Synthesis and characterization of a neutral, low spin iron(III) complex of a hexadentate tripodal ligand containing three imidazolate arms. Use as a dinucleating agent

Abstract

The iron(III) complex of the Schiff base formed from the condensation of 1 equiv. of trist(2-aminoethyl)amine (tren) and 3 equiv. of 4-methyl-5-imidazolecar☐aldehyde has been synthesized by the reaction of iron(III) methoxide, tren and 4-methyl-5-imidazolecar☐aldehyde in methanol. Fetren(meim)₃ is low spin as indicated by magnetic moment, Mo¨ssbauer and ESR measurements. The crystal structure of Fetren(meim)₃ was determined (space group Pna2₁, R₁ = 0.0331 and wR₂ = 0.0857). The complex is six-coordinate although the ligand is potentially heptadentate. Basicity of the three ‘backside’ imidazolate nitrogens is demonstrated in the crystal structure by H-bonding interactions and in solution by reactions with acidic metal complexes. ZnTPP and M(hfa)₂ (M = Cu(II), Ni(II)), to give imidazolate bridged adducts. Products of the reaction of Fetren(meim)₃ with M(hfa)₂ were isolated and identified as the 1:1 adducts.