Cluster-Based Networks: 1D and 2D Coordination Polymers Based on {MnFe2(μ3-O)}-Type Clusters

A straightforward approach to heterometallic Mn–Fe cluster-based coordination polymers is presented. By employing a mixed-valent μ3-oxo trinuclear manganese­(II/III) pivalate cluster, isolated as [MnIIMnIII2O­(O2CCMe3)6(hmta)3]·(solvent) (hmta = hexamethylenetetramine; solvent = n-propanol (1), toluene (2)) in the reaction with a μ3-oxo trinuclear iron­(III) pivalate cluster compound, [Fe3O­(O2CCMe3)6(H2O)3]­O2CCMe3·2Me3CCO2H, three new heterometallic {MnIIFeIII2} cluster-based coordination polymers were obtained: the one-dimensional polymer chain compounds {[MnFe2O­(O2CCMe3)6(hmta)2]·0.5MeCN}n (3) and {[MnFe2O­(O2CCMe3)6(hmta)2]·Me3CCO2H·(n-hexane)}n (4) and the two-dimensional layer compound {[MnFe2O­(O2CCMe3)6(hmta)1.5]·(toluene)}n (5). Single-crystal X-ray diffraction analysis reveals a μ3-oxo trinuclear pivalate cluster building block as the main constituent in all polymer compounds. Different M:hmta ratios in 1–5 are related to the different structural functions of the N-containing ligand. In clusters 1 and 2, three hmta ligands are monodentate, whereas in chains 3 and 4 two hmta ligands act as bridging ligands and one is a monodentate ligand; in 5, all hmta molecules act as bidentate bridges. Magnetic studies indicate dominant antiferromagnetic interactions between the metal centers in both homometallic {Mn3}-type clusters 1 and 2 and heterometallic {MnFe2}-type coordination polymers 3–5. Modeling of the magnetic susceptibility data to a isotropic model Hamiltonian yields least-squares fits for the following parameters: J1(MnII–MnIII) = −6.6 cm–1 and J2(MnIII–MnIII) = −5.4 cm–1 for 1; J1 = −5.5 cm–1 and J2(MnIII–MnIII) = −3.9 cm–1 for 2; J1(MnII–FeIII) = −17.1 cm–1 and J2(FeIII–FeIII) = −43.7 cm–1 for 3; J1 = −23.8 cm–1 and J2 = −53.4 cm–1 for 4; J1 = −13.3 cm–1 and J2 = −35.4 cm–1 for 5. Intercluster coupling plays a significant role in all compounds 1–5.