Mechanistic insight into alkali-metal mediation of styrene transfer hydrogenation: a DFT study

A computational mechanistic study was performed to investigate the transfer hydrogenation of styrene catalysed by a potassium tris-hexamethyldisilazide magnesiate in the presence of 1,4-cyclohexadiene. Exploiting cooperative effects between Mg and K centres present in this tris(amide) complex results in the selective formation of the desired product ethylbenzene. The calculations demonstrate the synergy of the metal centres within the bimetallic complex, since neither the monometallic potassium amide K(HMDS) nor the magnesium amide Mg(HMDS)2 on their own can efficiently execute this transformation under the experimental conditions. Several distinct mechanistic pathways have been explored, leading to the identification of the most plausible sequence in which both metal centres act in a synchronised manner.