Tetranuclear and Octanuclear Manganese Carboxylate Clusters: Preparation and Reactivity of (NBu(n)(4))[Mn(4)O(2)(O(2)CPh)(9)(H(2)O)] and Synthesis of (NBu(n)(4))(2)[Mn(8)O(4)(O(2)CPh)(12)(Et(2)mal)(2)(H(2)O)(2)] with a "Linked-Butterfly" Structure.

Abstract

The reaction of Mn(O2CPh)2·2H2O and PhCO2H in EtOH/MeCN with NBun4MnO4 gives (NBun4)[Mn4O2(O2CPh)9(H2O)] (4) in high yield (85−95%). Complex 4 crystallizes in monoclinic space group P21/c with the following unit cell parameters at −129 °C: a = 17.394(3) A, b = 19.040(3) A, c = 25.660(5) A, β = 103.51(1)°, V = 8262.7 A3, Z = 4; the structure was refined on F to R (Rw) = 9.11% (9.26%) using 4590 unique reflections with F > 2.33σ(F). The anion of 4 consists of a [Mn4(μ3-O)2]8+ core with a “butterfly” disposition of four MnIII atoms. In addition to seven bridging PhCO2- groups, there is a chelating PhCO2- group at one “wingtip” Mn atom and terminal PhCO2- and H2O groups at the other. Complex 4 is an excellent steppingstone to other [Mn4O2]-containing species. Treatment of 4 with 2,2-diethylmalonate (2 equiv) leads to isolation of (NBun4)2[Mn8O4(O2CPh)12(Et2mal)2(H2O)2] (5) in 45% yield after recrystallization. Complex 5 is mixed-valent (2MnII,6MnIII) and contains an [Mn8O4]14+ core that consists of two [Mn4O...