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Crystal structure of strontium Di[bis(iminodiacetato)cobaltate(III)] pentahydrate, Sr[cis(N)-Co(Ida)2]2 · 5H2O

Research paper by I. N. Polyakova, A. L. Poznyak, V. S. Sergienko

Indexed on: 03 Apr '12Published on: 03 Apr '12Published in: Crystallography Reports



Abstract

Compound Sr[cis(N)-Co(Ida)2]2 · 5H2O (I) is synthesized and its crystal structure is determined. The crystals are built of [Co(Ida)2]− anionic complexes, [Sr(H2O)3]2+ hydrated cations, and crystallization water molecules. Two independent anions are located on rotation axis 2 and have close structures. A distorted octahedral coordination of Co3+ atoms is formed by two N atoms and four O atoms of two Ida2− ligands [Co-N, 1.932(3) and 1.940(3) Å; Co-O, 1.879–1.899(3) Å]. [Sr(H2O)3]2+ cations randomly occupy half of the positions in the vicinity of centers of inversion. In addition to three water molecules, the environment of the Sr2+ atom includes five O atoms of five Ida2− ligands [Sr-O, 2.487(3)-2.889(5) Å]. Because of the disordering of [Sr(H2O)3]2+ cations, the structural function of the Ida2- ligands varies from tridentate chelate to pentadentate bridging chelate. Sr-O and hydrogen bonds connect structural elements into a three-dimensional framework. The structure of I is compared with that of a related compound Sr[CoEdta]2·9H2O (II). It is shown that the formation of N-H…O hydrogen bonds, which connect [Co(Ida)2]− anionic complexes in I into compact chains, is an important factor leading to the difference between packings I and II.