Cu2+coordination in aqueous solution

A neutron diffraction study has been made to determine the environment of the Cu 2+ ion in a 4.32 molal aqueous solution of copper chloride. The results show that the Cu 2+ ion coordination exhibits a clear 2-4 character. The two nearest neighbours are identified with (heavy) water molecules with atom positions of r CuO =2.05+or-0.02 AA and r CuD =2.56+or-0.10 AA. This coordination differs from that for divalent ions of comparable size and represents clear structural evidence that chemical effects are dominant in the immediate neighbourhood of Cu(II) ions.