2,6-bis(pyrazol-3-yl)pyridine as meridional capping ligand: Synthesis, characterization, and crystal structure of the first corresponding hexanuclear iron(III) complex

Abstract

Based on the 2,6-bis(pyrazol-3-yl)pyridine ligand (H2bpp) the hexanuclear iron(III) complex [Fe6(bpp)4(μ3- O)2(μ-OMe)3(μOH)Cl2] (1) was synthesized. The reaction with iron(II) chloride and additional pyridine leads to the exclusive formation of the complex through self-assembly process. Six octahedrally coordinated iron atoms are linked through the pyrazolido groups of four H2bpp ligands. These are further linked through bridging hydroxido, methoxido, and oxido groups. The complex has been characterized by IR spectroscopy, ESI mass spectrometry, elemental analysis and X-ray crystallography. Temperature-dependent magnetic measurements indicate strong antiferromagnetic exchange interaction between the high-spin iron(III) ions within, the complex, which leads to an S = 0 spin, ground state. As a result of the two Fe3(μ3-O) fragments two frustrated exchange pathways are present. In addition the properties of H2bpp as a potential capping ligand for the synthesis of heteroleptic trinuclear complexes based on the triaminoguanidine core is investigated. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.