Two State Reactivity Paradigm in Catalysis. The Example of X-H (X = O, N, C) and C-C Bonds Activation Mediated by Transition Metal Compounds

A brief review of the theoretical work carried out on the activation of O-H, N-H, C-H and C-C bonds of small prototypical molecules mediated by “bare” transition metal atoms and cations in gas-phase is reported. Potential energy surfaces are examined in light of the role that spin changes can play in determining the final outcome of this kind of reactions and the results are analyzed in terms of two state reactivity paradigm. The performance of Density Functional Theory, in its B3LYP formulation, in this field is discussed along with comparison with experimental findings and high level ab initio computations.