Generation and Applications of the Hydroxide Trihydrate Anion, [OH(OH2)3]−, Stabilized by a Weakly Coordinating Cation

Abstract

The reaction of a strongly basic phosphazene (Schwesinger base) with water afforded the corresponding metastable hydroxide trihydrate [OH(OH2)3]− salt. This is the first hydroxide solvate that is not in contact with a cation and furthermore one of rare known water-stabilized hydroxide anions. Thermolysis in vacuum results in the decomposition of the hydroxide salt and quantitative liberation of the free phosphazene base. This approach was used to synthesize the Schwesinger base from its hydrochloride salt after anion exchange in excellent yields of over 97 %. This deprotonation method can also be used for the phosphazene-base-catalyzed preparation of the Ruppert–Prakash reagent Me3SiCF3 using fluoroform (HCF3) as the trifluoromethyl building block and sodium hydroxide as the formal deprotonation agent.