Concepts for selective oxidation reactions

The development of a fundamental understanding of chemical reactions is of prime importance for the development of mankind. Among the central challenges of future research is the development of new strategies for the usage of the limited global energy resources as well as the utilization of biogenic sources. In this respect, new and improved methods for selective partial oxidation are a one of the central challenges for catalysis of the 21th century. The gas-phase studies of the team have provided new insights in this respect, far beyond the scope of usual mass-spectrometric research. To mention just a few of the achievements in this respect, it is referred to two publications. In a paper entitled "Two-state reactivity as a new concept in organometallic chemistry" in Accounts of Chemical Research (2000), a new reactivity paradigm has been presented. This article has meanwhile been cited more than 160 times, and about half of these citations come from biologists or biochemists, because two-state reactivity (TSR) appears of having fundamental relevance in the area of metalloenyzmes.

The essence of TSR is the occurrence of a spin change along the reaction coordinate of a chemical transformation, as shown in the right-hand figure for the oxidation of an alkane RH by a metal-oxo species MO. The TSR scenario has crucial consequences for reaction kinetics and product distributions and is hence of extreme importance for a deeper understanding of these reactions.

As second example, we mention a recent report about the activation of methane by the gaseous MgO⁺ cation in Angewandte Chemie International Edition (2006), which has repeatedly been predicted by theory, but could not have been realized in previous experimental studies. By means of electrospray ionization, bare MgO⁺ was generated for the first time in yields sufficient for subsequent reactivity studies. In addition to the experimental work, the potential-energy surface for the C-H bond activation of methane by MgO⁺ has been studied by adequate calculations which provide a complete picture of this also technologically important process (see Figure below).