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

Reactions of platinum clusters Ptn±, n = 1–21, with CH4: to react or not to react

“…12 A detailed description of our experimental procedures has recently been given, including details of the chemicals used, gas handling, and pressure calibration. 11,13 In the present experiment we used isotopically enriched 195 Pt (97.3%, Oak Ridge National Laboratories). Approximate methane-deuterium mixtures were prepared in situ by introducing the pure gases through two independent leak valves.…”

“…9 A characteristic number of hydrogen-deuterium exchanges can serve as a probe for particular structures of gaseous metal hydrocarbon clusters, such as the fivefold exchange of a rhodium allyl hydride, 10 or the four fold exchange for Rh,C 2 ,H 4 + . 11 Along these lines, we interpret the twofold hydrogen-deuterium exchanges with an intact CH 2 unit which is bound to either one or two platinum atoms. This interpretation is also consistent with the observed reversibility of H 2 loss for Pt 4 + .…”

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.…”

Density Functional Theory Study of RhnS0,± and Rhn+10,± (n = 1–9)

“…The size-dependent chemical and physical properties of transition metal (TM) clusters and the interest that these properties elicit are well-documented. − A clear picture is now emerging that shows that both electronic and geometric structures play a critical role in determining cluster properties. ,,,− The observation of multiple ionization energies (IEs) or rates of reaction , for a single TM n cluster size (where n is the number of atoms) has been attributed to the presence of multiple isomeric cluster forms, each of which exhibit distinct physicochemical properties. These conclusions are supported by high-level, typically density functional theory (DFT), computational studies wherein numerous low-energy isomers are often identified for a single TM n species. − …”