Christopher J. Warren

Substitution in Ce2TSi3 intermetallic compositions with T = (Cr, Mn, Fe, Co, or Ni)x(Pd or Au)1−x

Abstract Alloys of composition Ce 2 (3d/T)Si 3 , with 3d one of Cr, Mn, Fe, Co or Ni and T being Pd or Au, were prepared and examined by powder X-ray diffraction. Select single phase compositions were further examined by magnetic susceptibility, by resistivity for the Pd and Co end-members, and by specific heat for Ce 2 CoSi 3 . For compounds not containing cobalt, effective cerium moments consistent with trivalent cerium were observed. A re-examination of the AlB 2 related structure of Ce 2 CoSi 3 by single crystal methods revealed ordering of cobalt within the CoSi 3 hexagonal layer. Magnetic susceptibility, resistance and specific heat measurements suggest valence fluctuation behavior of the cerium in Ce 2 CoSi 3 . A return to trivalent cerium magnetic behavior occurs on increasing the palladium or gold substitution for cobalt.

Synthesis and structural characterization of Zintl anions containing the tris(ethylenediamine)-zinc cation: [Zn(N2C2H8)3][Te3]·(0.5en) and [Zn(N2C2H8)3]2[Sn2Te6]·(en)

Abstract Two Zintl anions which contain the [tris(ethylenediamine)-zinc]2+ cation have been synthesized and structurally characterized by single-crystal X-ray diffraction. When a constant current of 1 mA is applied between a ZnTe10 alloy cathode and a Ni plate anode, in a saturated solulion of tetrapropylammonium bromide in ethylenediamine, a deep red-purple solution is generated around the cathode as polyanions are generated. After a few days, small, black crystals formed, which were identified by single crystal X-ray diffraction as [Zn(N2C2H8)3][Te3]·0.5(N2C2H8) (1). The 1:1:1 stoichiometric reaction of the Zintl phase K4SnTe4 with ZnCl2 in the presence of (C2H5)4NBr in ethylenediamine at 100°C for 1 day in a sealed evacuated quartz tube gave crystals of [Zn(N2C2H8)3]2[Sn2Te6]·(en) (2). The structures of 1 adn 2 consist of discrete anions which are surrounded in the solid state by the tris(ethylenediamine)-zinc cations.

The electrochemical synthesis of telluride Zintl anions

Abstract A novel electrochemical synthetic technique has been developed recently for the generation of heteropolyatomic Zintl anion clusters via the cathodic dissolution of telluride electrodes. Whereas previous synthetic techniques for the generation of these compounds have relied on high temperature fusion of the elements and/or extraction methods, this technique simply relies on the constantly increasing concentration of anions as they are discharged from a cathode, is performed at room temperature and in many cases yields X-ray quality single crystals in as little as 3–5 days. In the process of our study of this technique, it has also been shown that it allows for the preparation of Zintl anions which have not been and may not be accessible by these standard high temperature and extraction techniques. The versatility of this synthetic technique has been demonstrated by the isolation of small six- to seven-atom anions, larger 15-atom cluster anions and one-dimensional chain materials from the Au, Ga, In, Sn, As and Sb telluride systems. Ongoing research suggests that the synthesis of additional materials should be possible.

Hydrothermal synthesis and characterization of an unusual polyoxovanadium borate cluster: structure of Rb4[(VO)6{ {B10O16(OH)6} }2] · 0.5H2O

Abstract The hydrothermal reaction of RbVO3, (NH4)2B4O7 · 4H2O, ethylenediamine (en), and H2O in a mole ratio of 1:8:2:135 heated at 170°C for 5 days produces pale green crystals of the novel polyoxovanadium borate cluster compound Rb4[(VO)6{B10O16(OH)6}2] · 0.5H2O (1) which contains [V6B20O38(OH)12]4− clusters, each cluster comprising a nearly hexagonal ring of six trans-edge-sharing VO5 square pyramids capped on each side by a B10O16(OH)68− triangle. The [V6B20O38(OH)12]4− clusters are separated in the solid state by Rb+ cations. Magnetic susceptibility and valence sum calculations indicate that all six of the vanadium atoms in the cluster are in the 4+ oxidation state.

A bimetallic main group oxide cluster of the oxovanadium borate system: (H3NCH2CH2NH3)4[(VO)12O4{B8O17(OH)4}2{Mn(H2O)2}2]·H2O

Abstract The hydrothermal reaction of (NH4)2B4O7, NaVO3, ethylenediamine, MnCl2·4H2O and H2O in the molar ratio 2.74:4:4:1:175 at 170°C for 5 days yields orange crystals of (H3NCH2CH2NH3)4[(VO)12O4[B8O17(OH)4)2 {Mn(H2O}2]·H2O(1·H2O) in 75% yield. The structure consists of a continuous contorted V12 ring, constructed from edge-sharing V(IV) square pyramids. Two {B8O17 (OH)4}14− chains nestle in the cavities formed by the V12 ring. The octahedral Mn(II) sites bridge two neighboring [(VO)12O4{B8 O17(OH)4}2]12− clusters to produce a mixed metal boron oxide network with two-dimensional covalent connectivity. Crystal data: monoclinic C2/c,a = 13.4324(2), b = 19.6998(1), c = 24.0521(3) A , β = 98.820(1)°, Z = 4, D cadv = 2.282 g cm −3 ; R = 0.0462 for 7299 reflections.

The first oxometalate borophosphate polyanion: hydrothermal synthesis and structure of (H3NCH2CH2NH3)2[Na(VO)10{HO3POB(O)2OPO3H}5]·22.5H2O

Abstract The first example of a molecular cluster of the metal–borophosphate class of compounds has been prepared.

HYDROTHERMAL SYNTHESIS AND CRYSTAL STRUCTURE OF (H3NCH2CH2NH3)V(OH)(HPO4)2. H2O WITH NOVEL 1-D V3+-OH-V3+ POLYMERIC CHAINS

Abstract A new VIII vanadium phosphate, (H3NCH2CH2NH3) [V (OH) (HPO4) 2] · H2O (1) , with a novel 1-D polymeric chain structure was prepared hydrothermally and its structure determined by X-ray diffraction. The structure consists of infinite {V (OH) (HPO4) 2} 2− chains, ethylenediammonium dications and lattice water molecules. The {V (OH) (HPO4) 2} 2− chains contain an infinite {V3 — OH — V3} backbone bridged by (HPO4) 2− groups. Each V3 atom has a quite regular octahedral configuration containing four phosphate oxygens and two trans positioned OH groups.

One- and two-dimensional organic-inorganic composite solids constructed from molybdenum oxide clusters and chains linked through {M(2,2′-bpy)}2+ fragments (M = Co, Ni, Cu)

Hydrothermal reactions of Na 2 MoO 4 ·2H 2 O and MoO 3 with MCl 2 ·xH 2 O (M = Co, Ni, Cu) and 2,2′-bipyridine yield one- and two-dimensional solids, characterized by molybdenum oxide monomers, clusters and chains linked by {M(2,2′-bpy)} 2+ groups and represented by the formulae [M(bpy) x - (H 2 O) y Mo n O 3n +1 ] (n = 2, M = Cu, x= 1, y = 0; n = 3, M = Co, x = 1, y = 0; n = 4, M = Ni, x = 2, y = 0).

Electrochemical synthesis of a pseudo-two-dimensional polytelluride containing Te2−12 anions: structure of [(C2H5)4N]2Te12

Abstract An unusual pseudo-two-dimensional polytelluride built up from Te2−12 anions was synthesized electrochemically from the cathodic dissolution reaction of an SbTe10 alloy electrode in an ethylenediamine solution of tetraethylammonium iodide, and represents the largest homoatomic polychacogenide anion characterized to date. The compound [(C2H5)4N]2Te12 crystallizes in the acentric monoclinic space group Pn (No. 7) with lattice constants of a = 7.934(1), b = 17.453(8) and c = 13.514(1) A , β = 104.671(10)° and V = 1810.4(7) A 3 , with Z = 2 and R(Rw) = 0.036(0.047). The structure consists of puckered Te122− chains, with internal Te-Te distances of 2.713(2)–2.881(2) A, loosely bound into infinite two-dimensional sheets via many Te-Te interactions in the range of 3.144(2)–3.504(2) A. These distances are somewhat shorter than the comparable interchain (2.835(2) A) and intrachain (3.495(3) A) Te-Te distances in elemental Te. The complete structure consists of these tellurium layers separated in the crystallographic b direction by layers of tetraethylammonium cations.

Hydrothermal synthesis and structural characterization of[Cu(en)2]2Cu7Cl11: athree-dimensional open-framework copper halide with occluded[Cu(en)2]2+ cations

A new type of three-dimensional open-framework copper chloride, prepared simply by the hydrothermal treatment of CuCl 2 ·H 2 O and en, is built up from unusual chloride bridged Cu 4 tetramers connected by CuCl 3/3 units and has voids in the framework that are filled with charge-compensating [Cu(en) 2 ] 2+ cations.