Multiple bonds between main-group elements and transition metals: Part 157 neutral and cationic ansa -metallocenes of niobium(V) and tantalum(V): Synthesis, structures and stereochemical non-rigidity
Identifieur interne : 004237 ( Istex/Corpus ); précédent : 004236; suivant : 004238Multiple bonds between main-group elements and transition metals: Part 157 neutral and cationic ansa -metallocenes of niobium(V) and tantalum(V): Synthesis, structures and stereochemical non-rigidity
Auteurs : Wolfgang A. Herrmann ; Walter Baratta ; Eberhardt HerdtweckSource :
- Journal of Organometallic Chemistry [ 0022-328X ] ; 1997.
English descriptors
- KwdEn :
Abstract
The metal amide route has been exploited to synthesize η5:η1- and η5:η5 ansa-metallocenes of pentavalent niobium and tantalum. Tris(dimethylamido)(2,6-diisopropylphenylimido)-niobium(V) 2a and -tantalum(V) 2b were found to be appropriate starting compounds to cleanly react with CH-acidic ligand precursors such as cyclopentadiene and 2,2-bis(cyclopentadienyl)propane. In the latter case, the novel ansa-metallocenes of formula [C5H4-C(CH3)2-C5H4]M[=N(2,6-iPr2C6H3)][N(CH3)2] (4a, M = Nb; 4b, M = Ta) result in high yields. While the hydrocarbon ligand adopts an η1:η5-coordination to the metals in the solid state (X-ray diffraction studies), a rapid η1:η5-η5:η1 equilibration occurs in solution. Complexes 4a,b react promptly with (CH3)3SiCl, thus affording the ansa-metallocenes [C5H4-C(CH3)2-C5H4]M[-N(2,6-iPr2C6H3)]Cl (5a, M = Nb; 5b, M = Ta) quantitatively. The crystal structures of the niobium(V) and tantalum(V) chloro derivatives 5a,b reveal a ‘conventional’ η5:η5-coordination for the chelating bis(cyclopentadienyl) ligand. Protonolysis of 4a,b with [NHMe3][B(C6H5)4] afforded the first cationic ansa-metallocenes [C5H4-C(CH3)2-C5H4]M[=N(2,6-iPr2C6H3)][NH(CH3)2][B(C6H5)4] (6a, M = Nb; 6b, M = Ta) in high yields. The crystal structure of 6a shows an η5:η5-coordination mode for the bis(cyclopentadienyl) ligand. The 1J(C,H) coupling constants of the bis(cyclopentadienyl) ligand of the ansa-metallocenes 4a,b, 5a,b and 6a,b are related to its hapticity, which is a result of the electronic properties of the metal center.
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DOI: 10.1016/S0022-328X(97)00121-6
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<record><TEI wicri:istexFullTextTei="biblStruct"><teiHeader><fileDesc><titleStmt><title xml:lang="en">Multiple bonds between main-group elements and transition metals: Part 157 neutral and cationic ansa -metallocenes of niobium(V) and tantalum(V): Synthesis, structures and stereochemical non-rigidity</title><author><name sortKey="Herrmann, Wolfgang A" sort="Herrmann, Wolfgang A" uniqKey="Herrmann W" first="Wolfgang A." last="Herrmann">Wolfgang A. Herrmann</name><affiliation><mods:affiliation>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</mods:affiliation></affiliation></author><author><name sortKey="Baratta, Walter" sort="Baratta, Walter" uniqKey="Baratta W" first="Walter" last="Baratta">Walter Baratta</name><affiliation><mods:affiliation>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</mods:affiliation></affiliation></author><author><name sortKey="Herdtweck, Eberhardt" sort="Herdtweck, Eberhardt" uniqKey="Herdtweck E" first="Eberhardt" last="Herdtweck">Eberhardt Herdtweck</name><affiliation><mods:affiliation>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</mods:affiliation></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">ISTEX</idno><idno type="RBID">ISTEX:41CB0416E99360E9FA83347C4AC6662777E99448</idno><date when="1997" year="1997">1997</date><idno type="doi">10.1016/S0022-328X(97)00121-6</idno><idno type="url">https://api.istex.fr/document/41CB0416E99360E9FA83347C4AC6662777E99448/fulltext/pdf</idno><idno type="wicri:Area/Istex/Corpus">004237</idno></publicationStmt><sourceDesc><biblStruct><analytic><title level="a" type="main" xml:lang="en">Multiple bonds between main-group elements and transition metals: Part 157 neutral and cationic ansa -metallocenes of niobium(V) and tantalum(V): Synthesis, structures and stereochemical non-rigidity</title><author><name sortKey="Herrmann, Wolfgang A" sort="Herrmann, Wolfgang A" uniqKey="Herrmann W" first="Wolfgang A." last="Herrmann">Wolfgang A. Herrmann</name><affiliation><mods:affiliation>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</mods:affiliation></affiliation></author><author><name sortKey="Baratta, Walter" sort="Baratta, Walter" uniqKey="Baratta W" first="Walter" last="Baratta">Walter Baratta</name><affiliation><mods:affiliation>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</mods:affiliation></affiliation></author><author><name sortKey="Herdtweck, Eberhardt" sort="Herdtweck, Eberhardt" uniqKey="Herdtweck E" first="Eberhardt" last="Herdtweck">Eberhardt Herdtweck</name><affiliation><mods:affiliation>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</mods:affiliation></affiliation></author></analytic><monogr></monogr><series><title level="j">Journal of Organometallic Chemistry</title><title level="j" type="abbrev">JOM</title><idno type="ISSN">0022-328X</idno><imprint><publisher>ELSEVIER</publisher><date type="published" when="1997">1997</date><biblScope unit="volume">541</biblScope><biblScope unit="issue">1–2</biblScope><biblScope unit="page" from="445">445</biblScope><biblScope unit="page" to="460">460</biblScope></imprint><idno type="ISSN">0022-328X</idno></series><idno type="istex">41CB0416E99360E9FA83347C4AC6662777E99448</idno><idno type="DOI">10.1016/S0022-328X(97)00121-6</idno><idno type="PII">S0022-328X(97)00121-6</idno><idno type="ArticleID">97001216</idno></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0022-328X</idno></seriesStmt></fileDesc><profileDesc><textClass><keywords scheme="KwdEn" xml:lang="en"><term>Multiple bonds</term><term>Niobium (V)</term><term>Tantalum (V)</term></keywords></textClass><langUsage><language ident="en">en</language></langUsage></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">The metal amide route has been exploited to synthesize η5:η1- and η5:η5 ansa-metallocenes of pentavalent niobium and tantalum. Tris(dimethylamido)(2,6-diisopropylphenylimido)-niobium(V) 2a and -tantalum(V) 2b were found to be appropriate starting compounds to cleanly react with CH-acidic ligand precursors such as cyclopentadiene and 2,2-bis(cyclopentadienyl)propane. In the latter case, the novel ansa-metallocenes of formula [C5H4-C(CH3)2-C5H4]M[=N(2,6-iPr2C6H3)][N(CH3)2] (4a, M = Nb; 4b, M = Ta) result in high yields. While the hydrocarbon ligand adopts an η1:η5-coordination to the metals in the solid state (X-ray diffraction studies), a rapid η1:η5-η5:η1 equilibration occurs in solution. Complexes 4a,b react promptly with (CH3)3SiCl, thus affording the ansa-metallocenes [C5H4-C(CH3)2-C5H4]M[-N(2,6-iPr2C6H3)]Cl (5a, M = Nb; 5b, M = Ta) quantitatively. The crystal structures of the niobium(V) and tantalum(V) chloro derivatives 5a,b reveal a ‘conventional’ η5:η5-coordination for the chelating bis(cyclopentadienyl) ligand. Protonolysis of 4a,b with [NHMe3][B(C6H5)4] afforded the first cationic ansa-metallocenes [C5H4-C(CH3)2-C5H4]M[=N(2,6-iPr2C6H3)][NH(CH3)2][B(C6H5)4] (6a, M = Nb; 6b, M = Ta) in high yields. The crystal structure of 6a shows an η5:η5-coordination mode for the bis(cyclopentadienyl) ligand. The 1J(C,H) coupling constants of the bis(cyclopentadienyl) ligand of the ansa-metallocenes 4a,b, 5a,b and 6a,b are related to its hapticity, which is a result of the electronic properties of the metal center.</div></front></TEI><istex><corpusName>elsevier</corpusName><author><json:item><name>Wolfgang A. Herrmann</name><affiliations><json:string>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</json:string></affiliations></json:item><json:item><name>Walter Baratta</name><affiliations><json:string>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</json:string></affiliations></json:item><json:item><name>Eberhardt Herdtweck</name><affiliations><json:string>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</json:string></affiliations></json:item></author><subject><json:item><lang><json:string>eng</json:string></lang><value>Multiple bonds</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>Niobium (V)</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>Tantalum (V)</value></json:item></subject><articleId><json:string>97001216</json:string></articleId><language><json:string>eng</json:string></language><abstract>The metal amide route has been exploited to synthesize η5:η1- and η5:η5 ansa-metallocenes of pentavalent niobium and tantalum. Tris(dimethylamido)(2,6-diisopropylphenylimido)-niobium(V) 2a and -tantalum(V) 2b were found to be appropriate starting compounds to cleanly react with CH-acidic ligand precursors such as cyclopentadiene and 2,2-bis(cyclopentadienyl)propane. In the latter case, the novel ansa-metallocenes of formula [C5H4-C(CH3)2-C5H4]M[=N(2,6-iPr2C6H3)][N(CH3)2] (4a, M = Nb; 4b, M = Ta) result in high yields. While the hydrocarbon ligand adopts an η1:η5-coordination to the metals in the solid state (X-ray diffraction studies), a rapid η1:η5-η5:η1 equilibration occurs in solution. Complexes 4a,b react promptly with (CH3)3SiCl, thus affording the ansa-metallocenes [C5H4-C(CH3)2-C5H4]M[-N(2,6-iPr2C6H3)]Cl (5a, M = Nb; 5b, M = Ta) quantitatively. The crystal structures of the niobium(V) and tantalum(V) chloro derivatives 5a,b reveal a ‘conventional’ η5:η5-coordination for the chelating bis(cyclopentadienyl) ligand. Protonolysis of 4a,b with [NHMe3][B(C6H5)4] afforded the first cationic ansa-metallocenes [C5H4-C(CH3)2-C5H4]M[=N(2,6-iPr2C6H3)][NH(CH3)2][B(C6H5)4] (6a, M = Nb; 6b, M = Ta) in high yields. The crystal structure of 6a shows an η5:η5-coordination mode for the bis(cyclopentadienyl) ligand. The 1J(C,H) coupling constants of the bis(cyclopentadienyl) ligand of the ansa-metallocenes 4a,b, 5a,b and 6a,b are related to its hapticity, which is a result of the electronic properties of the metal center.</abstract><qualityIndicators><score>7.34</score><pdfVersion>1.3</pdfVersion><pdfPageSize>634 x 850 pts</pdfPageSize><refBibsNative>true</refBibsNative><keywordCount>3</keywordCount><abstractCharCount>1534</abstractCharCount><pdfWordCount>10403</pdfWordCount><pdfCharCount>60664</pdfCharCount><pdfPageCount>16</pdfPageCount><abstractWordCount>195</abstractWordCount></qualityIndicators><title>Multiple bonds between main-group elements and transition metals: Part 157 neutral and cationic ansa -metallocenes of niobium(V) and tantalum(V): Synthesis, structures and stereochemical non-rigidity</title><pii><json:string>S0022-328X(97)00121-6</json:string></pii><genre><json:string>research-article</json:string></genre><host><volume>541</volume><pii><json:string>S0022-328X(00)X1452-0</json:string></pii><pages><last>460</last><first>445</first></pages><issn><json:string>0022-328X</json:string></issn><issue>1–2</issue><genre><json:string>Journal</json:string></genre><language><json:string>unknown</json:string></language><title>Journal of Organometallic Chemistry</title><publicationDate>1997</publicationDate></host><categories><wos><json:string>CHEMISTRY, INORGANIC & NUCLEAR</json:string><json:string>CHEMISTRY, ORGANIC</json:string></wos></categories><publicationDate>1997</publicationDate><copyrightDate>1997</copyrightDate><doi><json:string>10.1016/S0022-328X(97)00121-6</json:string></doi><id>41CB0416E99360E9FA83347C4AC6662777E99448</id><score>1</score><fulltext><json:item><original>true</original><mimetype>application/pdf</mimetype><extension>pdf</extension><uri>https://api.istex.fr/document/41CB0416E99360E9FA83347C4AC6662777E99448/fulltext/pdf</uri></json:item><json:item><original>true</original><mimetype>text/plain</mimetype><extension>txt</extension><uri>https://api.istex.fr/document/41CB0416E99360E9FA83347C4AC6662777E99448/fulltext/txt</uri></json:item><json:item><original>false</original><mimetype>application/zip</mimetype><extension>zip</extension><uri>https://api.istex.fr/document/41CB0416E99360E9FA83347C4AC6662777E99448/fulltext/zip</uri></json:item><istex:fulltextTEI uri="https://api.istex.fr/document/41CB0416E99360E9FA83347C4AC6662777E99448/fulltext/tei"><teiHeader><fileDesc><titleStmt><title level="a" type="main" xml:lang="en">Multiple bonds between main-group elements and transition metals: Part 157 neutral and cationic ansa -metallocenes of niobium(V) and tantalum(V): Synthesis, structures and stereochemical non-rigidity</title></titleStmt><publicationStmt><authority>ISTEX</authority><publisher>ELSEVIER</publisher><availability><p>ELSEVIER</p></availability><date>1997</date></publicationStmt><notesStmt><note>For the preceding communication, no. 156 of this series, see Ref. [1].</note></notesStmt><sourceDesc><biblStruct type="inbook"><analytic><title level="a" type="main" xml:lang="en">Multiple bonds between main-group elements and transition metals: Part 157 neutral and cationic ansa -metallocenes of niobium(V) and tantalum(V): Synthesis, structures and stereochemical non-rigidity</title><author><persName><forename type="first">Wolfgang A.</forename><surname>Herrmann</surname></persName><note type="correspondence"><p>Corresponding author.</p></note><affiliation>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</affiliation></author><author><persName><forename type="first">Walter</forename><surname>Baratta</surname></persName><affiliation>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</affiliation></author><author><persName><forename type="first">Eberhardt</forename><surname>Herdtweck</surname></persName><affiliation>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</affiliation></author></analytic><monogr><title level="j">Journal of Organometallic Chemistry</title><title level="j" type="abbrev">JOM</title><idno type="pISSN">0022-328X</idno><idno type="PII">S0022-328X(00)X1452-0</idno><imprint><publisher>ELSEVIER</publisher><date type="published" when="1997"></date><biblScope unit="volume">541</biblScope><biblScope unit="issue">1–2</biblScope><biblScope unit="page" from="445">445</biblScope><biblScope unit="page" to="460">460</biblScope></imprint></monogr><idno type="istex">41CB0416E99360E9FA83347C4AC6662777E99448</idno><idno type="DOI">10.1016/S0022-328X(97)00121-6</idno><idno type="PII">S0022-328X(97)00121-6</idno><idno type="ArticleID">97001216</idno></biblStruct></sourceDesc></fileDesc><profileDesc><creation><date>1997</date></creation><langUsage><language ident="en">en</language></langUsage><abstract xml:lang="en"><p>The metal amide route has been exploited to synthesize η5:η1- and η5:η5 ansa-metallocenes of pentavalent niobium and tantalum. Tris(dimethylamido)(2,6-diisopropylphenylimido)-niobium(V) 2a and -tantalum(V) 2b were found to be appropriate starting compounds to cleanly react with CH-acidic ligand precursors such as cyclopentadiene and 2,2-bis(cyclopentadienyl)propane. In the latter case, the novel ansa-metallocenes of formula [C5H4-C(CH3)2-C5H4]M[=N(2,6-iPr2C6H3)][N(CH3)2] (4a, M = Nb; 4b, M = Ta) result in high yields. While the hydrocarbon ligand adopts an η1:η5-coordination to the metals in the solid state (X-ray diffraction studies), a rapid η1:η5-η5:η1 equilibration occurs in solution. Complexes 4a,b react promptly with (CH3)3SiCl, thus affording the ansa-metallocenes [C5H4-C(CH3)2-C5H4]M[-N(2,6-iPr2C6H3)]Cl (5a, M = Nb; 5b, M = Ta) quantitatively. The crystal structures of the niobium(V) and tantalum(V) chloro derivatives 5a,b reveal a ‘conventional’ η5:η5-coordination for the chelating bis(cyclopentadienyl) ligand. Protonolysis of 4a,b with [NHMe3][B(C6H5)4] afforded the first cationic ansa-metallocenes [C5H4-C(CH3)2-C5H4]M[=N(2,6-iPr2C6H3)][NH(CH3)2][B(C6H5)4] (6a, M = Nb; 6b, M = Ta) in high yields. The crystal structure of 6a shows an η5:η5-coordination mode for the bis(cyclopentadienyl) ligand. The 1J(C,H) coupling constants of the bis(cyclopentadienyl) ligand of the ansa-metallocenes 4a,b, 5a,b and 6a,b are related to its hapticity, which is a result of the electronic properties of the metal center.</p></abstract><textClass xml:lang="en"><keywords scheme="keyword"><list><head>Keywords</head><item><term>Multiple bonds</term></item><item><term>Niobium (V)</term></item><item><term>Tantalum (V)</term></item></list></keywords></textClass></profileDesc><revisionDesc><change when="1997-01-21">Received</change><change when="1997">Published</change></revisionDesc></teiHeader></istex:fulltextTEI></fulltext><metadata><istex:metadataXml wicri:clean="Elsevier doc found" wicri:toSee="Elsevier, no converted or simple article"><istex:xmlDeclaration>version="1.0" encoding="utf-8"</istex:xmlDeclaration><istex:docType PUBLIC="-//ES//DTD journal article DTD version 5.0.1//EN//XML" URI="art501.dtd" name="istex:docType"></istex:docType><istex:document><article version="5.0" xml:lang="en" docsubtype="fla"><item-info><jid>JOM</jid><aid>97001216</aid><ce:pii>S0022-328X(97)00121-6</ce:pii><ce:doi>10.1016/S0022-328X(97)00121-6</ce:doi><ce:copyright type="unknown" year="1997">Elsevier Science S.A.</ce:copyright></item-info><head><ce:article-footnote><ce:label>2</ce:label><ce:note-para>For the preceding communication, no. 156 of this series, see Ref. [1].</ce:note-para></ce:article-footnote><ce:title>Multiple bonds between main-group elements and transition metals: Part 157 neutral and cationic <ce:italic>ansa</ce:italic>-metallocenes of niobium(V) and tantalum(V): Synthesis, structures and stereochemical non-rigidity</ce:title><ce:dedication>Dedicated to Professor Gottfried Huttner on the occasion of his 60th birthday.</ce:dedication><ce:author-group><ce:author><ce:given-name>Wolfgang A.</ce:given-name><ce:surname>Herrmann</ce:surname><ce:cross-ref refid="cor1"><ce:sup>*</ce:sup></ce:cross-ref></ce:author><ce:author><ce:given-name>Walter</ce:given-name><ce:surname>Baratta</ce:surname></ce:author><ce:author><ce:given-name>Eberhardt</ce:given-name><ce:surname>Herdtweck</ce:surname></ce:author><ce:affiliation id="aff1"><ce:textfn>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</ce:textfn></ce:affiliation><ce:correspondence id="cor1"><ce:label>*</ce:label><ce:text>Corresponding author.</ce:text></ce:correspondence></ce:author-group><ce:date-received day="21" month="1" year="1997"></ce:date-received><ce:abstract id="ab1" class="author" xml:lang="en"><ce:section-title>Abstract</ce:section-title><ce:abstract-sec><ce:simple-para>The metal amide route has been exploited to synthesize <ce:italic>η</ce:italic><ce:sup loc="post">5</ce:sup>:<ce:italic>η</ce:italic><ce:sup loc="post">1</ce:sup>- and <ce:italic>η</ce:italic><ce:sup loc="post">5</ce:sup>:<ce:italic>η</ce:italic><ce:sup loc="post">5</ce:sup> <ce:italic>ansa</ce:italic>-metallocenes of pentavalent niobium and tantalum. Tris(dimethylamido)(2,6-diisopropylphenylimido)-niobium(V) <ce:bold>2a</ce:bold> and -tantalum(V) <ce:bold>2b</ce:bold> were found to be appropriate starting compounds to cleanly react with CH-acidic ligand precursors such as cyclopentadiene and 2,2-bis(cyclopentadienyl)propane. In the latter case, the novel <ce:italic>ansa</ce:italic>-metallocenes of formula [C<ce:inf loc="post">5</ce:inf>H<ce:inf loc="post">4</ce:inf>-C(CH<ce:inf loc="post">3</ce:inf>)<ce:inf loc="post">2</ce:inf>-C<ce:inf loc="post">5</ce:inf>H<ce:inf loc="post">4</ce:inf>]M[=N(2,6-<ce:sup loc="post">i</ce:sup>Pr<ce:inf loc="post">2</ce:inf>C<ce:inf loc="post">6</ce:inf>H<ce:inf loc="post">3</ce:inf>)][N(CH<ce:inf loc="post">3</ce:inf>)<ce:inf loc="post">2</ce:inf>] (<ce:bold>4a</ce:bold>, M = Nb; <ce:bold>4b</ce:bold>, M = Ta) result in high yields. While the hydrocarbon ligand adopts an <ce:italic>η</ce:italic><ce:sup loc="post">1</ce:sup>:<ce:italic>η</ce:italic><ce:sup loc="post">5</ce:sup>-coordination to the metals in the solid state (X-ray diffraction studies), a rapid <ce:italic>η</ce:italic><ce:sup loc="post">1</ce:sup>:<ce:italic>η</ce:italic><ce:sup loc="post">5</ce:sup>-<ce:italic>η</ce:italic><ce:sup loc="post">5</ce:sup>:<ce:italic>η</ce:italic><ce:sup loc="post">1</ce:sup> equilibration occurs in solution. Complexes <ce:bold>4a,b</ce:bold> react promptly with (CH<ce:inf loc="post">3</ce:inf>)<ce:inf loc="post">3</ce:inf>SiCl, thus affording the <ce:italic>ansa</ce:italic>-metallocenes [C<ce:inf loc="post">5</ce:inf>H<ce:inf loc="post">4</ce:inf>-C(CH<ce:inf loc="post">3</ce:inf>)<ce:inf loc="post">2</ce:inf>-C<ce:inf loc="post">5</ce:inf>H<ce:inf loc="post">4</ce:inf>]M[-N(2,6-<ce:sup loc="post">i</ce:sup>Pr<ce:inf loc="post">2</ce:inf>C<ce:inf loc="post">6</ce:inf>H<ce:inf loc="post">3</ce:inf>)]Cl (<ce:bold>5a</ce:bold>, M = Nb; <ce:bold>5b</ce:bold>, M = Ta) quantitatively. The crystal structures of the niobium(V) and tantalum(V) chloro derivatives <ce:bold>5a,b</ce:bold> reveal a ‘conventional’ <ce:italic>η</ce:italic><ce:sup loc="post">5</ce:sup>:<ce:italic>η</ce:italic><ce:sup loc="post">5</ce:sup>-coordination for the chelating bis(cyclopentadienyl) ligand. Protonolysis of <ce:bold>4a,b</ce:bold> with [NHMe<ce:inf loc="post">3</ce:inf>][B(C<ce:inf loc="post">6</ce:inf>H<ce:inf loc="post">5</ce:inf>)<ce:inf loc="post">4</ce:inf>] afforded the first cationic <ce:italic>ansa</ce:italic>-metallocenes [C<ce:inf loc="post">5</ce:inf>H<ce:inf loc="post">4</ce:inf>-C(CH<ce:inf loc="post">3</ce:inf>)<ce:inf loc="post">2</ce:inf>-C<ce:inf loc="post">5</ce:inf>H<ce:inf loc="post">4</ce:inf>]M[=N(2,6-<ce:sup loc="post">i</ce:sup>Pr<ce:inf loc="post">2</ce:inf>C<ce:inf loc="post">6</ce:inf>H<ce:inf loc="post">3</ce:inf>)][NH(CH<ce:inf loc="post">3</ce:inf>)<ce:inf loc="post">2</ce:inf>][B(C<ce:inf loc="post">6</ce:inf>H<ce:inf loc="post">5</ce:inf>)<ce:inf loc="post">4</ce:inf>] (<ce:bold>6a</ce:bold>, M = Nb; <ce:bold>6b</ce:bold>, M = Ta) in high yields. The crystal structure of <ce:bold>6a</ce:bold> shows an <ce:italic>η</ce:italic><ce:sup loc="post">5</ce:sup>:<ce:italic>η</ce:italic><ce:sup loc="post">5</ce:sup>-coordination mode for the bis(cyclopentadienyl) ligand. 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GmbH</sb:name><sb:location>Germany</sb:location></sb:publisher></sb:edited-book></sb:host></sb:reference><sb:reference><ce:label>(b)</ce:label><sb:comment>and references cited therein</sb:comment><sb:contribution langtype="en"><sb:authors><sb:author><ce:given-name>W.</ce:given-name><ce:surname>Schütt</ce:surname></sb:author><sb:author><ce:given-name>E.</ce:given-name><ce:surname>Herdtweck</ce:surname></sb:author><sb:author><ce:given-name>F.</ce:given-name><ce:surname>Hahn</ce:surname></sb:author><sb:author><ce:given-name>F.R.</ce:given-name><ce:surname>Kreiβl</ce:surname></sb:author></sb:authors></sb:contribution><sb:host><sb:issue><sb:series><sb:title><sb:maintitle>J. Organomet. 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Sect. A</sb:maintitle></sb:title><sb:volume-nr>46</sb:volume-nr></sb:series></sb:book-series><sb:date>1990</sb:date></sb:edited-book><sb:pages><sb:first-page>C34</sb:first-page></sb:pages></sb:host></sb:reference></ce:bib-reference></ce:bibliography-sec></ce:bibliography></tail></article></istex:document></istex:metadataXml><mods version="3.6"><titleInfo lang="en"><title>Multiple bonds between main-group elements and transition metals: Part 157 neutral and cationic ansa -metallocenes of niobium(V) and tantalum(V): Synthesis, structures and stereochemical non-rigidity</title></titleInfo><titleInfo type="alternative" lang="en" contentType="CDATA"><title>Multiple bonds between main-group elements and transition metals: Part 157 neutral and cationic</title></titleInfo><name type="personal"><namePart type="given">Wolfgang A.</namePart><namePart type="family">Herrmann</namePart><affiliation>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</affiliation><description>Corresponding author.</description><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">Walter</namePart><namePart type="family">Baratta</namePart><affiliation>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">Eberhardt</namePart><namePart type="family">Herdtweck</namePart><affiliation>Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstraβe 4, D-85747 Garching, Germany</affiliation><role><roleTerm type="text">author</roleTerm></role></name><typeOfResource>text</typeOfResource><genre type="research-article" displayLabel="Full-length article"></genre><originInfo><publisher>ELSEVIER</publisher><dateIssued encoding="w3cdtf">1997</dateIssued><dateCaptured encoding="w3cdtf">1997-01-21</dateCaptured><copyrightDate encoding="w3cdtf">1997</copyrightDate></originInfo><language><languageTerm type="code" authority="iso639-2b">eng</languageTerm><languageTerm type="code" authority="rfc3066">en</languageTerm></language><physicalDescription><internetMediaType>text/html</internetMediaType></physicalDescription><abstract lang="en">The metal amide route has been exploited to synthesize η5:η1- and η5:η5 ansa-metallocenes of pentavalent niobium and tantalum. Tris(dimethylamido)(2,6-diisopropylphenylimido)-niobium(V) 2a and -tantalum(V) 2b were found to be appropriate starting compounds to cleanly react with CH-acidic ligand precursors such as cyclopentadiene and 2,2-bis(cyclopentadienyl)propane. In the latter case, the novel ansa-metallocenes of formula [C5H4-C(CH3)2-C5H4]M[=N(2,6-iPr2C6H3)][N(CH3)2] (4a, M = Nb; 4b, M = Ta) result in high yields. While the hydrocarbon ligand adopts an η1:η5-coordination to the metals in the solid state (X-ray diffraction studies), a rapid η1:η5-η5:η1 equilibration occurs in solution. Complexes 4a,b react promptly with (CH3)3SiCl, thus affording the ansa-metallocenes [C5H4-C(CH3)2-C5H4]M[-N(2,6-iPr2C6H3)]Cl (5a, M = Nb; 5b, M = Ta) quantitatively. The crystal structures of the niobium(V) and tantalum(V) chloro derivatives 5a,b reveal a ‘conventional’ η5:η5-coordination for the chelating bis(cyclopentadienyl) ligand. Protonolysis of 4a,b with [NHMe3][B(C6H5)4] afforded the first cationic ansa-metallocenes [C5H4-C(CH3)2-C5H4]M[=N(2,6-iPr2C6H3)][NH(CH3)2][B(C6H5)4] (6a, M = Nb; 6b, M = Ta) in high yields. The crystal structure of 6a shows an η5:η5-coordination mode for the bis(cyclopentadienyl) ligand. The 1J(C,H) coupling constants of the bis(cyclopentadienyl) ligand of the ansa-metallocenes 4a,b, 5a,b and 6a,b are related to its hapticity, which is a result of the electronic properties of the metal center.</abstract><note>For the preceding communication, no. 156 of this series, see Ref. [1].</note><subject lang="en"><genre>Keywords</genre><topic>Multiple bonds</topic><topic>Niobium (V)</topic><topic>Tantalum (V)</topic></subject><relatedItem type="host"><titleInfo><title>Journal of Organometallic Chemistry</title></titleInfo><titleInfo type="abbreviated"><title>JOM</title></titleInfo><genre type="Journal">journal</genre><originInfo><dateIssued encoding="w3cdtf">19970815</dateIssued></originInfo><identifier type="ISSN">0022-328X</identifier><identifier type="PII">S0022-328X(00)X1452-0</identifier><part><date>19970815</date><detail type="volume"><number>541</number><caption>vol.</caption></detail><detail type="issue"><number>1–2</number><caption>no.</caption></detail><extent unit="issue pages"><start>1</start><end>482</end></extent><extent unit="pages"><start>445</start><end>460</end></extent></part></relatedItem><identifier type="istex">41CB0416E99360E9FA83347C4AC6662777E99448</identifier><identifier type="DOI">10.1016/S0022-328X(97)00121-6</identifier><identifier type="PII">S0022-328X(97)00121-6</identifier><identifier type="ArticleID">97001216</identifier><accessCondition type="use and reproduction" contentType="">© 1997Elsevier Science S.A.</accessCondition><recordInfo><recordContentSource>ELSEVIER</recordContentSource><recordOrigin>Elsevier Science S.A., ©1997</recordOrigin></recordInfo></mods></metadata><enrichments><istex:catWosTEI uri="https://api.istex.fr/document/41CB0416E99360E9FA83347C4AC6662777E99448/enrichments/catWos"><teiHeader><profileDesc><textClass><classCode scheme="WOS">CHEMISTRY, INORGANIC & NUCLEAR</classCode><classCode scheme="WOS">CHEMISTRY, ORGANIC</classCode></textClass></profileDesc></teiHeader></istex:catWosTEI></enrichments><serie></serie></istex></record>Pour manipuler ce document sous Unix (Dilib)
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