Isolation and characterization of the dimetal decacarbonyl dication [Ru(CO)] and the metal-only Lewis-pair [Ag{Ru(CO)}] .

The reaction of Ag with Ru(CO) in a CO atmosphere under concommittant irradiation with UV-light yields a salt of the metal-only Lewis-pair [Ag{Ru(CO)}]. Switching the silver cation for a more process-selective deelectronator yields a salt of the homoleptic transition metal carbonyl cation [Ru(CO)], which fills the gap between the known cations [Ru(CO)] and [Ru(CO)]. The amount of π-backdonation in this series was studied by a combination of vibrational spectroscopy and computed relaxed force constants.