PNNL

Abstract

Small boron clusters as individual species in the gas phase and incorporated into solids and molecules are reviewed. While the family of known boron compounds is rich and diverse, a large body of hitherto unknown chemistry of boron has been recently identified. Free boron clusters have been recently characterized using photoelectron spectroscopy and ab initio calculations, which established the planar or quasi-planar shapes of small boron clusters for the first time. The establishment of the planar structures of small boron clusters has surprised the scientific community, as the chemistry of boron has been diversely featured by three-dimensional structures. The planarity of the small boron clusters has been further elucidated on the basis of multiple aromaticity and antiaromaticicity. Although mostly observed in the gas phase, pure boron clusters are promising molecules for coordination chemistry as potential new ligands and for materials science as new building blocks. The use of pure boron species as novel ligands has commenced, suggesting many new chemistries are ahead of us. Experimental and theoretical endeavors regarding pure boron clusters as such and incorporated into molecules and crystals are reviewed herein. The new spectroscopic results, chemical bonding, multiple aromaticity and antiaromaticity, leading to their unique structures and stability, receive our particular attention.