S(N)2-like reactions in hydrogen-bonded complexes have been investigated in this paper at a correlated MP2-C (full)/6-311++G(3df,3pd) level, employing (FHNH3HF)-N-...-H-... and (ClHNH3HCl)-N-...-H-... as model systems. The unconventional F(Cl)-(HN)-N-... noncovalent bond and the conventional F(Cl)-(HN)-N-... hydrogen bond can coexist in one complex which is taken as the reactant of the SN2-like reaction. The SN2-like reaction occurs along with the inversion of NH3 and the interconversion of the unconventional F(Cl)-(HN)-N-... noncovalent bond and the conventional F(Cl)-(HN)-N-... hydrogen bond. In comparison with that of the isolated NH3, the inversion barriers of the two complexes both are significantly reduced. The effect of carbon nanotube confinement on the inversion barrier is also discussed.