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

Abstract

The reactions of sodium ferrocenecarboxylate (FcCO 2Na) and Mn(ClO 4) 2 · 6H 2O 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: [Mn 2(FcCO 2) 3(phen) 2](ClO 4) · 2CH 2Cl 2 ( 1), [Mn 3(FcCO 2) 6(2,2′-bpy) 2] · 2H 2O ( 2) and [Mn 4O 2(FcCO 2) 7(2,2′-bpy) 2]ClO 4 · 2CH 2Cl 2 · 6H 2O ( 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 [Mn 3(μ 2-η 1:η 1-O 2CFc) 4(μ 2-η 1:η 2-O 2CFc) 2] core, in which six ferrocencarboxylato ligands show two different bridging modes. The cationic Mn 4O 2 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.