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Optically Active Zwitterionic λ 5 Si, λ 5 Si′‐Disilicates: Syntheses, Crystal Structures, and Behavior in Aqueous Solution
Author(s) -
Theis Bastian,
Burschka Christian,
Tacke Reinhold
Publication year - 2008
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.200701858
Subject(s) - aqueous solution , crystallography , tetracoordinate , silicon , chemistry , spectroscopy , nuclear magnetic resonance spectroscopy , protonation , alkyl , crystal structure , stereochemistry , ion , physics , organic chemistry , computer graphics (images) , quantum mechanics , computer science , planar
The zwitterionic λ 5 Si, λ 5 Si′‐disilicates 1 – 8 were synthesized and characterized by solid‐state and solution NMR spectroscopy. In addition, compounds 2⋅ 6 H 2 O, 3⋅ 2 CH 3 CN, 4⋅ 5/2 CH 3 CN, 6⋅ CH 3 OH, 7 , and 8⋅ CH 3 OH ⋅ CH 3 CN were studied by single‐crystal X‐ray diffraction. The optically active (Δ,Δ, R , R , R , R )‐configured compounds 1 – 8 contain two pentacoordinate (formally negatively charged) silicon atoms and two tetracoordinate (formally positively charged) nitrogen atoms. One (ammonio)alkyl group is bound to each of the two silicon centers, and two tetradentate ( R , R )‐tartrato(4−) ligands bridge the silicon atoms. Although these λ 5 Si, λ 5 Si′‐disilicates contain SiO 4 C skeletons, some of them display a remarkable stability in aqueous solution as shown by NMR spectroscopy and ESI mass spectrometry.