N-(2-Ammonioethyl)morpholinium tetrachlorocuprates(II). The first instance of two forms, one green and one yellow, both stable at room temperature

Crystals of the green form of the title compound are monoclinic, space group I2/a, with a = 15.934 (3) Å, b = 13.023 (1) Å, c = 14.069 (3) Å, ? = 118.89 (1)°, and Z = 8. Crystals of the yellow form are monoclinic, space group P21/a, with a = 15.909 (3) Å, b = 12.420 (3) Å, c = 6.355 (1) Å, ? = 98.77 (5)°, and Z = 4. The crystal structures were determined by three-dimensional X-ray diffraction and refined to R = 0.047 and 0.045 for the green and yellow forms, respectively. In the green crystals two crystallographically independent [CuCl4]2- anions are present, one of them with a flattened-tetrahedral geometry and the other square planar for symmetry requirements. In the yellow form only [CuCl4]2- distorted-tetrahedral ions are present. In both modifications, the anions form hydrogen bonds with the N-(2-ammonioethyl)morpholinium cation, with stronger bonds being present in the green modification. The spectroscopic and magnetic properties of the complexes are explained in the light of their known crystal structures