Manganese(II/II/II) and Manganese(III/II/III) Trinuclear Compounds. Structure and Solid and Solution Behavior

Two mixed-valence MnIIIMnII complexes and a homo-valence MnII trinuclear manganese complex of stoichiometry MnIIIMnIIMnIII(5-Cl-Hsaladhp)2(AcO)4(MeOH)2·4CH3OH (1a), MnIIIMnIIMnIII (Hsaladhp)2(AcO)2(5-Cl-Sal)2(thf)2 (3a) and MnIIMnIIMnII (AcO)6(pybim)2 (1b) where H3saladhp is a tridentate Schiff base ligand and pybim a neutral bidentate donor ligand, have been structurally characterized by using X-ray crystallography. The structurally characterized mixed-valence complexes have strictly 180° MnIII−MnII−MnIII angles as required by crystallographic inversion symmetry. The complexes are valence trapped with two terminal MnIII ions showing Jahn-Teller distortion along the acetate or salicylate−MnIII−X axis. The Mn···Mn separation is 3.511 Å and 3.507 Å respectively. The mixed-valence complexes have S = 3/2 ground state and the homovalence complex S = 5/2, with small antiferromagnetic exchange J couplings, −5.6 and −1.8 cm-1, respectively, while the powder ESR spectra at 4 K show a broad low field signal with g ≈ 4.3 for MnIIIMnIIMnIII and a broad temperature-dependent signal at g = 2 for MnIIMnIIMnII. Crystal data for 1a: [C36H60O20N2Cl2Mn3], triclinic, space group P1̄, a = 9.272(7) Å, b = 11.046(8) Å, c = 12.635(9) Å, α = 76.78(2)°, β = 81.84(2)°, γ = 85.90(2)°, Z = 1. Crystal data for 3a: [C48H56O18N2Cl2Mn3], monoclinic, space group P21/n, a = 8.776(3) Å, b = 22.182(7) Å, c = 13.575(4) Å, β = 94.44(1)°, Z = 2. Crystal data for 1b: [C36H36O12N6Mn3], triclinic, space group P1̄, a = 13.345(6) Å, b = 8.514(4) Å, c = 9.494(4) Å, α = 75.48(1)°, β = 75.83(1)°, γ = 76.42(1)°, Z = 1.