This perspective discusses the principles of the multistate scenario often encountered in transition metal catalyzed reactions, and is organized as follows. First, several important theoretical concepts (physical versus formal oxidation states, orbital interactions, use of (spin) natural and corresponding orbitals, exchange enhanced reactivity and the connection between valence bond and molecular orbital based electronic structure analysis) are presented. These concepts are then used to analyze the electronic structure changes occurring in the reaction of C-H bond oxidation by Fe(IV)oxo species. The analysis reveals that the energy separation and the overlap between the electron donating orbitals and electron accepting orbitals of the Fe(IV)oxo complexes dictate the reaction stereochemistry, and that the manner in which the exchange interaction changes depends on the identity of these orbitals. The electronic reorganization of the Fe(IV)oxo species during the reaction is thoroughly analyzed and it is shown that the Fe(IV)oxo reactant develops oxyl radical character, which interacts effectively with the σCH orbital of the alkane. The factors that determine the energy barrier for the reaction are discussed in terms of molecular orbital and valence bond concepts.

New high‐spin pathways: All four feasible reaction pathways for alkane hydroxylation by nonheme iron(IV)–oxo complexes have been investigated by computational methods. The triplet σ path is too high in energy to be involved in CH bond activation, but the reactivity of the quintet π channel competes with the triplet path and may thus offer a new approach for specific control of CH bond activation by iron(IV)–oxo species (see scheme).

A mechanistically unique, simultaneous activation of two C-H bonds of methane has been identified during the course of its reaction with the cationic copper carbide, [Cu-C]. Detailed high-level quantum chemical calculations support the experimental findings obtained in the highly diluted gas phase using FT-ICR mass spectrometry. The behavior of [Cu-C]/CH contrasts that of [Au-C]/CH, for which a stepwise bond-activation scenario prevails. An explanation for the distinct mechanistic differences of the two coinage metal complexes is given. It is demonstrated that the coupling of [Cu-C] with methane to form ethylene and Cu is modeled very well by the reaction of a carbon atom with methane mediated by an oriented external electric field of a positive point charge.