Crystals of a (μ-oxo) (μ-formato) diiron(III) complex [Fe2(μ-O) (TPA)2( O2CH)] (C1O4)3 (1) formed from a methanolic solution of Fe(ClO4)3 and the tetradentate tripodal ligand tris(2-pyridylmethyl) amine (TPA) in methanol when left standing for days under aerobic conditions, despite the fact that no formate ion had been added to the solution. Complex 1 was found to have UV-Vis and 1H NMR properties very similar to those of [Fe2( μ-O) (TPA) 2 (O2CCH3)] (ClO4)3 (2), and its formula weight was corroborated by fast atom bombardment mass spectrometry. Complex 1 crystallized in the monoclinic space group P21 ( No. 4) with α = 11.693(3), b = 10.414(4), c = 18,144(6) Å, and β = 93.98(3)°. The structure was determined at - 84°C from 4464 out of a total of 6753 reflections with R = 0.058 and Rw = 0.068. The crystal structure confirmed the presence of a (μ-oxo) ( μ-carboxylato)diiron(III) unit with distinct iron sites as found for 2. The formate bridge was shown to derive from the aerobic oxidation of methanol: 1 was not formed in the absence of air, and 2 was formed from the reaction carried out in ethanol solvent. Manometric measurements showed that the amount of dioxygen consumed was approximately stoichiometric to the combined amounts of formate found in 1 (80%) and formaldehyde (20%) found in the reaction mixture.
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work was supported by a grant from the National Institutes of Health (Grant No. GM-38767).
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- Crystal structures
- Dinuclear complexes
- Iron complexes
- Oxo-bridged complexes