The electronic properties and crystal structure of Na4Cu(NH3)4[Cu(S2O3)2]2,L (L = H2O or NH3)

Abstract

A re-examination of the analytical data and X-ray structure of Na₄Cu(NH₃)₄[Cu(S₂O₃)₂]₂ is inconsistent with this formulation and has established the existence of a monoaquo- and mono-ammonia-adduct. Both complexes are isostructural, with the adduct molecules in the [0,0,½] position of the tetragonal space group. Their electronic properties are slightly, but significantly, different and suggest that the ammonia and water molecules present are in different structural environments. In the monohydrate the molecule of water is considered to be freely rotating and is not co-ordinated to the copper(II) ion and the CuN₄ chromophore may be considered to be ‘essentially’ square-coplanar. In the monoammine, the molecule of ammonia is believed to be weakly co-ordinated to the copper(II) ion at a semico-ordinate distance, but is undergoing a vibrational inversion process about the [0,0,½] position. The average copper(II) ion environment is then tetragonal-octahedral.

The e.s.r. and i.r. spectra of the two complexes are compared and the combined orbital and spin-orbit reduction parameters are evaluated.