Boron atom has received much attention from scientists owing to its unique characters, such as short covalent radius, electron deficiency, large coordination number, sp² hybridization of valence electrons and three-center bonds. Due to the research of the electronic structure, stability, aromaticity and bonding nature, boron clusters have become a sparkling rising star on the horizon of chemistry. Meanwhile, boron compounds have a vast applications in optics, energy and industrial gas storage because of their rich features. This paper systematicly reviewes the recent research progresses of pure-boron clusters, borane and metal-doped boron clusters. The pure-boron clusters and borane are generalized from neutral, anionic and cationic three types. The metal-doped boron clusters mainly include metal-doped all-boron clusters and borane, transition-metal sandwich-type complexes as well as metal-centered boron molecular wheels.

Contents
1 Introduction
2 Pure-boron clusters
2.1 Neutral boron clusters
2.2 Anionic boron clusters
2.3 Cationic boron clusters
3 Borane clusters
3.1 Anionic borane clusters
3.2 Neutral borane clusters
3.3 Cationic borane clusters
4 Metal-doped boron clusters
4.1 Metal-doped all-boron clusters
4.2 Metal-doped borane compounds
4.3 Transition-metal sandwich-type complexes
4.4 Metal-centered boron molecular wheels
5 Conclusion