Guest driven rearrangements of protonation and hydrogen bonding in decavanadate anions as their tetraalkylammonium salts

Abstract

Single crystal X-ray structure determinations of [(n-C₅H₁₁)₄N]₃[H₃V₁₀O₂₈]·2(CH₃)₂CO (TAA-acetone), [(n-C₅H₁₁)₄N]₈[H₃V₁₀O₂₈]₂[H₄V₁₀O₂₈]·7C₄H₈O₂ (TAA-dioxane), [(n-C₅H₁₁)₄N]₃[H₃V₁₀O₂₈] (TAAh) and [(n-C₆H₁₃)₄N]₂[H₄V₁₀O₂₈]·4C₄H₈O₂ (THA-dioxane) revealed that protonation and hydrogen bond formation of decavanadate anions in their tetraalkylammonium salts are influenced by the nature of the solvent molecules incorporated as guests into the crystals. When crystallized with acetone molecules, the decavanadate anion forms a self-associated hydrogen-bonded dimer of {[H₃V₁₀O₂₈]³⁻}₂ to hide the protons from the aprotic protophobic acetone molecules. When crystallized with 1,4-dioxane molecules, the decavanadate anion exposes its protons to the aprotic protophilic 1,4-dioxane molecules to form a hydrogen-bond assisted solvation complex of {(C₄H₈O₂)₄⋯[H₄V₁₀O₂₈]²⁻}. Size effects of the tetraalkylammonium cations on crystallizing these hydrogen-bonded assemblies were also examined.