Optically Active Zwitterionic λ5Si,λ5Si′-Disilicates: Syntheses, Crystal Structures, and Behavior in Aqueous Solution

✍ Scribed by Bastian Theis; Christian Burschka; Reinhold Tacke

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 601 KB
• Volume: 14
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200701858

✦ Synopsis

Abstract

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.