Theoretical studies on the S-N interaction in sulfinamides

The potential energy surface of sulfinamide H(O)S-NH2 (1) was searched, using ab initio and density functional methods, to study the conformational preferences. High-accuracy G2MP2 calculations showed that the S-N rotational barrier in 1 is 7.0 kcal mol(-1). The inversion around N in 1 goes through a very low energy barrier. Charge analysis using the NPA method was performed to elucidate the electronic factors responsible for the observed trends in the S-N interactions. The strength of negative hyperconjugation in 1 was estimated using NBO analysis and by studying the substituent effect. The repulsions between the lone pairs on oxygen and nitrogen and the n(N) --> sigma*(S-O) negative hyperconjugation play an important role in the conformations. Copyright (C) 2002 John Wiley Sons, Ltd.