A di­iron(III) µ-oxido complex as catalyst precursor in the oxidation of alkanes and alkenes.

The oxido-bridged diiron(III) complex [Fe2(µ-O)(µ-OAc)(DPEAMP)2](OCH3) (1), based on a new unsymmetrical ligand with an N4O donor set, viz. [2-((bis(pyridin-2-ylmethyl)amino)methyl)-6-((ethylamino)methyl)-4-methylphenol (HDPEAMP)], has been prepared and characterized by spectroscopic methods and X-ray crystallography. The crystal structure of the complex reveals that each Fe(III) ion is coordinated by three nitrogen and three oxygen donors, two of which are the bridging oxido and acetate ligands. Employing H2O2 as a terminal oxidant, 1 is capable of oxidizing a number of alkanes and alkenes with high activity. The catalytic oxidation of 1,2-dimethylcyclohexane results in excellent retention of configuration. Monitoring of the reaction of 1 with H2O2 and acetic acid in the absence of substrate, using low-temperature UV-Vis spectroscopy, suggests the in situ formation of a transient Fe(III)2-peroxido species. While the selectivity and nature of oxidation products implicate a high-valent iron-oxido complex as a key intermediate, the low alcohol/ketone ratios suggest a simultaneous radical-based process.

Mixed-Valent Mn16-Containing Heteropolyanions: Tuning of Oxidation State and Associated Physicochemical Properties.

The two 16-manganese-containing, Keggin-based 36-tungsto-4-silicates [Mn(III)10Mn(II)6O6(OH)6(PO4)4(A-α-SiW9O34)4](28-) (1) and [Mn(III)4Mn(II)12(OH)12(PO4)4(A-α-SiW9O34)4](28-) (2) have been prepared by reaction of the trilacunary Keggin precursor [A-α-SiW9O34](10-) with either Mn(OOCCH3)3·2H2O (for 1) or MnCl2·4H2O (for 2), in aqueous phosphate solution at pH 9. Polyanions 1 and 2 comprise mixed-valent, cationic {Mn(III)10Mn(II)6O6(OH)6}(24+) and {Mn(III)4Mn(II)12(OH)12}(24+) cores, respectively, encapsulated by four phosphate groups and four {SiW9} units in a tetrahedral fashion. Both polyanions were structurally and compositionally characterized by single-crystal XRD, IR, thermogravimetric analysis, and X-ray absorption spectroscopy. Furthermore, studies were performed probing the magnetic, electrochemical, oxidation catalytic, and Li-ion battery performance of 1 and 2.

Tetradecanuclear Iron(III)-Oxo Nanoclusters Stabilized by Trilacunary Heteropolyanions.

The tetrameric, multi-Fe(III)-containing polyoxotungstates [Fe14O6(OH)13(P2W15O56)4](31-) (1) and [Na2Fe14(OH)12(PO4)4(A-α-XW9O34)4](20-) (X = Si(IV) (2), Ge(IV) (3)) have been successfully synthesized under conventional reaction conditions in aqueous, slightly acidic (1), or basic (2 and 3) media. Polyanions 1-3 were characterized in the solid state by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and magnetic studies, and in solution by electrochemistry.

Multinuclear cobalt(II)-containing heteropolytungstates: structure, magnetism, and electrochemistry.

Interaction of the trilacunary Keggin polyanions [A-α-XW9O34](10-) (X = Si(IV), Ge(IV)) with Co(II) and phosphate ions in aqueous, basic media and under mild heating leads to the formation of the tetrameric, Co16-containing heteropolytungstates [{Co4(OH)3PO4}4(A-α-XW9O34)4](32-) (X = Si(IV), Ge(IV)). Both polyanions were characterized in the solid state by single-crystal X-ray diffraction, IR spectroscopy, and thermogravimetric and elemental analyses. Furthermore, the electrochemical and magnetic properties of these isostructural polyanions were investigated.