Syntheses and Characterization of β ‐Chromium(II)‐orthophosphate

β ‐Cr 3 (PO 4 ) 2 was obtained by reducing CrPO 4 with elemental chromium. The new modification is stable between 1250 °C and its melting point at 1350 °C. Light‐blue single crystal were grown by isothermal heating ( T = 1300 °C, sealed double‐wall silica tubes, CrI 2 as mineralizer). The crystal structure is closely related to the Mg 3 (PO 4 ) 2 (Farringtonite) structure type ( P 2 1 / n , Z = 2, a = 4.9641(5), b = 9.492(1), c = 6.4849(5) Å, β = 91.412(8)°; 2868 independent reflections, 62 variables, seven atoms in the asymmetric unit, R 1 = 0.028, wR 2 = 0.061). The structure consists of elongated octahedra [Cr II O 6 ] (2.054(1) ≤ d (Cr–O) ≤ 2.743(4) Å). Electronic absorption spectra measured in the NIR/vis range for α ‐ and β ‐Cr 3 (PO 4 ) 2 , α ‐Cr 2 P 2 O 7 , and SrCrP 2 O 7 allow an estimation of 10Dq = 9000 cm –1 for the [Cr II O 6 ] chromophore. The observed transition energies for the low‐symmetry chromophores match remarkably well with calculations within the framework of the angular overlap model. Comparison of the magnetic behavior of α ‐ and β ‐Cr 3 (PO 4 ) 2 ( μ exp = 4.90 μ B ) reveals significant differences.