Statistical analysis of noncovalent interactions of anion groups in crystal structures. I. Hydrogen bonding of sulfate anions

Abstract

The hydrogen-bond acceptor characteristics of sulfate dianions are analyzed in crystal structures of small molecules. For 85 anions, neither coordinated to metal ions nor covalently bonded, 697 hydrogen bonds are faund. Of these, 266 (38%) are the O...H--O type and 431 (62%) are the O.-.H--N type, proportions that correspond well to the stoichiometry of the compounds studied and indicate no preference for a particular donor. The analysis of the data set, after classifying the hydrogen bonds according to the different types of donors, shows that O.-.H--O bonds are more linear than O...H--N. The anion oxygen-acceptor function is characterized by multiple hydrogen bonding. Only in 56 cases does a sulfate oxygen participate in a single hydrogen bond. In most cases every sulfate oxygen is coordinated by two (187 cases) or three (89 cases) hydrogen bonds. For three H donors, the preferred coordination geometry of the sulfate oxygen is pyramidal. The most frequent coordination around a sulfate dianion is with eight to ten H donors. Thus, sulfate dianions can play a significant cohesive role in molecular aggregation.

The Aza Curtius Rearrangement

“…[13] The geometric parameters of the intramolecular hydrogen bond O(1)···N(2) in 5 are unexceptional. [14,15] Carbodiimide 3a reacts with alcohols and secondary amines to give the corresponding isoureas and guanidine derivatives (Scheme 11). Scheme 11.…”

“…[17,18] In turn, the N(5)ϪC (7) bond [1.351(4) Å ] is noticeably elongated in comparison with the standard NϭC double bond (1.27 Å ), [14] but shorter than the standard N(sp 2 )ϪC(sp 2 ) single bond (1.45 Å ). [12] In this regard, one may suppose significant delocalization of the negative charge over the whole tetrazolimidatesulfonyl system.…”

The Nature of Hydrogen Bonding in Protic Ionic Liquids

“…In crystalline solids, R X:H N of 2 are associated with bifurcated H-bonds [3,6,8,35] and 3 with trifurcated Hbonds, [3,6,8] and similar relationships between R X:H N and Hbond geometry have been reported, notably for dithiocyanate salts, [36] or thiocyanate, [37,38] and sulfate [39] anions in the Cambridge Structural Database. The bifurcated and trifurcated definitions must be applied with caution for PILs because the ions are in motion rather than fixed in a lattice, so the R X:H N and angle distributions represent the average liquid state.…”

Statistical analysis of noncovalent interactions of anion groups in crystal structures. II. Hydrogen bonding of thiocyanate anions

“…This property is related to their interaction with the protein. In the course of our studies of the hydrogen bonding of anions in the crystal state (Chertanova & Pascard, 1996), we undertook systematic studies on the thiocyanate (isothiocyanate) anion whose H-coordination function has not previously been the subject of such an analysis.…”