Nb4Pd0.5ZSb2 (Z = Cr, Fe, Co, Ni, Si): the first ordered quaternary variants of the W5Si3-type structure

A family of quaternary (or pseudoquaternary) antimonides Nb4Pd0.5ZSb2 (Z = Cr, Fe, Co, Ni, Si) containing up to three transition metals in an ordered arrangement has been prepared by reactions of the elements. These antimonides are isostructural, crystallizing as substitutional variants of the W5Si3-type structure (tetragonal, space group -I4/mcm, Z = 4) with unit cell parameters a = 10.4407(3) A and c = 5.0020(2) A for Nb4Pd0.5Cr0.28(3)Si0.72Sb2, a = 10.4825(6) A and c = 4.9543(3) A for Nb4Pd0.5FeSb2, a = 10.4603(5) A and c = 4.9457(3) A for Nb4Pd0.5CoSb2, a = 10.4332(7) A and c = 4.9649(3) A for Nb4Pd0.5Ni0.78(1)Sb2, and a = 10.3895(10) A and c = 4.9634(4) A for Nb4Pd0.5SiSb2. They are distinguished by the filling of interstitial Z atoms into the centers of Nb8 square antiprismatic clusters that are linked by PdSb4 tetrahedra. The Nb8 square antiprisms share opposite square faces to form one-dimensional chains along the c axis so that Z-Z bonding distances of approximately 2.5 A result. Extended Hückel band structure calculations were carried out to interpret the homo- and heteroatomic metal-metal interactions in the structure. The resistivity of one member, Nb4Pd0.5SiSb2, was measured, indicating metallic behavior.     

Cs2Pd3(P2O7)2 and Cs2Pd3(As2O7)2: a 3D palladium phosphate with a tunnel structure and a 2D palladium arsenate containing strings of palladium atoms

Cs(2)Pd(3)(P(2)O(7))(2) (1) and Cs(2)Pd(3)(As(2)O(7))(2) (2) have been synthesized by molten flux reactions and characterized by single-crystal X-ray diffraction. The structure of 1 consists of discrete Pd(II)O(4) squares which are linked by P(2)O(7) groups via corner-sharing to generate a 3D framework containing 12-ring channels in which Cs(+) cations are located. Compound 2 adopts a 2D layer structure with the interlayer space filled with Cs(+) cations. Within a layer there are PdO(4) squares and As(2)O(7) groups fused together via corner-sharing. Adjacent layers are stacked such that strings of Pd atoms are formed. The PdO(4) squares show eclipsed and staggered stacks with alternate short and long Pd...Pd distances. The two compounds adopt considerably different structures although they have the same general formula: Cs(2)Pd(3)(X(2)O(7))(2). Compound 2 is the first palladium arsenate reported. Crystal data for 1: orthorhombic, space group Cmc2(1) (No. 36), a = 7.6061(4) A, b = 14.2820(7) A, c = 14.1840(7) A, and Z = 4. Crystal data for 2: tetragonal, space group P4/n (No. 85), a = 16.251(1) A, c = 5.9681(5) A, and Z = 4.     

Er3Pd7P4 — Kristallstrukturbestimmung und Extended Hückel Rechnungen

Er₃Pd₇P₄ — Crystal Structure Determination and Extended Hückel Calculations Er₃Pd₇P₄ was prepared by heating the elements (1050°C) and investigated by means of single-crystal X-ray methods. The compound crystallizes in a new structure (C2/m; a = 15.180(3) Å, b = 3.955(1) Å, c = 9.320(1) Å, β = 125,65(1)°; Z = 2) with a three-dimensional framework of Pd and P atoms and with Er atoms in the holes. The Pd atoms are surrounded tetrahedrally, trigonally or linearly by P atoms, which are coordinated by nine metal atoms in the form of a tricapped trigonal prism. Therefore the atomic arrangement of Er₃Pd₇P₄ is related to the structures of ternary transition metal phosphides with a metal: phosphorus ratio of 2:1. Band calculations using the Extended Hückel method show strong covalent Pd? P bonds and weak bonding interactions between Pd atoms with Pd? Pd distances shorter than 2.9 Å.     

Palladiumpnictide des Zirconiums und Hafniums mit einem Metall : Nichtmetall‐Verhältnis von 2 : 1

Palladium Pnictides of Zirconium and Hafnium with a Metal : Nonmetal Ratio of 2 : 1 The following compounds were prepared by heating the elements in the range of 800°–1100 °C and characterized by means of X‐ray single crystal methods: Zr₅Pd₉P₇ (a = 3.815(1), b = 26.319(5), c = 6.511(1) Å) and Hf₅Pd₉P₇ (a = 3.776(1), b = 26.382(7), c = 6.500(3) Å) are isotypic and crystallize in a new structure type (Amm2; Z = 2). This also applies to ZrPdAs (a = 3.887(1), b = 19.288(6), c = 6.690(2) Å; Pmmn; Z = 10), while ZrPdSb (a = 6.814(1), b = 4.289(1), c = 7.870(2) Å) forms a TiNiSi analogous structure (Pnma; Z = 4). Common feature of all structures is the tetrahedral environment of Pd by X atoms (X: P, As, Sb). The linking of the tetrahedra leads to a PdX framework with holes, in which the Zr and Hf atoms respectively are located. The non‐metal atoms have trigonal prismatic metal coordination with three additional metal atoms outside the rectangular faces of the prisms. This XMe₉ polyhedron (Me = metal) is typical for the large family of ternary pnictides with a metal : non‐metal ratio of 2 : 1.     

Tetracyanoborate salts M[b(CN)4] with M = singly charged cations: properties and structures

A series of tetracyanoborate salts M[B(CN)4] with the singly charged cations of Li+, Na+, Rb+, Cs+, [NH4]+, Tl+, and Cu+ as well as the THF solvate tetracyanoborates Na[B(CN)4] x THF and [NH4][B(CN)4] x THF were synthesized and their X-ray structures, vibrational spectra, solubilities in water, and thermal stabilities determined and compared with already known M[B(CN)4] salts. Crystallographic data for these compounds are as follows: Na[B(CN)4], cubic, Fd3m, a = 11.680(1) A, Z= 8; Li[B(CN)4], cubic, P43m, a = 5.4815(1) A, Z= 1; Cu[B(CN)4], cubic, P43m, a = 5.4314(7) A, Z= 1; Rb[B(CN)4], tetragonal, /4(1)/a, a = 7.1354(2) A, c= 14.8197(6) A, Z= 4; Cs[B(CN)4], tetragonal, /4(1)/a, a = 7.300(2) A, c = 15.340(5) A, Z= 4; [NH4][B(CN)4], tetragonal, /4(1)/a, a = 7.132(1) A, c = 14.745(4) A, Z= 4; Tl[B(CN)4], tetragonal, /4(1)/a, a = 7.0655(2) A, c = 14.6791(4) A, Z= 4; Na[B(CN)4] x THF, orthorhombic, Pnma, a = 13.908(3) A, b = 9.288(1) A, c = 8.738(1) A, Z= 4; [NH4][B(CN)4] x THF, orthorhombic, Pnma, a = 8.831(1) A, b = 9.366(2) A, c = 15.061(3) A, Z= 4. The cubic Li+, Na+, and Cu+ salts crystallize in a structure consisting of two interpenetrating independent tetrahedral networks of M cations and [B(CN)4]- ions. The compounds with the larger countercations (Rb+, Cs+, Tl+, and [NH4]+) crystallize as tetragonal, also with a network arrangement. The sodium and ammonium salts with the cocrystallized THF molecules are both orthorhombic but are not isostructural. In the vibrational spectra the two CN stretching modes A1 and T2 coincide in general and the band positions are a measure for the strength of the interionic interaction. An interesting feature in the Raman spectrum of the copper salt is the first appearance of two CN stretching modes.     

Mixed-metal tellurites: synthesis, structure, and characterization of Na1.4Nb3Te4.9O18 and NaNb3Te4O16

Two new mixed-metal tellurites, Na1.4Nb3Te4.9O18 and NaNb3Te4O16, have been synthesized by standard solid-state techniques using Na2CO3, Nb2O5, and TeO2 as reagents. The structures of Na1.4Nb3Te4.9O18 and NaNb3Te4O16 were determined by single-crystal X-ray diffraction. Both of the materials exhibit three-dimensional structures composed of NbO6 octahedra, TeO4, and TeO3 polyhedra. The Nb5+ and Te4+ cations are in asymmetric coordination environments attributable to second-order Jahn-Teller (SOJT) effects. The Nb5+ cations undergo an intraoctahedral distortion toward a corner (local C4 direction), whereas the Te4+ cations are in distorted environments owing to their nonbonded electron pair. Infrared and Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, thermogravimetric analysis, and dielectric measurements were also performed on the reported materials. Crystal data: Na1.4Nb3Te4.9O18, monoclinic, space group C2/m (No. 12), with a = 32.377(5) A, b = 7.4541(11) A, c = 6.5649(9) A, beta = 95.636(5) degrees, V = 1576.7(4) A3, and Z = 4; NaNb3Te4O16, monoclinic, space group P2(1)/m (No. 11), with a = 6.6126(13) A, b = 7.4738(15) A, c = 14.034(3) A, beta = 102.98(3) degrees, V = 675.9(3) A3, and Z = 2.     

Zr(7)Sb(4): a new binary zirconium-rich antimonide

Zr(7)Sb(4) has been prepared by arc-melting of the elemental components and annealing at 1000-1150 degrees C. Its crystal structure was determined by X-ray diffraction (Pearson symbol mP44, monoclinic, space group P2(1)/c, Z = 4, a = 8.4905(6) A, b = 11.1557(8) A, c = 11.1217(8) A, beta = 111.443(2) degrees at 295 K). Zr(7)Sb(4) is isotypic to Hf(6)TiSb(4), a compound stabilized by differential fractional site occupancy. It is the first binary group-4 antimonide with this metal-to-antimony ratio, but it differs from the corresponding phosphides and arsenides M(7)Pn(4) (M = Ti, Zr, Hf; Pn = P, As), which adopt the Nb(7)P(4)-type structure. Zr(7)Sb(4) is built up from layers excised from the tetragonal W(5)Si(3)-type structure; these layers are displaced relative to each other to maximize interlayer Zr-Zr and Zr-Sb bonding, as confirmed by band structure calculations.     

Examining the out-of-center distortion in the [NbOF5]2- anion

Out-of-center "primary" electronic distortions are inherent to the oxide fluoride anions of the early d0 transition metals. In the [NbOF5]2- anion, the Nb5+ moves from the center of the octahedron toward the oxide ligand to form a short Nb=O bond and long trans Nb-F bond. The combined results of single-crystal X-ray diffraction and electronic structure calculations indicate that the primary distortion of the [NbOF5]2- anion is affected by the coordination environment that is created by the three-dimensional extended structure. The formation of bonds between an M(L)4(2+) (M = Cd2+, Cu2+; L = 3-aminopyridine, 4-aminopyridine) cation and the oxide and/or trans-fluoride ligands of the [NbOF5]2- anion weakens the pi component of the Nb=O bond. At the same time, hydrogen bond interactions between the equatorial fluorides and the aminopyridine groups both lengthen the equatorial Nb-F bonds and can further reduce the symmetry of the [NbOF5]2- anion. These combined three-dimensional bond network interactions that serve to lengthen the Nb=O bond and thereby decrease the primary distortion of the [NbOF5]2- anion are illustrated in the structures of three new niobium oxide fluoride phases, [4-apyH]2[Cu(4-apy)4(NbOF5)2] (4-apy = 4-aminopyridine), Cd(3-apy)4NbOF5 (3-apy = 3-aminopyridine), and Cu(3-apy)4NbOF5, that were synthesized and characterized using X-ray diffraction. Crystal data for [4-apyH]2[Cu(4-apy)4(NbOF5)2]: tetragonal, space group /4(1)/ acd (No. 142), with a = 20.8745(8) A, c = 17.2929(9) A, and Z= 8. Cd(3-apy)4NbOF5: tetragonal, space group P4(3) (No. 78), with a = 8.4034(4) A, c = 34.933(3) A, and Z = 4. Cu(3-apy)4NbOF5: monoclinic, space group P2(1)/n (No. 14), with a = 8.822(1) A, b = 16.385(3) A, c = 8.902(1) A, beta = 109.270(3) degrees, and Z = 2.     

A theoretical and experimental study on the Lewis acid-base adducts (P(4)E(3)).(BX(3)) (E = S, Se; X = Br, I) and (P(4)Se(3)).(NbCl(5))

The Lewis acid-base adducts (P(4)E(3)).(BX(3)) (E = S, Se; X = Br, I) and (P(4)Se(3)).(NbCl(5)) have been prepared and characterized by Raman, IR, and solid-state (31)P MAS NMR spectroscopy. Hybrid density functional calculations (B3LYP) have been carried out for both the apical and the basal (P(4)E(3)).(BX(3)) (E = S, Se; X = Br, I) adducts. The thermodynamics of all considered species has been discussed. In accordance with solid-state (31)P MAS NMR and vibrational data, the X-ray powder diffraction structures of (P(4)S(3)).(BBr(3)) [monoclinic, space group P2(1)/m (No. 11), a = 8.8854(1) A, b = 10.6164(2) A, c = 6.3682(1) A, beta = 108.912(1) degrees, V = 568.29(2) A(3), Z = 2] and (P(4)S(3)).(BI(3)) [orthorhombic, space group Pnma (No. 62), a = 12.5039(5) A, b = 11.3388(5) A, c = 8.9298(4) A, V = 1266.09(9) A(3), Z = 4] indicate the formation of an apical P(4)S(3) complex in the reaction of P(4)S(3) with BX(3) (X = Br, I). Basal adducts are formed when P(4)Se(3) is used as the donor species. Vibrational assignment for the normal modes of these adducts has been made on the basis of comparison between theoretically obtained and experimentally observed vibrational data.     

Crystal structure of 12-methoxy-8,8,21,21-tetramethyl-5-(3-methylbut-2,4-dienyl)-19-(3-methylpent-4-enyl)-3,7,20-trioxahexacyclo[15.4.1.0<2,15>.0<2,19>.0<4,13>.0<6,11>]docosa-4(13),5,9,11,15-pentaene-14,18-dione.

The title compound was extracted from the natural product of plant origin. It crystallizes in tetragonal space group P4(1) or P4(3), with cell parameters a = 15.795(2)A, c = 11.970(5)A and Z = 4. The structure exhibits intermolecular hydrogen bonds of the type C-H...O.     

High-pressure synthesis, crystal structure, and properties of BiPd2O4 with Pd2+ and Pd4+ ordering and PbPd2O4

BiPd(2)O(4) and PbPd(2)O(4) were synthesized at high pressure of 6 GPa and 1500 K. Crystal structures of BiPd(2)O(4) and PbPd(2)O(4) were studied with synchrotron X-ray powder diffraction. BiPd(2)O(4) is isostructural with PbPt(2)O(4) and crystallizes in a triclinic system (space group P1, a = 5.73632(4) ?, b = 6.02532(5) ?, c = 6.41100(5) ?, α = 114.371(1)°, β = 95.910(1)°, and γ = 111.540(1)° at 293 K). PbPd(2)O(4) is isostructural with LaPd(2)O(4) and BaAu(2)O(4) and crystallizes in a tetragonal system (space group I4(1)/a, a = 5.76232(1) ?, and c = 9.98347(2) ? at 293 K). BiPd(2)O(4) shows ordering of Pd(2+) and Pd(4+) ions, and it is the third example of compounds with ordered arrangements of Pd(2+) and Pd(4+) in addition to Ba(2)Hg(3)Pd(7)O(14) and KPd(2)O(3). In PbPd(2)O(4), the following charge distribution is realized Pb(4+)Pd(2+)(2)O(4). PbPd(2)O(4) shows a structural phase transition from I4(1)/a to I2/a at about 240 K keeping basically the same structural arrangements (space group I2/a, a = 5.77326(1) ?, b = 9.95633(2) ?, c = 5.73264(1) ?, β = 90.2185(2)° at 112 K). BiPd(2)O(4) is nonmagnetic while PbPd(2)O(4) exhibits a significant temperature-dependent paramagnetic moment of 0.46μ(B)/f.u. between 2 and 350 K. PbPd(2)O(4) shows metallic conductivity, and BiPd(2)O(4) is a semiconductor between 2 and 400 K.     

Reduced zirconium halide clusters in aqueous solution

Reduced hexazirconium halide cluster compounds have good solubility and stability in strongly acidic and/or halide-rich aqueous solutions. Cyclic voltammetric (CV) measurements in aqueous media established that [(Zr6BCl12)(H2O)6]2+/+ and [(Zr6BBr12)(H2O)6]2+/+ exhibited positive half-wave potentials (E1/2 = 0.059V and 0.160 V, respectively) vs the SHE, indicating that these clusters are only modestly reducing. Several new crystalline cluster compounds have been isolated from cold 12 M HCl solutions; the structures of each contain extended hydrogen-bonding water networks. Crystallographic data for these compounds are reported as follows: [Rb0.44(H3O)4.56][(Zr6BCl12)Cl6].19.44H2O (3), cubic, Im3m, a = 13.8962(3) A, Z = 2; (H3O)5[(Zr6BeCl12)Cl6].19H2O (4), cubic, Im3m, a = 13.8956(4) A, Z = 2; (H3O)5[(Zr6MnCl12)Cl6].19H2O (5), cubic, Im3m, a = 14.029(3) A, Z = 2; (H3O)4[(Zr6BCl12)Cl6].12.97H2O (6), tetragonal, P4(2)/mnm, a = 11.5373(2) A, c = 15.7169(4) A, Z = 2; (H3O)4[(Zr6BCl2)Br6].13.13H2O (7), tetragonal, P4(2)/mnm, a = 11.7288(6) A, c = 15.931(1) A, Z = 2.     

Synthesis of TiRru2 heterobimetallic and TiRuM (M = Rh, Rr, Pd, Pt) heterotrimetallic sulfido clusters from a hydrosulfido-bridged titanium-ruthenium complex

Treatment of the hydrosulfido-bridged titanium-ruthenium heterobimetallic complex [Cp2Ti(mu2-SH)2RuCl(eta5-C5Me5)] (1; Cp = eta5-C5H5) with an excess of triethylamine followed by addition of [RuCl2(PPh3)3] and [[(cod)M]2(mu2-Cl)2] (M = Rh, Ir; cod = 1,5-cyclooctadiene) led to the formation of the TiRu2 and TiRuM mixed-metal sulfido clusters [(CpTi)[(eta5-C5Me5)Ru][Ru(PPh3)2](mu3-S)2(mu2-Cl)2] (3) and [(CpTi)[(eta5-C5Me5)Ru][M(cod)](mu3-S)2(mu2-Cl)] (M = Rh (4a), Ir (4b)), respectively. On the other hand, the reactions of 1 with [M(PPh3)4] (M = Pd, Pt) afforded the TiRuM trinuclear clusters [(CpTiCl)[(eta5-C5Me5)Ru][M(PPh3)2](mu3-S)(mu2-S)(mu2-H)] (M = Pd (5a), Pt (5b)) with an unprecedented M3(mu3-S)(mu2-S) core. The detailed structures of these triangular clusters 3-5 have been determined by X-ray crystallography. Crystal data: 3, triclinic, P1, a = 12.448(4) A, b = 12.773(4) A, c = 17.270(4) A, alpha = 100.16(2) degrees, beta = 99.93(2) degrees, gamma = 114.11(3) degrees, V = 2373(1) A(3), Z = 2; 4a, triclinic, P1, a = 7.714(2) A, b = 11.598(3) A, c = 14.802(4) A, alpha = 80.46(2) degrees, beta = 82.53(2) degrees, gamma = 71.47(2) degrees, V = 1234.0(6) A3, Z = 2; 4b, triclinic, P1, a = 7.729(1) A, b = 11.577(2) A, c = 14.766(3) A, alpha = 80.14(1) degrees, beta = 82.71(1) degrees, gamma = 71.55(1) degrees, V = 1231.1(4) A3, Z = 2; 5a, monoclinic, P2(1)/c, a = 11.259(4) A, b = 16.438(4) A, c = 26.092(5) A, beta = 102.23(3) degrees, V = 4719(2) A(3), Z = 4; 5b, monoclinic, P2(1)/n, a = 11.369(2) A, b = 16.207(3) A, c = 26.116(2) A, beta = 102.29(1) degrees, V = 4701(1) A3, Z = 4.     

Ca3Pd4Bi8: Kristall‐ und elektronische Struktur

Ca₃Pd₄Bi₈: Crystal and Electronic Structure Ca₃Pd₄Bi₈ (a = 10.814(4), b = 17.050(6), c = 4.149(4) Å) was prepared by heating the elements at 900 °C and investigated by single crystal X‐ray methods. The compound crystallizes in a new structure type (Pbam; Z = 2). Six Bi atoms form distorted trigonal prisms around the Pd atoms. The polyhedra share common corners, edges or faces building up a three dimensional Pd, Bi network, whose holes are occupied by Ca atoms. A special feature is a distorted octahedron of four Pd and two Bi atoms connected via short homonuclear bonds. The metallic behaviour of the compound derived from the bond lengths is discussed by LMTO band structure calculations.     

AVNb3Cl11 (A = K, Rb, Cs, Tl): a series of layered vanadium niobium halides based on triangular Nb3 clusters

The first quaternary vanadium niobium compounds containing triangular Nb(3) clusters corresponding to the general formula, AVNb(3)Cl(11) (A = K, Rb, Cs, Tl), have been prepared in sealed quartz tubes from stoichiometric amounts of ACl (A = K, Rb, Cs), or Tl metal, VCl(3), Nb powder, and NbCl(5) heated at 740 degrees C. The compounds crystallize in the orthorhombic space group Pnma (No. 62). The crystal structures of the Rb and Tl members were determined by single-crystal X-ray diffraction techniques. Crystal data: a = 12.771(3) A, b = 6.811(2) A, c = 17.183(3) A, V = 1494.6(1) A(3), and Z = 4 for A = Rb; and a = 12.698(5) A, b = 6.798(3) A, c = 17.145(10) A, V = 1480.0(13) A(3), and Z = 4 for A = Tl. The crystal structure of AVNb(3)Cl(11) consists of triangular Nb(3)Cl(13) clusters (Nb-Nb = 2.826 A) connected to each other via four outer ligands to form infinite chains along the b-axis. The chains are connected by vanadium atoms located in an octahedral environment to form puckered sheets. The A(+) counterions are located between adjacent sheets and coordinate to twelve chlorine ligands in anticubeoctahedral geometry. Electronic structure calculations show bonding orbitals similar to those in Nb(3)Cl(8). Magnetic susceptibility measurements show paramagnetic Curie Weiss behavior.     

Kristallstrukturen von Säurehydraten und Oxoniumsalzen. 36 [1]. Selensäure-Tetrahydrat. Ionisch gemäß (H5O2)2SeO4 in einer orthorhombischen sowie einer tetragonalen Form

Crystal Structures of Acid Hydrates and Oxonium Salts. 36 [1]. Selenic Acid Tetrahydrate. Ionic as (H₅O₂)₂SeO₄ in an Orthorhombic as well as a Tetragonal Form Low-melting selenic acid tetrahydrate has been studied for the first time by crystal structure analysis. Two forms have been observed, an orthorhombic one with space group Pnma and Z = 4 and a tetragonal one with space group P4 2₁c and Z = 2. The lattice parameters at ?150°C are a = 6.130(3), b = 12.776(6) and c = 9.299(5) Å for the orthorhombic and a = 7.676(4) and c = 6.378(3) Å for the tetragonal form. Both forms are oxonium salts, corresponding to (H₅O₂)₂SeO₄. The ions are hydrogen-bonded into a three-dimensional array. The bonds within the diaquahydrogen cations have O ?O distances of 2.422(5) and 2.425(4) Å. The tetragonal form is isotypic to the tetrahydrate of sulfuric acid.     

Synthesis, structure, and infrared spectroscopy of the first Np5+ neptunyl silicates, Li6(NpO2)4(H2Si2O7)(HSiO4)2(H2O)4 and K3(NpO2)3(Si2O7)

Two Np(5+) silicates, Li(6)(NpO(2))(4)(H(2)Si(2)O(7))(HSiO(4))(2)(H(2)O)(4) (LiNpSi1) and K(3)(NpO(2))(3)(SiO(3)OH)(2) (KNpSi1), were synthesized by hydrothermal methods. The crystal structures were determined using direct methods and refined on the basis of F(2) for all unique data collected with Mo Kalpha radation and an APEX II CCD detector. LiNpSi1 crystallizes in orthorhombic space group Pnma with a =13.189(6) A, b = 7.917(3) A, c = 10.708(5) A, V = 1118.1(8) A3, and Z = 2. KNpSi1 is hexagonal, P62m, a = 9.734(1) A, c = 3.8817(7) A, V = 318.50(8) A3, and Z = 1. LiNpSi1 contains chains of edge-sharing neptunyl pentagonal bipyramids linked into two-dimensional sheets through direct linkages between the neptunyl polyhedra and the vertex sharing of the silicate tetrahedra. The structure contains both sorosilicate and nesosilicate units, resulting in a new complex neptunyl silicate sheet. KNpSi1 contains edge-sharing neptunyl square bipyramids linked into a framework structure through the sharing of vertices with the silicate tetrahedra. The neptunyl silicate framework contains channels approximately 6.0 A in diameter. These structures exhibit significant departures from other reported Np(5+) and U(6+) compounds and represent the first reported Np(5+) silicate structures.     

Study of the structural,electronic, and magnetic properties of the barium-rich iron(IV) oxides,Ba(2)FeO(4) and Ba(3)FeO(5)

Crystals of Ba(2)FeO(4) and Ba(3)FeO(5), grown from a "self-sealing" KOH-Ba(OH)(2) flux, have been characterized by single-crystal X-ray diffraction, M?ssbauer spectroscopy, and magnetic measurements. Ba(2)FeO(4) forms nonmerohedral twinned crystals with the monoclinic space group P2(1)/n, a = 6.034(2) A, b = 7.647(2) A, c = 10.162(3) A, beta = 92.931(6) degrees, and Z = 4. Ba(3)FeO(5) crystallizes in the orthorhombic space group Pnma, with a = 10.301(1) A, b = 8.151(1) A, c = 7.611(1) A, and Z = 4. While both compounds feature discrete FeO(4)(4-) tetrahedra, the anion found in Ba(2)FeO(4) has shorter Fe-O bonds and is significantly distorted relative to the Ba(3)FeO(5) anion. An iron valence of 4+ was confirmed by magnet susceptibility measurements and by the low-temperature isomer shifts of -0.152 and -0.142 mm/s relative to alpha-iron for Ba(2)FeO(4) and Ba(3)FeO(5), respectively.     

Syntheses, Crystal Structures, and Antimicrobial Activities of 3-Bromo-N'-(2-chloro-5-nitrobenzylidene)benzohydrazide and 3-Bromo-N'-(4-nitrobenzylidene)benzohydrazide

Two new hydrazone compounds, 3-bromo-N'-(2-chloro-5-nitrobenzylidene)-ben- zohydrazide 1 and 3-bromo-N'-(4-nitrobenzylidene)benzohydrazide 2, have been synthesized and characterized by elemental analysis, IR spectra, <'1>H NMR, and single-crystal X-ray diffraction.Compound 1 crystallizes in monoclinie, space group P2<,1>/c with a = 7.7924(10), b = 24.490(3), c =7.8989(9)(A),β = 94.987(6)°, V = 1501.7(3)(A)<'3>, Z = 4, R = 0.0345 and wR = 0.0739. Compound 2 crystallizes in monoclinic, space group P2<,1>/c with a = 7.4099(11), b = 24.868(4), c = 8.3255(12)(A),β= 112.796(8)°, V= 1414.3(4)(A)<'3>, Z = 4, R = 0.0744 and wR = 0.1912. Both compounds display E configurations with respect to the C=N double bonds. In the crystal structure of 1, molecules are linked through N-H…N and N-H…O hydrogen bonds, forming chains running along the c axis. In the crystal structure of 2, molecules are linked through N-H…O hydrogen bonds, forming chains running along the c axis. The preliminary antimicrobial activities were studied.     

Nb(9)PdAs(7): a unique arrangement in the M(n2+3n+2)X(n2+n)Y family of hexagonal structures

The ternary transition-metal arsenide Nb(9)PdAs(7) has been prepared through reaction of the elements, and its structure has been determined by single-crystal X-ray diffraction methods. It adopts a new structure type (Pearson symbol hP51, hexagonal, space group P6, Z = 3), with unit cell parameters a = 16.6955(6) and c = 3.5582(1) A. The structure contains assemblies of As-centered trigonal prisms that extend as triangular columns through sharing of the triangular faces. Not only does Nb(9)PdAs(7) extend a family of hexagonal structures with general formula M(n2+3n+2)X(n2+n)Y to n = 4, the highest member known thus far, but it also displays the unique feature in which there are two distinct types of triangular columns, one having corner atoms (Pd) different from the other atoms (Nb). Structural relationships between members of the M(n2+3n+2)X(n2+n)Y family are presented. The chemical bonding in Nb(9)PdAs(7) was analyzed through an extended Hückel band structure calculation.