Jian Tian, Chen Xuenian, Li Si-Dian, Boldyrev Alexander I, Li Jun, Wang Lai-Sheng
Department of Chemistry, Brown University, Providence, RI 02912, USA.
Chem Soc Rev. 2019 Jul 1;48(13):3550-3591. doi: 10.1039/c9cs00233b.
Because of their interesting structures and bonding and potentials as motifs for new nanomaterials, size-selected boron clusters have received tremendous interest in recent years. In particular, boron cluster anions (Bn-) have allowed systematic joint photoelectron spectroscopy and theoretical studies, revealing predominantly two-dimensional structures. The discovery of the planar B36 cluster with a central hexagonal vacancy provided the first experimental evidence of the viability of 2D borons, giving rise to the concept of borophene. The finding of the B40 cage cluster unveiled the existence of fullerene-like boron clusters (borospherenes). Metal-doping can significantly extend the structural and bonding repertoire of boron clusters. Main-group metals interact with boron through s/p orbitals, resulting in either half-sandwich-type structures or substitutional structures. Transition metals are more versatile in bonding with boron, forming a variety of structures including half-sandwich structures, metal-centered boron rings, and metal-centered boron drums. Transition metal atoms have also been found to be able to be doped into the plane of 2D boron clusters, suggesting the possibility of metalloborophenes. Early studies of di-metal-doped boron clusters focused on gold, revealing ladder-like boron structures with terminal gold atoms. Recent observations of highly symmetric Ta2B6- and Ln2Bn- (n = 7-9) clusters have established a family of inverse sandwich structures with monocyclic boron rings stabilized by two metal atoms. The study of size-selected boron and doped-boron clusters is a burgeoning field of research. Further investigations will continue to reveal more interesting structures and novel chemical bonding, paving the foundation for new boron-based chemical compounds and nanomaterials.
由于其有趣的结构、键合以及作为新型纳米材料基序的潜力，近年来，尺寸选择的硼簇受到了极大的关注。特别是，硼簇阴离子（Bn-）使得光电子能谱和理论研究得以系统结合，揭示了主要为二维的结构。具有中心六边形空位的平面B36簇的发现为二维硼的可行性提供了首个实验证据，从而引出了硼烯的概念。B40笼状簇的发现揭示了类似富勒烯的硼簇（硼球烯）的存在。金属掺杂可以显著扩展硼簇的结构和键合种类。主族金属通过s/p轨道与硼相互作用，产生半夹心型结构或取代结构。过渡金属与硼键合的方式更为多样，形成包括半夹心结构、以金属为中心的硼环和以金属为中心的硼鼓等多种结构。还发现过渡金属原子能够掺杂到二维硼簇的平面中，这暗示了金属硼烯的可能性。早期对双金属掺杂硼簇的研究集中在金上，揭示了带有末端金原子的梯状硼结构。最近对高度对称的Ta2B6-和Ln2Bn-（n = 7 - 9）簇的观察建立了一类反夹心结构，其中单环硼环由两个金属原子稳定。对尺寸选择的硼和掺杂硼簇的研究是一个新兴的研究领域。进一步的研究将继续揭示更多有趣的结构和新型化学键，为新型硼基化合物和纳米材料奠定基础。
