Search for the shortest intermetallic Tl—Tl contacts: Synthesis and characterization of Thallium(I) coordination polymers with several mono- and bis-cyanoximes


Five new Tl(I) coordination compounds based on aryl monocyanoximes, such as phenylcyanoxime – HPhCO, 1, 2-fluorophenylcyanoxime – H(2F-PhCO, 2, 3-fluorophenylcyanoxime – H(3F-PhCO), 3, of TlL composition, and aryl biscyanoximes, such as 1,3-cyanoxime (benzene) – H2(1,3-BCO, 4 and 1,4-cyanoxime (benzene) – H2(1,4-BCO), 5 of Tl2L stoichiometry were synthesized and characterized using spectroscopic methods, thermal stability studies, and X-ray analysis. All obtained complexes represent coordination polymers of different complexity, ranging in dimensionality from 1D in Tl(2F-PhCO) to 3D in Tl2(1,3-BCO). The most interesting feature of all synthesized complexes is the formation of Tl2O2 rhombs: non planar and non-centrosymmetric in Tl(PhCO), and planar and centrosymmetric in the other three compounds. These rhombi are interconnected, forming zigzag and ladder-type polymers in which very short thallophilic Tl—Tl distances were observed. Thus, in the structure of Tl2(1,3-BCO) the closest distance between metal centers was found to be 3.670 Å. This is the second shortest on-record intermetallic contact in non-organometallic and non-cluster, but Werner type complexes, and is close to that in metallic thallium: 3.456 Å. In all five new coordination polymers the central atom has a stereo-active 6 s2 lone pair that significantly distorts the shape of the coordination polyhedron of Tl(I). The first time, Tl–O vibrations in Tl2O2 rhombs were observed in Raman spectra of the obtained complexes. Thermal analysis studies evidenced stability of all complexes, but Tl(PhCO), to ∼200 °C. The Tl2(1,3-BCO) compound demonstrates properties of the high energy compound, and violently exothermically decomposes at ∼255 °C with the release of a significant amount of kinetic energy. The final product of anaerobic decomposition of all studied Tl-cyanoximates is metallic thallium sponge.



Document Type





Cyanoxime ligands, Electronic spectra, Raman spectra, Thallium(I) coordination polymers, Thermal analysis, X-ray analysis

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Journal Title

Inorganica Chimica Acta