Mechanism of formation of iron(ii) complexes with pentadentate ligandsvia C–C bond formation between trans-[Fe(2,4-bis(2-pyridylmethylimino)pentane)(MeCN)2][ClO4]2·MeCN and various nitriles

Abstract

The order of relative reactivity of nitriles for the formation of Fe(II) complexes (2s) with 3-(1-alkyl(or aryl)methyl)-1-imino-2,4-bis(2-pyridylmethylimine) (L²s) from that with 2,4-bis(2-pyridylmethylimono)pentane (L¹), trans-[FeL¹(MeCN)₂][ClO₄]₂·MeCN (1), and various nitriles has been determined based on the following order: C₆F₅CN > 3,4-difluorobenzonitrile > 4-fluorobenzonitrile > C₆H₅CN > C₆H₅CH₂CN > C₂H₅CN > MeCN > Me₂CHCN ≫ Me₃CN. An iron(II) complex with L¹ in a cis-configuration was prepared as the ternary complex [FeL¹(bpy)][ClO₄]₂·1.5MeNO₂·0.5H₂O, 3a (bpy = bipyridine). Compounds 2s and 3a undergo enantiomeric interconversion with an activation energy of ca. 60 kJ mol⁻¹.