Reactions of benzene with rhodium cluster cations: Competition between chemisorption and physisorption

Abstract

Collision induced dissociation of metal cluster ions: Bare aluminum clusters, Al+ n (n=3-26) J. Chem. Phys. 86, 3876 (1987); 10.1063/1.451948Femtosecond resolution ultrafast ion reaction time measurement a pulsedlaser field desorption timeofflight spectroscopy AIP Conf.The reactions of Rh n ϩ cations, nϭ1-40, with C 6 H 6 and C 6 D 6 were investigated under single collision conditions in a Fourier-transform-ion-cyclotron-resonance mass spectrometer. For clusters with up to 18 rhodium atoms, dissociative chemisorption, accompanied by total or partial dehydrogenation in competition with nondissociative adsorption of an intact benzene molecule ͑physisorption͒ was observed. For clusters with nϾ18 only the nondissociative adsorption was observed in the primary reaction step. Besides some enhancement of the nondissociative adsorption channel for cluster sizes nϭ9, 11, 12, and 13, deuteration has little effect upon the observed reactions. The atomic rhodium cation reacts after a few seconds induction time to an arene complex, which then forms a bis-arene complex in a secondary reaction step. Rhodium dimer alone exhibits some cleavage of the Rh-Rh bond, resulting also in the Rh-C 6 H 6 ϩ complex.

Probing the structures of gas-phase rhodium cluster cations by far-infrared spectroscopy

“…The magnetic moments, 4,5 electric polarizability, 6 and reactivity with a range of small molecules [7][8][9][10][11][12][13][14][15][16] have been investigated, in many instances revealing a significant size dependence of these properties. In several cases, reaction rate measurements on monodisperse cluster samples have suggested multiple reactivities, indicating the presence of multiple forms of clusters of the same size.…”

Theoretical study of the electronic states of Rhn+ (n=3–5)

“…27. Although Berg et al 19 have estimated the dissociation energy Refer to Fig. 2͑c͒ for the definitions of a, b, c, d, and e. of Rh 2 ϩ to be 3.15 eV, the ground state geometry of Rh 2 ϩ is not known.…”

“…19 They have found the rate of such adsorption reactions to be dependent on the cluster size. Our preliminary investigations on the reaction of benzene with Rh ϩ and Rh 2 ϩ have revealed that electronic properties of Rh ϩ and Rh 2 ϩ are of paramount importance in such reactions.…”

Mechanisms of catalytic dehydrogenation of alkanes by rhodium clusters Rhn+ probed by isotope labelling

“…Further insights are gained by directly comparing the behaviour of gaseous and supported atoms and clusters, as demonstrated for instance for rhodium in catalysing the trimerisation of acetylene [7]. Numerous experimental studies on rhodium cations [8][9][10][11][12][13][14] and rhodium clusters [15][16][17] as well as theoretical calculations [18][19][20] have aimed in understanding the principles for dehydrogenation of hydrocarbons, in particular alkanes. The metal clusters mimic essential features * Corresponding author.…”