Quaternary tellurides with different valent Ge centers: Cs2Ge3M6Te14 (M = Ga, In)

New quaternary tellurides, Cs(2)Ge(3)M(6)Te(14) (M = Ga, In), were discovered by solid-state reactions. These compounds crystallize in space group P3ml (No. 164), with a = b = 8.2475(2) ?, c = 14.2734(8) ?, and V = 840.82(6) ?(3) (Z = 1) for Cs(2)Ge(3)Ga(6)Te(14) (1) and a = b = 8.5404(2) ?, c = 14.6766(8) ?, and V = 927.07(6) ?(3) (Z = 1) for Cs(2)Ge(3)In(6)Te(14) (2). The remarkable structural feature is the novel three-dimensional [Ge(3)M(6)Te(14)](2-) anionic framework made by condensed In(6)Te(14) (or Ga(6)Te(14)) layers that are connected alternately by dimeric Ge(3+)(2)Te(6) units and Ge(2+)Te(6) octahedra along the c direction. The presence of Ge centers with different oxidation states is also supported by the results of the electron localization function calculation and X-ray photoelectron spectroscopy measurement.     

Syntheses, structure, some band gaps, and electronic structures of CsLnZnTe3 (Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Y)

Eleven new quaternary rare-earth tellurides, CsLnZnTe3 (Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Y), were prepared from solid-state reactions at 1123 K. These isostructural materials crystallize in the layered KZrCuS3 structure type in the orthorhombic space group Cmcm. The structure is composed of LnTe6 octahedra and ZnTe4 tetrahedra that share edges to form [LnZnTe3] layers. These layers stack perpendicular to [010] and are separated by layers of face- and edge-sharing CsTe8 bicapped trigonal prisms. There are no Te-Te bonds in the structure of these CsLnZnTe3 compounds so the formal oxidation states of Cs/Ln/Zn/Te are 1+/3+/2+/2-. Optical band gaps of 2.13 eV for CsGdZnTe3 and 2.12 eV for CsTbZnTe3 were deduced from single-crystal optical absorption measurements. A first-principles calculation of the density of states and the frequency-dependent optical properties was performed on CsGdZnTe3. The calculated band gap of 2.1 eV is in good agreement with the experimental value. A quadratic fit for the lanthanide contraction of the Ln-Te distance is superior to a linear one if the closed-shell atom is included.     

Crystal structure and physical properties of the new one-dimensional metal Ba2Cu(7-x)Te6

The telluride Ba(2)Cu(7-x)Te(6) was synthesized from the elements in stoichiometric ratios, heated to 1073 K, followed by slow cooling to 873 K over 120 h. Ba(2)Cu(7-x)Te(6) crystallizes in space group P2(1)/m with lattice dimensions of a = 6.8591(7) ?, b = 12.1439(12) ?, c = 9.0198(9) ?, β = 110.7509(14)°, V = 702.58(12) ?(3), and Z = 2. The structure is comprised of Cu atoms forming a six-membered ring and triangles, interconnected to an infinite ribbon of Cu atoms. The ribbons are connected to each other via Cu-Te bonds to yield a three-dimensional structure, wherein each Cu atom is tetrahedrally coordinated by four Te atoms. A special feature of this telluride is the occurrence of a quasi-linear Te atom chain, which causes one-dimensional metallic properties, in accordance with electronic structure calculations and property measurements.     

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.     

Chemistry in Molten Alkali Metal Polyselenophosphate Fluxes. Influence of Flux Composition on Dimensionality. Layers and Chains in APbPSe(4), A(4)Pb(PSe(4))(2) (A = Rb, Cs), and K(4)Eu(PSe(4))(2)

The reaction of Pb and Eu with a molten mixture of A(2)Se/P(2)Se(5)/Se produced the quaternary compounds APbPSe(4), A(4)Pb(PSe(4))(2) (A = Rb,Cs), and K(4)Eu(PSe(4))(2). The red crystals of APbPSe(4) are stable in air and water. The orange crystals of A(4)Pb(PSe(4))(2) and K(4)Eu(PSe(4))(2) disintegrate in water and over a long exposure to air. CsPbPSe(4) crystallizes in the orthorhombic space group Pnma (No. 62) with a = 18.607(4) ?, b = 7.096(4) ?, c = 6.612(4) ?, and Z = 4. Rb(4)Pb(PSe(4))(2) crystallizes in the orthorhombic space group Ibam (No. 72) with a = 19.134(9) ?, b = 9.369(3) ?, c = 10.488(3) ?, and Z = 4. The isomorphous K(4)Eu(PSe(4))(2) has a = 19.020(4) ?, b = 9.131(1) ?, c = 10.198(2) ?, and Z = 4. The APbPSe(4) have a layered structure with [PbPSe(4)](n)()(n)()(-) layers separated by A(+) ions. The coordination geometry around Pb is trigonal prismatic. The layers are composed of chains of edge sharing trigonal prisms running along the b-direction. [PSe(4)](3)(-) tetrahedra link these chains along the c-direction by sharing edges and corners with the trigonal prisms. A(4)M(PSe(4))(2) (M = Pb, Eu) has an one-dimensional structure in which [M(PSe(4))(2)](n)()(n)()(-) chains are separated by A(+) ions. The coordination geometry around M is a distorted dodecahedron. Two [PSe(4)](3)(-) ligands bridge two adjacent metal atoms, using three selenium atoms each, forming in this way a chain along the c-direction. The solid state optical absorption spectra of the compounds are reported. All compounds melt congruently in the 597-620 degrees C region.     

Structural Variability of the Vanadium-Organodiphosphonate System: Hydrothermal Syntheses and Structural Characterizations of One-Dimensional, Two-Dimensional, and Three-Dimensional Phases

The hydrothermal chemistry of the CsVO(3)/methylenediphosphonate system was investigated. Variations in reaction temperatures, heating times, and stoichiometries of reactants resulted in the isolation of mononuclear, one-, two-, and three-dimensional species: Cs[VO(HO(3)PCH(2)PO(3)H)(2)(H(2)O)] (1), Cs[VO(HO(3)PCH(2)PO(3))] (2), Cs[(VO)(2)V (O(3)PCH(2)PO(3))(2)(H(2)O)(2)] (3), and [V(HO(3)PCH(2)PO(3))(H(2)O)] (4), respectively. The structure of the anion of 1 consists of isolated V(IV) octahedra. Phase 2 adopts a chain structure constructed from corner-sharing V(IV) octahedra, forming infinite {-V=OV=O-} linkages. The layer structure of 3 contains trinuclear units of corner-sharing {VO(6)} octahedra with the central V site in the III oxidation state and V(IV) centers at the extremities of the cluster. The diphosphonate ligands serve to link neighboring trinuclear motifs into a layer structure three octahedra in depth. The Cs(+) cations occupy cavities within the layers, rather than the more common interlamellar positions. The structure of 4 consists of isolated {V(III)O(6)} octahedra linked by diphosphonate groups into a three-dimensional framework. Crystal data: for 1, CH(6)O(7)P(2)V(0.5)Cs, monoclinic C2, a = 10.991(2) ?, b = 10.161(2) ?, c = 7.445(1) ?, beta = 92.97(3) degrees, Z = 4; for 2, CH(3)O(7)P(2)VCs, monoclinic C2, a = 10.212(2) ?, b = 10.556(2) ?, c = 14.699(3) ?, beta = 94.57(2) degrees, Z = 8; for 3, C(2)H(8)O(16)P(4)V(3)Cs, monoclinic C2/m, a = 9.724(2) ?, b = 8.136(2) ?, c = 10.268(2) ?, beta = 103.75(3) degrees, Z = 2; for 4, CH(5)O(7)P(2)V, monoclinic P2(1)()/n, a = 5.341(1) ?, b = 11.516(2) ?, c = 10.558(2) ?, beta = 99.89(1) degrees, Z = 4.     

New Layered Polyborates Cs(2)M(2)B(10)O(17) (M = Na, K)

The polyborates Cs(2)M(2)B(10)O(17) (M = Na, K) have been prepared and their structures determined by single-crystal X-ray diffraction methods. They crystallize in the monoclinic space group C2/c (Z = 8) with unit-cell parameters a = 21.643(3) ?, b = 6.558(2) ?, c = 11.072(2) ?, beta = 105.43(1) degrees, V = 1514.8(6) ?(3) for the Na compound and a = 22.547(9) ?, b = 6.614(2) ?, c = 11.288(4) ?, beta = 103.25 degrees, V = 1638.3(8) ?(3) for the K analogue. The new structural type contains a 2-dimensional borate matrix that is built from a complete condensation of the ring system B(5)O(11). The Cs atoms reside within the borate matrix, and the Na (K) atoms are placed between the thick Cs borate sheets.     

CsMBi(3)Te(6) and CsM(2)Bi(3)Te(7) (M = Pb, Sn): new thermoelectric compounds with low-dimensional structures

The new materials CsPbBi(3)Te(6) and CsPb(2)Bi(3)Te(7) were discovered through reactions of CsBi(4)Te(6) with PbTe, whereas the isostructural materials CsSnBi(3)Te(6) and CsSn(2)Bi(3)Te(7) were discovered through corresponding reactions with SnTe. The compounds can also be prepared from stoichiometric mixtures of Cs(2)Te, Pb (Sn), Bi, and Te. The crystal structures show a layered architecture of NaCl-type slabs alternating with layers of Cs atoms. This group of compounds offers a new quaternary system, Cs-M-Bi-Te (M = Pb and Sn), available for thermoelectric investigations, including fine-tuning of compositions and doping.     

Diverse closed cavities in condensed rare earth metal-chalcogenide matrixes: Cs[Lu7Q11] and (ClCs6)[RE21Q34] (RE = Dy, Ho; Q = S, Se, Te)

Two types of novel ordered chalcogenids Cs[Lu(7)Q(11)] (Q = S, Se) and (ClCs(6))[RE(21)Q(34)] (RE = Dy, Ho; Q = S, Se, Te) were discovered by high-temperature solid state reactions. The structures were characterized by single-crystal X-ray diffraction data. Cs[Lu(7)Q(11)] crystallize in the orthorhombic Cmca (no. 64) with a = 15.228(4)-15.849(7) ?, b = 13.357(3)-13.858(6) ?, c = 18.777(5)-19.509(8) ?, and Z = 8. (ClCs(6))[RE(21)Q(34)] crystallize in the monoclinic C2/m (no. 12) with a = 17.127(2)-18.868(2) ?, b = 19.489(2)-21.578(9) ?, c = 12.988(9)-14.356(2) ?, β = 128.604(2)-128.738(4)°, and Z = 2. Both types of compounds feature 3D RE-Q network structures that embed with dual tricapped cubes Cs(2)@Se(18) in the former or unprecedented matryoshka nesting doll structure cavities of (ClCs(6))@Se(32) in the latter. The band gap, band structure, as well as a structure change trend of the majority of A/RE/Q compounds are presented.     

A new thermoelectric material: CsBi4Te6

The highly anisotropic material CsBi(4)Te(6) was prepared by the reaction of Cs/Bi(2)Te(3) around 600 degrees C. The compound crystallizes in the monoclinic space group C2/m with a = 51.9205(8) A, b = 4.4025(1) A, c = 14.5118(3) A, beta = 101.480(1) degrees, V = 3250.75(11) A(3), and Z = 8. The final R values are R(1) = 0.0585 and wR(2) = 0.1127 for all data. The compound has a 2-D structure composed of NaCl-type [Bi(4)Te(6)] anionic layers and Cs(+) ions residing between the layers. The [Bi(4)Te(6)] layers are interconnected by Bi-Bi bonds at a distance of 3.2383(10) A. This material is a narrow gap semiconductor. Optimization studies on the thermoelectric properties with a variety of doping agents show that the electrical properties of CsBi(4)Te(6) can be tuned to yield an optimized thermoelectric material which is promising for low-temperature applications. SbI(3) doping resulted in p-type behavior and a maximum power factor of 51.5 microW/cm.K(2) at 184 K and the corresponding ZT of 0.82 at 225 K. The highest power factor of 59.8 microW/cm.K(2) at 151 K was obtained from 0.06% Sb-doped material. We report here the synthesis, physicochemical properties, doping characteristics, charge-transport properties, and thermal conductivity. Also presented are studies on n-type CsBi(4)Te(6) and comparisons to those of p-type.     

Synthesis and structural characterization of some selenoruthenates and telluroruthenates

The reaction of solid [RuClCp(PPh(3))(2)] with TeSe(3)(2-) or Se(n)(2-) in DMF leads to the formation of [RuCp(PPh(3))(mu(2)-Se(2))](2) (1). In the structure of this compound the two bridging Se(2) groups lead to a six-membered Ru(2)Se(4) ring in a chair conformation. Attached to each Ru center is a PPh(3) ligand in an equatorial position and a Cp ring in an axial position. The compound is diamagnetic. The compound [Ru(2)Cp(2)(mu(3)-Se(2))(mu(3)-Se)](2) (2) is obtained under similar conditions in the presence of air. This structure comprises a centrosymmetric Ru(4)Se(6) dimer formed from the two bridging Se groups and the two bridging Se(2) groups. Each Ru center is pi-bonded to a Cp ring. The reaction of solid [RuClCp(PPh(3))(2)] with a Te(n)(2-) polytelluride solution in DMF leads to the diamagnetic compound [(RuCp(PPh(3)))(2)(mu(2)-(1,4-eta:3,6-eta)Te(6))] (3). Here the Ru centers are bound to a bridging Te(6) chain at the 1, 4, 3, and 6 positions, leading to a bicyclic Ru(2)Te(6) ring. Each Ru atom is bound to a Cp ring and a PPh(3) group. This dimer possesses a center of symmetry. The structure of 3 is the first example of a bicyclic complex where fusion occurs along a Te-Te bond. If the same reaction is carried out in DMF/CH(2)Cl(2), rather than DMF, then [(RuCp(PPh(3)))(2)(mu(2)-(1,4-eta:3,6-eta)Te(6))].CH(2)Cl(2) (4) is obtained. In the solid state it possesses the same Ru(2)Te(6) structural unit as does 3, but the unit lacks a crystallographically imposed center of symmetry. The electronic structures of 3 and 4 have been analyzed with the use of first principles density functional theory. Bond order analysis indicates that the Te-Te bond where fusion occurs has a shared bonding charge of about (2)/(3) of that found for Te-Te single bonds.     

Syntheses and characterization of some mixed Te/Se polychalcogenide anions [Te(m)Se(n)]2-

Several mixed Te/Se polychalcogenide anions [Te(m)Se(n)](2-) were synthesized at 293 K by reactions between Te(n)(2-)and Se(n)(2-) anions in N,N-dimethylformamide (DMF) in the presence of different-size ammonium or phosphonium cations, in some cases in the presence of metal species. The structures of these anions were determined by single-crystal X-ray diffraction methods. The crystal structures of [NEt(4)](2)[Te(3)Se(6)] (1) and [NEt(4)](2)[Te(3)Se(7)] (2) consist, respectively, of one-dimensional infinite 1(infinity)[Te(3)Se(6)(2-)] and 1(infinity)[Te(3)Se(7)(2-)] anionic chains separated by NEt(4)(+) cations. In compound 1, each chain comprises Te(3)Se(5) eight-membered rings bridged by Se atoms. The Te(3)Se(5) ring has an "open book" conformation. The NMR spectrum of a DMF solution of [NEt(4)](2)[Te(3)Se(6)] crystals at 223 K shows (77)Se resonances at delta = 290, 349, and 771 ppm and a single (125)Te resonance at delta = 944.7 ppm. In compound 2, each chain comprises Te(3)Se(6) five- and six-membered rings bridged by Se atoms. The Te(3)Se(6) ring can be regarded as an inorganic analogue of bicyclononane. The anion of [PPh(4)](2)[Te(2)Se(2)] (4) contains a Se-Te-Te-Se chain with the terminal Se atoms trans to one another. The new compounds [PPN](2)[TeSe(10)] (3), [NMe(4)](2)[TeSe(3)].DMF (5), and [NEt(4)](2)[TeSe(3)] (6) contain known anions.     

Synthesis, structure, and properties of Cs(4)Th(4)P(4)Se(26): a quaternary thorium selenophosphate containing the (P(2)Se(9))(6-) anion

Orange crystals of Cs(4)Th(4)P(4)Se(26) were grown from the reaction of (232)Th and P in a Cs(2)Se(3)/Se molten salt flux at 750 degrees C. Cs(4)Th(4)P(4)Se(26) crystallizes in the orthorhombic space group Pbca with the unit cell parameters: a = 12.0130(6), b = 14.5747(7), c = 27.134(1) A; Z = 8. The compound exhibits a three-dimensional structure, consisting of dimeric [Th(2)Se(13)] polyhedral units. The two crystallographically independent, nine-coordinate, bicapped trigonal prismatic thorium atoms share a triangular face to form the dimer, and each dimer edge-shares two selenium atoms with two other dimers to form kinked chains along the [010] direction. While this structure shares features of the previously reported Rb(4)U(4)P(4)Se(26), including phosphorus in the 5+ oxidation state, careful inspection of the structure reveals that the selenophosphate anion that knits the structure together in three directions in both compounds is a unique (P(2)Se(9))(6-) anion. The formula may be described best as [Cs(2)Th(2)(P(2)Se(9))(Se(2))(2)](2). The (P(2)Se(9))(6-) anion features a nearly linear Se-Se-Se backbone with an angle of 171 degrees and Se-Se distances that are approximately 0.2-0.3 A longer than the typical single Se-Se bond. Magnetic studies confirm that this phase contains Th(IV). Raman data for this compound is reported, and structural comparisons will be drawn to its uranium analogue, Rb(4)U(4)P(4)Se(26).     

The related compounds MThTe3 (M = Mn, Mg) and ACuThSe3 (A = K, Cs): syntheses and characterization

Single crystals of MnThTe3 (1) and MgThTe3 (2) grow as small black plates from the stoichiometric reaction of the elements, the former at 1,000 degrees C and the latter at 900 degrees C with the aid of a Sn flux. Both compounds crystallize in the space group Cmcm of the orthorhombic system with four formula units in cells of dimensions a = 4.2783(6) A, b = 13.8618(11) A, and c = 9.9568(15) A for 1 and a = 4.2854(6) A, b = 14.042(2) A, and c = 9.9450(14) A for 2 at T = 153(2) K. KCuThSe3 (3) forms as red blocks from a stoichiometric mixture of K2Se, Cu, Th, and Se at 800 degrees C, and CsCuThSe3 (4) forms as yellow blocks from a stoichiometric mixture of Cs2Se3, Cu, Th, and Se at 850 degrees C. Compounds 3 and 4 also crystallize in the space group Cmcm of the orthorhombic system with four formula units in cells of dimensions a = 4.1832(8) A, b = 14.335(3) A, and c = 10.859(2) A for 3 and a = 4.2105(7) A, b = 15.715(3) A, and c = 10.897(2) A for 4 at 153(2) K. Compounds 1 and 2 are isostructural with each other as well as with several uranium analogues and comprise pseudolayered structures with slabs of corner-shared MTe6 octahedra alternating with slabs of cap- and edge-shared ThTe8 bicapped trigonal prisms. The slabs are bonded together through the sharing of edges and vertices of the various polyhedra to form three-dimensional structures. Compounds 3 and 4 are two-dimensional layered structures that are closely related to 1 and 2. In 3 and 4, ThSe6 octahedra form the same slabs as MTe6 in 1 and 2 and Cu atoms occupy the tetrahedral holes in the layers. Alkali metal cations occupy bicapped trigonal prismatic sites between the layers. Neither structure type has short Q-Q interactions, and therefore the oxidation states of all atoms are straightforwardly assigned on the assumption of Th4+. Magnetic susceptibility measurements on compound 1 show a ferromagnetic transition at 70 K and a magnetic moment of 5.9(2) muB per Mn ion, indicating low-spin Mn2+.     

Synthesis and structure of A4V6[Te2(4+)Te6+]O24 (A = K, Rb)-two new quaternary mixed-valent tellurium oxides

Two new mixed-valent tellurium oxides with vanadium(V), A(4)V(6)[Te(2)(4+)Te(6+)]O(24) (A = K and Rb), have been synthesized by hydrothermal and conventional solid state techniques. Their structures were determined by single-crystal X-ray diffraction analysis. These two iso-structural compounds exhibit layered structural topologies consisting of [V(6)Te(3)O(24)](4-) anionic units. In these anionic structural units, a Te(6+)O(6) octahedron is connected to six VO(4) tetrahedra by corner-sharing to generate a [V(6)TeO(24)] unit, and each of these [V(6)TeO(24)] units are interconnected by sharing two Te(4+)O(3) polyhedra to complete the infinite [V(6)Te(3)O(24)](4-) sheets. Infrared spectroscopy, UV-Visible diffuse reflectance spectroscopy, and thermogravimetric analysis were also performed on these two compounds. Crystal data: K(4)V(6)Te(3)O(24), trigonal, space group R ?3c (No. 167) with a = b = 9.7075(6) ?, c = 42.701(3) ?, V = 3484.9(4) ?(3), and Z = 6; Rb(4)V(6)Te(3)O(24), trigonal, space group R ?3c (No. 167) with a = b = 9.8399(9) ?, c = 43.012(4) ?, V = 3606.6(6) ?(3), and Z = 6.     

Syntheses, structure, and selected physical properties of CsLnMnSe3 (Ln = Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y) and AYbZnQ3 (A = Rb, Cs; Q = S, Se, Te)

CsLnMnSe(3) (Ln = Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y) and AYbZnQ(3) (A = Rb, Cs; Q = S, Se, Te) have been synthesized from solid-state reactions at temperatures in excess 1173 K. These isostructural materials crystallize in the layered KZrCuS(3) structure type in the orthorhombic space group Cmcm. The structure is composed of LnQ(6) octahedra and MQ(4) tetrahedra that share edges to form [LnMQ(3)] layers. These layers stack perpendicular to [010] and are separated by layers of face- and edge-sharing AQ(8) bicapped trigonal prisms. There are no Q-Q bonds in the structure of the ALnMQ(3) compounds so the formal oxidation states of A/Ln/M/Q are 1+/3+/2+/2-. The CsLnMnSe(3) materials, with the exception of CsYbMnSe(3), are Curie-Weiss paramagnets between 5 and 300 K. The magnetic susceptibility data for CsYbZnS(3), RbYbZnSe(3), and CsYbMSe(3) (M = Mn, Zn) show a weak cusp at approximately 10 K and pronounced differences between field-cooled and zero-field-cooled data. However, CsYbZnSe(3) is not an antiferromagnet because a neutron diffraction study indicates that CsYbZnSe(3) shows neither long-range magnetic ordering nor a phase change between 4 and 295 K. Nor is the compound a spin glass because the transition at 10 K does not depend on ac frequency. The optical band gaps of the (010) and (001) crystal faces for CsYbMnSe(3) are 1.60 and 1.59 eV, respectively; the optical band of the (010) crystal faces for CsYbZnS(3) and RbYbZnSe(3) are 2.61 and 2.07 eV, respectively.     

AVSeO(5) (A = Rb, Cs) and AV(3)Se(2)O(12) (A = K, Rb, Cs, NH(4)): Hydrothermal Synthesis in the V(2)O(5)-SeO(2)-AOH System and Crystal Structure of CsVSeO(5)

Hydrothermal reactions in the V(2)O(5)-SeO(2)-AOH systems (A = Na, K, Rb, Cs, NH(4)) were studied with various reagent mole ratios. Typical millimole ratios were V(2)O(5)/SeO(2)/AOH = 5 or 3/15/x in 10-mL aqueous solutions, where x was 5, 10, 15, and 20. The reactions with x = 5 for A = K, Rb, Cs, and NH(4) at 230 degrees C produced single-phase products of the general formula AV(3)Se(2)O(12) with the (NH(4))(VO)(3)(SeO(3))(2) structure type. The x = 15 reactions for A = Rb and Cs yielded AVSeO(5) phases with a new structure type. The crystal structure for CsVSeO(5) was determined with X-ray single-crystal diffraction techniques to be monoclinic (P2(1) (No. 4), a = 7.887(3) ?, b = 7.843(2) ?, c = 9.497(3) ?, beta = 92.13(3) degrees, Z = 4). The structure of this compound consists of interwoven helixes extended in all three directions. The spires are composed of alternating SeO(3) and VO(5) units sharing common-edge oxygens in all three directions. For A = K and NH(4), the reactions of this mole ratio did not produce any identifiable phases. Each of the compounds is characterized by powder X-ray diffraction, infrared spectroscopic, and thermogravimetric techniques. The dependency of the synthesis results on the reaction conditions is discussed and rationalized.     

Crystal structure and physical properties of the new chalcogenides Ba3Cu(17-x)(S,Te)11 and Ba3Cu(17-x)(S,Te)11.5 with two different Cu clusters

The sulfide-tellurides Ba(3)Cu(17-x)(S,Te)(11) and Ba(3)Cu(17-x)(S,Te)(11.5) were synthesized from the elements in stoichiometric ratios heated to 1073 K, followed by slow cooling to 873 K over 100 h. Ba(3)Cu(17-x)(S,Te)(11) is isostructural to Ba(3)Cu(17-x)(Se,Te)(11) when [S] > [Te], space group R ?3m, with lattice dimensions of a = 12.009(1) ?, c = 27.764(2) ?, V = 3467.6(5) ?(3), for Ba(3)Cu(15.7(4))S(7.051(5))Te(3.949) (Z = 6). The structure is composed of Cu atoms forming paired hexagonal antiprisms, capped on the two outer hexagonal faces, where each Cu atom is tetrahedrally coordinated by four Q (= S, Te) atoms. The new variant is formed when [Te] > [S]; then Ba(3)Cu(17-x)(S,Te)(11.5) adopts space group Fm3?m with a = 17.2095(8) ?, V = 5096.9(4) ?(3), for Ba(3)Cu(15.6(2))S(5.33(4))Te(6.17) (Z = 8). This structure consists of eight Te-centered Cu(16) icosioctahedra per cell interconnected by cubic Cu(8) units centered by Q atoms. Electronic structure calculations and property measurements illustrate that these compounds behave as extrinsic p-type semiconductors-toward metallic behavior for the latter compound. With standard oxidation states Ba(2+), Cu(+), and Q(2-), the electron precise formulas are Ba(3)Cu(16)Q(11) and Ba(3)Cu(17)Q(11.5).     

Crystal Structure and Magnetic Behavior of [(C(2)H(5))(4)N](2)Cu(5)Cl(12). A Novel Two-Dimensional Copper(II) Halide Network Derived from the CuCl(2) Structure

A new chlorocuprate(II), [(C(2)H(5))(4)N](2)Cu(5)Cl(12), was prepared by reaction of CuCl(2).2H(2)O and (C(2)H(5))(4)NCl in 1,1,2-trichloroethane-ethanol followed by water-ethanol evaporation. The crystal structure, solved by single-crystal X-ray diffraction at room temperature, was found to be triclinic, space group P&onemacr;, with cell parameters a = 8.9123(9) ?, b = 11.0690(8) ?, c = 11.2211(9) ?, alpha = 118.766(6) degrees beta = 109.041(8) degrees, gamma = 97.465(7) degrees, and Z = 1, and consists of a two-dimensional network of [(Cu(5)Cl(12))(2)(-)](infinity) parallel to the a, b plane, alternating with layers of the organic cations along c. The anionic sheets are built up by aggregation of infinite zigzag chains of alternating tetranuclear and mononuclear subsequences. This structure can be related to the anhydrous CuCl(2) structure by systematic removal of (Cu(2)Cl(6))(2+) fragments. The magnetic susceptibility of this compound can be described by a simple model, suggested by the structural data, that considers independent contributions of linear tetramers, with antiferromagnetically coupled pairs of copper atoms (J(1)/k = -64(2) K), and almost magnetically isolated Cu(II) centers, that obey a Curie-Weiss law with a Θ = -2.7(8) K.     

Investigations of the TeCl(4)-(t)BuNHLi Reaction: Synthesis, X-ray Structures, and Fluxional Behavior of the Tellurium-Nitrogen Compounds [Li(2)Te(N(t)Bu)(3)](2), {[LiTe(N(t)Bu)(2)(NH(t)Bu)](2)LiCl}(2), and {Te(2)(N(t)Bu)(4)[LiTe(N(t)Bu)(2)(NH(t)Bu)]LiCl}(2)

The reaction of (t)BuNHLi with TeCl(4) in toluene at -78 degrees C produces (t)BuNTe(&mgr;-N(t)Bu)(2)TeN(t)Bu (1) (55%) or [((t)BuNH)Te(&mgr;-N(t)Bu)(2)TeN(t)Bu]Cl (2) (65%) for 4:1 or 7:2 molar ratios, respectively. The complex {Te(2)(N(t)Bu)(4)[LiTe(N(t)Bu)(2)(NH(t)Bu)]LiCl}(2) (5) is obtained as a minor product (23%) from the 4:1 reaction. It is a centrosymmetric dimer in which each half consists of the tellurium diimide dimer 1 bonded through an exocyclic nitrogen atom to a molecule of LiTe(N(t)Bu)(2)(NH(t)Bu) which, in turn, is linked to a LiCl molecule. Crystals of 5 are monoclinic, of space group C2/c, with a = 27.680(6) ?, b = 23.662(3) ?, c = 12.989(2) ?, beta = 96.32(2) degrees, V = 8455(2) ?(3), and Z = 4. The final R and R(w) values were 0.046 and 0.047. At 65 degrees C in toluene solution, 5 dissociates into 1, LiCl, and {[LiTe(N(t)Bu)(2)(NH(t)Bu)](2)LiCl}(2) (4), which may also be prepared by treatment of [Li(2)Te(N(t)Bu)(3)](2) (6) with 2 equiv of HCl gas. The centrosymmetric structure of 6 consists of a distorted hexagonal prism involving two pyramidal Te(N(t)Bu)(3)(2)(-) anions linked by four Li atoms to give a Te(2)N(6)Li(4) cluster. Crystals of 6 are monoclinic, of space group P2(1)/c, with a = 10.194(2) ?, b = 17.135(3) ?, c = 10.482(2) ?, beta = 109.21(1) degrees, V = 1729.0(5) ?(3), and Z = 2. The final R and R(w) values were 0.026 and 0.023. VT (1)H and (7)Li NMR studies reveal that, unlike 1, compounds 2, 4, and 6 are fluxional molecules. Possible mechanisms for these fluxional processes are discussed.