Tetravalent Oxygen and Sulphur Centres Mediated by Carborane Superacid: Theoretical Analysis

The tetravalent oxygen or sulphur centres, especially in H₄ O²⁺ and H₄ S²⁺ dications, were analysed experimentally and theoretically in various studies. Herein, we discuss stabilities of such centres in related H(CH₃ )₃ O²⁺ and H(CH₃ )₃ S²⁺ dications mediated by carborane superacid. The ωB97X-D/6-311++G(d,p) calculations were performed for a gas phase and for different solvents characterized by a wide range of dielectric constants for complexes of these dications with the conjugated base of H(CHB₁₁ F₁₁ ) carborane superacid, CHB₁₁ F₁₁^- , which indicate that these complexes are linked by hydrogen bonds. The Quantum Theory of 'Atoms in Molecules' (QTAIM) approach is applied to characterize these interactions. DFT results show that tetravalent oxygen and sulphur structures are additionally stabilized by polar solvents.