Composition, structure and IR spectra peculiarities of proton hydratosolvates H+(H2O)NLpformed in tributylphosphate solutions of strong acid HFeCl4

Abstract

Stepwise formation of several H⁺· NH₂O · pTBP proton hydrates in tributylphosphate (TBP) solutions of HFeCl₄ has been studied under a slight, disturbing action of unsolvated FeCl₄^- anions. As the basic properties of TBP and H₂O molecules are comparable, consecutive proton hydration in the liquid phase takes place under conditions where proton hydrates interact with surrounding TBP molecules with the same strength as with water molecules. Symmetric and asymmetric trisolvates of hydroxonium ion [H₃O⁺· 3TBP], dihydratosolvate [H₅O₂⁺· 4TBP], dimer {[H₅O₂⁺ · µH₂O · 2TBP] · 2TBP}₂ and associates {[H₅O₂⁺· 2H₂O · 2TBP] · 2TBP · nH₂O}_p, where n=0–2.5 (N=4–6.5), have been found to form. The associates containing H₅O₂⁺ as a structural unit have characteristic IR bands. A profile of continuous background absorption (cba) free from other absorption bands has been obtained for the first time. This absorption appeared to be extended, its intensity rising almost proportionally to the frequency decrease in the 3000–1000 cm^-1 interval and attaining a maximum at ca. 1000–220 cm^-1. Cba is observed in IR spectra of those cations whose H₅O₂⁺ ions are bound with water molecules and are associated.