An Unprecedented-Type Intramolecular Redox Reaction of Solid Tetraamminecopper(2+) Bis(permanganate) ([Cu(NH3)4](MnO4)2) – A Low-Temperature Synthesis of Copper Dimanganese Tetraoxide-Type (CuMn2O4) Nanocrystalline Catalyst Precursors

Abstract

b ), Istva ¬ n Sajo ¬ a ), Ja ¬ nos Kristo ¬f c Tetraamminecopper(2) bis(permanganate) ((Cu(NH3)4)(MnO4)2; 1) was prepared, and its properties were studied in both aqueous solution and the solid phase. The presence of H-bond interactions between the ammonia ligand of the complex cation and an O-atom of the permanganate ion was detected by IR and Raman methods. The solid-phase thermal deammoniation of 1 led to an unusual intramolecular redox reaction between the MnO¥¥¥H N linkage with formation of NH4NO3 and CuMn2O4-type mixed oxides instead of stepwise deammoniation, even below 100. The thermal deammoniation of 1 in aqueous solution led, instead of to hydrated copper(2) bis(permanganate), to the formation of NH4MnO4 (2). Since the temperature of the thermal deammoniation of 1 is lower than the decomposition temperature of the permanganate ion, the regulated solid-phase decomposition of 1 allowed preparation of CuMn2O4-type oxides with mixing of copper and manganese at the atomic level.