AUTHOR=Gao Shu-Juan , Guo Jin-Chang , Zhai Hua-Jin 

TITLE=Boron Oxide B5O6− Cluster as a Boronyl-Based Inorganic Analog of Phenolate Anion

JOURNAL=Frontiers in Chemistry

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2022.868782

DOI=10.3389/fchem.2022.868782

ISSN=2296-2646

ABSTRACT=<p>Boron oxide clusters have structural richness and exotic chemical bonding. We report a quantum chemical study on the binary B<sub>5</sub>O<sub>6</sub><sup>−</sup> cluster, which is relatively oxygen-rich. A global structural search reveals planar <italic>C</italic><sub>2<italic>v</italic></sub> (<sup>1</sup>A<sub>1</sub>) geometry as the global minimum structure, featuring a heteroatomic hexagonal B<sub>3</sub>O<sub>3</sub> ring as its core. The three unsaturated B sites are terminated by two boronyl (BO) groups and an O<sup>−</sup> ligand. The B<sub>5</sub>O<sub>6</sub><sup>−</sup> cluster can be faithfully formulated as B<sub>3</sub>O<sub>3</sub>(BO)<sub>2</sub>O<sup>−</sup>. This structure is in stark contrast to that of its predecessors, <italic>C</italic><sub><italic>s</italic></sub> B<sub>5</sub>O<sub>5</sub><sup>−</sup> and <italic>T</italic><sub><italic>d</italic></sub> B<sub>5</sub>O<sub>4</sub><sup>−</sup>, both of which have a tetrahedral B center. Thus, there exists a major structural transformation in B<sub>5</sub>O<sub><italic>n</italic></sub><sup>−</sup> series upon oxidation, indicating intriguing competition between tetrahedral and heterocyclic structures. The chemical bonding analyses show weak 6π aromaticity in the B<sub>5</sub>O<sub>6</sub><sup>−</sup> cluster, rendering it a boronyl analog of phenolate anion (C<sub>6</sub>H<sub>5</sub>O<sup>−</sup>) or boronyl boroxine. The calculated vertical detachment energy of B<sub>5</sub>O<sub>6</sub><sup>−</sup> cluster is 5.26 eV at PBE0, which greatly surpasses the electron affinities of halogens (Cl: 3.61 eV), suggesting that the cluster belongs to superhalogen anions.</p>