RESUMO
A cyano-bridged heterometallic coordination polymer with partial deficiencies of CN- ligands, [MnII(H2O)8/3]3/2[FeII(CN)5(NH3)], forms open metal sites both on MnII and FeII ions by liberation of monodentate ligands such as NH3 and H2O. [MnII(H2O)8/3]3/2[FeII(CN)5(NH3)] exhibits high catalytic activity and selectivity of benzene oxygenation to phenol in the presence of m-chloroperoxybenzoic acid as an oxidant. The postcatalytic spectroscopy of [MnII(H2O)8/3]3/2[FeII(CN)5(NH3)] and catalysis comparison with a physical mixture of [MnII(H2O)3]2[FeII(CN)6] and [Fe(H2O)3/2]4/3[Fe(CN)6], which has open metal sites on both MnII and Fe ions separately, indicated that the high activity resulted from high oxidation ability and phenol adsorption ability of FeII and MnII ions, respectively.
RESUMO
CN-deficient Prussian blue analogues (PBAs), [MN(H2O)x]y[FeII(CN)5(NH3)] (MN = CuII, CoII, or GaIII), were synthesized and examined as a new class of heterogeneous catalysts for hydrolytic decomposition of organophosphates often used as pesticides. The active species of the CN-deficient PBAs were mainly C-bound FeII ions with only single open sites generated by liberation of the NH3 ligand during the catalytic reactions. [CuII(H2O)8/3]3/2[FeII(CN)5(NH3)] showed higher catalytic activity than [CoII(H2O)8/3]3/2[FeII(CN)5(NH3)] and [GaIII(H2O)][FeII(CN)5(NH3)], although N-bound CuII species has been reported as less active than CoII and GaIII species in conventional PBAs. IR measurements of a series of the CN-deficient PBAs after the catalytic reactions clarified that a part of the NH3 ligands remained on [CoII(H2O)8/3]3/2[FeII(CN)5(NH3)] and that hydrogen phosphate formed as a product strongly adsorbed on the FeII ions of [GaIII(H2O)][FeII(CN)5(NH3)]. Hydrogen phosphate also adsorbed, but weakly, on the FeII ions of [CuII(H2O)8/3]3/2[FeII(CN)5(NH3)]. These results suggest that heterogeneous catalysis of the FeII ions with single open sites were tuned by the MN ions through metal-metal interaction.
