Kinetics of ligand exchange in iron(II) complexes of 2,3,9,10-tetramethyl-1,4,8,11-tetra-azacyclotetradeca-1,3,8,10-tetraene

Abstract

Variable-temperature ¹H n.m.r. lineshape analysis has been used to determine the kinetics of axial ligand exchange in some iron(II) complexes of 2,3,9,10-tetramethyl-1,4,8,11-tetra-azacyclotetradeca-1,3,8,10-tetraene (L¹). Exchange rates on FeL¹ follow the order 2-methylimidazole 1-methylimidazole ≃ imidazole. Rates of 1-methyl-imidazole exchange show cis effects of the order tetraphenylporphinate L¹ > tetrabenzo[b,f,j,n][1,5,9,13]tetra-azacyclohexadecine ∼ bis[dimethylglyoximate(1–)]∼ phthalocyaninate(2–), which are interpreted in terms of σ and π bonding and the hole size of the macrocycle.