Synthesis and structural analysis of some trinitromethanide salts

Two trinitromethanide (TNM) salts containing weakly coordinating cations (t etrabutylammonium and cesium) were synthesized via incomplete nitration of acetic anhydride followed by cation exchange with tetrabutylammonium bromid e and cesium fluoride. Their structural characteristics were determined by single crystal X-ray crystallography [J.C. Bryan, M.N. Burnett, A.A. Gakh, Acta Crystallogr., Sect. C (Cr. Str. Comm.) 54 (1998) 1229] followed by com parative analysis with the literature data, In all cases, the TNM anion was found to be a non-planar system, The sum of dihedral angles between the ce ntral (C-N-3) plane of the anion and the planes of the individual nitro gro ups varies from 60 to 100 degrees. C-N and N-O interatomic distances in TNM anion can be correlated with the dihedral angles of the corresponding nitr o groups. The C-13 and N-14 NMR spectra of the TNM anion are very simple (b road singlets), an indication of the equivalence (on the NMR time scale) of the nitro groups in solution. The distribution ratio between organic phase (tributyl phosphate) and water is 5000 times higher for Cs+C(NO2)(3)(-) co mpared to Cs+NO3-, presumably due to size and/or charge delocalization diff erences between nitrate and TNM anions. (C) 2000 Elsevier Science B.V. All rights reserved.