The characterization of tetrameric complexes of copper(I) halides with phosphine and amine ligands by far infrared spectroscopy

Abstract

The far i.r. spectra of "cubane" [Ph3PCuCl]4, [Ph3PCuBr]4, and [Ph3PCuI]4, and "step" [Ph3PCuBr]4, and [Ph3PCuI]4, have been measured at ca 298 K and ca 125 K. The spectra of the "cubane" structures show two strong T2?(CuX) bands at: 160 and 180 cm- for the chloride, 119 and 144 cm- for the bromide and 100 and 140 cm- for the iodide, with resolution increasing along the sequence Cl < Br < I. The spectra of the "step" structures were virtually identical with previously reported data, with doubly and triply bridged ?(CuX) being observed at: 135 cm- and 174 cm- for the bromide, and 109 and 162 cm- for the iodide. The far i.r. spectra of [Et3PCuX]4, [Et3NCuX]4 (X = Cl, Br), [Et3N]3[CuI]4 and [Et3NAgI]4, all of which contain a "cubane" M4X4 core, have also been measured. Band assignments are supported by a normal coordinate calculation for isolated Td Cu4X4 units.