Solvation and reactivity of a helical binuclear iron(II) complex with a tetradentate Schiff-base ligand

Reaction of 2-acetylpyridine, hydrazine, and an iron(II) salt gives a low-spin binuclear iron( II) complex, [Fe-2(pmk)(3)](4+), in which three tetradentate Schiff base ligands span the two metal centres to give a complex of helical geometry. We report solubilities of the iodide and perchlorate salts, in H2O, in aqueous MeOH, and in aqueous DMSO ( perchlorate only), up to 60% by vol of organic cosolvent. Transfer chemical potentials for the complex cation from H2O into the respective mixed solvents have been derived from these solubilities, to give a picture of solvation of this complex in the media studied. Kinetics of base hydrolysis of [Fe-2( pmk)(3)](4+) have been established, in H2O and in 40% MeOH, 20 and 40% i-PrOH, and 20 and 40% DMSO, at 298.2 K. The reactivity of [Fe-2(pmk)(3)](4+) is discussed in relation to reactivities of a selection of iron( II)-diimine complexes, ranging from [Fe(bipy)(3)](2+) and [Fe( phen)(3)](2+) to ligand-encapsulated cage complexes.