URANIUM TELLURIDES - NEW ONE-DIMENSIONAL AND 2-DIMENSIONAL COMPOUNDS CSUTE6, CSTIUTE5, CS8HF5UTE30.6, AND CSCUUTE3

The new compounds CsUTe6, CsTiUTe5, Cs8Hf5UTe30.6, and CsCuUTe3 have been synthesized through the reaction of the metals with a Cs2Ten flux. CsUTe6 crystallizes in space group D-2h(16)-Pnma of the orthorhombic system with eight formula units in a cell of dimensions a = 30.801(7), b = 8.143(2), and c = 9.174(2) Angstrom and V = 2301(1) Angstrom(3) (T = 113 K). CsTiUTe5 crystallizes in space group D-2h(5)-Pmma of the orthorhombic system with two formula units in a cell of dimensions a = 6.130(1), b = 8.240(2), and c = 10.363(2) Angstrom and V = 523.4(2) Angstrom(3) (T = 113 K). Cs8Hf5UTe30.6 crystallizes in space group C-2h(5)-P2(1)/c of the monoclinic system with four formula units in a cell of dimensions a = 12.043(3), b = 18.724(4), and c = 30.496(6) Angstrom, beta = 97.64(3)degrees, and V = 6816(2) Angstrom(3) (T = 113 K). CsCuUTe3 crystallizes in space group D-2h(17)-Cmcm of the orthorhombic system with four formula units in a cell of dimensions a = 4.327(1), b = 16.661(4), and c = 11.337(3) Angstrom, and V = 817.3(3) Angstrom(3) (T = 113 K). The structures of all four compounds were determined by single-crystal X-ray methods. CsUTe6 has a one-dimensional structure that contains pairs of U/Te chains coupled by Te-Te bonds and separated by Cs+ cations. There are many Te-Te distances less than 3.1 Angstrom; if an arbitrary maximum Te-Te single bond distance is taken as 2.98 Angstrom, then the chains may be formulated (1)(infinity)[U-2(Te-3)(3)(Te-2)(Te)2-], with U in the +IV oxidation state. The U atoms are coordinated to nine Te atoms in a tricapped trigonal-prismatic arrangement. Electrical resistivity measurements give conductivities of 1.6(4) x 10(-2) Ohm(-1) cm(-1) (298 K) and 1.5(2) x 10(-3) Ohm(-1) cm(-1) (77 K). CsTiUTe5 has a layered structure that contains UTe8 bicapped trigonal prisms sharing a common edge and TiTe6 octahedra sharing faces. Cs+ cations, located in pentagonal prisms of Te atoms, separate the layers. The structure contains an infinite linear Te-Te chain with a separation of 3.065(1) Angstrom. Assignment from the structural results of formal oxidation states is difficult. Magnetic susceptibility data for CsTiUTe5 give a curvilinear chi(-1) vs T plot. When fit to a modified Curie-Weiss law, the values C = 8.8(3) x 10(-2) emu K/mol, Theta = -1.5(2) K, and chi(0) = 2.11(8) x 10(-3) emu/mol result. The value of mu(eff) (300 K) is 2.23(1) mu(B) for each CsTiUTe5 unit. The resistivity of CsTiUTe5 at 77 K is beyond the detection limits of our instrument, but it is 1.2(9) x 10(-3) Ohm(-1) cm(-1) at 298 K. Cs8Hf5UTe30.6 is a one-dimensional compound with ordered Hf and U atoms and disordered Te atoms in two unique chains that may be formulated (1)(infinity)[Hf3Te15.64-] and (1)(infinity)[Hf2UTe154-]. Cs+ cations separate the chains. The Hf and Uatoms are coordinated to Te atoms in a distorted trigonal prismatic framework. Since there are many short Te-Te distances the assignment of formal oxidation states is not possible. CsCuUTe3 is a layered compound with no Te-Te bonding. Formal oxidation states are unambiguously Cs-I, Cu-I, U-IV, and Te-II- As expected, Cs+ cations separate the (2)(infinity)[CuUTe3-] layers, which contain UTe6 octahedra and CuTe4 tetrahedra. This structure differs markedly from the channel structure of CsAg5Te3 formed through an analogous synthesis with Cu replaced by Ag.