A number of different mechanisms are proposed in the literature, explaining the experimental observations on C-H activation reactions, depending on the nature of a ligand (Ln) and transition metal (M) in the catalytically active species (LnM). These mechanisms include four elementary steps: oxidative addition, σ-bond metathesis, electrophilic substitution and 1,2-addition, respectively . Even though the mechanisms are inherently different, three most important aspects should be primarily taken into account when classifying and rationalising C-H activation reactions: the proximity of C-H bond to the transition metal;