95674-15-0Relevant academic research and scientific papers
Structural and electronic properties of six-coordinate mixed aquo(imidazole)iron(III) schiff-base complexes. Crystal structure of [Fe(3-MeO-salen)(5-Ph-imd)(H2O)]BPh4
Kennedy, Brendan J.,Brain, Gavin,Horn, Ernst,Murray, Keith S.,Snow, Michael R.
, p. 1647 - 1653 (2008/10/08)
The first structurally characterized mixed aquo-imidazole axially ligated iron(III) chelate complexes are described. These cationic complexes contain a tetradentate Schiff-base ligand such as N,N′-ethylenebis(3-methoxysalicylaldimine) (i.e., S-MeO-salen2-) in the equatorial plane and have a tetraphenylborate counterion. Reasons are given for the preferred crystallization of the 1:1 Fe:imidazole adduct rather than the 1:2 adduct. A crystal structure determination of one example, [Fe(3-MeO-salen)(5-Ph-imd)(H2O)]BPh4·H 2O, shows that the iron atom is in the plane of the N2O2 donor set with axial distances of Fe-OH2 = 2.205 A? and Fe-N(imd) = 2.132 A?. The compound (C51H48BFeN4O5) crystallizes in the triclinic space group P1 with a = 13.290 (3) A?, b = 14.536 (4) A?, c = 14.673 (3) A?, α = 68.00 (2)°, β = 58.64 (2)°, γ = 69.54 (2)°, and Z = 2. The cationic complex molecules are held together as weakly bridged dimeric units via hydrogen bonding between the axial water and the phenoxo oxygen and methoxo oxygen of the Schiff base in the neighboring molecule. This interaction is detected in low-temperature susceptibility studies that display evidence for weak antiferromagnetic exchange interactions between the high-spin 6A1 iron(III) centers. A combination of variable-temperature susceptibilities and Mo?ssbauer effect and ESR spectroscopies has yielded values of the zero-field splitting parameter in these compounds. Finally, a brief comparison of the electronic and structural features of the present compounds is made with those of iron(III) hemes such as sperm whale metaquomyoglobin, which also possess aquo-imidazole ligation. Synthetic iron(III) porphyrins of this type are not yet known.
