The stabilisation and characterisation by infrared spectroscopy of the different bonding modes of copper(I) thiocyanate adsorbed on high surface area solids

Abstract

High surface area solids such as alumina, silica or charcoal, have been used to stabilise the various bonding modes of copper(I) thiocyanate. Infrared spectroscopy was used to characterise the different species, for example on alumina sulfur bonded, nitrogen bonded and bridged thiocyanate species were observed. The effect of the high surface area solid was in some cases dramatic and the bonding modes stabilised were found to be dependent upon the concentration of the impregnating solution, relative to the amount of high surface area solid present. The most striking differences were between charcoal and the other two solids, in the former case high loadings of copper(I) thiocyanate resulted in stabilisation of a bridged species, whereas only low loadings of copper(I) thiocyanate on alumina or silica resulted in stabilisation of a bridged thiocyanate species. Both nitrogen and sulfur bonded thiocyanate species were evident on all the supports. The N-bonded species were generated in dimethyl sulfoxide solvent before impregnation onto the solids, whereas the S-bonded species were generated in either N-methyl pyrollidone or aqueous KSCN prior to impregnation. The effect of the high surface area solid manifests itself in the reaction chemistry of copper(I) thiocyanate with 1-iodo-2-nitrobenzene (an ipso substitution reaction) by altering the proportion of aryl isothiocyanate to aryl thiocyanate to aryl nitrile products.