Chemical bonding in electron-deficient boron oxide clusters: core boronyl groups, dual 3c–4e hypervalent bonds, and rhombic 4c–4e bonds

Abstract

We explore the structural and bonding properties of the electron-deficient boron oxide clusters, using a series of B₃O_n^−/0/+ (n = 2–4) clusters as examples. Global-minimum structures of these boron oxide clusters are identified via unbiased Coalescence Kick and Basin Hopping searches, which show a remarkable size and charge-state dependence. An array of new bonding elements are revealed: core boronyl groups, dual 3c–4e hypervalent bonds (ω-bonds), and rhombic 4c–4e bonds (o-bonds). In favorable cases, oxygen can exhaust all its 2s/2p electrons to facilitate the formation of B–O bonds. The current findings should help understand the bonding nature of low-dimensional boron oxide nanomaterials and bulk boron oxides.