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.