Methods of chemical preparation and crystal data are reported for two new anhydrous cyclotriphosphates MIIK4(P3O9)2 (MII=Co2+ and Mn2+). These anhydrous cyclotriphosphates CoK4(P3O9)2 and MnK4(P3O9)2 were obtained by total dehydration of corresponding hydrated cyclotriphosphates CoK4(P3O9)2.7H2O and MnK4(P3O9)2.2H2O. CoK4(P3O9)2 is triclinic, space group P−1, Z=1 with the following unit-cell dimensions: a=6.29(3) Å, b=8.00(1)Å, c=13.05(8)Å, α=86.03(5)°, β=98.00(1)°, γ=68.11(2)°. MnK4(P3O9)2 crystallizes in the rhombohedral system, space group P−31c, Z=2 with the following unit-cell dimensions: a=b=7.337(3)Å, c=19.920(1)Å.
