Eight-co-ordination in manganese(II) and iron(II) complexes with a pyrazole-functionalised tetraazamacrocycle

Abstract

The potentially octadentate ligand 1,4,7,10-tetrakis(pyrazol-1-ylmethyl)-1,4,7,10-tetraazacyclododecane (L) gives with manganese(II) the complex [MnL][PF₆]₂·(CH₃)₂CO and with iron(II) species of formula [FeL_xL'_1–x][PF₆]₂·solvent where the ligand L' originates from L by substitution of an ethoxy group for a pyrazolyl group in one of the pendant arms of the macrocycle. The crystal structure of [MnL][PF₆]₂·(CH₃)₂CO has been determined by X-ray diffraction: orthorhombic, space group Pcab, with a= 15.801(6), b= 17.973(4), c= 26.793(3)Å and Z= 8. The manganese(II) atom is co-ordinated by the eight nitrogen atoms of the L ligand. X-Ray analyses on the isomorphous crystals of the iron(II) species have shown that these contain both eight- and seven-co-ordinate iron(II) in complex cations respectively formed by the L and L' ligands.