Abstract
<jats:p>Transition-metal formyl complexes are crucial organometallic intermediates in the chemical reduction of CO and CO2 and serve as fundamental building blocks for the challenging C–C coupling of these C1 compounds. Herein, the first synthesis and characterization of selected Ru-triphos-based mono-formyl and bis-formyl complexes are disclosed. NaBHEt3 was utilized as a hydride source to transform the corresponding tricarbonyl complex, which was utilized as a starting compound, into the corresponding formyl complexes. Kinetic studies in NMR monitoring experiments were used to investigate the impact of ligand properties on the stability and reactivity of the formed formyl complexes. Importantly, these findings paved the way for an unprecedented unimolecular C–C coupling reaction at the ruthenium metal center that yielded ethylene glycol—a result confirmed by 13C labeling experiments and the formation of 2-ethyl-1,3,2-dioxaborolane. This reaction thus initiates the first steps towards a direct catalytic method for the sustainable production of ethylene glycol derivatives from CO or CO2.</jats:p>