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 rarely 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 behavior was used for the synthesis of the Schwesinger base with anion exchange resin from the hydrochloride salt 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 trifluoromethyl building block and sodium hydroxide as the formal deprotonation agent. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.