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Anionic Siliconoids from Zintl Phases: R 3 Si 9 − with Six and R 2 Si 9 2− with Seven Unsubstituted Exposed Silicon Cluster Atoms (R=Si( t Bu) 2 H)
Author(s) -
Schiegerl Lorenz J.,
Karttunen Antti J.,
Klein Wilhelm,
Fässler Thomas F.
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201805442
Subject(s) - delocalized electron , chemistry , crystallography , heteronuclear molecule , silicon , zintl phase , cluster (spacecraft) , silicide , single crystal , silylation , nuclear magnetic resonance spectroscopy , crystal structure , analytical chemistry (journal) , stereochemistry , catalysis , organic chemistry , computer science , programming language
Neutral and anionic silicon clusters (siliconoids) are regarded as important model systems for bulk silicon surfaces. For 25 years their formation from binary alkali metal silicide phases has been proposed, but experimentally never realized. Herein the silylation of a silicide, leading to the anionic siliconoids (Si( t Bu) 2 H) 3 Si 9 − ( 1 a ) and (Si( t Bu) 2 H) 2 Si 9 2− ( 2 a ) with the highest known number of ligand‐free silicon atoms is reported for the first time. The new anions are obtained in a one‐step reaction of K 12 Si 17 /NH 3 (liq.) and Si( t Bu) 2 HCl/THF. Electrospray ionization spectrometry and 1 H, 13 C, 29 Si, as well as 29 Si‐HMBC (heteronuclear multiple bond correlation) NMR spectroscopy, confirm the attachment of three silyl groups at a [Si 9 ] 4− cluster under formation of 1 a , in accordance with calculated NMR shifts. During crystal growth the siliconoid di‐anion 2 a is formed. The single‐crystal X‐ray structure determination reveals that two silyl groups are connected to the deltahedral Si 9 cluster core, revealing seven unsubstituted exposed silicon cluster atoms with a hemispheroidal coordination. The negative charges −1 and −2 are delocalized over the six and seven siliconoid Si atoms in 1 a and 2 a , respectively.