Synthesis, crystal structure and magnetic properties of three polynuclear manganese compounds bearing ferrocenecarboxylato ligands

The reactions of sodium ferrocenecarboxylate (FcCO2Na) and Mn(ClO4)2 · 6H2O in methanol in the presence of ancillary ligands of 1,10-phenanthroline (phen) or 2,2′-bipyridine (2,2′-bpy) produce three discrete polynuclear complexes bearing ferrocenecarboxylato ligands: [Mn2(FcCO2)3(phen)2](ClO4) · 2CH2Cl2 (1), [Mn3(FcCO2)6(2,2′-bpy)2] · 2H2O (2) and [Mn4O2(FcCO2)7(2,2′-bpy)2]ClO4 · 2CH2Cl2 · 6H2O (3). It is shown that their composition and skeletons are tuned by the ancillary ligands and the ratios of starting materials. In dimanganese complex 1, both Mn(II) ions are pentacoordinated in a distorted trigonal bipyramidal geometry and bridged by three ferrocenecarboxylato ligands in a distorted syn–syn bridging mode, which is rare in triply carboxylato-bridged dimanganese complexes. Compound 2 presents a linear trinuclear [Mn3(μ2-η1:η1-O2CFc)4(μ2-η1:η2-O2CFc)2] core, in which six ferrocencarboxylato ligands show two different bridging modes. The cationic Mn4O2 core of 3 has a butterfly structure, in which two Mn(III) ions at “body” sites are bridged by an additional ferrocenecarboxylato ligand and they are further connected to the Mn(III) ions at “wing-tip” sites by ferrocenecarboxylato ligands. Magnetic susceptibilities of 1 and 2 were measured. Both of them mediate a weak antiferromagnetic coupling between the Mn(II) ions bridged by ferrocenecarboxylato ligands.