Hydrogen-bonding landscape of the carbamoyl-cyano-nitro-somethanide anion in the crystal structure of its ammonium salt

Abstract

The structure of the title salt, ammonium carbamoyl-cyano-nitro-somethanide, NH₄ ⁺·C₃H₂N₃O₂ ^-, features the co-existence of different hydrogen-bonding patterns, which are specific to each of the three functional groups (nitroso, carbamoyl and cyano) of the methanide anion. The nitroso O-atoms accept as many as three N-H⋯O bonds from the ammonium cations [N⋯O = 2.688 (3)-3.000 (3) Å] to form chains of fused rhombs [(NH₄)(O)₂]. The most prominent bonds of the carbamoyl groups are mutual and they yield 2₁ helices [N⋯O = 2.903 (2) Å], whereas the cyano N-atoms accept hydrogen bonds from sterically less accessible carbamoyl H-atoms [N⋯N = 3.004 (3) Å]. Two weaker NH₄ ⁺⋯O=C bonds [N⋯O = 3.021 (2), 3.017 (2) Å] complete the hydrogen-bonded environment of the carbamoyl groups. A Hirshfeld surface analysis indicates that the most important inter-actions are overwhelmingly O⋯H/H⋯O and N⋯H/H⋯N, in total accounting for 64.1% of the contacts for the individual anions. The relatively simple scheme of these inter-actions allows the delineation of the supra-molecular synthons, which may be applicable to crystal engineering of hydrogen-bonded solids containing polyfunctional methanide anions.

Keywords: carbamoyl­cyano­nitro­somethanide; crystal structure; hydrogen bonding; supra­molecular synthon.