A-bond activation

Most catalytic cycles at some point involve a bond activation step, be it of one specific bond in a larger molecule or be it the coordination and activation of a small (e.g. diatomic) system like H2, CO, N2,02 etc. 

There are two completely different pathways for the cleavage of H-H bonds oxidative addition and heterolytic cleavage. Both pathways have been identified in catalytic hydrogenation and may also be applicable to other types of X-H a bond activation such as C-H cleavage. 

Scheme 8 presents a plausible mechanism for the intermolecular hydroamination of terminal alkynes promoted by the organothorium complex 1. The first step in the catalytic cycle involves the N-H a-bond activation of the primary amine by the organothorium complex yielding the bisamido-amine complex Cp2 Th(NHR )2 (H2NR ) (28) and two equivalents of methane (step 1). Complex 22 was found to be in rapid equilibrium with the corresponding bis(amido) complex 18 (step 2) [57, 60]. An additional starting point involved a similar C-H activation of the terminal alkyne with complex 1 yielding methane and the bis(acetylide) complex 17 (step 3). 

Musaev G, Morokuma K (2005) Transition Metal Catalyzed a-Bond Activation and Formation Reactions. 12 1-30... 

Keywords a-Bond activation and formation Transition metal systems Catalytic activity... 

Transition Metal Catalyzed a-Bond Activation and Formation Reactions... 

Several Examples of Catalytic Reaction via a-Bond Activation. 72... 

Keywords Theoretical approach C-H a-bond activation Oxidative addition ... 

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