Chemistry with Methane: Concepts Rather than Recipes

Four seemingly simple transformations related to the chemistry of methane will be addressed from mechanistic and conceptual points of view: 1) metal-mediated dehydrogenation to form metal carbene complexes, 2) the hydrogen-atom abstraction step in the oxidative dimerization of methane, 3) the mechanisms of the CH4→CH3OH conversion, and 4) the initial bond scission (C-H vs. O-H) as well as the rate-limiting step in the selective CH3OH→CH2O oxidation. State-of-the-art gas-phase experiments, in conjunction with electronic-structure calculations, permit identification of the elementary reactions at a molecular level and thus allow us to unravel detailed mechanistic aspects. Where appropriate, these results are compared with findings from related studies in solution or on surfaces. Elementary steps associated with the activation of methane are addressed from experimental and computational viewpoints; what matters most are relativistic effects, two-state reactivity scenarios, and cluster-size and ligand effects, which all play a role in the organometallic chemistry of methane at ambient conditions. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.