TOPOTACTIC INTERCALATION OF WATER AND PYRIDINE INTO CO(H2PO2)2NH2O (0-LESS-THAN-OR-EQUAL-TO-N-LESS-THAN-OR-EQUAL-TO-0.69) - CRYSTAL-STRUCTURE OF CO(H2PO2)20.53H2O SOLVED FROM X-RAY-POWDER DIFFRACTION DATA

The synthesis of differently hydrated layered cobalt hypophosphites, Co(H2PO2)2.nH2O (0 less-than-or-equal-to n less-than-or-equal-to 0.69), has been possible by carefully controlling the water content in the reaction medium. The crystal structure of Co(H2-PO2)2.0.53H2O has been refined from X-ray powder diffraction data by the Rietveld method, using as a starting model the structural parameters of the orthorhombic anhydrous zinc hypophosphite Zn(H2PO2)2. The cell is monoclinic (space group P112/a; Z = 2) with a = 6.4722(3) angstrom, b = 5.3411(3) angstrom, c = 7.4900(3) angstrom and gamma = 90.087(12)-degrees. The final reliability factors were, R(I) = 5.38%, R(p) = 7.31%, and R(wp) = 9.05%. The lamellar structure can be thought of as constructed from corrugated rutile like chains of cationic edge-sharing octahedra running along the a axis and interconnected in the b direction through hypophosphite bridges. Co(H2PO2)2.nH2O compounds are suitable hosts lattices for intercalation reactions. Water and pyridine intercalation processes in these matrices have been studied by thermal analysis, variable-temperature X-ray powder diffraction, and spectroscopic techniques. A structural proposal for Co(H2PO2)2.1.86(C5H5N).0.31H2O is presented.