Z. Naturforsch. 2014, 69b, 1149 – 1163
Ion Pairs of Weakly Coordinating Cations and Anions: Synthesis and Application for Sulfide to Sulfoxide Oxidations
Bo Zhang1, Su Li1, Mirza Cokoja1, Eberhardt Herdtweck1, János Mink2, Shu-Liang Zang3, Wolfgang A. Herrmann1, and Fritz E. Kühn1
1 Chair of Inorganic Chemistry/Molecular Catalysis, Catalysis Research Center, Technische Universität München, Ernst-Otto-Fischer-Straße 1, D-85747 Garching bei München, Germany
2 Institute of Molecular Pharmacology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, H-1525 Hungary; Faculty of Information Technology, University of Pannonia, Research Institute of Chemical and Process Engineering, Veszprém, H-8201, Hungary
3 Department of Petroleum and Chemical Technology, Liaoning University of Petroleum and Chemical Technology, Dandong Road, No. 1, 113001 Fushun, P. R. China; Institute of Rare and Scattered Elements Chemistry, Liaoning University, Chongshan Middle Road No. 66, 110036 Shenyang, P. R. China
Reprint requests to Prof. Dr. F. E. Kühn. Tel: +49 89 289 13096. Fax: +49 89 289 13473. E-mail: fritz.kuehn@ch.tum.de
Received July 31, 2014 / published online December 19, 2014
Dedicated to Professor Hubert Schmidbaur on the occasion of his 80th birthday
A series of salts containing the weakly coordinating cations (WCC) 1-butyl-3-methylimidazolium ([Bmim]+), 1-butyl-2,3-dimethylimidazolium ([Bdmim]+), 1-dodecyl-3-methylimidazolium ([C12mim]+), tetrabutylphosphonium ([PBu4]+), tributyltetradecylphosphonium ([P4,4,4,14]+), tetrabutylammonium ([NBu4]+), and 1,1,3,3-tetramethylguanidium ([TMG]+) and fluorinated tetraarylborate anions of the type [B(ArF)4] (ArF = C6F5, C6H3-3,5-(CF3)2) were synthesized and characterized. The influence of cations and anions on the physical properties of the obtained compounds was examined. In case of the compound [TMG][B(C6F5)4] hydrogen-fluorine contacts between cation and anion are present in the solid state. Owing to HF contacts between hydrogen peroxide and the fluorine substituents of the anion and the resulting activation of H2O2 in solution, the compound [P4,4,4,14][B(C6H3-3,5-(CF3)2)4] is applicable as an efficient mediator for the oxidation of sulfides to sulfoxides.
Key words: Weakly Coordinating Anion, Hydrogen Peroxide, Oxidation, Sulfide, Sulfoxide
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