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.
Highlights
Resonance-stabilized methanide-type anions are excellent ligands in metal–organic chemistry, which reveal a variety of coordination modes toward metal ions (Gerasimchuk, 2019; Turner et al, 2011)
The rich molecular functionality of such species, as is exemplified by different nitrile, nitroso- and carbamoyl-substituted derivatives, predetermines their special properties as potent acceptors of conventional hydrogen bonds. These kinds of interactions are important for the solvation and solvatochromism of cyanoanions (Gerasimchuk et al, 2010) and intermolecular bonding in the crystal structures of metal complexes (Gerasimchuk et al, 2015), but it could influence the specific targeting of cyanoanions in biomedical systems (Gerasimchuk et al, 2007) and their behavior as anionic components for ionic liquids (Janikowski et al, 2013)
We report the construction of a three-dimensional hydrogen-bonded framework in ammonium carbamoylcyanonitrosomethanide NH4(nccm), which features the co-existence and interplay of the abovementioned anion–cation and mutual anion–anion interactions
Summary
Resonance-stabilized methanide-type anions are excellent ligands in metal–organic chemistry, which reveal a variety of coordination modes toward metal ions (Gerasimchuk, 2019; Turner et al, 2011). The rich molecular functionality of such species, as is exemplified by different nitrile-, nitroso- and carbamoyl-substituted derivatives, predetermines their special properties as potent acceptors of conventional hydrogen bonds These kinds of interactions are important for the solvation and solvatochromism of cyanoanions (Gerasimchuk et al, 2010) and intermolecular bonding in the crystal structures of metal complexes (Gerasimchuk et al, 2015), but it could influence the specific targeting of cyanoanions in biomedical systems (Gerasimchuk et al, 2007) and their behavior as anionic components for ionic liquids (Janikowski et al, 2013). Such an evolution is clearly reflected in the positions of the (NO) bands in the IR spectra (cmÀ1): they are 1098 for H(nccm); 1140 for H(nccm)2À; 1212 for the title compound; 1253 for NMe4(nccm) and 1290 for Cs(nccm), demonstrating the systematic blue shift as the N—O bond order increases
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