Experimental characterization of the chemical bonds in boron allotropes and boron-rich compounds

点击翻译按钮获取中文摘要

Chemical bonding involving boron atoms is not understood, despite intensive research over many years. For example, it is not known, which allotrope of boron is the stable form at ambient conditions. This project aims at an experimental characterization by single-crystal X-ray diffraction of allotropes of boron, like beta-B106 und alpha-tetragonal boron, and boron-rich solids, like B13C2 and B50C2. Structure refinements of the multipole (MP) model and data analysis according to the Maximum Entropy Method (MEM) will produce electron-density maps that reflect the spatial distribution of the valence electrons in full detail. A quantitative topological analysis of electron densities according to Bader's Atoms-in-Molecules (AIM) theory will classify the different kinds of chemical interactions through bond critical points (BCP), ring critical points (RCP) and bond paths. Next to normal two-electron-two-center (2e2c) bonds between pairs of atoms, we expect that the electron deficient nature of the boron atom will lead to polycenter bonds, two-electron-three-center (2e3c) bonds and one-electron-two-center (1e2c) bonds of various types. Goal is to develop a generalized description of chemical bonds involving boron atoms across the different allotropes and compounds.