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

The iron(III) complex of the Schiff base formed from the condensation of 1 equiv. of tris(2-aminoethyl)amine (tren) and 3 equiv. of 4-methyl-5-imidazolecarboxaldehyde has been synthesized by the reaction of iron(III) methoxide, tren and 4-methyl-5-imidazolecarboxaldehyde in methanol. Fetren(meim)(3) is low spin as indicated by magnetic moment, Mossbauer and ESR measurements. The crystal structure of Fetren(meim)3 was determined (space group Pna2(1), R-1 = 0.0331 and wR(2) = 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 ii-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. (C) 1998 Elsevier Science S.A. All rights reserved.