Symmetrical and asymmetrical bis(amine)carboxyhydroboron(+1) and bis(amine)cyanohydroboron(+1) cations: synthesis and properties

József Emri, Zoltán Kovács, Béla Gyo

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Symmetrical bis(amine)(methoxycarbonyl)hydroboron(+1) cations have been prepared by treatment of trimethylaminebromo(methoxycarbonyl)borane [Me3N·BH(Br)COOMe] with an excess of tertiary amines (tetramethylethylenediamine, TMEDA; quinuclidine, Q), as well as pyridine bases (pyridine, Py; 4-methylpyridine, 4-Pic; 4-dimethylaminopyridine, DMAP) at higher temperature. Asymmetrical bis(amine)(methoxycarbonyl)hydroboron(+1) cations, which contain a chiral boron atom, have been synthesized, in good yields, in the reaction of 4-Pic·BH2COOMe and DMAP·BH2COOMe with amine perbromides (L·Br2, L = Q, Py, 4-Pic, DMAP) performed in CH2Cl2 at room temperature. Besides these novel cationic carboxyboron compounds several new cationic cyanoboron complexes with an [LL′BH(CN)]+ composition have been prepared by utilizing the efficient method employing amine-perbromides (L·Br2; L = Py, 4-Pic, DMAP) and amine-cyanoboranes (L′·BH2CN, L′ = 4-Pic, DMAP). The bis(amine)boronium cations have been prepared and characterized by IR, 1H and 11B NMR spectra as PF6 salts. Investigations of the water-soluble bis(amine)(methoxycarbonyl)hydroboron(+1) bromides, some of which could be prepared, showed that the hydrolytic stability of the ester group highly depends on the character of the amine: the complexes formed with tertiary amines are much more stable. This phenomenon is similar to that observed for the amine-(methoxycarbonyl)boranes (L·BH2COOMe, L = tertiary amine, pyridine base).

Original languageEnglish (US)
Pages (from-to)119-125
Number of pages7
JournalInorganica Chimica Acta
Issue number1-2
Publication statusPublished - 1995



  • Alkoxycarbonyl complexes
  • Amine complexes
  • Boron complexes
  • Cyano complexes
  • Hydride complexes

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Materials Chemistry

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