NEUTRON AND X-RAY-DIFFRACTION STUDY OF MAGNESIUM PHOSPHITE HEXAHYDRATE, [MG(H2O)6]2-([PHO3]2)

The original structure determination [Corbridge (1956). Acta Cryst. 9, 991-994] indicated an ordered structure of [PHO3]2- and [Mg(H2O)6]2ions lying on threefold,symmetry axes. Current refinement of H-atom po sitions allows full elucidation of the hydrogen-bonding network. This network connects each [PHO3]2- anion to seven [Mg(H2O)]2+ cations by n ine hydrogen bonds. Each [Mg(H2O)6]2+ complex makes three additional h ydrogen bonds to neighboring cations producing a three-dimensional net work. The Mg atom is surrounded by six H2O molecules at the vertices o f an octahedron.