Synthesis, characterization and in situ monitoring of the mechanochemical reaction process of two manganese(II)-phosphonates with N-containing ligands

Two divalent manganese aminophosphonates, manganese mono(nitrilotrimethylphosphonate) (MnNP 3 ) and manganese bis( N -(carboxymethyl)iminodi(methylphosphonate)) (Mn(NP 2 AH) 2 ), have been prepared by mechanochemical synthesis and characterized by powder X-ray diffraction (PXRD). The structure of the novel compound Mn(NP 2 AH) 2 was determined from PXRD data. MnNP 3 as well as Mn(NP 2 AH) 2 exhibits a chain-like structure. In both cases, the manganese atom is coordinated by six oxygen atoms in a distorted octahedron. The local coordination around Mn was further characterized by extended X-ray absorption fine structure. The synthesis process was followed in situ by synchrotron X-ray diffraction revealing a three-step reaction mechanism. The as-prepared manganese(II) phosphonates were calcined on air. All samples were successfully tested for their suitability as catalyst material in the oxygen evolution reaction.