Iron complexes of pyridylimidazole derivatives

Abstract

Complexes of iron(II) with 2-(2-pyridyl)benzimidazole (pbi) and 2-(6- methyl-2-pyridyl)benzimidazole (mpbi) have been characterized. [Fe(pbi)3] [BF₄]₂ undergoes a temperature-induced spin transition the course of which is determined by the extent of hydration. [Fe(mpbi)₃] [ClO₄]₂ is high-spin and the differences in the properties of the two complexes are correlated with electronic spectral data. [Fe(pbi)2(CN)₂] is low-spin. Iron(III) complexes of deprotonated pbi and 2-(2- pyridyl)imidazole (pyim), [Fe(pbi-H)₃] and [Fe(pyim-H)₃], result when the cationic iron(II) complexes are treated with base. Magnetic and Mossbauer effect data show that these complexes, which display strong π → t₂ charge-transfer absorption, are low-spin.