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-CH(3)sal), salicylaldehyde and pyrrole-2-carboxaldehyde (pyr), and 4-methyl-5-imidazole-carboxaldehyde (4-CH(3)ImH) and salicylaldehyde yielded mixtures of all four possible iron complexes, [Fe(tren)LxLy'](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-CH(3)ImH)(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-CH(3)Im)] and [Fetren(sal)(4-CH(3)Im)(2)], which were identified by mass spectroscopy. (C) 2004 Elsevier B.V. All rights reserved.