Five-coordinate Co(II) complexes with nitrilotriacetic acid: Crystal structures of Ca[Co(Nta)X] · nH2O (X − = Cl, Br, or NCS)

Abstract

The synthesis and X-ray diffraction study of three Ca[Co(Nta)X] · nH2O complexes [X − = Cl, n = 2.3 (I); X − = Br, n = 2 (II); and X − = NCS, n = 2 (III)] are performed. The main structural units of crystals I–III are the [CoX(Nta)]2− anionic complexes and hydrated Ca2+ cations. The anionic complexes have similar structures. The coordination of the Co2+ atom in the shape of a trigonal bipyramid is formed by N + 3O atoms of the Nta 3− ligand and the X − anion in the trans position with respect to N. In structures I–III, the Co-O and Co-N bond lengths lie in the ranges 1.998–2.032 and 2.186–2.201 A, respectively. The Co-X bond lengths are 2.294 (I), 2.436 and 2.445 (II), and 1.982 A (III). The environments of the Ca2+ cations include oxygen atoms of one or two water molecules and six or seven O(Nta) atoms with the coordination number of 9 in I or 8 in II and III. The Ca-O(Nta) bonds form a three-dimensional framework in I or layers in II and III. Water molecules are involved in the hydrogen bonds O(w)-H···O(Nta), O(w)-H···X, and O(w)-H···O(w). Structural data for crystals I–III are deposited with the Cambridge Structural Database (CCDC nos. 287 814–287 816).