Synthesis and investigation of the boron cluster anion [7-(2′-pyridyl)-7,8-nido-dicarbaundecaborate] and its protonated form†‡§
Abstract
The structurally chiral [7-(2′-pyridyl)-7,8-nido-C2B9H11]−, [1]−, anion was prepared by a partial degradation reaction of 1-(2′-pyridyl)-1,2-closo-C2B10H11. From this anion a protonated specie, H[7-(2′-pyridyl)-7,8-nido-C2B9H11] 2, and a tetramethylammonium salt, [NMe4][7-(2′-pyridyl)-7,8-nido-C2B9H11], [NMe4][1] can be obtained. The 1H{11B} DNMR study on 2 in the temperature range from 298 to 203 K identified the weakly basic nitrogen atom in the pyridine ring as the proton accepting site in solid state and low temperature and revealed pronounced weakening of the nitrogen–proton interaction while the temperature increases. Capillary electrophoresis and X-ray diffraction confirmed the pyridine nitrogen atom as the proton binding site. Separation of the electrophoretically pure racemic [7-(2′-pyridyl)-7,8-nido-C2B9H11]− ion into two peaks by the chiral selector β-cyclodextrine has been achieved.