Professor Ekkehard Fluck zum 70. Geburtstag gewidmet Inhaltsu È bersicht. Die Oxidation der Decachlor-closodecaborate(2±) Cs 2 [B 10 Cl 10 ] oder [Me 4 N] 2 [B 10 Cl 10 ] mit Tl(CF 3 COO) 3 ergibt das Radikal-Monoanion hypercloso-[B 10 Cl 10 ]´±, das durch ESR-und UV/Vis-Spektroskopie charakterisiert wurde. [B 10 Cl 10 ]´± dimerisiert nicht wie [B 10 H 10 ]´±, es wird aber durch Acetonitril zum Dianion [B 10 Cl 10 ] 2± reduziert. Cs 2 [B 10 Cl 10 ] reagiert mit sta È rkeren Oxidationsmitteln wie CoF 3 (in Dichlormethan) oder XeF 2 (in Perfluorhexan) unter Bildung von B 9 Cl 9 und ± in Spuren ± B 8 Cl 8 . Im Gegensatz zu diesen Befunden zeigt der Decabrom-closo-decaborat-Cluster Cs 2 [B 10 Br 10 ] keine Reaktionen mit Tl(CF 3 COO) 3 in Acetonitril oder mit CoF 3 in CH 2 Cl 2 . Die Oxidation der Dianionen [B 10 X 10 ] 2± (X = Cl, Br) wurde durch elektroanalytische Methoden (Cyclovoltammetrie, Chronoamperometrie, Chronocoulometrie) untersucht. Fu È r die zwei Stufen der Reaktion wurden die Formalpotentiale bestimmt, die keinen Einfluû von Struktura È nderungen erkennen lassen. Die Struktur von Cs 2 [B 10 Br 10 ]´2 H 2 O wurde an einem Einkristall durch Ro È ntgendiffraktometrie bestimmt. Cs 2 [B 10 Br 10 ]2 H 2 O kristallisiert monoklin (Raumgruppe I 2/a (Nr. 15), Z = 8, a = 1361,54(9) pm, b = 1215,89(5) pm, c = 3108,4(2) pm, a = 90°, b = 97,916(8)°, c = 90°). Der closo-Cluster [B 10 Br 10 ] 2± hat die Struktur des zweifach u È berkappten quadratischen Antiprismas mit idealisierter D 4d -Symmetrie. Chemical and Cyclovoltammetric Investigation of the Redoxreactions of the Decahalodecaborates closo-[B 10 X 10 ] 2± and hypercloso-[B 10 X 10 ]´± (X = Cl, Br) 1) . Crystal Structure Analysis of Cs 2 [B 10 Br 10 ]´2 H 2 O Abstract. The oxidation of the decachloro-closo-decaborates(2±) Cs 2 [B 10 Cl 10 ] or [Me 4 N] 2 [B 10 Cl 10 ] with Tl(CF 3 COO) 3 leads to the corresponding radical monoanion hypercloso-[B 10 Cl 10 ]´±, which was characterized by ESR and UV/Vis spectroscopy. [B 10 Cl 10 ]´± does not dimerize like [B 10 H 10 ]´± but it is reduced by acetonitrile to the dianion [B 10 Cl 10 ] 2± . Cs 2 [B 10 Cl 10 ] reacts with stronger oxidation agents like CoF 3 (in dichloromethane) or XeF 2 (in perfluorhexane), respectively, to yield B 9 Cl 9 and, in traces, B 8 Cl 8 . In opposite to this, the decabromoderivative Cs 2 [B 10 Br 10 ] does not show any reaction with Tl(CF 3 COO) 3 in acetonitrile or with CoF 3 in CH 2 Cl 2 .The oxidation of the dianions [B 10 X 10 ] 2± (X = Cl, Br) was studied by electroanalytical methods (cyclic voltammetry, chronoamperometry, chronocoulometry). Formal potentials were determined for the two steps of the reaction, which do not seem to be affected by structural rearrangements.The crystal structure of Cs 2 [B 10 Br 10 ]´2 H 2 O was analyzed by single-crystal X-ray diffraction. Cs 2 [B 10 Br 10 ]´2 H 2 O crystallizes monoclinic (space group I2/a, (no. 15), Z = 8, a = 1361.54(9) pm, b = 1215.89(5) pm, c = 3108.4(2) pm, a = 90°, b = 97.916(8)°, c = 90°). The closo-cluster B 10 Br 10 2± has a bi...

Boron subhalide cluster dianions B6X 2- 6 (X = Cl, Br, I) are electrochemically oxidized in two steps. According to cyclic voltammograms, the first step is chemically reversible and yields the corresponding radical anions B6X .- 6. The electron transfer is nearly diffusion controlled. The second, slower electron-transfer step leads to a species which we assume to be the hitherto not yet described neutral compounds B6X 2- 6. The voltammograms indicate a coupled fast catalytic reaction, producing the radical anions in a reduction by an electrolyte component. Computer simulations of the cyclic voltammograms reveal mechanistic details of the redox reactions, as well as quantitative values for formal potentials, rate constants, and diffusion coefficients. The results are compared to other BnXn redox systems.

Electrolysis Electrolysis F 4000Two-Electron-Transfer Redox Systems. Part 7. Two-Step Electrochemical Oxidation of the Boron Subhalide Cluster Dianions B 6 (X: Cl, Br, I). -As revealed by cyclic voltammetry, the title dianions are electrochemically oxidized in two steps. The first step reversibly yields the corresponding radical anions B6 (X: Cl, Br, I). The second, slower electron-transfer step leads to a species which is assumed to be the hitherto not yet described neutral compound B 6 . Computer simulations of the cyclic voltammograms reveal mechanistic details of the redox reactions, as well as quantitative values for formal potentials, rate constants, and diffusion coefficients. -(SPEISER*, B.; WIZEMANN, T.; WUERDE, M.; Inorg.

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