Observation of the Transition from Triple Bonds to Single Bonds between Ru-Ge Bonding in RuGeO(CO) n - (n=3-5)

This work reports the observation and characterization of heterobinuclear transition-metal main-group metal oxide carbonyl complex anions, RuGeO(CO)(n) - (n = 3-5), by combining mass-selected photoelectron velocity map imaging spectroscopy and quantum chemistry calculations. The experimentally determined vertical electron detachment energy of RuGeO(CO)(3)(-) surpasses those of RuGeO(CO)(4)(-) and RuGeO(CO)(5)(-), which is attributed to distinctive bonding features. RuGeO(CO)(3)(-) manifests one covalent sigma and two Ru-to-Ge dative pi bonds, contrasting with the sole covalent sigma bond present in RuGeO(CO)(4)(-) and RuGeO(CO)(5)(-). Unpaired spin density distribution analysis reveals a 17-electron configuration at the Ru center in RuGeO(CO)(3)(-) and an 18-electron configuration in RuGeO(CO)(4)(-) and RuGeO(CO)(5)(-). This work closes a gap in the quantitative physicochemical characterization of heteronuclear oxide carbonyl complexes, enhancing our insights into catalytic processes of CO/GeO on the metal surface at the molecular level.