New vanadium selenites: centrosymmetric Ca2(VO2)2(SeO3)3(H2O)2, Sr2(VO2)2(SeO3)3, and Ba(V2O5)(SeO3), and noncentrosymmetric and polar A4(VO2)2(SeO3)4(Se2O5) (A = Sr2+ or Pb2+)

Five new vanadium selenites, Ca(2)(VO(2))(2)(SeO(3))(3)(H(2)O)(2), Sr(2)(VO(2))(2)(SeO(3))(3), Ba(V(2)O(5))(SeO(3)), Sr(4)(VO(2))(2)(SeO(3))(4)(Se(2)O(5)), and Pb(4)(VO(2))(2)(SeO(3))(4)(Se(2)O(5)), have been synthesized and characterized. Their crystal structures were determined by single crystal X-ray diffraction. The compounds exhibit one- or two-dimensional structures consisting of corner- and edge-shared VO(4), VO(5), VO(6), and SeO(3) polyhedra. Of the reported materials, A(4)(VO(2))(2)(SeO(3))(4)(Se(2)O(5)) (A = Sr(2+) or Pb(2+)) are noncentrosymmetric (NCS) and polar. Powder second-harmonic generation (SHG) measurements revealed SHG efficiencies of approximately 130 and 150 × α-SiO(2) for Sr(4)(VO(2))(2)(SeO(3))(4)(Se(2)O(5)) and Pb(4)(VO(2))(2)(SeO(3))(4)(Se(2)O(5)), respectively. Piezoelectric charge constants of 43 and 53 pm/V, and pyroelectric coefficients of -27 and -42 μC/m(2)·K at 70 °C were obtained for Sr(4)(VO(2))(2)(SeO(3))(4)(Se(2)O(5)) and Pb(4)(VO(2))(2)(SeO(3))(4)(Se(2)O(5)), respectively. Frequency dependent polarization measurements confirmed that the materials are not ferroelectric, that is, the observed polarization cannot be reversed. In addition, the lone-pair on the Se(4+) cation may be considered as stereo-active consistent with calculations. For all of the reported materials, infrared, UV-vis, thermogravimetric, and differential thermal analysis measurements were performed. Crystal data: Ca(2)(VO(2))(2)(SeO(3))(3)(H(2)O)(2), orthorhombic, space group Pnma (No. 62), a = 7.827(4) ?, b = 16.764(5) ?, c = 9.679(5) ?, V = 1270.1(9) ?(3), and Z = 4; Sr(2)(VO(2))(2)(SeO(3))(3), monoclinic, space group P2(1)/c (No. 12), a = 14.739(13) ?, b = 9.788(8) ?, c = 8.440(7) ?, β = 96.881(11)°, V = 1208.8(18) ?(3), and Z = 4; Ba(V(2)O(5))(SeO(3)), orthorhombic, space group Pnma (No. 62), a = 13.9287(7) ?, b = 5.3787(3) ?, c = 8.9853(5) ?, V = 673.16(6) ?(3), and Z = 4; Sr(4)(VO(2))(2)(SeO(3))(4)(Se(2)O(5)), orthorhombic, space group Fdd2 (No. 43), a = 25.161(3) ?, b = 12.1579(15) ?, c = 12.8592(16) ?, V = 3933.7(8) ?(3), and Z = 8; Pb(4)(VO(2))(2)(SeO(3))(4)(Se(2)O(5)), orthorhombic, space group Fdd2 (No. 43), a = 25.029(2) ?, b = 12.2147(10) ?, c = 13.0154(10) ?, V = 3979.1(6) ?(3), and Z = 8.     

Synthesis of a family of solids through the building-block approach: a case study with Ag(+) substitution in the ternary Na-Ge-Se system

A new family of Ag-substituted pseudoquaternary alkali-seleno-germanates has been synthesized by two solid-state routes: the conventional flux method and metathesis. This family includes a series of semiconductors with varying amounts of Ag+ substituted for Na+ in Na8Ge4Se10 to form AgxNa(8-x)Ge4Se10, [x = 0.31 (I), 0.67 (II), 0.77 (III), 0.87 (IV), 1.05 (V), 1.09 (VI)] and another phase with a different composition AgxNa(6-x)Ge2Se7 (x = 1.76), VII, related to Na6Ge2Se7. In I-VI, Ge4Se10(8-) constitutes a 6-membered chairlike unit with a Ge-Ge bond, while in VII, a corner-shared dimer of GeSe4 tetrahedra (Ge2Se76-) acts as the building unit. The single-crystal structure analysis indicates that there is a phase transition from P to C2/c, in changing from pure Na8Ge4Se10 to AgxNa(8-x)Ge4 Se10 (I-VI), while there is no phase transition between pure Na6Ge2Se7 and AgxNa(6-x)Ge2Se7 (x = 1.76). The structures of I-VI may be described in terms of layers of cubic close-packed Se2- anions. In between the Se layers, octahedral holes fully occupied by Na+ and mixed Ag+/Na+ cations alternate with layers formed of octahedral holes fully occupied by Na+ and Ge26+ cations. Two adjacent Ge26+ cations form a chairlike Ge4Se10(8-) anion in which Ge-Ge bonds are oriented almost parallel to the Se layers. In contrast, VII does not have close-packed anions. Corner-shared GeSe4 tetrahedra (Ge2Se7(6-) dimer) and AgSe4 tetrahedra form layers that are cross-linked by Na/AgSe4 tetrahedra to form a 3-dimensional (3-D) structure. An optical property investigation indicates a red shift in the band gap of AgxNa(8-x)Ge4Se10 (x = 0.67)(II) as compared to that of pure Na8Ge4Se10. Raman data also indicate a red shift of the Ge-Se stretching mode in the Ag+-substituted phase II (x = 0.67) compared to that of Na8Ge4Se10.     

Synthesis, structure, and thermal properties of soluble hydrazinium germanium(IV) and tin(IV) selenide salts

The crystal structures of two hydrazinium-based germanium(IV) and tin(IV) selenide salts are determined. (N(2)H(5))(4)Ge(2)Se(6) (1) [I4(1)cd, a = 12.708(1) Angstroms, c = 21.955(2) Angstroms, Z = 8] and (N(2)H(4))(3)(N(2)H(5))(4)Sn(2)Se(6) (2) [P, a = 6.6475(6) Angstroms, b = 9.5474(9) Angstroms, c = 9.8830(10) Angstroms, alpha = 94.110(2) degrees, beta = 99.429(2) degrees, gamma = 104.141(2) degrees, Z = 1] each consist of anionic dimers of edge-sharing metal selenide tetrahedra, M(2)Se(6)(4-) (M = Ge or Sn), separated by hydrazinium cations and, for 2, additional neutral hydrazine molecules. Substantial hydrogen bonding exists among the hydrazine/hydrazinium molecules as well as between the hydrazinium cations and the selenide anions. Whereas the previously reported tin(IV) sulfide system, (N(2)H(5))(4)Sn(2)S(6), decomposes cleanly to microcrystalline SnS(2) when heated to 200 degrees C in an inert atmosphere, higher temperatures (>300 degrees C) are required to dissociate selenium from 1 and 2 for the analogous preparations of single-phase metal selenides. The metal chalcogenide salts are highly soluble in hydrazine, as well as in a variety of amines and DMSO, highlighting the potential usefulness of these compounds as precursors for the solution deposition of the corresponding metal chalcogenide films.     

High-pressure synthesis and transport properties of a new binary germanide, SrGe6-delta (delta congruent with 0.5), with a cagelike structure

A new germanide, SrGe6-delta (delta congruent with 0.5), was synthesized by the reaction of Sr and Ge mixtures under a pressure of 5 GPa at 1200 degrees C. It crystallized in the orthorhombic space group Cmcm (No. 63) with a = 4.0981(6) A, b = 11.159(1) A, c = 12.6825(8) A, V = 580.0(1) A3, and Z = 4. SrGe6-delta is composed of a Ge covalent network having a cagelike structure and Sr atoms situated in the cages. Each Ge atom is coordinated by four neighboring Ge atoms. The coordination polyhedra are fairly distorted from an ideal tetrahedron, and the Ge network contains vacancies and disordering. The resistivity shows metallic behavior down to 2 K, and the positive thermoelectric power indicates the dominant carriers to be holes.     

Structures and physical properties of new semiconducting polyselenides Ba2CudeltaAg4-deltaSe5 with unprecedented linear Se(3)4- units

The title compounds were prepared from the elements in evacuated silica tubes at 650 degrees C, followed by slow cooling. Ba2Ag4Se5 forms a new structure type, space group C2/m, with a=16.189(2) A, b=4.5528(6) A, c=9.2500(1) A, beta=124.572(3) degrees, and V=561.4(1) A3 (Z=2). A maximum of 44% of the Ag atoms may be replaced with Cu atoms without changing the structure type. The crystal structure is composed of Ag4Se(5)4- layers, interconnected via the Ba2+ cations. The Ag atoms show irregular [3+1] coordination by the Se atoms, and the Ba atoms are located in capped square antiprisms formed by Se atoms. Most intriguing is the unprecedented occurrence of linear Se(3)4- units. According to the formulation (Ba2+)2(Ag+)4Se(3)4-(Se2-)2, this selenide is electron-precise with eight positive charges equalizing the eight negative charges. Electronic structure calculations indicated the presence of a band gap, as was experimentally confirmed: the electrical conductivity measurement revealed a gap of 0.6 eV for Ba2CuAg3Se5.     

High-pressure synthesis and superconductivity of a new binary lanthanum germanide LaGe3 with triangular Ge3 cluster units

We prepared a new binary lanthanum germanide, LaGe(3), under high-pressure and high-temperature conditions (3-12 GPa, 500-1200 °C). It crystallizes in the BaPb(3) structure (the space group R ?3m) with lattice constants of a = 6.376(1) ?, c = 22.272(3) ?, and V = 784.1(2) ?(3). We refined the structure using Rietveld analysis from X-ray powder data. The structure is composed of two types of close-packed atom layers. In one layer, every La atom is surrounded solely by Ge atoms with the same distance of 3.188 ?. The other layer contains Ge(3) regular, triangular cluster units with a Ge-Ge distance of 2.634 ?. The electron localization function and crystal orbital Hamilton population calculations suggest that the triangular cluster is composed of three Ge-Ge covalent bonds and that each Ge atom has a lone pair. The temperature dependence of the magnetic susceptibility and electrical conductivity measurements revealed that LaGe(3) is metallic and shows superconductivity at 7.4 K. This critical temperature is highest for the La-Ge system.     

Crystal structures of Sr4Sn2Se9 and Sr4Sn2Se10 and the oxidation state of tin in an unusual geometry

The new ternary selenostannates Sr(4)Sn(2)Se(9) and Sr(4)Sn(2)Se(10) have been synthesized by heating the elements at 1023 K in an argon atmosphere. Their structures were determined by single-crystal X-ray methods. Sr(4)Sn(2)Se(9) crystallizes in a new structure type (Pbam, a = 12.042(2) A, b = 16.252(3) A, c = 8.686(2) A, Z = 4) with Sn(2)Se(6)(4-), SnSe(4)(4-), and Se(2)(2-) subunits. Sr(4)Sn(2)Se(10) (P2(1)2(1)2, a = 12.028(2) A, b = 16.541(3) A, c = 8.611(2) A, Z = 4) has a similar structure with Se(3)(2-) triangles instead of Se(2)(2-) dumbbells. Strontium is 8-fold-coordinated by selenium in both cases. The opening angles between tin and the terminal selenium atoms in the Sn(2)Se(6) subunits are close to 160 degrees , which is nearer a typical Sn(2+) coordination geometry than classical SnSe(4) tetrahedra. This result suggests the tin oxidation state in the Sn(2)Se(6) units to be lower than the expected Sn(4+). This question is examined by self-consistent LMTO and LAPW band structure calculations expanded by the Bader analysis of the charge density to assign reliable atomic charges.     

First examples of thallium chalcogenide cages. Syntheses, 77Se, 203Tl, and 205Tl NMR study of the Tl4Se5(4-) and Tl4Se6(4-) anions, the X-ray crystal structure of (2,2,2-crypt-K+)3Tl5Se5(3-), and theoretical studies

The Tl5Se5(3-) anion has been obtained by extracting KTlSe in ethylenediamine in the presence of 2,2,2-crypt. The salt, (2,2,2-crypt-K+)3Tl5Se5(3-), crystallizes in the triclinic system, space group P1, with Z = 2 and a = 11.676(2) A, b = 16.017(3) A, c = 25.421(5) A, alpha = 82.42(3) degrees, beta = 88.47(3) degrees, gamma = 69.03(3) degrees at -123 degrees C. Two other mixed oxidation state TlI/TlIII anions; Tl4Se5(4-) and Tl4Se6(4-), have been obtained by extracting KTlSe into liquid NH3 in the presence of 2,2,2-crypt and have been characterized in solution by low-temperature 77Se, 203Tl, and 205Tl NMR spectroscopy and were shown to exist as a 1:1 equilibrium mixture at -40 degrees C. The couplings, 1J(203,205Tl-77Se) and 2J(203,205Tl-203,205Tl), have been observed for Tl4Se5(4-) and Tl4Se6(4-) and have been used to arrive at the solution structures of both anions. Structural assignments were achieved by detailed analyses and simulations of all spin multiplets that comprise the 205,203Tl NMR spectra and that arise from natural abundance 205,203Tl and 77Se or enriched 77Se isotopomer distributions. The structures of all three anions are based on a Tl4Se4 cube in which Tl and Se atoms occupy alternate corners. There are one and two exo-selenium atoms bonded to thallium in Tl4Se5(4-) and Tl4Se6(4-), respectively, so that these thalliums are four-coordinate and possess a formal oxidation state of +3 and the remaining three-coordinate thallium atoms are in the +1 oxidation state. The structure of Tl5Se5(3-) may be formally regarded as an adduct in which Tl+ is coordinated to the unique exo-selenium and to two seleniums in a cube face containing the TlIII atom. The Tl4Se5(4-), Tl4Se6(4-), and Tl5Se5(3-) anions and the presently unknown, but structurally related, Tl4Se4(4-) anion can be described as electron-precise cages. Ab initio methods at the MP2 level of theory show that Tl4Se5(4-), Tl4Se6(4-), and Tl5Se5(3-) exhibit true minima and display geometrical parameters that are in excellent agreement with their experimental cubanoid structures, and that Tl4Se4(4-) is cube-shaped (Td point symmetry). The gas-phase energetics associated with plausible routes to the formation and interconversions of these anions have been determined by ab initio methods and assessed. It is proposed that all three cubanoid anions are derived from the known Tl2Se2(2-), TlSe3(3-), Se2(2-), and polyselenide anions that have been shown to be present in the solutions they are derived from.     

Synthesis, crystal and electronic structures of the new quaternary phases A5Cd2Sb5F (A = Sr, Ba, Eu), and Ba5Cd2Sb5O(x) (0.5<x<0.7)

A new family of quaternary fluoro-antimonides A(5)Cd(2)Sb(5)F (A = Sr, Ba, Eu) and oxyantimonides Ba(5)Cd(2)Sb(5)O(x) (0.5相似文献   

Ba5Ga4Se10: a new selenidogallate containing the novel [Ga4Se10](10-) anionic cluster with Ga in a mixed-valence state

The new compound Ba(5)Ga(4)Se(10) has been synthesized for the first time. It crystallizes in the tetragonal space group I4/mcm with a = 8.752(2) ?, c = 13.971(9) ?, and Z = 2. The structure contains discrete [Ga(4)Se(10)](10-) anions and charge-compensating Ba(2+) cations. The novel highly anionic [Ga(4)Se(10)](10-) cluster is composed of two Ga(Se)(4) tetrahedra and two Ga(Ga)(Se)(3) tetrahedra with Ga in the 2+/3+ valence states. It also exhibits an unusually long Ga-Se distance of 2.705(2) ?, which has only been observed under high pressure conditions before. A band gap of 2.20(2) eV was deduced from the UV/vis diffuse reflectance spectrum.     

Metal complexes of tetrapodal ligands: synthesis, spectroscopic and thermal studies, and X-ray crystal structure studies of Na(I), Ca(II), Sr(II), and Ba(II) complexes of tetrapodal ligands N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine and N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine

Twelve complexes 1-12 of general category [M(ligand)(anion)(x)(water)(y)], where ligand = N,N,N',N'-tetrakis(2-hydroxypropyl/ethyl)ethylenediamine (HPEN/HEEN), anion = anions of picric acid (PIC), 3,5-dinitrobenzoic acid (DNB), 2,4-dinitrophenol (DNP), and o-nitrobenzoic acid (ONB), M = Ca(2+), Sr(2+), Ba(2+), or Na(+), x = 1 and 2, and y = 0-4, were synthesized. All of these complexes were characterized by elemental analysis, IR, (1)H and (13)C NMR, and thermal studies. X-ray crystal studies of these complexes 1-12, [Ca(HPEN)(H(2)O)(2)](PIC)(2).H(2)O (1), [Ca(HEEN)(PIC)](PIC) (2), Ba(HPEN)(PIC)(2) (3), [Na(HPEN)(PIC)](2) (4), Ca(HPEN)(H(2)O)(2)](DNB)(2).H(2)O (5),Ca(HEEN)(H(2)O)](DNB)(2).H(2)O (6), [Sr(HPEN)(H(2)O)(3)](DNB)(2) (7), [Ba(HPEN)(H(2)O)(2)](DNB)(2).H(2)O](2) (8), [[Ba(HEEN)(H(2)O)(2)](ONB)(2)](2) (9), [[Sr(HPEN)(H(2)O)(2)](DNP)(2)](2) (10), [[Ba(HPEN)(H(2)O)(2)](DNP)(2)](2) (11), and [Ca(HEEN)(DNP)](DNP) (H(2)O) (12), have been carried out at room temperature. Factors which influence the stability and the type of complex formed have been recognized as H-bonding interactions, presence/absence of solvent, nature of the anion, and nature of the cation. Both the ligands coordinate the metal ion through all the six available donor atoms. The complexes 1 and 5-11 have water molecules in the coordination sphere, and their crystal structures show that water is playing a dual character. It coordinates to the metal ion on one hand and strongly hydrogen bonds to the anion on the other. These strong hydrogen bonds stabilize the anion and decrease the cation-anion interactions by many times to an extent that the anions are completely excluded out of the coordination sphere and produce totally charge-separated complexes. In the absence of water molecules as in 2 and 3 the number of hydrogen bonds is reduced considerably. In both the complexes the anions case interact more strongly with the metal ion to give rise to a partially charge-separated 2 or tightly ion-paired 3 complex. High charge density Ca(2+) forms only monomeric complexes. It has more affinity toward stronger nucleophiles such as DNP and PIC with which it gives partially charge-separated eight-coordinated complexes. But with relatively weaker nucleophile like DNB, water replaces the anion and produces a seven coordinated totally charge-separated complex. Sr(2+) with lesser charge/radius ratio forms only charge-separated monomeric as well as dimeric complexes. Higher coordination number of Sr(2+) is achieved with coordinated water molecules which may be bridging or nonbridging in nature. All charge-separated complexes of the largest Ba(2+) are dimeric with bridging water molecules. Only one monomeric ion-paired complex was obtained with Ba(PIC)(2). Na(+) forms a unique dinuclear cryptand-like complex with HPEN behaving as a heptadentate chelating-cum-bridging ligand.     

New barium copper chalcogenides synthesized using two different chalcogen atoms: Ba2Cu(6-x)STe4 and Ba2Cu(6-x)Se(y)Te(5-y)

Ba(2)Cu(6-x)STe(4) and Ba(2)Cu(6-x)Se(y)Te(5-y) were prepared from the elements in stoichiometric ratios at 1123 K, followed by slow cooling. These chalcogenides are isostructural, adopting the space group Pbam (Z = 2), with lattice dimensions of a = 9.6560(6) ?, b = 14.0533(9) ?, c = 4.3524(3) ?, and V = 590.61(7) ?(3) in the case of Ba(2)Cu(5.53(3))STe(4). A significant phase width was observed in the case of Ba(2)Cu(6-x)Se(y)Te(5-y) with at least 0.17(3) ≤ x ≤ 0.57(4) and 0.48(1) ≤ y ≤ 1.92(4). The presence of either S or Se in addition to Te appears to be required for the formation of these materials. In the structure of Ba(2)Cu(6-x)STe(4), Cu-Te chains running along the c axis are interconnected via bridging S atoms to infinite layers parallel to the a,c plane. These layers alternate with the Ba atoms along the b axis. All Cu sites exhibit deficiencies of up to 26%. Depending on y in Ba(2)Cu(6-x)Se(y)Te(5-y), the bridging atom is either a Se atom or a Se/Te mixture when y ≤ 1, and the Te atoms of the Cu-Te chains are partially replaced by Se when y > 1. All atoms are in their most common oxidation states: Ba(2+), Cu(+), S(2-), Se(2-), and Te(2-). Without Cu deficiencies, these chalcogenides were computed to be small gap semiconductors; the Cu deficiencies lead to p-doped semiconducting properties, as experimentally observed on selected samples.     

Syntheses; 77Se, 203Tl, and 205Tl NMR; and theoretical studies of the Tl2Se6(6-), Tl3Se6(5-), and Tl3Se7(5-) anions and the X-ray crystal structures of [2,2,2-crypt-Na]4[Tl4Se8].en and [2,2,2-crypt-Na]2[Tl2Se4](infinity)1.en

The 2,2,2-crypt salts of the Tl4Se8(4-) and [Tl2Se4(2-)]infinity1 anions have been obtained by extraction of the ternary alloy NaTl0.5Se in ethylenediamine (en) in the presence of 2,2,2-crypt and 18-crown-6 followed by vapor-phase diffusion of THF into the en extract. The [2,2,2-crypt-Na]4[Tl4Se8].en crystallizes in the monoclinic space group P2(1)/n, with Z = 2 and a = 14.768(3) angstroms, b = 16.635(3) angstroms, c = 21.254(4) angstroms, beta = 94.17(3) degrees at -123 degrees C, and the [2,2,2-crypt-Na]2[Tl2Se4]infinity1.en crystallizes in the monoclinic space group P2(1)/c, with Z = 4 and a = 14.246(2) angstroms, b = 14.360(3) angstroms, c = 26.673(8) angstroms, beta = 99.87(3) degrees at -123 degrees C. The TlIII anions, Tl2Se6(6-) and Tl3Se7(5-), and the mixed oxidation state TlI/TlIII anion, Tl3Se6(5-), have been obtained by extraction of NaTl0.5Se and NaTlSe in en, in the presence of 2,2,2-crypt and/or in liquid NH3, and have been characterized in solution by low-temperature 77Se, 203Tl, and 205Tl NMR spectroscopy. The 1J(203,205Tl-77Se) and 2J(203,205Tl-203,205Tl) couplings of the three anions have been used to arrive at their solution structures by detailed analyses and simulations of all spin multiplets that comprise the 205,203Tl NMR subspectra arising from natural abundance 205,203Tl and 77Se isotopomer distributions. The structure of Tl2Se6(6-) is based on a Tl2Se2 ring in which each thallium is bonded to two exo-selenium atoms so that these thalliums are four-coordinate and possess a formal oxidation state of +3. The Tl4Se8(4-) anion is formally derived from the Tl2Se6(6-) anion by coordination of each pair of terminal Se atoms to the TlIII atom of a TlSe+ cation. The structure of the [Tl2Se4(2-)]infinity1 anion is comprised of edge-sharing distorted TlSe4 tetrahedra that form infinite, one-dimensional [Tl2Se42-]infinity1 chains. The structures of Tl3Se6(5-) and Tl3Se7(5-) are derived from Tl4Se4-cubes in which one thallium atom has been removed and two and three exo-selenium atoms are bonded to thallium atoms, respectively, so that each is four-coordinate and possesses a formal oxidation state of +3 with the remaining three-coordinate thallium atom in the +1 oxidation state. Quantum mechanical calculations at the MP2 level of theory show that the Tl2Se6(6-), Tl3Se6(5-), Tl3Se7(5-), and Tl4Se8(4-) anions exhibit true minima and display geometries that are in agreement with their experimental structures. Natural bond orbital and electron localization function analyses were utilized in describing the bonding in the present and previously published Tl/Se anions, and showed that the Tl2Se6(6-), Tl3Se6(5-), Tl3Se7(5-), and Tl4Se8(4-) anions are electron-precise rings and cages.     

Synthetic, structural and theoretical studies of amidinate and guanidinate stabilised germanium(I) dimers

The neutral germanium(i) dimers, [{Ge(Piso)}(2)] and [{Ge(Giso)}(2)], Piso = [(ArN)(2)CBu(t)](-), Giso = [(ArN)(2)CNPr(i)(2)](-), Ar = C(6)H(3)Pr(i)(2)-2,6, which are stabilised by bulky amidinate and guanidinate ligands respectively, have been prepared by reduction of the corresponding germanium(ii) chlorides, [Ge(Piso)Cl] and [Ge(Giso)Cl]; theoretical studies suggest that the Ge-Ge bonds of [{Ge(Piso)}(2)] and [{Ge(Giso)}(2)] are associated with their HOMOs, whilst their LUMOs have substantial Ge-Ge pi-bonding character.     

Contribution of disulfide S2(2-) anions to the crystal and electronic structures in ternary sulfides, Ba12In4S19, Ba4M2S8 (M=Ga, In)

Three semiconducting ternary sulfides have been synthesized from the mixture of elements with about 20% excess of sulfur (to establish oxidant rich conditions) by solid-state reactions at high temperature. Ba(12)In(4)S(19) ≡ (Ba(2+))(12)(In(3+))(4)(S(2-))(17)(S(2))(2-), 1, crystallizes in the trigonal space group R ?3 with a = 9.6182(5) ?, b = 9.6182(5) ?, c = 75.393(7) ?, and Z = 6, with a unique long period-stacking structure of a combination of monometallic InS(4) tetrahedra, linear dimeric In(2)S(7) tetrahedra, disulfide S(2)(2-) anions, and isolated sulfide S(2-) anions that is further enveloped by Ba(2+) cations. Ba(4)In(2)S(8) ≡ (Ba(2+))(4)(In(3+))(2)(S(2-))(6)(S(2))(2-), 2, crystallizes in the triclinic space group P ?1? with a = 6.236(2) ?, b = 10.014(4) ?, c = 13.033(5) ?, α = 104.236(6)°, β = 90.412(4)°, γ = 91.052(6)°, and Z = 2. Ba(4)Ga(2)S(8) ≡ (Ba(2+))(4)(Ga(3+))(2)(S(2-))(6)(S(2))(2-), 3, crystallizes in the monoclinic P2(1)/c with a = 12.739(5) ?, b = 6.201(2) ?, c = 19.830(8) ?, β = 104.254(6)° and Z = 4. Compounds 2 and 3 represent the first one-dimensional (1D) chain structure in ternary Ba/M/S (M = In, Ga) systems. The optical band gaps of 1 and 3 are measured to be around 2.55 eV, which agrees with their yellow color and the calculation results. The CASTEP calculations also reveal that the disulfide S(2)(2-) anions in 1-3 contribute mainly to the bottom of the conduction bands and the top of valence bands, and thus determine the band gaps.     

Syntheses, crystal and electronic structures, and characterizations of quaternary antiferromagnetic sulfides: Ba2MFeS5 (M = Sb, Bi)

Two new quaternary sulfides, Ba(2)SbFeS(5) and Ba(2)BiFeS(5), were synthesized by using a conventional high-temperature solid-state reaction method in closed silica tubes at 1123 K. The two compounds both crystallize in the orthorhombic space group Pnma with a = 12.128(6) ?, b = 8.852(4) ?, c = 8.917(4) ?, and Z = 4 for Ba(2)SbFeS(5) and a = 12.121(5) ?, b = 8.913(4) ?, c = 8.837(4) ?, and Z = 4 for Ba(2)BiFeS(5). The crystal structure unit can be viewed as an infinite one-dimensional edge-shared MS(5) (M = Sb, Bi) tetragonal-pyramid chain with FeS(4) tetrahedra alternately arranged on two sides of the MS(5) polyhedral chain via edge-sharing (so the chain can also be written as (1)(∞)[MFeS(5)](4-)). Interestingly, the compounds have the structural type of a Ba(3)FeS(5) high-pressure phase considering one Ba(2+) is replaced by one Sb(3+)/Bi(3+), with Fe(4+) reduced to Fe(3+) for in order to maintain the electroneutrality of the system. As a result, the isolated iron ions in Ba(3)FeS(5) are bridged by intermediate MS polyhedra in Ba(2)MFeS(5) (M = Sb, Bi) compounds and form the (1)(∞)[MFeS(5)](4-) chain structure. This atom substitution of Ba(2+) by one Sb(3+)/Bi(3+) leads to a magnetic transition from paramagnetic Ba(3)FeS(5) to antiferromagnetic Ba(2)MFeS(5), resulting from an electron-exchange interaction of the iron ions between inter- or intrachains. Magnetic property measurements indicate that the two compounds are both antiferromagnetic materials with Ne?el temperatures of 13 and 35 K for Ba(2)SbFeS(5) and Ba(2)BiFeS(5), respectively. First-principles electronic structure calculations based on density functional theory show that the two compounds are both indirect-band semiconductors with band gaps of 0.93 and 1.22 eV for Ba(2)SbFeS(5) and Ba(2)BiFeS(5), respectively.     

Ae2Sb2X4F2 (Ae = Sr, Ba): new members of the homologous series Ae2M(1+n)X(3+n)F2 designed from rock salt and fluorite 2D building blocks

We have designed new compounds within the homologous series Ae2F2M(1+n)X(3+n) (Ae = Sr, Ba; M = main group metal; n = integer) built up from the stacking of 2D building blocks of rock salt and fluorite types. By incrementally increasing the size of the rock salt 2D building blocks, we have obtained two new n = 1 members of this homologous series, namely, Sr2F2Sb2Se4 and Ba2F2Sb2Se4. We then succeeded in synthesizing these compounds using a high-temperature ceramic method. The structure refinements from the powder or single-crystal X-ray diffraction data confirmed presence of the expected alternating stacking of fluorite [Ae2F2] (Ae = Sr, Ba) and rock salt [Sb2Se4] 2D building blocks. However the Ba derivative shows a strong distortion of the [Sb2Se4] block and a concomitant change of the Sb atom coordination likely related to the lone-pair activity.     

Synthesis and structural characterization of a new series of vanadoselenites, [Se(x)V(4-x)O(12-x)](4-x)- (x=1,2)

Two new vanadoselenites, [SeV(3)O(11)](3)(-) and [Se(2)V(2)O(10)](2)(-), were synthesized by reacting SeO(2) with VO(3)(-). Single-crystal X-ray structural analyses of [(n-C(4)H(9))(4)N](3)[SeV(3)O(11)].0.5H(2)O [orthorhombic, space group P2(1)2(1)2, a = 22.328(5) A, b = 44.099(9) A, c = 12.287(3) A, Z = 8] and [[(C(6)H(5))(3)P](2)N](2)[Se(2)V(2)O(10)] [monoclinic, space group P2(1)/n, a = 12.2931(3) A, b = 13.5101(3) A, c = 20.9793(5) A, beta = 106.307(1) degrees, Z = 2] revealed that both anions are composed of Se(x)()V(4)(-)(x)()O(4) rings. The (51)V, (77)Se, and (17)O NMR spectra established that both [SeV(3)O(11)](3)(-) and [Se(2)V(2)O(10)](2)(-) anions maintain this ring structure in solution.     

Selenium oxoanion compounds of palladium(II)

Three new palladium compounds, PdSeO3, PdSe2O5, and Na2Pd(SeO4)2, containing selenium oxoanions of both Se(IV) and Se(VI) have been prepared under mild hydrothermal conditions. PdSe2O5 and Na2Pd(SeO4)2 both possess one-dimensional structures. Within the structure of PdSe2O5, [PdO4] square planar building blocks are joined together through diselenite, Se2O52-, anions, and form a zigzag chain along the c axis. In Na2Pd(SeO4)2, [PdO4] units are connected by two selenate, SeO42-, anions, and extend along the a axis to form a [Pd(SeO4)2]2- chain. Na+ cations reside in the space between the [Pd(SeO4)2]2- chains and act as counter cations. Unlike above two compounds, PdSeO3 exhibits a layered structure. In the structure of PdSeO3, [PdO4] units are connected to each other by corner-sharing and form a zigzag chain along the b axis. The chains are further joined together by tridentate selenite, SeO32-, anions to form layers in the [ab] plane that stack along the c axis. Crystallographic data: (193 K; Mo Kalpha, lambda=0.71073 A): PdSeO3, monoclinic, space group P21/m, a=3.8884(5) A, b=6.4170(8) A, c=6.1051(7) A, beta=96.413(2) degrees, V=151.38(3) A3, Z=2; PdSe2O5, monoclinic, space group C2/c, a=12.198(2) A, b=5.5500(8) A, c=7.200(1) A, beta=107.900(2) degrees , V=463.8(1) A3, Z=4; Na2Pd(SeO4)2, triclinic, space group P, a=4.9349(11) A, b=5.9981(13) A, c=7.1512 (15) A, alpha=73.894(4) degrees, beta=86.124(4) degrees, gamma=70.834(4) degrees, V=192.03(7) A3, Z=1.     

Two new structurally related strontium gallium nitrides: Sr4GaN3O and Sr4GaN3(CN2)

The strontium gallium oxynitride Sr(4)GaN(3)O and nitride-carbodiimide Sr(4)GaN(3)(CN(2)) are reported, synthesized as single crystals from molten sodium at 900 degrees C. Red Sr(4)GaN(3)O crystallizes in space group Pbca (No. 61) with a = 7.4002(1) Angstroms, b = 24.3378(5) Angstroms, c = 7.4038(1) Angstroms, and Z = 8, as determined from single-crystal X-ray diffraction measurements at 150 K. The structure may be viewed as consisting of slabs [Sr(4)GaN(3)](2+) containing double layers of isolated [GaN(3)](6-) triangular anions arranged in a "herringbone" fashion, and these slabs are separated by O(2-) anions. Brown Sr(4)GaN(3)(CN(2)) has a closely related structure in which the oxide anions in the Sr(4)GaN(3)O structure are replaced by almost linear carbodiimide [CN(2)](2-) anions [Sr(4)GaN(3)(CN(2)): space group P2(1)/c (No. 14), a = 13.4778(2) Angstroms, b = 7.4140(1) Angstroms, c = 7.4440(1) Angstroms, beta = 98.233(1) degrees, and Z = 4].