title: Hydrido-ruthenium cluster complexes as models for reactive surface hydrogen species of ruthenium nanoparticles. Solid-state 2H NMR and quantum chemical calculations.
abstract: The (2)H quadrupolar interaction is a sensitive tool for the characterization of deuterium-metal binding states. In the present study, experimental solid-state (2)H MAS NMR techniques are used in the investigations of two ruthenium clusters, D(4)Ru(4)(CO)(12) (1) and D(2)Ru(6)(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 (2)H 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 [DRu(6)(CO)(18)](-) (2(-)) and cationic [D(3)Ru(6)(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 interaction is similar to that of the neutral 2. Quantum chemical DFT calculations at different model structures for these ruthenium clusters were arranged in order to help in the interpretation of the experimental results. It is shown that the (2)H nuclear quadrupolar interaction is a sensitive tool for distinguishing the binding state of the deuterons to the transition metal. Combining the data from the polynuclear complexes with the data from mononuclear complexes, a molecular ruler for quadrupolar interactions is created. This ruler now permits the solid-state NMR spectroscopic characterization of deuterium adsorbed on the surfaces of catalytically active metal nanoparticles.
authors.affiliation: Institut für Physikalische Chemie, Technische Universität Darmstadt, Petersenstrasse 20, D-64287 Darmstadt, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Gutmann
authors.forename: Bernadeta
authors.initials: B
authors.lastname: Walaszek
authors.forename: Xu
authors.initials: X
authors.lastname: Yeping
authors.forename: Maria
authors.initials: M
authors.lastname: Wächtler
authors.forename: Iker
authors.initials: I
authors.lastname: del Rosal
authors.forename: Anna
authors.initials: A
authors.lastname: Grünberg
authors.forename: Romuald
authors.initials: R
authors.lastname: Poteau
authors.forename: Rosa
authors.initials: R
authors.lastname: Axet
authors.forename: Guy
authors.initials: G
authors.lastname: Lavigne
authors.forename: Bruno
authors.initials: B
authors.lastname: Chaudret
authors.forename: Hans-Heinrich
authors.initials: HH
authors.lastname: Limbach
authors.forename: Gerd
authors.initials: G
authors.lastname: Buntkowsky
mesh_terms: D002384:Catalysis; D006859:Hydrogen / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D053768:Metal Nanoparticles / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D009942:Organometallic Compounds / Q000737:chemistry*; D011789:Quantum Theory; D012428:Ruthenium / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D009942:Organometallic Compounds; D012428:Ruthenium; D006859:Hydrogen