Aurophilic attractions: one cation, [Au{C(OMe)NMeH}2]+, but three different structural arrangements in the solid state salts

Abstract

Three salts of the cation [Au{C(OMe)NMeH}₂]⁺, formed by protonation of the solvoluminescent gold(I) trimer [Au₃(MeNCOMe)₃], have been prepared and spectroscopically and structurally characterized. Each crystallizes as a unique form with varying aurophilic interactions between the linear, two-coordinate cations. Thus, the chloroform solvate, [Au{C(OMe)NMeH}₂][C₇Cl₂NO₃]·CHCl₃, (where [C₇Cl₂NO₃]⁻ is an anion obtained by hydrolysis of 2,3-dichloro-4,5-dicyano-1,4-benzoquinone, DDQ), contains the cation as an isolated monomer, while unsolvated [Au{C(OMe)NMeH}₂][C₇Cl₂NO₃] contains pairs of cations that are linked by a single Au⋯Au interaction with a 3.1955(3) Å separation between the gold centers. In [Au{C(OMe)NMeH}₂][O₂CCF₃] the cations associate to form infinite, nearly linear (Au⋯Au⋯Au angle, 172.209(7)°) chains that have the gold centers only 3.27797(15) Å apart. The luminescent behavior of [Au{C(OMe)NMeH}₂][O₂CCF₃] is reported.