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 η³ type coordination of methane. In contrast, binding governed by orbital interactions results in a η² 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.

中文翻译：

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甲烷活化中的离子光谱

这篇综述致力于配合物的离子光谱研究，这些研究与理解甲烷与金属离子和簇的活化有关。甲烷活化始于与金属离子形成络合物。完整的甲烷分子与离子之间的相互作用程度可以通过甲烷分子中 C-H 伸缩振动的扰动来监测。由静电相互作用介导的结合导致甲烷的 η ³型配位。相反，由轨道相互作用控制的结合导致 η ²甲烷的类型配位。我们进一步回顾了金属 - 甲烷反应活化产物的光谱表征，例如由选定的 5d 金属与甲烷相互作用产生的金属 - 卡宾和卡宾产物。该领域最近研究的重点已转向研究甲烷和金属簇之间的相互作用。我们展示的例子强调了金属簇在甲烷活化反应中的反应性更强。