Formation of thermodynamically stable dications in the gas phase by thermal ion-molecule reactions: tantalum(2+) and zirconium(2+) with small alkanes

Size‐Dependent Binding Energies of Methane to Small Gold Clusters

“…[7] In contrast, an uptake of several CH 4 molecules was observed under multi-collision conditions. [8] Although dehydrogenation of CH 4 was not directly observed in the latter study, it was proposed that methane was dissociatively bound as methyl plus hydride (CH 3 ÀAu x + ÀH). However, only recently a combined theoretical and experimental study [9] could directly prove that the positively charged gold dimer, Au 2 + , is able to adsorb methane, to activate it through coadsorption of a second molecule of CH 4 , and, most surprisingly, to selectively catalyze the formation of ethylene at temperatures as low as 250 K.…”

“…While small platinum clusters Pt x + were found to be able to activate and dehydrogenate methane, yielding Pt x CH 2 + (x 9) as well as Pt x C 2 H 4 + (x = 1, 5), [6] the reactivity of the binary platinum-gold clusters Pt x Au y + decreased with increasing gold content. Consequently, pure gold clusters Au x + were found to be completely unreactive toward CH 4 under the single-collision conditions employed in these experiments. [7] In contrast, an uptake of several CH 4 molecules was observed under multi-collision conditions.…”

“…[3] In previous studies, the activation and dehydrogenation of methane, yielding the product MCH 2 + , has been observed for a variety of third-row transition metal cations (M + ). [4,5] However, Au + was found previously to be among the few 5d metals that are completely unreactive toward methane. [5] In contrast to the numerous experimental data on methane adsorption and activation on atomic transition metal ions, only few investigations concerning methane adsorption on cationic metal clusters are available.…”

“…Besides the reaction mechanisms, experimentally and theoretically obtained cluster-sizedependent methane binding energies to the gold cluster cations are presented for the first time. Furthermore, calculations of the optimal atomic adsorption geometries as well as of The reactions of small gold cluster cations Au x + (x = 2-6) with CH 4 were studied by joint gas-phase kinetics and first-principles density functional theory calculations. The experimentally obtained temperature-dependent low pressure rate constants were analyzed by employing the Lindemann energy transfer model for association reactions in conjunction with statistical RRKM theory.…”

Gas-phase activation of methane by ligated transition-metal cations

“…In fact, most of the above-mentioned examples of methane activation lead to species that do not react further with methane; exceptions are found among 5d metals (2,3,13,14,19,20). In addition, bare transition-metal ions correspond to the oxidation state (ϩI), which is unusual in condensed-phase chemistry.…”