Variable temperature proton chemical shifts of aqueous beryllium salt solutions

Abstract

Proton chemical shifts have been measured in ∼1 mol kg^–1 aqueous solutions of beryllium nitrate and chloride from 0 to 100°C. The results can be interpreted as arising from rapid proton exchange between bulk water and water in three ionic environments; the cationic complex Be(H₂O)²⁺₄ with effectively a temperature independent shift, a second hydration sphere oriented sufficiently by the electric field of the ion to have a small low field chemical shift, and water near the anions which has an upfield shift due to some structural effect. That a known tetrahydrated cation gives results which are consistent with a primary hydration number of four, is a key result and gives strong support to the contention, based on similar results obtained with M^I cations, that these are also tetrahyrated.