Second order perturbation from the NBO calculations show donation of electron density from the C atom (35.2 kcal mol -1 ), C-C bond (17.5 kcal mol -1 ), C-C bond (2.6 kcal mol -1 ) and C atom (1.4 kcal mol -1 ) to Mg. An NCI plot further supports the proposed allyl character of the hydrocarbon ligand, as it shows attractive interactions between each carbon atom and the magnesium site (Figure ). Activation Strain Analysis: While relief of ring strain is clearly an important thermodynamic driving force for these reactions, it is not immediately clear if this is also a factor in determining the kinetics of C-C bond activation. Activation Strain Analysis (ASA) was performed to address this question. This approach interrogates energy changes on the potential energy surface around the transition state, at the simplest level deconvoluting the total energy of the system into the interaction energy Eint() between two fragments and the strain energy Estrain() required to distort said fragments along the potential energy surface. Typically, ASA is applied to bimolecular reactions, although there are examples of unimolecular systems where this approach has provided useful insight. In intramolecular cases, the choice of fragments has been proposed to be crucial in obtaining meaningful information on the factors that impact reactivity. Here the interaction of the cycloalkane fragment (e.g. C4H7 or C5H9) with the metal fragment [M{(NArCMe)2CH}] was considered (M = Mg, Zn; Ar = 2,6di-iso-propylphenyl). Hence, our ASA calculations should provide insight into the strain required to distort each of these fragments to the TS geometry, and the difference in interaction energies (i.e. the binding energy) between the metal and the hydrocarbon ligand as the TS is approached.