Crystal structure of calcium (ornithinato-N-(alpha),N-(delta),N-(delta)-triacetato)cobaltate(III) octahydrate Ca[Co(Orntra)](2)center dot 8H(2)O

The X-ray crystal structure of calcium (ornithinato-N(alpha)N(delta)N(delta )-triacetato)cobaltate(III) octahydrate Ca[Co(Ornata)](2) . 8H(2)O has been determined. The crystals are orthorhombic, a = 21.163(4) Angstrom, b = 8.3 91(2) Angstrom, c = 19.101(4) Angstrom, V= 3391.9(9) Angstrom(3), Z= 4, and space group Pca2(1). In the trinuclear linear molecule [Co(mu-Orntra)](2)C a(H2O)(5), two independent anions [Co(Orntra)](-) are joined with the Ca2cation by the bridging bonds through the terminal O atoms. In each [Co(Ornt ra)](-) anion, the Co atom occurs in the octahedral environment of two N at oms and four O atoms of the Orntra ligand and closes four five-membered and one seven-membered chelate rings. Two O atoms of two anions occupy axial v ertices in a pentagonal bipyramid of the Ca2+ ion. Five O(H2O) atoms are lo cated in the equatorial plane. The asymmetric C atoms in the anions bound t o the same Ca2+ cation have an identical absolute configuration. The crysta l involves the molecules belonging to both configurations. The coordinated and outer-sphere H2O molecules participate in an extended system of hydroge n bonds. (C) 2000 MAIK "Nauka/Interperiodica".