Ion spectroscopy in methane activation

Abstract

This review is devoted to ion spectroscopy studies of complexes relevant for the understanding of methane activation with metal ions and clusters. Methane activation starts with the formation of a complex with a metal ion. The degree of the interaction between an intact methane molecule and the ion can be monitored by the perturbations of C-H stretch vibrations in the methane molecule. Binding mediated by the electrostatic interaction results in a η 3 type coordination of methane. In contrast, binding governed by orbital interactions results in a η 2 type coordination of methane. We further review the spectroscopic characterization of activation products of metal-methane reactions, such as the metal-carbene and carbyne products resulting from the interaction of selected 5d metals with methane.The focus of recent research in the field has shifted towards the investigation of interactions between methane and metal clusters. We show examples highlighting that metal clusters can be more reactive in methane activation reactions.

IR Spectroscopic Characterization of Methane Adsorption on Copper Clusters Cun+ (n = 2–4)

“…By isolating the reactants and studying the products formed with mass-spectrometric or spectroscopic techniques, it is possible to reconstruct element-, size-, and structure-specific reactivity information with the aid of computational methods. Reactions between metal ions and clusters with methane have been studied extensively. − Because of their electrophilic nature, positively charged ions are generally more reactive toward CH 4 than neutrals or anions . Products formed when reacting atomic metal ions M + and methane have been widely studied using optical spectroscopy to uncover their structures. − Possible binding motifs cover the spectrum from η 3 for electrostatic dominated interactions and η 2 for orbital interactions, to C–H activation and subsequent H 2 elimination yielding a [M,C,2H] + product that can adopt carbene or hydrido carbyne structures.…”

Vibrational Spectroscopy and Structural Analysis of V+(C2H6)n Clusters (n = 1–4)

“…The use of solid-state or surface-based transition metal catalysis is widespread in industry, but it is also possible to catalyze hydrocarbon functionalization using small clusters. , Such cluster studies are not only a means of catalysis but can also serve as experimentally tractable models for understanding catalysis in larger systems. When hydrocarbons interact with individual transition metal atoms and ions, as well as small clusters of atoms, the resulting chemistry can be similar to what occurs at surface defects in bulk systems. ,− …”

Cation‐π Interactions between a Noble Metal and a Polyfunctional Aromatic Ligand: Ag+(benzylamine)

“…[29,30] In a recent report, cation-π complexes of Ag + with benzene, toluene and furan have been studied with ultraviolet laser photodissociation and photofragment imaging, providing new information on the cation-π bond energies. [31] IR ion spectroscopy has proven to be a valuable tool to shed light on the structural features of complexes of the noble metals silver, [17,[32][33][34][35][36][37][38][39][40] gold [41][42][43][44][45][46] and platinum, [47][48][49][50][51][52][53] with a variety of ligands yielding a wealth of valuable information such that only partial reference may be given here. It has been reported that complexation of Ag + with polycyclic aromatic hydrocarbons is accompanied by substantial charge transfer, emerging from the analysis of the IR bands of the complexes compared to those of the bare ligands.…”