The reaction of Ag+ with Ru3(CO)12 in a CO atmosphere under concommittant irradiation with UV-light yields a salt of the metal-only Lewis-pair [Ag{Ru(CO)5}2]+. Switching the silver cation for a more process-selective deelectronator yields a salt of the homoleptic transition metal carbonyl cation [Ru2(CO)10]2+, which fills the gap between the known cations [Ru(CO)6]2+ and [Ru3(CO)14]2+. The amount of π-backdonation in this series was studied by a combination of vibrational spectroscopy and computed relaxed force constants.