Crystal structure of strontium aqua(ethylenediaminetetraacetato)cobaltate(II) tetrahydrate Sr[CoEdta(H2O)]center dot 4H(2)O

The complex Sr[Co(II)Edta].5H(2)O (I) (where Edta(4-) is the ethylenediamin etetraacetate ion) has been synthesized. The crystal structure of this comp ound is determined by X-ray diffraction. Crystals are monoclinic, a = 7.906 (2) Angstrom, b, = 12.768(2) Angstrom, c = 18.254(3) Angstrom, beta = 95.30 (3)degrees, V= 1834.8 Angstrom (3), space group P2(1)/n, Z= 4, and R = 0.03 6. The structure is built up of the binuclear fragments {Sr(H2O)(3)[CoEdta( H2O)]}, which consist of the anionic [CoEdta(H2O)](2-) and cationic [Sr(H2O )(3)](2+) units linked by the Sr-O bonds into a three-dimensional framework . The coordination polyhedra of the Co and Sr atoms are mono- and bicapped trigonal prisms. The coordination sphere of the Co atom (the coordination n umber is equal to 6 + 1) involves six donor atoms (2N and 4O) of the Edta(4 -) ligand and the O-w atom of water molecule. One of the Co-O distances (2. 718 Angstrom) is considerably longer than the other Co-O-lig distances (2.0 92-2.190 Angstrom) and the Co-O,,(l) distance (2.079 Angstrom). The Sr coor dination polyhedron (the coordination number is eight) contains three water molecules, three carbonyl O atoms of the three different anionic complexes , and two O atoms of one acetate group of the fourth anionic complex. The S r-O distances fall in the range 2.535-2.674 Angstrom. The structural formul a of the compound is {Sr(H2O)(3)[CoEdta(H2O)]}(3 infinity) . H2O. (C) 2001 MAIK "Nauka/lnterperiodica".