Cd3Cu2Te7 and U2Cu0.78Te6: Two examples of linear Te chains

The compounds Gd3Cu2Te7 and U2Cu0.78Te6 have been synthesized by reactions of the elements at 1123 K in a KI flux. Gd3Cu2,Te-7 crystallizes in the ort horhombic space group Cmcm with four formula units in a cell of dimensions a = 11.4994(8), b = 19.170(1), and c = 6.1251(4) Angstrom at T = 153 K. Gd3 Cu2Te7 can be considered to consist of one-dimensional isolated Te chains a nd two-dimensional (2)(x)[Cu2Te5] layers separated by Gd atoms along the b axis, U2Cu0.78Te6 crystallizes in the monoclinic space group P2(1)/m with o ne formula unit in a cell of dimensions a = 6.100(1), b = 4.2150(7), c = 10 .365(2) Angstrom, and beta = 98.978(3)degrees at T = 153 K. U2Cu0.78Te6 con tains two-dimensional (2)(x)[UTe3] layers joined by Cu atoms along the c ax is. In both structures the Gd and U atoms are coordinated to bicapped trigo nal prisms of eight Te atoms, and the Cu atoms are coordinated to tetrahedr a of four Te atoms. Both structures contain linear Te chains. (C) 2001 Acad emic Press.