Hydrido-Ruthenium Cluster Complexes as Models for Reactive Surface Hydrogen Species of Ruthenium Nanoparticles. Solid-State 2H NMR and Quantum Chemical Calculations

The 2H quadrupolar interaction is a sensitive tool for the characterization of deuterium−metal binding states. In the present study, experimental solid-state 2H MAS NMR techniques are used in the investigations of two ruthenium clusters, D4Ru4(CO)12 (1) and D2Ru6(CO)18 (2), which serve as model compounds for typical two-fold, three-fold, and octahedral coordination sites on metal surfaces. By line-shape analysis of the 2H MAS NMR measurements of sample 1, a quadrupolar coupling constant of 67 ± 1 kHz, an asymmetry parameter of 0.67 ± 0.1, and an isotropic chemical shift of −17.4 ppm are obtained. In addition to the neutral complex, sample 2 includes two ionic clusters, identified as anionic [DRu6(CO)18]− (2−) and cationic [D3Ru6(CO)18]+ (2+). By virtue of the very weak quadrupolar interaction (<2 kHz) and the strong low-field shift (+16.8 ppm) of 2−, it is shown that the deuteron is located in the symmetry center of the octahedron spanned by the six ruthenium atoms. For the cationic 2+, the quadrupolar in...