Electrophoretic investigation of the boron cluster anion [7‐(2′‐pyridyl)‐nido‐7,8‐dicarbaundecaborate]– and its protonated zwitterionic product

ACN is a better solvent than methanol for both [NMe4] [7-(2′-pyridyl)-nido-7,8-C2B9H11] and its protonated anion. The investigated laboratory preparations of the salt and of its protonated anion are electrophoretically pure solids stable for 2 months at 4°C. At a longer storage, the solid salt is more stable than the solid protonated anion. In the 40:60 v/v water–methanol solvent, decomposition products of the salt anion are detectable after one-week storage of the salt solution at 4°C. The protonated anion does not decompose for almost 1 year in water–organic solutions at 4°C. The exchange of the proton between the protonated anion and the solution is reversible and fast at room temperature. The pH dependence of the mobility of the [7-(2(-pyridyl)-nido-7,8-C2B9H11]– anion reveals that the basicity of the nitrogen atom in the pyridine ring is not significantly affected by the bonding of the pyridyl group to the nido-7,8-C2B9H11 cluster in position 7 and that the proton from the solution is accepted by the nitrogen atom in the 2-pyridyl ring. The UV-spectra of the salt and of its protonated anion indicate that the accepted proton is probably slightly shifted to the open face of the nido-7,8-C2B9H11 cluster. The [1]– is chiral.