The insertion reactions of silylenoid [(tert-butoxy)diphenylsilyl]lithium Ph2SiLi(OBu-t) into HF, H2O, and NH3 molecules have been studied by using density functional theory at the B3LYP/6-31G(d) level. To better understand the reactivity of silylenoid Ph2SiLi(OBu-t), its two most stable isomers, the p-complex (1) and the three-membered ring (2), were selected for reactants. Natural bond orbital (NBO) analysis has been performed to study the effects of charge transfer and to understand the nature of different interactions between atoms or groups. The results indicate that (i) the insertion of Ph2SiLi(OBu-t) into X-H bond proceeds in a concerted manner via a three-membered-ring transition state to form substituted silane Ph2SiHX with dissociation of LiOBu-t; (ii) the activation barrier increases in the order of HF < H2O < NH3, and the barrier heights of the 1 insertions are higher than those of the 2 insertions, respectively; (iii) both I and 2 display ambiphilic character in their insertion reactions.