Mechanism of Alkaline Earth Metal Amide Catalyzed Hydrogenation of Challenging Alkenes and Arenes.

Recently, bulky alkaline earth (Ae=Mg, Ca, Sr, Ba) metal amide complexes AeN" (N"=N[Si(iPr)]) are shown to be active for catalyzing the hydrogenation of unactivated alkenes and arenes, presumably via the monomer N"AeH as catalyst. In sharp contrast, our extensive DFT calculations disclose that the double Ae-H-Ae bridged dimer (N"AeH) is kinetically more favorable in catalytic hydrogenation with H, although rate-limited by the initial hydrogenolysis of AeN" to form the monomer N"AeH.