assumed. Comparisons with molybdenum oxides and oxyacids are discussed with regard to the structure, the Mo–Mo distances and Mo–O distances.