Rare Nuclearities and Unprecedented Structural Motifs in Manganese Cluster Chemistry from the Combined Use of Di-2-Pyridyl Ketone with Selected Diols

Abstract

The combined use of di-2-pyridyl ketone ((py)2CO) with various diols in Mn cluster chemistry has afforded five new compounds, namely, [Mn11O2(OH)2{(py)2CO2}5(pd)(MeCO2)3(N3)3(NO3)2(DMF)4](NO3)∙2DMF∙H2O (1∙2DMF∙H2O), [Mn11O2(OH)2{(py)2CO2}5(mpd)(MeCO2)3(N3)3(NO3)2(DMF)4](NO3) (2), [Mn12O4(OH)2{(py)2CO2}4(mpd)2(Me3CCO2)4(NO3)4(H2O)6](NO3)2∙2MeCN (3∙2MeCN), [Mn4(OMe)2{(py)2C(OMe)O}2(2-hp)2(NO3)2(DMF)2] (4), and [Mn7{(py)2CO2}4(2-hp)4(NO3)2(DMF)2](ClO4)∙DMF (5∙DMF) ((py)2CO22− and (py)2C(OMe)O− = gem-diol and hemiketal derivatives of di-2-pyridyl ketone, pdH2 = 1,3-propanediol, mpdH2 = 2-metly-1,3-propanediol, 2-hpH2 = 2-(hydroxymethyl)phenol). Complexes 1 and 2 are isostructural, possessing an asymmetric [MnIII5MnII6(μ4-O)(μ3-O)(μ3-OH)(μ-OH)(μ3-OR)2(μ-OR)10(μ-N3)]8+ core. Compound 3 is based on a multilayer [MnIII8MnII4(μ4-O)2(μ3-O)2(μ3-OH)2(μ-OR)12]10+ core, while complex 4 comprises a defective dicubane core. The crystal structure of 5 reveals that it is based on an unusual non-planar [MnIII5MnII2(μ-OR)12]7+ core with a serpentine-like topology. Direct current (dc) magnetic susceptibility studies revealed the presence of dominant antiferromagnetic exchange interactions in complex 3, while ferromagnetic coupling between the Mn ions was detected in the case of compound 5. Fitting of the magnetic data for complex 4 revealed weak antiferromagnetic interactions along the peripheral MnII∙∙∙MnIII ions (Jwb = −0.33 (1) cm−1) and ferromagnetic interactions between the central MnIII∙∙∙MnIII ions (Jbb = 6.28 (1) cm−1).

Keywords

• manganese
• di-2-pyridyl ketone
• metal complexes
• cluster chemistry
• molecular magnetism