Dititanium-Containing 19-Tungstodiarsenate(III) [Ti2(OH)2As2W19O67(H2O)]8-(1):Synthesis, Structure, Electrochemistry, and Oxidation Catalysis
Научная публикация
| Общее |
Язык:
Английский,
Жанр:
Статья (Full article),
Статус опубликования:
Опубликована,
Оригинальность:
Оригинальная
|
| Журнал |
Chemistry - A European Journal
ISSN: 0947-6539
, E-ISSN: 1521-3765
|
| Вых. Данные |
Год: 2007,
Том: 13,
Номер: 17,
Страницы: 4733-4742
Страниц
: 10
DOI:
10.1002/chem.200700043
|
| Ключевые слова |
Electrochemistry homogeneous catalysis, Polyoxometalates, Self-assembly, Titanium, Tungsten |
| Авторы |
Hussain Firasat
1,4
,
Bassil Bassem S.
1
,
Kortz Ulrich
1
,
Kholdeeva Oxana A.
2
,
Timofeeva Maria N.
2
,
de Oliveira Pedro de
3
,
Keita Bineta
3
,
Nadjo Louis
3
|
| Организации |
| 1 |
International University Bremen, School of Engineering and Science, P.O. Box 750 561, 28725 Bremen (Germany)
|
| 2 |
Boreskov Institute of Catalysis, Russian Academy of Sciences, Lavrentiev avenue 5, Novosibirsk 630090 (Russia)
|
| 3 |
Laboratoire de Chimie Physique, UMR 8000, CNRS, Equipe d’Electrochimie et PhotoJlectrochimie UniversitJ Paris-Sud, Batiment 350
|
| 4 |
School of Chemistry, University of Melbourne, Parkville, Victoria 3010 (Australia)
|
|
The dititanium-containing 19-tungstodiarsenate(III) [Ti2(OH)2As2W19O67(H2O)]8− (1) has been synthesized and characterized by IR, TGA, elemental analysis, electrochemistry, and catalytic studies. Single-crystal X-ray analysis was carried out on Cs8[Ti2(OH)2As2W19O67(H2O)]⋅2 CsCl⋅12 H2O (Cs-1), which crystallizes in the monoclinic system, space group P21/m, with a=12.7764(19), b=19.425(3), c=18.149(3) Å, β=110.234(3)°, and Z=2. Polyanion 1 comprises two (B-α-AsIIIW9O33) Keggin moieties linked through an octahedral {WO5(H2O)} fragment and two unprecedented square-pyramidal {TiO4(OH)} groups, leading to a sandwich-type structure with nominal C2v symmetry. Synthesis of 1 was accomplished by reaction of TiOSO4 and K14[As2W19O67(H2O)] in a 2:1 molar ratio in aqueous, acidic medium (pH 2). Polyanion 1 could also be isolated as a tetra-n-butyl ammonium (TBA) salt, {(n-C4H9)4N}5H3[Ti2(OH)2As2W19O67(H2O)] (TBA-1). TBA-1 was studied by cyclic voltammetry in acetonitrile (MeCN) solutions containing 0.1 M LiClO4 and compared with the results obtained with Cs-1 in aqueous media. In MeCN, the TiIV and WVI waves could not be separated distinctly. An important adsorption phenomenon on the glassy carbon working electrode was encountered both in cyclic voltammetry and in controlled potential electrolysis and was confirmed by Electrochemical Quartz Crystal Microbalance (EQCM) studies on a carbon film. TBA-1, dissolved in MeCN, reacts with H2O2 to give peroxo complexes stable enough for characterization by UV-visible spectroscopy, cyclic voltammetry, and EQCM. TBA-1 shows high catalytic activity (TOF=11.3 h−1) in cyclohexene oxidation with aqueous H2O2 producing products typical of a heterolytic oxidation mechanism. The stability of TBA-1 under turnover conditions was confirmed by using IR, UV-visible spectroscopy as well as cyclic voltammetry.