The NHR2/CO2 system as a metal ion extraction reagent from aqueous solution into hydrocarbons: copper(II) and zinc(II)

A substantially quantitative transfer of copper(II) or zinc(II) salts from aqueous solution into a hydrocarbon (heptane or toluene) promptly occurs under carbon dioxide in the presence of a dialkylamine (NHR2, R = Bu, Bz). Recovery of the metal complexes from the organic phase affords copper dialkylcarbamates of the formula Cu(O2CNR2)2(NHR2)2 or μ-oxo tetranuclear zinc carbamato complexes, Zn4(μ4-O)(O2CNR2)6, respectively, in high yield and purity. An X-ray diffraction study on a single crystal of Cu(O2CNBz2)2(NHBz2)2 1 has shown the compound to be mononuclear with tetracoordinated copper in an almost perfect square-planar geometry. The zinc derivative has the well-established oxo-centred tetranuclear structure (R = Bu, 2).