Halocuprates(II) of the N-phenylpiperazinium mono- and dications: crystal and molecular structure of N-phenylpiperazinum tetrachlorocuprate(II). Correlation of the electronic spectrum vs. distortion of the CuCl42- anions from tetrahedral symmetry.

The X-ray structure of N-phenylpiperazinium tetrachlorocuprate(II), (C10H16N2)CuCl4, was determined by X-ray diffraction methods. Crystals are orthorhombic, P212121, with a = 17.698 (2) Å, b = 8.615 (1) Å, c = 9.841 (1) Å, and Z = 4. A final R value of 4.3 was obtained. The structure consists of [CuCl4]2- anions and N-phenylpiperazinium diprotonated cations. The [CuCl4]2- anions show a flattened tetrahedral geometry, the two larger Cl-Cu-Cl angles being 141.1 and 143.0°; the dihedral angle is 51.6°. The Cu-Cl distances range from 2.23 to 2.27 Å. All four chlorine atoms are involved in Cl?N interactions, which may be responsible for the large distortion of the [CuCl4]2- ion from the tetrahedral configuration. The N-phenylpiperazinium dication shows the usual "chair" configuration. The spectroscopic and magnetic results of the [CuCl4]2- and [CuCl3Br]2- anions are in agreement with a high distortion of these ions from tetrahedral symmetry. A study of the d-d transition maximum vs. the distortion of the CuCl4 chromophore from the Td symmetry is also reported. Some compounds containing the monoprotonated amine such as (NPhpipzH)2Cu2X6 (X = Cl, Br) and (NPhpipzH)2Cu2Cl2Br4 are also studied. Their spectroscopic data suggest the presence of dimeric species in them with highly distorted tetrahedral symmetry