Manganese(II) and Iron(III) Complexes of the Tridentate Ligands Bis(benzimidazol-2-ylmethyl)-amine (L1) and -methylamine (L2). Crystal Structures of 1(CH3CO2)2>, 2Cl3>, and 12(μ-O)2>2

Article abstract of DOI:10.1039/DT9900001727

The preparation and characterisation of 1(CH3CO2)2> (1), (9), 1Cl3> (10), 2Cl3> (2), and 12(μ-O)<μ-(CH3)3CCO2>2>2 (3) are reported where L¹ and L² are bis(benzimidazol-2-ylmethyl)amine and bis(benzimidazol-2-ylmethyl)methylamine.The molecular structures of (1), (2), and (3) were determined by X-ray diffraction.Complex (1) exists as a discrete, neutral, mononuclear species in the solid state.The manganese(II) ion is five-coordinate with the tridentate ligand bound in a meridional manner.Both acetates are monodentate with Mn-O distances of 2.076(5) and 2.158(5) Angstroem.Complex (9) contains a ¹⁰⁺ core, formally 4Mn^II:2Mn^III.Complex (2) is neutral, mononuclear, distorted octahedral.The ligand co-ordinates in a similar manner to that seen in (1) and the chlorides occupy the three remaining meridional sites, with Fe-Cl(equatorial) 2.318(5) Angstroem and Fe-Cl(axial) 2.322(5) and 2.433(5) Angstroem.The Moessbauer spectrum of (10) at room temperature comprises a quadrupole doublet: δ= 0.40(1), ΔE_Q= 0.33(2) mm s^-1.Complex (3) is a dinuclear iron(III) species containing the triply bridged ²⁺ core.The Fe...Fe distance is 3.075(5) Angstroem and the Fe-O(oxo)-Fe angle is 117.0(6) deg.The high-spin iron(III) centres are antiferromagnetically coupled with J= -116 cm^-1.The Moessbauer spectra of (3) at room temperature and 70 K consist of doublets with δ= 0.44(1), ΔE_Q= 1.37(2), and δ= 0.55(1), ΔE_Q= 1.30(2) mm s^-1 respectively.