Preparation and separation of asymmetric tripodal iron complexes of tren and selected aldehydes

Reaction of iron salts with the tripodal ligands formed from the condensation of tris-(2-aminoethyl)amine (tren) with the following mixtures of aldehydes, 2-pyridinecarboxaldehyde (py) and 6-methyl-2-pyridinecarboxaldehyde (6-CH3py), salicylaldehyde (sal) and 2-hydroxy-5-methylbenzaldehyde (5-CH3sal), salicylaldehyde and pyrrole-2-carboxaldehyde (pyr), and 4-methyl-5-imidazolecarboxaldehyde (4-CH3ImH) and salicylaldehyde yielded mixtures of all four possible iron complexes, [Fe(tren)LxL′y]z (x +y = 3), where L and L′ represent different aldehydes. Preliminary indication of mixtures of products was provided by IR and UV–Vis spectroscopy. Conclusive proof of the existence of all four components (x = 0–3) in each of the reaction mixtures is provided by mass spectroscopy. Separation of the [Fetren(sal)x(4-CH3ImH)y](ClO4)y mixture can be achieved using a Sephadex ion exchange column. Treatment of the two observed fractions with base yields greatly enriched [Fetren(sal)2(4-CH3Im)] and [Fetren(sal)(4-CH3Im)2], which were identified by mass spectroscopy.