Structure of [Mg(HO3PCH(C6H5)2)2].8H2O, a layered phosphonate salt

Bis(hydrogen diphenylmethylphosphonato)-magnesium octahydrate, [Mg(C13H12O3P)2].8H2O. Mr = 662.85, triclinic, P1, a = 6.1051 (15), b = 8.8308(14), c = 15.312(3) A, alpha = 78.514(13), beta = 83.993(11), gamma = 75.772(15) degrees, V = 782.8(3) A3, Z = 1, Dx = 1.41 g cm-3 (163 K), Mo K alpha, lambda = 0.71069 A, mu = 2.171 cm-1, F(000) = 350, T = 163 K, R = 0.0351 for 3749 reflections [F0 greater than or equal to 4 sigma(F0)]. The structure consists of alternating polar and nonpolar layers stacked along the crystallographic c axis. The polar layers contain Mg(H2O)26+ ions, water of hydration and the phosphonate O atoms, and the nonpolar layers contain the benzhydryl groups. Two-dimensional hydrogen-bonding networks link Mg(H2O)26+ and the water of hydration to the phosphonate O atoms. The shortest hydrogen bonds in the structure, 1.68(2) A, connect the P-OH H atom and the water of hydration. Slightly longer contacts [1.79(2), 1.85(2), 1.91(2), 1.92(2) A] connect the phosphonate O atoms (O1 and O3) to the H atoms of the Mg(H2O)26+ group. The coordination environment of the Mg atom is a very nearly regular octahedron of water O atoms.