Syntheses, crystal structures, and magnetic properties of the oxalato-bridged mixed-valence complexes (FeII(bpm)3]2[FeIII2(ox)5].8H2O and FeII(bpm)3Na(H2O)2Fe(ox)(3).4H2O (bpm = 2,2'-bipyrimidine).

The preparation and crystal structures of two oxalato-bridged FeII−FeIII mixed-valence compounds, [FeII(bpm)3]2[FeIII2(ox)5]·8H2O (1) and FeII(bpm)3Na(H2O)2FeIII(ox)3·4H2O (2) (bpm = 2,2‘-bipyrimidine; ox = oxalate dianion) are reported here. Complex 1 crystallizes in the triclinic system, space group P1, with a = 10.998(2) A, b = 13.073(3) A, c = 13.308(3) A, α = 101.95(2)°, β = 109.20(2)°, γ = 99.89(2)°, and Z = 1. Complex 2 crystallizes in the monoclinic system, space group P21/c, with a = 12.609(2) A, b = 19.670(5) A, c = 15.843(3) A, β = 99.46(1)°, and Z = 4. The structure of complex 1 consists of centrosymmetric oxalato-bridged dinuclear high-spin iron(III) [Fe2(ox)5]2- anions, tris-chelated low-spin iron(II) [Fe(bpm)3]2+ cations, and lattice water molecules. The iron atoms are hexacoordinated:  six oxygen atoms (iron(III)) from two bidentate and one bisbidentate oxalato ligands and six nitrogen atoms (iron(II)) from three bidentate bpm groups. The Fe(III)−O(ox) and Fe(II)−N(bpm) bond distances var...