Structure of disodium methyl phosphate hexahydrate.

2Na+.CH3O4P2-.6H2O, Mr = 264.09, monoclinic, Pc, a = 7.277 (1), b = 6.298 (2), c = 11.477 (4) A, beta = 92.44 degrees, V = 525.5 A3, Z = 2, Dx = 1.669 g cm-3, lambda (Cu K alpha) = 1.5418 A, mu = 35.26 cm-1, F(000) = 276, T = 298 K, R = 0.028 for 781 independent reflections. Three P-O bond lengths are the same (1.513 A) within experimental error, with the ester P-O bond length significantly longer [1.626 (3) A]. The Na ions are octahedrally coordinated by water O atoms and have no direct interaction with the phosphate O atoms. Water molecules form three hydrogen bonds with each phosphate O atom, except the ester O atom which at most forms one weak interaction.