Sc@B, Ti@B, V@B, and V@B: Spherically Aromatic Endohedral Seashell-like Metallo-Borospherenes.

Transition-metal-doped boron nanoclusters exhibit unique structures and bonding in chemistry. Using the experimentally observed seashell-like borospherenes B and B as ligands and based on extensive first-principles theory calculations, we predict herein a series of novel transition-metal-centered endohedral seashell-like metallo-borospherenes Sc@B (), Ti@B (), V@B (), and V@B () which, as the global minima of the complex systems, turn out to be the boron analogues of dibenzenechromium Cr(CH) with two B ligands on the top and bottom interconnected by four or five corner boron atoms on the waist and one transition-metal "pearl" sandwiched at the center in between. Detailed molecular orbital, adaptive natural density partitioning (AdNDP), and iso-chemical shielding surface (ICSS) analyses indicate that, similar to Cr(CH), these endohedral seashell-like complexes follow the 18-electron rule in bonding patterns (1S1P1D), rendering spherical aromaticity and extra stability to the systems.

Perfect Core-Shell Octahedral B@B , Be@B , and Zn@B with an Octa-Coordinate Center as Superatoms Following the Octet Rule.

The front cover artwork is provided by Prof. Si-Dian Li's group at Shanxi University, China. The image shows the smallest perfect core-shell octahedral borospherene O B@B and its endohedral metallo-borospherene analogs O Be@B and O Zn@B obtained at first-principles theory.

Perfect Core-Shell Octahedral B@B , Be@B , and Zn@B with an Octa-Coordinate Center as Superatoms Following the Octet Rule.

Planar, tubular, cage-like, and bilayer boron clusters B (n=3∼48) have been observed in joint experimental and theoretical investigations in the past two decades. Based on extensive global searches augmented with first-principles theory calculations, we predict herein the smallest perfect core-shell octahedral borospherene O B@B (1) and its endohedral metallo-borospherene analogs O Be@B (2), and O Zn@B (3) which, with an octa-coordinate B, Be or Zn atom located exactly at the center, turn out to be the well-defined global minima of the systems highly stable both thermodynamically and dynamically. B@B (1) represents the first boron-containing molecule reported to date which contains an octa-coordinate B center covalently coordinated by eight face-capping boron atoms at the corners of a perfect cube in the first coordination sphere.

Boron-lead multiple bonds in the PbBO and PbBO clusters.

Despite its electron deficiency, boron can form multiple bonds with a variety of elements. However, multiple bonds between boron and main-group metal elements are relatively rare. Here we report the observation of boron-lead multiple bonds in PbBO and PbBO, which are produced and characterized in a cluster beam.

A bottom-up approach from medium-sized bilayer boron nanoclusters to bilayer borophene nanomaterials.

Inspired by the experimentally observed bilayer B and theoretically predicted bilayer B-B and based on extensive density functional theory calculations, we report herein a series of novel medium-sized bilayer boron nanoclusters B (I), B (II), B (III), B (IV), B (V), B (VI), B (VII), and B (VIII) which are the most stable isomers of the systems reported to date effectively stabilized by optimum numbers of interlayer B-B σ bonds between the inward-buckled atoms on top and bottom layers. Detailed bonding analyses indicate that these bilayer species follow the universal bonding pattern of σ + π double delocalization, rendering three-dimensional aromaticity in the systems. More interestingly, the AA-stacked bilayer structural motif in B (VII) with a B bilayer hexagonal prism at the center can be extended to form bilayer B (IX), B (X), B (XI), B (XII), and B (XIII) which contain one or multiple conjoined B bilayer hexagonal prisms sharing interwoven zig-zag boron triple chains between them.

Predicting bilayer B, B, B, and B: structural evolution in bilayer B-B clusters.

The successive experimental observations of planar, cage-like, seashell-like, and bilayer B clusters in the size range between n = 3-48 well demonstrate the structural diversity and rich chemistry of boron nanoclusters. Based on extensive global minimum search and density functional theory calculations, we predict herein the bilayer C B (I), C B (II), C B (IV), and C B (V) as the global minima of the systems to fill in the missing gap in the bilayer B series between B-B. These highly stable species all contain a B bilayer hexagonal prism at the center, with 2, 2, 3, and 3 effective interlayer B-B σ-bonds formed between inward-buckled atoms on the top and bottom layers, respectively.