Mn-N (Å) 2.14 2.14 a 2.24 2.23 a The bond length for Mn-5 was determined by DFT analysis previously. Based on the results above we conclude that metal-alkyl mechanism is likely manifested in the present catalytic system (Figure ). The activated Mn(I)-hydride precatalyst 8 enters the cycle via the reaction with alkene via the intermediate I. This step requires the dissociation of a CO ligand detected experimentally. Further transformation of I involves the hydride transfer to form Mn-alkyl species II aided by the reattachment of N-donor ligand. Subsequent β-hydride elimination furnishes the isomerized olefin product 2 and dicarbonyl Mn hydride III. The final coordination of another alkene substrate can be kinetically unfavourable due to the saturation of Mn centre with strong field ligands. However, we speculate that this step can be facilitated by the dissociation of the labile N donor within Mn-CN(Me)P complex that would liberate the vacant site for olefin coordination regenerating the species I.