Open AccessStrong asymmetric hydrogen bonding in 2‐(oxamoylamino)ethylammonium oxamate–oxamic acid (1/1)
Author(s) -
Martinez Belmonte Marta,
Price Daniel J.
Publication year - 2010
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
eISSN - 1600-5759
pISSN - 0108-2701
DOI - 10.1107/s0108270110004233
Subject(s) - hydrogen bond , chemistry , molecule , crystallography , amide , ion , hydrogen , stereochemistry , organic chemistry
The title compound, C 4 H 10 N 3 O 2 + ·C 2 H 2 NO 3 − ·C 2 H 3 NO 3 , contains at least 11 distinct hydrogen‐bond interactions showing a great variety of bond strengths. The shortest and strongest hydrogen bond [O...O = 2.5004 (12) Å] is found between the uncharged oxamic acid molecule and the oxamate monoanion. The grouping formed by such a strong hydrogen bond can thus be considered as a hydrogen bis(oxamate) monoanion. It lacks crystallographic symmetry and the two oxamate groups have different conformations, showing an asymmetric hydrogen‐bond interaction. Significantly, the asymmetry allows us to draw a direct comparison of site basicity for the two inequivalent carboxylate O atoms in the planar oxamate anion. The constituent molecular ions of (I) form ribbons, where all amide and carboxylate groups are coplanar. Graph‐set analysis of the hydrogen‐bonded networks reveals the R 2 2 (10) and R 2 2 (9) homodromic nets as important structure‐directing motifs, which appear to be a common feature of many oxamate‐containing compounds.