Oxidationsreaktionen an ΧnB6Η6-n 2-, Χ = Cl, Br, I; n = 1-6 und Kristallstrukturen von [(n-C4H9)4N]B6I6 und [(n-C4H9)4N]2B6I6 / Oxidation Reactions on XnB6H6-n 2-, X = Cl, Br, I; n = 1-6, and Crystal Structures of [(n-C4H9)4N]B6I6 and [(n-C4H9)4N],B6I6

Abstract

By cyclic voltammetry investigations in acetonitrile solution it has been shown, that the halogenohydrohexaborates X„B6H6-n 2-, X = Cl, Br, I; n = 1-6, undergo a one-electron oxidation to form the corresponding radical anions. The reactions are completely reversible only for the perhalogenated ions B6X6 2- and for trans-Br4Β6Η2 2-. The oxidation by Ce(IV) in CH3CN yields deep blue B6I6, orange B6Br6- and yellow green B6Cl6-, characterized by their UV-VIS, IR/Raman spectra and by magnetic measurements. The crystal structures of the paramagnetic, air-stable, blue-black [(n-C4H9)4N]B6I6 (I) and the diamagnetic, colourless [(n-C4H9)4N]2B6I6 (II) were determined from single crystal X-ray diffraction analyses. I is monoclinic, space group P21/c, with a = 14.398(7), b = 14.638(3), c = 16.511(6) Å, β = 109.24(1)° (at —50°C), containing two crystallographically independent centrosymmetric B6 entities, which are strongly distorted with B— B bond lengths between 1.63 and 1.91 and I— I between 2.02 and 2.22 A. II is monoclinic, space group P21, with a = 11.246(3), b = 15.576(4), c = 14.900(4) Å, β = 92.10(1)° (at 23 °C) and contains nearly regular octahedral anions with bond lengths B—B 1.64-1.68 and B—I 2.17-2.21 A.