Assembly of a mononuclear ferrous site using a bulky aldehyde-imidazole ligand

Abstract

A new iron(II) complex has been prepared and characterized. [Fe(TrImA)2(OTf)2] (1, TrImA = 1-Tritylimidazole-4-carboxaldehyde). The solid state structure of 1 has been determined by X-ray crystallography. Compound 1 crystallizes in monoclinic space group P21/c, with a = 10.8323(18) Å, b = 8.1606(13) Å and c = 24.818(4) Å. The iron center is coordinated to two imidazole groups, two pendant aldehyde-derived carbonyl oxygens and two triflate oxygens. The complex is high spin between 300 and 20 K as indicated by variable field variable temperature magnetic measurements. A fit of the magnetic data yielded g = 2.17 and D = 4.05 cm−1. A large HOMO-LUMO gap energy (4.49 eV) exists for 1 indicating high stability.

Generation and Stability of the gem-Diol Forms in Imidazole Derivatives Containing Carbonyl Groups. Solid-State NMR and Single-Crystal X-ray Diffraction Studies

“…Taking into account these results, it can be postulated that the lower reactivity of the aldehyde group in A 3 toward the addition of water would explain why in copper, cadmium, zinc, and cobalt complexes the formyl group remains unhydrated. , The same results have been obtained for a complex of zinc­(II) and A 4 . An iron­(III) complex was also reported with a new 4-imidazolecarboxaldehyde ligand in which the formyl group was not altered . In contrast, the aldehyde group is hydrated to the gem -diol form in ruthenium­(III) complexes with 2-imidazolecarboxaldehyde ( A 1 ) molecules in the solution state …”

“…23 An iron(III) complex was also reported with a new 4-imidazolecarboxaldehyde ligand in which the formyl group was not altered. 41 In contrast, the aldehyde group is hydrated to the gem-diol form in ruthenium-(III) complexes with 2-imidazolecarboxaldehyde (A 1 ) molecules in the solution state. 22 To demonstrate that the second position of the imidazole ring is particularly effective for the generation of gem-diol derivatives when the carbonyl group is present in this position, other aromatic compounds were analyzed (Table 1 and Supporting Information).…”