Technetium (Z = 43) is the lightest element on the periodic table with no stable isotopes.  The most common isotope, 99Tc (t1/2 = 2.1 x 105 a), is produced in nuclear fuels as a primary fission product in ~6% yield.   In comparison to the surrounding stable transition metals, the fundamental chemistry of technetium has been poorly studied.  An example of this is the binary halide system, which prior to 2008 there only 3 known compounds for technetium (TcF6, TcF5, and TcCl4), whereas for there have been 12 identified. In this work low-valent binary technetium bromides were synthesized in the solid state and analyzed using various physicochemical characterization methods including single-crystal and powder X-ray diffraction (XRD), UV-Vis, X-ray absorption fine structure (XAFS), and elemental analysis.TcBr3 has been prepared via two different methods: the stoichiometric reaction of the elements in sealed Pyrex tubes or by passing HBr(g) over Tc2(O2CCH3)4Cl2 at elevated temperatures.  Both synthetic methods yield the infinite-chain structure of distorted TcBr6 face-sharing octahedra.  Technetium tetrabromide was synthesized from the reaction of Tc metal with excess Br2(l).  It is isostructural to technetium tetrachloride, and similarly decomposes to lower-valent technetium bromides.  When performed in Pyrex tubes the decomposition of the tetrabromide yields a novel trigonal prismatic Tc(II) bromide cluster, Na{[Tc6Br12]2Br}. The low-valent technetium bromides synthesized exhibit interesting chemical and physical properties, and may serve as potential synthetic inorganic and radiopharmaceutical precursors, as well as potential waste form-type material in the nuclear fuel cycle.

Exploring the synthesis and characterization of binary technetium bromides

246th National Meeting (2013)

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