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

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) A and 2.054(1) A, respectively, while the Ag–F distance of 2.274(1) A 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 Ru26/5+ 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.