For electron-rich substrates, migratory inserQon would be expected to be more facile with the equilibrium displaced further towards the products. For electron-poor substrates the barriers of migratory inserQon are higher, and the equilibrium is less displaced towards the products. Taken in combinaQon, the new mechanisQc model not only fits the complete kineQc data, but also explains the two kineQc regimes apparent from the Hammee analysis. In regime 1, the contribuQon of the migratory inserQon pre-equilibrium to turnover is small, the electronic effect from this step and dihydrogen acQvaQon step oppose each another, leading to near net zero influence of electronics on rate (r of zero). In regime 2, the contribuQon of the migratory inserQon pre-equilibrium to the turnover limiQng sequence becomes more significant, the electronic influence of this step now outweighs that of dihydrogen acQvaQon and results in more electron-deficient substrates reacQng slower (r = -1.4).