Polynuclear Manganese Complexes with the Dicarboxylate Ligand m-Phenylenedipropionate:A Hexanuclear Mixed-Valence (3Mn~III,3Mn~IV) Complex

摘要

The dicarboxylate group m-phenylenedipropionate (mpdp~(2-) has been used for the synthesis of four new Mn compounds of different nuclearities and oxidation states:[Mn_2O(mpy)_2(H_2O)(MeCN)](ClO_4)_2 (3),[Mn_3O(mpdp)_3-(py)_3](ClO_4) (4),[Mn_3O(mpdp)_3(py)_3] (5),and [Mn_6O_7(mpdp)_3](ClO_4) (6).Compound 3 (2Mn~III) contains a [Mn_2(mu-O)]~(4+) core,whereas 5 (Mn~II,2Mn~III) and 4 (3Mn~III) contain the [Mn_3(mu_3-O)]~(6+,7+) core,respectively.In all three compounds,the mpdp~(2-) ligand is flexible enough to adopt the sites occupied by two monocarboxylates in structurally related compounds,without noticeable distortion of the cores.Variable-temperature magnetic susceptibility studies establish that 3 and 5 have ground-state spin values of S=0 and S=1/2,respectively.Comopound 6 is a highly unusual 3Mn~III,3Mn~IV trapped-valent compound,and it is also a new structural type,with six Mn atoms dispoosed in a distorted trigonal antiprismatic topology.Its electronic structure has been explored by variable-temperature measurements of its dc magnetic susceptibility,magnetization vs field rsponse,and EPR spectrum.The magnetic data indicate that it possesses an S=3/2 ground state with an axial zero-field splitting parameter of D=-0.79 cm~(-1),and this conclusion is supported by the EPR data.The combined results demonstrate the ligating flexibility of the mpdp~(2-) ligand and its usefulness in the synthesis of a variety of Mn_x species.