Hydrothermal synthesis and solid-state structures of polynuclear technetium iodide compounds

• Published in: Inorganica Chimica Acta Vol. 424
• Main Authors: Kerlin, William M., Poineau, Frederic, Forster, Paul M., Czerwinski, Kenneth R., Sattelberger, Alfred P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier 01.01.2015
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2014.09.024

Two new technetium iodide compounds, Tc-2(O2CCH3)(4)I and K[Tc-8(mu-I)(8)I-4] I, were synthesized in an autoclave from the reaction of KTcO4 in glacial acetic acid with hydroiodic acid and/or alkali metal iodide salts at 210 degrees C under 60-70 atm hydrogen pressure. The structures of Tc-2(O2CCH3)(4)I and K[Tc-8(mu-I)(8)I-4] I were solved by single-crystal X-ray diffraction. The compound Tc-2(O2CCH3)(4)I crystallizes in the monoclinic space group C2/m with a = 7.1194(6) angstrom, b = 14.5851(13) angstrom, c = 7.1586(6) angstrom, and beta = 110.9540(10)degrees. The structure of Tc-2(O2CCH3)(4)I consists of infinite chains of Tc-2(O2CCH3)(4)(+) units linked by bridging iodides, an arrangement similar to the one found in Tc-2(O2CCH3)(4)X (X = Cl, Br). The TcATc separation in Tc-2 (O2CCH3)(4)I (i.e., 2.1146(4) angstrom) is consistent with the presence of a TcATc bond of order 3.5. Magnetic susceptibility measurements reveal Tc-2(O2CCH3)(4)I to be paramagnetic (mu(eff) = 1.84 B.M.) and support the electronic configuration sigma(2)pi(2)delta(2)delta*(1) for the Tc-2(5+) unit in the compound. The compound K[Tc-8(mu-I)(8)I-4]I crystallizes in the monoclinic space group P2(1)/n with a = 8.0018(5) angstrom, b = 14.5125(10) angstrom, c = 13.1948(9) angstrom, and beta = 102.3090(10) degrees, and is the first octanuclear technetium iodide cluster to be reported. The Tc-Tc separations in the [Tc-8(mu-I)(8)I-4] cluster (i.e., 2.164(3) angstrom, 2.5308(8) angstrom and 2.72(3) angstrom suggest the presence of Tc equivalent to Tc triple bonds, Tc=Tc double bonds and Tc-Tc single bonds.