Reactions of noble-metal oxides in ionic liquids near room temperature.

Abstract

The reaction of Ag2O, Au2O3, and HgO with CuCl, CuI, AgCl, AgI, AuCl, and AuI in ionic liquids ([EMIm]Cl, [BMIm]Cl) near room temperature (20-80 °C) is evaluated and results in the new compounds (C8H14N2)CuCl, (C8H14N2)AgI, (C6H10N2)AuCl, [(C8H14N2)2Hg][CuCl3], [(C8H14N2)2Hg][AgCl3], and [EMIm][Ag2I2Cl]. Thereof, (C8H14N2)CuCl, (C8H14N2)AgI, (C6H10N2)AuCl, [(C8H14N2)2Hg][CuCl3], and [(C8H14N2)2Hg][AgCl3] are NHC complexes (NHC: N-heterocyclic carbene) with M-C bonds (M: Cu, Ag, Au, Hg). Whereas (C8H14N2)CuCl and (C8H14N2)AgI crystallize as single molecules, (C6H10N2)AuCl is dimerized via aurophilic interactions. [(C8H14N2)2Hg][CuCl3] and [(C8H14N2)2Hg][AgCl3] exhibit Hg atoms with two Hg-C bonds. Moreover, (C8H14N2)AgI shows intense green fluorescence at room temperature with a quantum yield of 44%, whereas all other compounds do not show any emission at room temperature. Finally, [EMIm][Ag2I2Cl] is not an NHC compound but contains ∞ 1[AgI1/2I2/4Cl1/2]- chains with infinite d10-d10 interaction of the silver atoms. The title compounds are characterized by single-crystal structure analysis, infrared spectroscopy, thermogravimetry, and fluorescence spectroscopy.