Capturing the missing [AgF2]− anion within an Ru2(iii/iii) dimeric dumbbell complex

Abstract

The complex {[Ru₂(ap)₄]₂[AgF₂]}[BF₄]₃ ({2}[BF₄]₃, ap = 2-anilinopyridine), containing the [AgF₂]⁻ anion ligated to two [Ru₂]⁶⁺ cores, is prepared, characterized, and compared to dimeric dumbbell-type structures, monomeric Ru₂ structures, as well as the known set of dihalo coinage-metalate anions. X-ray crystallography indicates that the Ru–Ru and Ru–F distances are rather short, 2.2835(3) Å and 2.054(1) Å, respectively, while the Ag–F distance of 2.274(1) Å is longer than that calculated for the free/un-ligated anion. Cyclic voltammetry in dichloromethane indicates that, while some of {2}³⁺ breaks apart into an [Ru₂(ap)₄F]⁺ ([3]⁺) monomer in solution, the remaining dimer has a single reversible two-electron redox feature for the Ru₂^6/5+ couple that is at a lower potential than that of [3]⁺. This is one of the few examples of a ligated dihalo coinage-metalate, and it is the first example of a coinage metal difluoride anion, either free or ligated.