Abstract A new phosphate of molybdenum (V) K 4Mo v 8P 12O 52 has been isolated and its structure solved from a single crystal X-ray diffraction study. It crystallizes in a monoclinic cell, space group C2–c, with the parameters a = 10.7433(16)Å, b = 14.0839(9)Å, c = 8.8519(7)Å, and β = 126.42(1)°. After refinement of the different parameters, the reliability factors were lowered to R = 0.026 and w = 0.029. The framework “Mo 8P 12O 52” can be described as corner-sharing PO 4 tetrahedra, P 2O 7groups, and MoO 6 octahedra. Although the “O 6” octahedron surrounding the molybdenum ion is almost regular, the metal ion is strongly off center so that its coordination is better described as a MoO 5 pyramid. This particular coordination, which characterizes Mo(V), is discussed.