Refinement of the crystal structure of Ca(H2PO4)2.H2O

Abstract

Ca(H2PO4)2. H20 crystallizes in space group PI in the triclinic unit cell a= 5.6261 (5), b = 11.889 (2), c = 6-4731 (8) ~, ~ = 98"633 (6), fl= 118.262 (6), and 7' = 83.344 (6) ° at 25 °C with Z= 2. The structure was refined with 3401 observed reflections measured on a diffractometer to Rw = 0-033, Ro = 0.069. Corrections were made for absorption, anomalous dispersion, and isotropic secondary extinction. The structure contains Ca(H2PO4) + chains which form corrugated layers. Between these layers are layers of (H2PO4)-ions and water molecules. Hydrogen atoms have been located approximately; ideal positions for the hydrogen atoms have been calculated. The two sets of hydrogen positions differ by ~ 0.28 ,&. One hydrogen bond, in which the water molecule is the donor, is apparently bifurcated. All other hydrogen atoms form normal hydrogen bonds, with each hydrogen site seemingly fully occupied. The disorder of one hydrogen atom between the centrosymmetrically related atoms O(1) and O(1') was postulated by earlier workers. The P-O and O...O distances and electron-density maps obtained here show that there is no hydrogen atom in this position.

The crystal structure of 1,3,5,7-tetraceto-1,3,5,7-tetrazacyclooctane

“…Chemical formula" Space group" An approximately spherically shaped crystal, 0.50 + 0.03 mm in diameter, was mounted on an automated 4-circle X-ray diffractometer equipped with a graphite monochromator to reflect Mo K0~ radiation (Dickens & Bowen, 1971). Preceding the measurement of reflection intensities, the unit-cell dimensions were determined by the least-squares fit to observed 20 angles of 30 of the most intense reflections having scattering angles greater than 35 ° .…”

Bis(bis-η-cyclopentadienylmolybdenumdi-μ-oxo)phosphorus hexafluorophosphate

“…This provides further confirmation for the belief (Prout, Allison, Delbaere & Gore, 1972) that the choice of conformation can be attributed to crystal-packing effects. The MOOEPO:Mo bridging system can be compared to phosphate structures such as calcium bis-(dihydrogenphosphate) monohydrate (Dickens & Bowen, 1971) and calcium hydrogenphosphate dihydrate (Jones & Smith, 1962) in which chains of alternating Ca ions and phosphate groups are present. The mean P-O length of 1.538 (7)/k obtained here is intermediate between the values obtained in Ca(H2PO4)2.H20, 1.496 (1)/!t for the oxo bridges and 1.571 (2), 1.578 (2) A for the hydroxo bridges.…”

Orthorhombic barium dihydrogenphosphate

“…2) but otherwise confirm the features discussed in the earlier paper. The Ba(H2PO4) 2 structure can be compared with two calcium phosphate structures: Ca(HzPO4)2.H20 (Dickens & Bowen, 1971) and Ca(H2PO4) 2 (Dickens, Prince, Schroeder & Brown, 1973). In both calcium phosphate structures the H2PO; hydrogen-bonded network is three dimensional; however, the H2PO 4 groups in Ba(H2PO4) 2 form a two-dimensional hydrogen-bonded network where the only links between layers are through the Ba-O coordination bonds.…”