ABSTRACT
Highly cross-linked cluster precursors KZr6I14B, Zr6I12B, KZr6I14C, and Zr6I12C were, successfully excised in deoxygenated water, and the resulting red aqueous solutions of clusters exhibit better kinetic stability with respect to decomposition than their chloride and bromide analogues. On traversing the Cl-->I series, NMR measurements show increasing deshielding of the interstitial atoms (Z = B, C) in Zr6ZX12 clusters and cyclic voltammetry reveals increasingly positive reduction potentials for the [(Zr6BX12)(H2O)6]+ ions. Several new cluster complexes have been crystallized from aqueous or methanolic solutions. Crystallographic data for these compounds are as follows: [(Zr6BI12)(H2O)6]Ix11.7(H2O) (1), triclinic, P1, a = 10.2858(7) A, b = 11.3045(8) A, c = 20.808(1) A, alpha = 77.592(1) degrees, beta = 79.084(1) degrees, gamma = 77.684(1) degrees, Z = 2; [(Zr6BI12)]+[I(CH3OH)6]- (2), hexagonal, R3, a = 17.706(1) A, c = 13.910(1) A, Z = 3, [(Zr6CI12)(H2O)6]I(2).4(H2O) (3), triclinic, P1, a = 10.1566(5) A, b = 10.4513(5) A, c = 10.7549(6) A, alpha = 117.552(1) degrees, beta = 96.443(1) degrees, gamma = 96.617(1) degrees, Z = 1.
ABSTRACT
The synthesis and crystal structures of new ternary aluminum chalcogenides, LiAlSe2, alpha-LiAlTe2, and beta-LiAlTe2, are reported. These compounds are synthesized by solid-state reaction at 800 degrees C. The single-crystal X-ray structures of these compounds have been determined. LiAlSe2: a = 68228(9) A, b = 8266(1) A, c = 65236(7) A, Pna2(1) (No 33, Z = 4) alpha-LiAlTe2: a = 65317(4) A, c = 116904(9) A, I42d (No 122, Z = 4) beta-LiAlTe2: a = 44810(6) A, c = 7096(1) A, P3m1 (No 156, Z = 1). These ternary compounds are formed by fusion of AlQ4 (Q = Se, Te) tetrahedra. LiAlSe2 shows beta-NaFeO2 structure type, which can be viewed as a wurtzite superstructure. alpha-LiAlTe2 adopts chalcopyrite structure type. In LiAlSe2 and alpha-LiAlTe2, AlQ4 (Q = Se, Te) tetrahedra share four corners to build three-dimensional structures and Li atoms are located in the tetrahedral sites between the chalcogen layers. beta-LiAlTe2 has polar layers formed by three-corner shared AlTe4 tetrahedra, and Li cations are in the distorted antiprisms between the layers. 7Li MAS NMR studies show that chemical shifts of Li in these ternary chalcogenides are nearly identical regardless of different chemical environments.
ABSTRACT
Ambient-temperature chloroaluminate molten salts, mixtures of aluminum trichloride (AlCl3) and 1-ethyl-3-methylimidazolium chloride (ImCl), have been used as solvents to excise and isolate centered hexanuclear zirconium halide clusters from their solid-state precursors. Cluster compounds synthesized via high-temperature reactions, KZr6CCl15 and Li2Zr6MnCl15, were dissolved into basic molten salts at 100-110 degrees C. The C-centered cluster compound, Im4Zr6CCl18, was isolated in 70% yield, and the Mn-centered cluster compound, Im5Zr6MnCl18.C7H(8).2CH3CN, was isolated in 54% yield. Im5Zr6BCl18 is efficiently oxidized by ferrocenium tetrafluoroborate, and one-electron-oxidized B-centered cluster, [(Zr6B)Cl18]4-, was isolated in 90% yield as the salt Im4Zr6BCl18.
ABSTRACT
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.
ABSTRACT
Large single crystals of NbP have been prepared. A single-crystal X-ray diffraction study shows that it crystallizes in tetragonal symmetry with space group I4(1)md (No. 109) and lattice parameters a = 3.3324(2) Å, c = 11.3705(7) Å, and Z = 4. A full matrix least-squares refinement based on a unique data set of 285 reflections (I> 2sigma(I)) yielded R(F) = 0.017 and R(w)(F(2)) = 0.046 for nine variables. The unit cell consists of one unique Nb and one P, each in trigonal prismatic coordination with the other element. There are two short and four long bond distances of Nb-P. The Nb-Nb bond distances are significantly shorter than R(c) = 4.09 Å, the critical distance required for good Nb-Nb 4d orbital overlap for niobium metal-metal bonds. NbP shows metallic behavior with rho = 4.5 x 10(-)(5) Omega cm at room temperature. Magnetic susceptibility measurements on a collection of randomly oriented single crystals indicate very weak Pauli paramagnetism ( approximately 10(-)(5) emu/mol). A discussion of the structure as well as the physical properties of NbP compared with those of previous results are presented. The band structure of NbP based on the extended Hückel (tight-binding) calculations is presented along with an analysis that reveals that the valence band is built up from three center bonds localized within Nb(3) triangles.