Chapter 43 Boron compounds

TL;DR: The separation of rigid boron compounds is based on differences in the sizes and shapes of the molecules, in dipole moments, Bronsted or Lewis acidities, and in the characters of the substituents.

Abstract: Publisher Summary The separation of rigid boron compounds is based on differences in the sizes and shapes of the molecules, in dipole moments, Bronsted or Lewis acidities, and in the characters of the substituents. In some instances, the use of liquid–solid chromatography is limited by the reactivity of the compounds to be separated toward water, air, or some solvents. However, a careful choice of chromatographic conditions can decrease this sensitivity to an acceptable level. Water- and air-stable borane compounds (most ligand derivatives, closo -carboranes, and metallocarboranes) are chromatographed on silica gel or aluminum oxide. Some of the air-sensitive boron compounds can be separated in an inert atmosphere on an activated and gas-free stationary phase. The chromatographic behavior of various carboranes is based on their dipole moments (dependent on the character of the skeleton, the location of heteroatoms, or the different locations of substituents) and on the character and number of substituents. Higher boranes and their substituted derivatives are mildly sensitive to air and show different sensitivities towards water and heat.