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Cation–Cation Pairing by NCH⋅⋅⋅O Hydrogen Bonds
Author(s) -
Gamrad Waltraud,
Dreier Angelika,
Goddard Richard,
Pörschke KlausRichard
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201408278
Subject(s) - chemistry , hydrogen bond , salt (chemistry) , crystallography , amide , inorganic chemistry , pairing , ion , hydrogen , molecule , organic chemistry , physics , superconductivity , quantum mechanics
The pairing of ions of opposite charge is a fundamental principle in chemistry, and is widely applied in synthesis and catalysis. In contrast, cation–cation association remains an elusive concept, lacking in supporting experimental evidence. While studying the structure and properties of 4‐oxopiperidinium salts [OC 5 H 8 NH 2 ]X for a series of anions X − of decreasing basicity, we observed a gradual self‐association of the cations, concluding in the formation of an isolated dicationic pair. In 4‐oxopiperidinium bis(trifluoromethylsulfonyl)amide, the cations are linked by NH⋅⋅⋅OC hydrogen bonds to form chains, flanked by hydrogen bonds to the anions. In the tetra(perfluoro‐ tert ‐butoxy)aluminate salt, the anions are fully separated from the cations, and the cations associate pairwise by NCH⋅⋅⋅OC hydrogen bonds. The compounds represent the first genuine examples of self‐association of simple organic cations based merely on hydrogen bonding as evidenced by X‐ray structure analysis, and provide a paradigm for an extension of this class of compounds.