A SYNCHROTRON SINGLE-CRYSTAL X-RAY STRUCTURE DETERMINATION OF A SMALL CRYSTAL - MO-MO DOUBLE-BONDS IN THE 3-D MICROPOROUS MOLYBDENUM PHOSPHATE NH4[MO2P2O10].H2O

Black crystals of NH4[Mo2P2O10] · H2O, (1), can be isolated by reacting MoO3, Mo, (NH4)2HPO4, H3PO4, and H2O in a mole ratio of 3:1.1:2:4:120 for 16 hr at 360°C. The structure of phosphate (1) was determined and refined from single crystal data collected on a 35 × 20 × 10 μm3 crystal at beamline X10A at NSLS, Brookhaven National Laboratory. Compound (1) is monoclinic, space group P21 n with a = 9.780(10), b = 9.681(5), c = 9.884(8) Å, β = 102.17(8)°, V = 915(1) Å3 and R(Rw) = 0.029(0.024) and contains MoO6 octahedra and PO4 tetrahedra. The structure is built up from Mo4 oxo units that have two edge-sharing Mo4+O6 octahedra that contain MoMo double bonds (2.453(2) Å), with the same two oxygens that bridge the Mo4+ also serving as a corner for two additional Mo5+O6 octahedra. The Mo4 units are connected by phosphate groups into a 3-D array which generates several types of tunnel which are filled with NH+4 cations and H2O. The material is isotypic with the mineral leucophosphite, K[Fe2(OH)(H2O)(PO4)2] · H2O. Water absorption isotherms show that (1) is microporous and has about 10-12 vol% internal void space that can be filled by water. © 1991.