Comproportionation Reactions to Manganese(III/IV) Pivalate Clusters: A New Half-Integer Spin Single-Molecule Magnet

The comproportionation reaction between MnII and MnVII reagents under acidic conditions has been investigated in the presence of pivalic acid as a route to new high oxidation state manganese pivalate clusters containing some MnIV. The reaction of Mn(O2CBut)2 and NBun4MnO4 with an excess of pivalic acid in the presence of Mn(ClO4)2 and NBun4Cl in hot MeCN led to the isolation of [Mn8O6(OH)(O2CBut)9Cl3(ButCO2H)0.5(MeCN)0.5] (1). In contrast, the reaction of Mn(NO3)2 and NBun4MnO4 in hot MeCN with an excess of pivalic acid gave a different octanuclear complex, [Mn8O9(O2CBut)12] (2). The latter reaction but with Mn(O2CBut)2 in place of Mn(NO3)2, and in a MeCN/THF solvent medium, gave [Mn9O7(O2CBut)13(THF)2] (3). Complexes 1–3 possess rare or unprecedented Mnx topologies: 1 possesses a [MnIII7MnIV(μ3-O)4(μ4-O)2(μ3-OH)(μ4-Cl)(μ2-Cl)]8+ core consisting of two body-fused Mn4 butterfly units attached to the remaining Mn atoms via bridging O2–, OH–, and Cl– ions. In contrast, 2 possesses a [Mn6IVMn2III(μ3-O)6(μ-O)3...