1994 Fiscal Year Final Research Report Summary
Creation, Structure, and Reactivity of Novel Hypercoordinate Organosilicon Compounds
| Project/Area Number |
05640587
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Organic chemistry
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| Research Institution | Tohoku University |
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Principal Investigator |
KIRA Mitsuo TOHOKU UNIV., DEPT.CHEM., ASSOC.PROF., 理学部, 助教授 (40004452)
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| Co-Investigator(Kenkyū-buntansha) |
KIRA Mitsuo TOHOKU UNIV., DEPT.CHEM., ASSOC.PROF. (40004452)
KIRA Mitsuo TOHOKU UNIV., DEPT.CHEM., ASSOC.PROF. (40004452)
KIRA Mitsuo TOHOKU UNIV., DEPT.CHEM., ASSOC.PROF. (40004452)
KIRA Mitsuo TOHOKU UNIV., DEPT.CHEM., ASSOC.PROF. (40004452)
KIRA Mitsuo TOHOKU UNIV., DEPT.CHEM., ASSOC.PROF. (40004452)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Hypercoordinate silicon / Fluoride Ion / Atom Transfer / Reaction Mechanism / Dynamic NMR / X-ray Crystallography |
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| Research Abstract |
Fluoride-ion exchange reactions between a tetracoordinate silane and the corresponding pentaccordinate fluorosilicate constitute a class of atom-transfer selfexchange reactions at a main-group atom center, the mechanism has been studied very scarcely. The exchange has been supposed to proceed via a transition state having linear arrangement of [Si-F-Si]. A theoretical study have shown that SiH_nF_<4-n> (n=1-3) forms a stable linear Si-F-Si bridge with [SiH_nF_<5-n>]^- in the gas phase. We have developed the synthesis and structure of novel intramolecular fluoride-ion donor-acceptor systems and related bissilicates. A dynamic ^<13>C NMR study has shown exchange of the fluoride-ions in the fluoride-ion donor-acceptor systems in both unimolecular and bimolecular processes. The large negative activation entropies for the bimolecular exchange suggest that the reaction proceeds via a rather unusual fluorine-bridged cyclophane-like transition states.
Crystal structures of the intramolecular fluoride-ion donor-acceptor systems have been analyzed by X-ray crystallography. These systems are expected to give a novel concept to design the ion conducting materials.
Novel neutral hexacoordinate silicates having tropolonate ligands were synthesized. X-ray crystallographic analysis for diphenyl- and dimethylbis (tropolonato)- silicates showed that these silicates have octahedral structure with the two alkyl and phenyl groups at the cis positions. Essentially no bond alternation in the C-C bonds of tropolonate rings suggests that the tropolonates serve as intramolecular countercations in the silicates. Analysis of the dynamic ^<13>C NMR spectra of these silicates revealed that there exists an isomerization process through a bond-rupture-recombination mechanism rather than a concerted mechanism.
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Research Products
(6 results)
