Geometries, frequencies, energies, and rate constants of the reaction N(S-4) + CH4 -> NH + CH3 were computed using coupled-cluster theory, correlation-consistent basis sets, and extrapolations schemes to assess the complete basis set limit energies. Our best calculation gives a classical barrier height and reaction energy of 32.9 and 29.3 kcal/mol, respectively, and 24.6 kcal/mol for the reaction enthalpy (Delta H-0(0)). Thermal (200-2000 K) rate constants were calculated with the canonical variational transition state theory, and indicate a very slow reaction when compared with the ones with N(D-2) and N(P-2). Using the CVT/mu OMT method, the value of H/D KIE is 6.3 (300 K). (c) 2006 Elsevier B.V. All rights reserved.