Crystal structure of a new copper(II) complex with borodicitric acid

The crystal structure of the double copper(II) complex with borodicitric acid [Cu(H₂O)₅(C₆H₆O₇)₂B]⁺ · [(C₆H₆O₇)₂B]^? · 5H₂O of composition Cu[(C₆H₆O₇)₂B]₂ · 10H₂O has been studied by X-ray crystallography. The crystals are monoclinic, space group P2₁): a = 10.7852(2) ?, b = 9.9980(2) ?, c = 17.9500(5) ?; ?? = 101.126(1)°, FW = 1025.75, V = 1899.18(7) ?³, Z = 2. The dicitratoborate anions with a spirane structure have a normal geometry. The coordination polyhedron of the copper atoms is a distorted octahedron (CN 6 = 4 + 2) with an average equatorial Cu-O distance of 1.965 ± 0.023 ?. The axial positions in the CuO₆ octahedron are occupied by a water molecule and an oxygen atom of one of the citrate ligands: Cu-O(5w), 2.430(3) ?; Cu-O(8), 2.382(3) ?. The crystals have an extended intricate system of hydrogen bonds consisting of 27 unique three-center O-H??O, O(w)??O, and O(w)??O(w??) bonds and four-center O(w)??O, O(w??) bonds with different structural functions.