[Fe(µ₂-OH)₆]^3- Linked Fe₃O Triads: Mössbauer Evidence for Trigonal µ₃-O^2- or µ₃-OH^- Groups in Bridged versus Unbridged Complexes

The syntheses, coordination chemistry, and Mössbauer spectroscopy of hepta-iron(III) complexes using derivatised salicylaldoxime ligands from two categories; namely, 'single-headed' (H₂L) and 'double-headed' (H₄L) salicylaldoximes are described. All compounds presented here share a [Fe₃-µ₃-O] core in which the iron(III) ions are µ₃-hydroxo-bridged in the complex C1 and µ₃-oxo-bridged in C2 and C3. Each compound consists of 2 × [Fe₃-µ₃-O] triads that are linked via a central [Fe(µ₂-OH)₆]^3- ion. In addition to the charge balance and microanalytical evidence, Mössbauer measurements support the fact that the triads in C1 are µ₃-OH bridged and are µ₃-O bridged in C2 and C3.