The new compounds CsUTe6, CsTiUTe5, Cs8HfsUTe30.6, and CsCuUTe3 have been synthesized through the reaction of the metals with a Cs2Ten flux. CsUTe6 crystallizes in space group D2h16-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) Å and V = 2301(1) Å3 (T = 113 K). CsTiUTe5 crystallizes in space group D2h5-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) Å and V = 523.4(2) Å3 (T = 113 K). Cs8Hf5UTe30.6 crystallizes in space group C2H5-P21/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) Å, β = 97.64(3)°, and V = 6816(2) Å3 (T= 113 K). CsCuUTe3 crystallizes in space group D2h17-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) Å, and V= 817.3(3) Å3 (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 Å; if an arbitrary maximum Te-Te single bond distance is taken as 2.98 Å, then the chains may be formulated 1∞[U2(Te3)3(Te2)(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) × 10‒2 Ω‒1 cm‒1 (298 K) and 1.5(2) × 10‒3 Ω‒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) Å. Assignment from the structural results of formal oxidation states is difficult. Magnetic susceptibility data for CsTiUTe5 give a curvilinear x‒1 vs T plot. When fit to a modified Curie-Weiss law, the values C = 8.8(3) × 10‒2 emu K/mol, ⦵ = −1.5(2) K, and x0 = 2.11(8) × 10‒3 emu/mol result. The value of μeff (300 K) is 2.23(1) μB 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) × 10‒3 Ω‒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∞[Hf3Te15 64_] and l∞[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 Cs1, Cu1, UIV, and TeII‒. As expected, Cs+ cations separate the 2∞[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.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry