Lewis acid stabilization and activation of primary N-nitrosamides

Abstract

The primary nitrosamides, here exemplified by the N-nitrosoalkylcarbamates, ROC(O)NHNO [R = CH₃ (1), R = C₂H₅ (2)], show a markedly Lewis acid dependent chemistry. Although their alkali metal salts M[ROC(O)NNO] [M = K, R = CH₃ (3), M = Na, R = CH₃ (3-Na), M = K, R = C₂H₅ (4), M = Na, R = C₂H₅ (4-Na)] are stable isolable yellow solids, in solution they undergo pH dependent decomposition to give nitrogen and nitrous oxide as the primary nitrogen containing gaseous products. However chelation to a transition metal, [Re(L)(CO)₂(PPh₃)₂], L = ROC(O)NNO⁻ gives rise to isomeric kinetic and thermodynamic products. Both are thermally stable and together illustrate the stability provided by a chelating low valent transition metal. The preparation, IR, NMR, and X-ray crystallographic characterization of these derivatives are reported. Taken together, these results demonstrate that the Lewis acid identity is an important factor in primary nitrosamide chemistry.