Jenne C, Kirsch C. Alkoxy substituted halogenated closo-dodecaborates as anions for ionic liquids.
Dalton Trans 2015;
44:13119-24. [PMID:
26107425 DOI:
10.1039/c5dt01633a]
[Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Halogenated and alkoxylated closo-dodecaborates [B12X11OR](2-) (X = Cl, Br; R = propyl, octyl, dodecyl) have been synthesized by halogenation of the known [B12H11OH](2-) anion followed by alkylation in the superbasic medium DMSO/KOH. The obtained sodium salts were transformed by simple metathesis reactions in aqueous solution to the tetrabutylammonium ([NBu4](+)) and 1-hexyl-3-methylimidazolium ([C6mim](+)) salts. All compounds were fully characterized by heteronuclear NMR, IR and Raman spectroscopy, ESI mass spectrometry, and thermal analytical measurements. Selected anions were also structurally characterized as their [Ph4P](+) salts by single crystal X-ray diffraction. The [C6mim](+) salts are thermally stable up to more than 300 °C and show clear melting points. Surprisingly, the compound [C6mim]2[B12Cl11O-propyl] having the short propyl group bound to the boron cluster shows the lowest melting point (96 °C) of all the investigated compounds. Thus this compound is a rare member of the class of ionic liquids consisting of dianions.
Collapse