Chemische und cyclovoltammetrische Untersuchung der Redoxreaktionen der Decahalogendecaboratecloso-[B10X10]2- undhypercloso-[B10X10]· - (X = Cl, Br). Kristallstrukturanalyse von Cs2[B10Br10] · 2 H2O

Abstract

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...

Photoelectrochemical oxidation of anions by WO3 in aqueous and nonaqueous electrolytes

“…31 The Nernst potential of the solution as probed by a Pt wire was observed to be 1.68 V vs. NHE, therefore providing an opportunity to produce large barrier heights, and correspondingly large open-circuit voltages from regenerative photoelectrochemical cells that use this redox system in contact with WO 3 photoanodes. redox system provided an approach to convert the chemical energy that was stored in (CH 3 SO 3 ) 2 into a solution potential that could readily generate electrical power, at the expense of a loss in potential of 0.2-0.3 V. A drawback to the use of this redox couple is that the oxidized species, B 10 Br 10 _ À , absorbed a portion of the incoming light, and contributed to a reduction of J ph from $1.4 mA cm À2 in Fig.…”

Synthesis and Properties of the Octaboron Cluster Series hypercloso‐B8Cl8, the Radical Anion hypercloso‐[B8Cl8].− and the Dianion closo‐[B8Cl8]2−

“…*À ) = + 0.959 V vs a ferrocene (fc/fc + ) reference electrode, [11,23] i.e + 1.583 V vs. the standard hydrogen electrode (SHE).…”

“…[B 8 Cl 8 ] *À is another member in the series of the boron subhalide cluster radical anions [B n Hal n ] *À (n = 6, 8-12). [11,[23][24][25]36,37] Probably [B 12 Cl 12 ] *À which was synthesized and investigated by C. Knapp et al [25] is the most important member in this series.…”

Multidimensional potential of boron-containing molecules in functional materials

“…X = H, n = 8). 43,44 Several theoretical studies have appeared later for species with X = H 45,46 and the attention was also extended to perhalide compounds (X = Hal, n = 6, 8, 9, 10), [47][48][49][50][51][52][53][54][55][56] to peralkylated species such as [B 12 Me 12 ] •-, 57 and to related OR substituted derivatives (R = CH 2 Ph, H). [58][59][60] The substituted 'hypercloso' compounds, typically generated by one-electron oxidation from dianionic closo precursors, are stabilized with electronegative substituents because neither Hal + nor R + or RO + are good leaving groups such as H + .…”