Synthesis, Crystal Structure, Magnetic Susceptibility, and Mössbauer Spectroscopy of a Mixed-Valence Organic−Inorganic Hybrid Compound: (H₃DETA)[Fe₃(C₂O₄)₂(HPO₄)₂(PO₄)] (DETA = Diethylenetriamine)

A mixed-valence organic−inorganic hybrid compound, (H 3 DETA)[Fe 3 (C 2 O 4 ) 2 (HPO 4 ) 2 (PO 4 )] (DETA = diethylenetriamine), has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, magnetic susceptibility, 57 Fe powder absorption Mössbauer spectroscopy, and electric field gradient calculations. It crystallizes in the triclinic space group P 1̄ (No. 2) with a = 9.6367(7) Å, b = 10.1760(7) Å, c = 12.6164(9) Å, α = 86.302(1)°, β = 68.880(1)°, γ = 61.800(1)°, and Z = 2 with R 1 = 0.0397. The structure can be described as layers of trigonal bipyramidal Fe II O 5, octahedral Fe III O 6, tetrahedral PO 4 moieties, and monobidentate oxalate ligands, which are pillared through bisbidentate oxalate ligands to form a 3-D framework structure. The title compound is not only the first oxalatophosphate that contains two types of oxalate ligands but also the first example of mixed-valence transition metal oxalatophosphate.