Rg_nBe₃B₃⁺: theoretical investigation of Be₃B₃⁺ and its rare gas capability

A series of Be₃B₃⁺ and its rare gas (Rg) containing complexes Rg_nBe₃B₃⁺ (Rg = He-Rn, n = 1-6) have been predicted theoretically using the B3LYP, MP2, and CCSD(T) methods to explore structures, stability, charge distributions, and nature of bonding. Both Be₃B₃⁺ and RgBe₃B₃⁺ are the global minima on the potential energy surfaces. In the Rg_nBe₃B₃⁺ complexes, the dissociation energy drops with the increase in number of Rg. Natural bond orbital (NBO) and topological analysis of the electron density (AIM) show that the Rg-Be bonds for Kr-Rn have some covalent character. The Rg-Be bond is stabilized dominantly by the Rg → Be₃B₃⁺ σ-donation from the valence p orbital of Rg to the vacant valence LUMO orbital of Rg_n-1Be₃B₃⁺. Besides, other two π-donations also play important roles in stabilizing the Rg-Be bonds.