Source:http://linkedlifedata.com/resource/pubmed/id/15479095
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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
41
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| pubmed:dateCreated |
2004-10-13
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| pubmed:abstractText |
The reaction of [Ta(=CHtBu)(CH2tBu)3] or [Cp*Ta(CH3)4] with a silica partially dehydroxylated at 700 degrees C gives the corresponding monosiloxy surface complexes [([triple bond]SiO)Ta(=CHtBu)(CH2tBu)2] and [([triple bond]SiO)Ta(CH3)3Cp*] by eliminating a sigma-bonded ligand as the corresponding alkane (H-CH2tBu or H-CH3). EXAFS data show that an adjacent siloxane bridge of the surface plays the role of an extra surface ligand, which most likely stabilizes these complexes as in [([triple bond]SiO)Ta(=CHtBu)(CH2tBu)2([triple bond]SiOSi[triple bond])] (1a') and [([triple bond]SiO)Ta(CH3)3Cp*([triple bond]SiOSi[triple bond])] (2a'). In the case of [(SiO)Ta(=CHtBu)(CH2tBu)2([triple bond]SiOSi[triple bond])], the structure is further stabilized by an additional interaction: a C-H agostic bond as evidenced by the small J coupling constant for the carbenic C-H (JC-H = 80 Hz), which was measured by J-resolved 2D solid-state NMR spectroscopy. The product selectivity in propane metathesis in the presence of [([triple bond]SiO)Ta(=CHtBu)(CH2tBu)2([triple bond]SiOSi[triple bond])] (1a') as a catalyst precursor and the inactivity of the surface complex [([triple bond]SiO)Ta(CH3)3Cp*([triple bond]SiOSi[triple bond])] (2a') show that the active site is required to be highly electrophilic and probably involves a metallacyclobutane intermediate.
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| pubmed:language |
eng
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| pubmed:journal | |
| pubmed:status |
PubMed-not-MEDLINE
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| pubmed:month |
Oct
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| pubmed:issn |
0002-7863
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| pubmed:author |
pubmed-author:BassetJean-MarieJM,
pubmed-author:BaudouinAnneA,
pubmed-author:ChabanasMathieuM,
pubmed-author:CopéretChristopheC,
pubmed-author:EmsleyLyndonL,
pubmed-author:Le RouxErwanE,
pubmed-author:LesageAnneA,
pubmed-author:LukensWayneW,
pubmed-author:QuadrelliE AlessandraEA,
pubmed-author:SunleyGlenn JGJ,
pubmed-author:Thivolle-CazatJeanJ,
pubmed-author:de MallmannAimeryA
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| pubmed:issnType |
Print
|
| pubmed:day |
20
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| pubmed:volume |
126
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| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
13391-9
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| pubmed:year |
2004
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| pubmed:articleTitle |
Detailed structural investigation of the grafting of [Ta(=CHtBu)(CH2tBu)3] and [Cp*TaMe4] on silica partially dehydroxylated at 700 degrees C and the activity of the grafted complexes toward alkane metathesis.
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| pubmed:affiliation |
Laboratoire de Chimie Organométallique de Surface, UMR 9986 CNRS/ESCPE Lyon, Villeurbanne, France.
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| pubmed:publicationType |
Journal Article
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