SYMMETRICAL AND ASYMMETRICAL BIS(AMINE)CARBOXYHYDROBORON(- SYNTHESIS AND PROPERTIES(1) AND BIS(AMINE)CYANOHYDROBORON(+1) CATIONS )

Symmetrical bis(amine)(methoxycarbonyl)hydroboron(+1) cations have bee n prepared by treatment of trimethylaminebromo(methoxycarbonyl)borane [Me(3)N . BH(Br)COOMe] with an excess of tertiary amines (tetramethyle thylenediamine, TMEDA; quinuclidine, Q), as well as pyridine bases (py ridine, Py; 4-methylpyridine, 4-Pic; 4-dimethylaminopyridine, DMAP) at higher temperature. Asymmetrical bis(amine)(methoxycarbonyl)hydroboro n(+1) cations, which contain a chiral boron atom, have been synthesize d, in good yields, in the reaction of 4-Pic . BH(2)COOMe and DMAP . BH (2)COOMe with amine perbromides (L . Br-2, L=Q, Py, 4-Pic, DMAP) perfo rmed in CH2Cl2 at room temperature. Besides these novel cationic carbo xyboron compounds several new cationic cyanoboron complexes with an [L L'BH(CN)](+) composition have been prepared by utilizing the efficient method employing amine-perbromides (L . Br-2; L=Py, 4-Pic, DMAP) and amine-cyanoboranes (L'. BH2CN, L'=4-Pic, DMAP). This bis(amine)boroniu m cations have been prepared and characterized by IR, H-1 and B-11 NMR spectra as PF6 salts. Investigations of the water-soluble bis(amine)( methoxycarbonyl)hydroboron(+1) bromides, some of which could be prepar ed, showed that the hydrolytic stability of the ester group highly dep ends on the character of the amine: the complexes formed with tertiary amines are much more stable. This phenomenon is similar to that obser ved for the amine-(methoxycarbonyl)boranes (L . BH(2)COOMe, L=tertiary amine, pyridine base).