Synthesis and magnetic properties of new octahedral iron(II) complexes

The reaction of iron(II) acetate with the tetradentate Schiff base like ligands H(2)Ll ((E,E)-[{diethyl 2,2'-[1,2-phenylene-bis-(iminomethylidyne)]bis[3-oxobutanato]}]) and H2L2 ([([3,3']-[1,2-phenylenebis(iminomethylidyne)]bis(2,4-pentatne-dionato)(2-)- N,N',O2,O2']) in the presence of 1-meim (1-methylimidazole) or 2-meim (2-methylimidazole) leads to the formation of pentacoordinated or octahedral complexes depending on the used reaction conditions. Two pentacoordinated and four octahedral iron(II) complexes of the composition [FeL1(1-meim)(2)] (1), [FeL2(1-meim)] (2), [FeL2(1-meim)(2)] (3), [FeL2(1-meim)(2)](DMF) (3(DMF)), [FeL1(2-meim)](MeOH)(0.5) (4) and [FeL1(2-meim)(2)] (5) were isolated and structurally characterized. For the 2-meim complexes a hydrogen bond network between the imidazole N-H hydrogen and the carbonyl oxygen of the equatorial ligand is formed, while for the 1-meim derivatives only weak van der Waals interactions are observed. Magnetic measurements were performed on all samples. As expected, the pentacoordinated complexes remain in the high-spin state in the whole temperature range investigated. For the octahedral complexes, I and 5 are pure high-spin complexes while for 3 and 3(DMF) spin transition behaviour is observed.