2000 Fiscal Year Final Research Report Summary
Hypervalency of Organogermanium Compounds-Scope and Limitation
| Project/Area Number |
11640547
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Organic chemistry
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| Research Institution | Kanagawa University |
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Principal Investigator |
TAKEUCHI Yoshito Kanagawa University, Faculty of Science, Professor, 理学部, 教授 (80012384)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Organogermanium compounds / dynamic NMR method / hyper coordination / pseudorotation / prototropy / Xray crystallographic analysis / trigonal bipyramid / high resolution solid state NMR |
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| Research Abstract |
1 The structure of hypercoordinate organogermanium comounds in solid-ohase and in solution.
The structure of 2-(2-t-butyl-5-oxo-1, 3, 2-oxathiagermolan-2-ylthio) acetic acid (1) and its phenyl derivative (2) and their pyridiumu salts (3) and (4) was investigated. In the solid phase, all compounds investigated were in trigonal bipyramidal structure.
In solid-state, the two trigonal bipyramids are different while in solution these are equivalent in the NMR timescale. Thus, there is observed only one CH_2 proton and carbon signals, indicating a rapid exchange. Furthermore, the methylene peak split into two peaks, indicating a slow exchange. The barrier is ca 12 kcal mol^<-1>. We believe this exchange is Berry pseudorotation or turnstile rotation.
2 Hypercoordinate structure of triarylgermanes.
We prepared a variety of triarylgermanes with some ligands at ortho position such as chlorotris [2-(methoxymethyl) phenyl] germane and methyltris [2-(methoxymethyl)-phenyl] germane. Both compounds are pentavalent in a trigonal bipyramidal structure. The reason why such compounds did not show hexa or hepta coordination is not clear at all.
3 Synthesis of novel hosts modified with germanium.
We prepared a variety of novel organogermanium compounds as possible hosts for anions and neutral molecules. These include calixarenes with some side-chain containing germanium, azacrown with germanium-containing side-chain on nitrogen, and cyclophanes including germanium in the bridge.
4 High-resolution solid-state ^<73>Ge NMR spectroscopy.
We firstly observed germanium resonance of solid tetraphenylgermane in high-resolution condition. Ge-73 NMR may be a powerful tool for studying hyper valency of germanium.
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