K ₃[Fe 3.2₆V 0.7₄(OH)O(PO ₄) ₄(H ₂O) ₂]·2H ₂O: A synthetic leucophosphite

A new iron(III)/vanadium(III) phosphate, K₃[Fe3.2 ₆V0.7₄(OH)O(PO₄)₄(H ₂O)₂]·2H₂O (1), has been obtained by hydrothermal synthesis and characterized by single crystal X-ray diffraction, Scanning electron microscopy-energy dispersive X-ray spectroscopy, Inductively coupled plasma atomic emission spectroscopy (ICP), thermogravimetric analysis, and FTIR spectroscopy. Single crystal X-ray diffraction reveals a 3D open framework (monoclinic, space group P2₁/n, a = 9.6391(7) Å, b = 9.8063(7) Å, c = 9.7268(7) Å, β = 100.71(1)°, and V = 903.38(11) ų). This structure presents Fe^III and V^III in a 4.4: 1 M ratio with the metal ions in two different crystallographic sites. Both metallic centers have distorted octahedral environments, linked by PO₄ tetrahedra, forming channels along the a-axis. The asymmetric unit of K₃[Fe3.2₆V0.7 ₄(OH)O(PO₄)₄(H₂O) ₂]·2H₂O presents a {M₄(OH)O(PO ₄)₄(H₂O)₂}^3- anionic entity, charge balanced by three K⁺, which are located within the channels. It is also possible to distinguish M₄O₂ units whose M^III polyhedra are linked by vertex and edges.