Theoretical study of the potential-energy surface related to H2N+NS reaction: N-2 vs H-2 elimination

The potential-energy surface related to the H2N + NS reaction, which involv es 13 intermediates and fragment products, as well as 14 transition structu res has been fully characterized using both molecular orbital (MP2) and den sity functional theory (B3LYP) and the 6-311+ +G(d,p) basis set. Improved e lectronic energies have also been obtained using single-point coupled-clust er CCSD(T) calculations. The system is shown to have three different groups of products: N2H + SH, N2S + H-2 and N-2 + H2S and a rather complex reacti on mechanism. Starting from H2N + NS, several low-lying [H2N2S] isomers par ticipate in the elimination of H-2 and N-2. The N-2 elimination appears to be favoured over other reaction channels in the destruction of NS. The stan dard enthalpies of formation of the most stable isomers have been estimated , Delta(f)H(298)(degrees), in kJ mol(-1): H2N-N=S: 250, H2N-S drop N: 262, NH=NH=S: 264, NH=N-SH :247 and NH=S=NH: 318.