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Issue 15, 1996
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A FeIIIO4N2 co-ordination sphere assembled via an enolate–imine–amide ligand. Effect of amide protonation on the redox behaviour and stereochemistry of the iron(III) centre

Abstract

The reaction of anhydrous FeCl3, acetylacetone benzoylhydrazone (H2L) and KOH (1 : 2 : 3 mole ratio) in methanol produced an iron(III) complex, [FeL(HL)]1, the crystal structure of which was determined. Each ligand binds through enolate O, imine N and amide O atoms in meridional fashion. In the dianionic L both the enolic OH and the amide protons are dissociated, whereas in the monoanionic HL only the enolic OH is deprotonated. Addition of 1 equivalent of HClO4 to 1 in MeOH gave [Fe(HL)2]ClO42. Similarly reaction of 1 equivalent of KOH with 1 yielded K[FeL2]3. All the complexes were characterized by analytical, spectroscopic, electrochemical and magnetic measurements. The metal centre in 1 is redox inactive. However, in cyclic voltammetric experiments 2 displayed FeIII→ FeII reduction at –0.21 V and for 3 an oxidation at 0.40 V (vs. saturated calomel electrode) was observed due to FeIII→ FeIV oxidation. Magnetic moments (at 298 K) of the three complexes reflect a S= 5/2 spin state in each. The ESR spectra (at 298 K) of polycrystalline 1 and 2 are rhombic. On the other hand, an ideal axial spectrum was observed for 3.

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Article type: Paper
DOI: 10.1039/DT9960003293
Citation: J. Chem. Soc., Dalton Trans., 1996,0, 3293-3296
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    A FeIIIO4N2 co-ordination sphere assembled via an enolate–imine–amide ligand. Effect of amide protonation on the redox behaviour and stereochemistry of the iron(III) centre

    N. R. Sangeetha, C. K. Pal, P. Ghosh and S. Pal, J. Chem. Soc., Dalton Trans., 1996, 0, 3293
    DOI: 10.1039/DT9960003293

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