Monocations of bismuth and indium in arene media: A spectroscopic and EXAFS investigation

Abstract

The composition of In–GaCl₃–benzene and In–BiCl₃–GaCl₃–benzene solutions was investigated by Raman, UV/Vis, ⁷¹Ga and ¹¹⁵In NMR spectroscopy as well as by X-ray absorption fine structure spectroscopy (EXAFS). Indium metal was found to be soluble in GaCl₃–benzene solution at room temperature through the reduction of Ga^III, producing Ga⁺ and In⁺ species. The subvalent cations are likely to be stabilized by the interaction with benzene. The use of these solutions as reducing media for BiCl₃ leads to the formation of Bi₅³⁺ polycations, with Bi⁺ as an intermediate product. No other subvalent bismuth species were detected. Multinuclear NMR experiments show that the reducing agent is Ga⁺ rather than In⁺. Indium K-edge EXAFS data recorded from solutions without and with subvalent bismuth species present show that In⁺ is co-ordinated by benzene (at about 2.9 Å) and chlorine atoms from chlorometalate anions (at about 3.3 Å) in a formal ratio of 1∶2. Electrospray mass spectroscopic data show that In⁺ is most likely co-ordinated by one arene molecule.