X-ray structure and magnetic properties of dinuclear and polymer iron(II) complexes

Five new octahedral iron(II) complexes [FeL2(4-dpa)]n (EtOH) (1), [FeL2(bipy)]n (DMF) (2), [FeL1(bpee)]n (3), [Fe2L3(1-meim)4](1-meim)4 (4) and [FeL1(DMAP)2] (5), with L1 and L2 being tetradentate View the MathML sourceN2O22- coordinating Schiff base like ligands (L1 = (E,E)-[{diethyl-2,2′-[1,2-phenylenebis(iminomethylidyne)]bis[3-oxobutanato](2-)-N,N′,O3,O3′}, L2 = (3,3′)-[{1,2-phenylenebis(iminomethylidyne)]bis(2,4-pentane-dionato)(2-)-N,N′,O2,O2′}) and L3 being a octadentate dinucleating View the MathML sourceN2O22- coordinating Schiff base like ligand ({tetraethyl-(E,E,E,E)-2,2′,2′′,2′′′-[1,2,4,5-phenylentetra(iminomethylidine)]tetra[3-oxobutanoato](2-)-N,N′,N′′,N′′′,O3,O3′,O3′′,O3′′′}); 4-dpa = di(4-picolyl)-amine, bipy = 4,4′-bipyridine, bpee = trans-1,2-bis(4-pyridyl)ethylene, 1-meim = 1-methylimidazole and DMAP = 4-dimethylaminopyridine, have been synthesized and characterised using X-ray structure analysis and T-dependent susceptibility measurements. Both methods indicate that all iron(II) centres are in the paramagnetic high-spin state over the whole temperature range investigated. The O–Fe–O angle, the so called bit of the equatorial ligand, is with an average of 111° in the region typical for high-spin iron(II) complexes of this ligand type. In the case of compound 1 an infinite two-dimensional hydrogen bond network can be found, for the compounds 2–4 no hydrogen bond interactions are observed between the complex molecules. A comparison of the curve progression obtained from the magnetic measurements of the mononuclear complex 5 and the polymeric complexes 1–3 leads to the conclusion that no magnetic interactions are mediated over the bridging axial ligands. For the dinuclear complex 4 weak antiferromagnetic interactions between the two iron centres are found.