Two new coordination polymers containing the triangular [Mn3O(O2CR)6]0/+ units

Abstract

The preparation and crystal structures of two linear chain compounds of oxo-centered triangular Mn clusters are reported. {[Mn4O(O2CMe)8(py)] · 2MeCN}∞ (1 · 2MeCN)∞ was formed when a concentrated solution of [Mn3O(O2CMe)6(py)3] · py in MeCN was left undisturbed at room temperature for several weeks. The repeating unit of the chain polymer (1 · 2MeCN)∞ consists of an oxo-centered trinuclear [Mn3O]6+ unit linked to a MnII center through μ- and μ3-O2CMe ligands. {[Mn3O(O2CPh)7(4,4′-bpy)] · 3H2O}∞ (2 · 3H2O)∞ was prepared by reductive aggregation of NBu4n MnO4 in MeOH/benzoic acid in the presence of 4,4′-bipyridine. The structure consists of chains of [Mn3O(O2CPh)7(4,4′-bpy)] units. The one-dimensional chains are linked into 2D networks by π-stacking interactions between benzoate phenyl rings. Variable-temperature, solid-state dc magnetic susceptibility studies revealed the existence of antiferromagnetic exchange interactions within (1 · 2MeCN)∞. Complex (2 · 3H2O)∞, exhibits two different exchange couplings within its repeating unit and negligible intercluster interactions. The intracluster interactions stabilize an S = 2 ground state, but due to the topology of the cluster, two different parameter sets successfully reproduced the experimental data, i.e. J = 2.8 cm-1, J′ = -22.5 cm-1 (A) and J = -22.2 cm-1, J′ = 2.6 cm-1 (B). © 2008 Elsevier B.V. All rights reserved.