Saal T, Rahm M, Christe KO, Haiges R. Protonation of Nitramines: Where Does the Proton Go?
Angew Chem Int Ed Engl 2017. [PMID:
28628721 DOI:
10.1002/anie.201705397]
[Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The reactions of nitramine, N-methyl nitramine, and N,N-dimethyl nitramine with anhydrous HF and the superacids HF/MF5 (M=As, Sb) were investigated at temperatures below -40 °C. In solution, exclusive O-protonation was observed by multinuclear NMR spectroscopy. Whereas no solid product could be isolated from the neat HF solutions even at -78 °C, in the HF/MF5 systems, protonated nitramine MF6- salts were isolated for the first time as moisture-sensitive solids that decompose at temperatures above -40 °C. In the solid state, depending on the counterion, O-protonated or N-protonated cations can be formed, in accord with theoretical calculations which show that the energy differences between O-protonation and N-protonation are very small. The salts [H2 N-NO2 H][AsF6 ], [H3 N-NO2 ][SbF6 ], [MeHNNO2 H][SbF6 ], and [Me2 NNO2 H][SbF6 ] were characterized by their X-ray crystal structures.
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