CRYSTAL-STRUCTURE OF CALCIUM ADIPATE MONOHYDRATE

The crystal structure of calcium adipate monohydrate, Ca(C6H8O4) . H2O , has been determined by single crystal X-ray diffraction study. The c rystals are triclinic with a = 5.8990(3), b = 6.7985(5), c = 10.8212(6 ) angstrom, alpha = 78.999(5), beta = 81.831(5), and gamma = 82.971(5) -degrees, space group P1BAR, Z = 2, V = 419.65(8) angstrom3, d(m) = 1. 59, d(c) = 1.600 Mg M-3. The structure was refined by full-matrix leas t-squares techniques to R = 0.040, R(w) = 0.058 for 1283 reflections w ith I greater-than-or-equal-to 3sigma(I). Ca is coordinated to seven o xygen atoms and the coordination polyhedron is best described as penta gonal bipyramid. The coordinations of the two carboxylate groups in ad ipate ion are quite different. One carboxylate group binds three diffe rent Ca ions forming a four-membered chelate ring with one Ca ion and unidentate bridge bonds to two other Ca ions. The other carboxylate gr oup links to two Ca ions through unidentate bonds. The structure is hi ghly polymeric, but with a layer-type structure parallel to (001) with the hydrocarbon chains sandwiched between the polar regions consistin g of Ca, carboxylate and water molecules.