Since the 4CN Ga is in a more constrained environment, the Si-OH group formed due to ethylene activation is not far from the Ga site (2.7 Å, species 4), allowing for a relatively facile protontransfer step to recover the original 4CN Ga site with an accessible activation barrier (step 4 to ‡ a , 1.1 eV). Therefore, the 4CN site is more likely to catalyze olefin oligomerization through the proton transfer cycle, though a fairly low turnover frequency is expected due to the high barrier of olefin insertion. On the other hand, a pathway transfer to C-A mechanism is very likely to occur on the 3CN Ga site, forming a Ga-alkyl intermediate.