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 σ and two Ru-to-Ge dative π bonds, contrasting with the sole covalent σ 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.