Inorganic Chemistry, Vol.34, No.22, 5403-5404, 1995
A Crystalline (H9O4)(+) Hydronium Ion Salt with a Weakly Coordinating Anion
The crystalline salt [H9O4][CB11H6Br6] is a weighable Bronsted acid reagent with precisely defined solvation of the hydronium ion. The X-ray structure is a rare example of discrete H9O4+ cations. It shows the essential structural features proposed by Eigen some 40 years ago for the hydronium ion in liquid water and is properly formulated as the trigonal-pyramidal [H3O(H2O)(3)](+) ion.