Comparison of the species formed upon base hydrolyses of gallium(III) and iron(III) aqueous solutions: the possibility of existence of an [FeO4Fe12(OH)24(H2O)12]7+ Polyoxocation

Abstract

The hydrolytic behaviour of iron(III) has been investigated. The infrared spectrum of the sulfate salt of a hydrolysed iron(III) solution was found to match that of a gallium sulfate that had been shown through magic angle spinning NMR spectroscopy in combination with powder X-ray diffraction studies to contain the Ga₁₃ ion. This supports the view that an [FeO₄Fe₁₂(OH)₂₄(H₂O)₁₂]⁷⁺ ion forms. It appeared, however, that this Fe₁₃ ion is extremely unstable and decomposes very rapidly in solution. The addition of small amounts of Fe¹¹ ions seems to stabilize the structure somewhat, however, and allowed it to be used as a clay mineral pillaring agent. The resulting d₀₀₁ spacing of ca. 19.3 Å is similar to that seen in similar studies of [GaO₄Ga₁₂(OH)₂₄(H₂O)₁₂]⁷⁺