Two new examples of very short thallium-transition metal contacts: Tl(3)Ag(3)Sb(2)S(6) and Tl(3)Ag(3)As(2)S(6)

Abstract

Two new sulphosalts Tl(3)Ag(3)Sb(2)S(6), (1) and Tl(3)Ag(3)AS(2)S(6), (2) were prepared in reaction of synthetic binary sulfides: argentite (Ag(2)S), carlinite (Tl(2)S) and orpiment (As(2)O(3)) or stibnite (Sb(2)S(3)), and their crystal structures have been determined using single-crystal data. The compounds are isostructural and crystallize in the space group P2(1)/C (Z = 4), with a = 11.6854(17) angstrom, b = 11.8602(17) angstrom, c = 12.1294(18) angstrom, beta = 123.356(2)degrees, V = 1404.1(4) angstrom(3) for 1, and a = 11.4415(14) angstrom, b = 11.7530(15) angstrom, c = 11.9880(16) angstrom, beta = 123.516(3)degrees, V= 1344.0(3) angstrom(3) for2. Refinements involving anisotropic displacement parameters for all atoms converged to the conventional R-factors: R(1) = 0.0496 for 1 and R(1) = 0.0372 for 2. The structures consist of two kinds of slabs alternately situated along [1 0 0] direction and sharing S atoms located between them. The first slab is built up of Tl1S(8), Tl(2)S(6), Tl(3)S(5)Ag(3) coordination polyhedra and Ag(3)S(3)n(3) distorted trigonal pyramid (the average lt Ag(3)-S gt distance is 2.542 for 1 and 2.539 angstrom for 2) combined with trigonal Sb1S(3) or As1S(3) coordination pyramids ( lt Sb1-S gt and lt As1-S gt are 2.438 and 2.259 angstrom, respectively). The thallium atom Tl1 is surrounded by eight S atoms forming a square anti-prism ( lt Tl1-S gt : 3.393 for 1 and 3.356 angstrom for 2), while the coordination polyhedron of Tl2 can be described as a significantly distorted trigonal prism or as an extremely distorted octahedron ( lt Tl2-S gt : 3.236 angstrom for 1 and 3.238 angstrom for 2). Thallium Tl3 is surrounded by six atoms (one Ag, four S at shorter and one S at longer distance), which form a distorted trigonal prism ( lt Tl3-S gt : 3.165 angstrom in 1 and 3.155 angstrom in 2). The second slab consists of trigonal Sb(2)S(3) or As(2)S(3) coordination pyramids combined with Ag1S(4) and Ag(2)S(4) coordination tetrahedra ( lt Sb2-S gt and lt As2-S gt are 2.433 and 2.251 angstrom, respectively; lt Ag1-S gt : 2.623 angstrom for 1 and 2.612 A for 2; lt Ag2-S gt : 2.623 angstrom for 1 and 2.630 angstrom for 2). The most interesting feature of both structures is the existence of short Tl3-Ag(3) contacts of 2.959(2) angstrom in 1 and 2.922(1) angstrom in 2. These contacts are the shortest found so far and indicate very strong Tl-Ag interactions. They are discussed in terms of metallophilicity principle and relativistic effects. It is also pointed out that if only valence shell electrons are considered (Tl-Ag)(2+) group is isoelectronic with the (Hg-Hg)(2+) ion, therefore new examples of short Tl-Ag contacts could be expected. (C) 2007 Elsevier B.V. All rights reserved.