Crystal structure of calcium (Ornithinato-N (α), N (δ), N (δ )-triacetato)cobaltate(III) octahydrate Ca[Co(Orntra)]2 ⋅ 8H2O

Abstract

The X-ray crystal structure of calcium (ornithinato-N(α)N(δ)N(δ )-triacetato)cobaltate(III) octahydrate Ca[Co(Orntra)]2 ⋅ 8H2O has been determined. The crystals are orthorhombic, a = 21.163(4) A, b = 8.391(2) A, c = 19.101(4) A, V = 3391.9(9) A3, Z = 4, and space group Pca21. In the trinuclear linear molecule [Co(μ-Orntra)]2Ca(H2O)5, two independent anions [Co(Orntra)]− are joined with the Ca2+ cation by the bridging bonds through the terminal O atoms. In each [Co(Orntra)]− anion, the Co atom occurs in the octahedral environment of two N atoms 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 vertices in a pentagonal bipyramid of the Ca2+ ion. Five O(H2O) atoms are located in the equatorial plane. The asymmetric C atoms in the anions bound to the same Ca2+ cation have an identical absolute configuration. The crystal involves the molecules belonging to both configurations. The coordinated and outer-sphere H2O molecules participate in an extended system of hydrogen bonds.