THE PREPARATION AND CRYSTAL-STRUCTURE OF AMMONIUM BIS[CITRATO(3-)]CUPRATE(II)

The copper(II) complex with citric acid (NH4)4 [Cu(C6H5O7)2] has been prepared, and its structure determined by X-ray diffraction, giving a residual R 0.035 for 1208 observed reflections. Crystals are monoclinic, space group P2(1)/c with Z 2 in a cell of dimensions a 8.755(3), b 13.185(4), c 9.364(2)angstrom, beta 113-73(2)-degrees. The complex is a centrosymmetric six-coordinate monomer which is isomorphous with ammonium zinc(II) citrate. However, the Cu-O(hydroxyl) bonds [2 . 341(3) angstrom] show jahn-Teller distortion relative to the Cu-O(carboxyl) bonds [1 . 969(3) and 1 . 977(3) angstrom].