Synthesis of stable dodecaalkoxy derivatives of hypercloso-B 12H12

Omar K. Farha, Richard L. Julius, Mark W. Lee, Ramon E. Huertas, Carolyn B. Knobler, M. Frederick Hawthorne*

*Corresponding author for this work

Research output: Contribution to journalArticle

59 Scopus citations

Abstract

The scope and limitations of the alkylation of [closo-B12(OH) 12]2- using a series of fourteen alkyl and aralkyl halides and two p-toluenesulfonic acid esters in the presence of N,N- diisopropylethylamine have been investigated. The dodecaalkoxy-closo- dodecaborate products, [closo-B12(OR)12]2-, and their hypercloso two-electron oxidation products have been explored. The species [closo-B12(OR)12]2- containing 26 cage-bonding electrons may undergo two reversible, sequential, one-electron oxidation processes, producing a 25-electron radical anion and a 24-electron neutral species. Several oxidizing reagents were investigated for the chemical oxidation of [closo-B12(OR)12]2- and [hypercloso-B12(OR)12]- to [hypercloso-B 12(OR)12]. Both FeCl3·6H2O and K3Fe(CN)6 in 90/5/5 ethanol/acetonitrile/H 2O were found to be the reagents of choice. The reverse reaction leading from the neutral species to the radical anion and subsequently to the dianion was achieved using sodium borohydride in ethanol. A variety of alkoxyl derivatives have been synthesized by heating the reactants for extended periods of time in acetonitrile at the reflux temperature. The use of elevated reaction temperatures attained by employing moderate argon pressure (autoclave) over the reaction mixture led to drastic reductions in reaction times and increased efficiency. X-ray diffraction studies of substituted dodecabenzyl ether derivatives proved that 22- has approximate Ih symmetry while hypercloso-2, -3, -9, -11, -12, and -13 have approximate D3d point group symmetry due to Jahn-Teller distortion from Ih.

Original languageEnglish (US)
Pages (from-to)18243-18251
Number of pages9
JournalJournal of the American Chemical Society
Volume127
Issue number51
DOIs
StatePublished - Dec 28 2005

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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    Farha, O. K., Julius, R. L., Lee, M. W., Huertas, R. E., Knobler, C. B., & Hawthorne, M. F. (2005). Synthesis of stable dodecaalkoxy derivatives of hypercloso-B 12H12. Journal of the American Chemical Society, 127(51), 18243-18251. https://doi.org/10.1021/ja0556373