Iron complexes of terdentate nitrogen ligands: formation and X-ray structure of three new dicationic complexes

Abstract

Dicationic iron complexes were obtained upon complexation of the ligands 6,6″-di( p-tolyl)-2,2′:6′,2″-terpyridine (L 1) or 2,6-bis-(3-mesitylpyrazol-1-yl)pyridine (L 2) with iron dichloride or iron trichloride. They were characterized by X-ray diffraction and FT-IR spectroscopy. Single crystal structure determinations of ( L 1 ) 2 Fe 2 + ( FeCl 4 - ) 2 , ( L 2 ) 2 Fe 2 + FeCl 4 2 - and ( L 2 ) 2 Fe 2 + ( FeCl 4 - ) 2 ( THF ) 4 all show six-coordinate metal center. These complexes were obtained from L 1FeCl 2 and L 2FeCl 2 during recrystallization attempts. (L 1) 2Fe 2+ was shown to be a high-spin complex, whereas (L 2) 2Fe 2+ was shown to be low-spin. For ( L 2 ) 2 Fe 2 + FeCl 4 2 - , two independent dications of very similar geometry but with distinctive distortion were observed by X-ray analysis.