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Elusive Zintl Ions [μ‐HSi 4 ] 3− and [Si 5 ] 2− in Liquid Ammonia: Protonation States, Sites, and Bonding Situation Evaluated by NMR and Theory
Author(s) -
Hastreiter Florian,
Lorenz Corinna,
Hioe Johnny,
Gärtner Stefanie,
Lokesh Nanjundappa,
Korber Nikolaus,
Gschwind Ruth M.
Publication year - 2019
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.201812955
Subject(s) - protonation , delocalized electron , chemistry , ion , crystallography , cluster (spacecraft) , atom (system on chip) , liquid ammonia , computational chemistry , ammonia , organic chemistry , computer science , embedded system , programming language
The existence of [μ‐HSi 4 ] 3− in liquid ammonia solutions is confirmed by 1 H and 29 Si NMR experiments. Both NMR and quantum chemical calculations reveal that the H atom bridges two Si atoms of the [Si 4 ] 4− cluster, contrary to the expectation that it is located at one vertex Si of the tetrahedron. The calculations also indicate that in the formation of [μ‐HSi 4 ] 3− , protonation is driven by a high charge density and an increase of electron delocalization compared to [Si 4 ] 4− . Additionally, [Si 5 ] 2− was detected for the first time and characterized by NMR. Calculations show that it is resistant to protonation, owing to a strong charge delocalization, which is significantly reduced upon protonation. Thus, our methods reveal three silicides in liquid ammonia: unprotonated [Si 5 ] 2− , terminally protonated [HSi 9 ] 3− , and bridge‐protonated [μ‐HSi 4 ] 3− . The protonation trend can be roughly predicted by the difference in charge delocalization between the parent compound and the product, which can be finely tuned by the presence of counter ions in solution.