{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,4]],"date-time":"2026-10-04T18:24:47Z","timestamp":1791138287148,"version":"4.1.0"},"reference-count":57,"publisher":"Wiley","issue":"36","license":[{"start":{"date-parts":[[2007,10,4]],"date-time":"2007-10-04T00:00:00Z","timestamp":1191456000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Chemistry A European J"],"published-print":{"date-parts":[[2007,12,17]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>Treatment of <jats:italic>p<\/jats:italic>\u2010<jats:italic>tert<\/jats:italic>\u2010butylcalix[6]areneH<jats:sub>6<\/jats:sub> (H<jats:sub>6<\/jats:sub><jats:italic>t<\/jats:italic>Bu\u2010L) or <jats:italic>p<\/jats:italic>\u2010<jats:italic>tert<\/jats:italic>\u2010butylcalix[8]areneH<jats:sub>8<\/jats:sub> (H<jats:sub>8<\/jats:sub><jats:italic>t<\/jats:italic>Bu\u2010L<jats:sup>1<\/jats:sup>) with [MCl<jats:sub>5<\/jats:sub>] (M=Nb, Ta) in refluxing toluene or dichloromethane affords, after work\u2010up, the complexes [{M(NCMe)Cl<jats:sub>2<\/jats:sub>}<jats:sub>2<\/jats:sub>(<jats:italic>t<\/jats:italic>Bu\u2010L)] (M=Nb (<jats:bold>1<\/jats:bold>), Ta (<jats:bold>2<\/jats:bold>)) and [(MCl<jats:sub>2<\/jats:sub>)<jats:sub>2<\/jats:sub>(<jats:italic>t<\/jats:italic>Bu\u2010L<jats:sup>1<\/jats:sup>H<jats:sub>2<\/jats:sub>)] (M=Nb (<jats:bold>4<\/jats:bold>), Ta (<jats:bold>5<\/jats:bold>)), respectively. Complex <jats:bold>1<\/jats:bold>, as well as [{Nb<jats:sub>2<\/jats:sub>(\u03bc\u2010O)<jats:sub>2<\/jats:sub>(\u03bc\u2010Cl)(<jats:italic>t<\/jats:italic>Bu\u2010LH)}<jats:sub>2<\/jats:sub>] (<jats:bold>3<\/jats:bold>), is also available from [NbOCl<jats:sub>3<\/jats:sub>] and H<jats:sub>6<\/jats:sub><jats:italic>t<\/jats:italic>Bu\u2010L. Reaction of [MOCl<jats:sub>3<\/jats:sub>] (M=Nb, Ta) with Li<jats:sub>3<\/jats:sub>(<jats:italic>t<\/jats:italic>Bu\u2010L<jats:sup>2<\/jats:sup>) in diethyl ether, where H<jats:sub>3<\/jats:sub><jats:italic>t<\/jats:italic>Bu\u2010L<jats:sup>2<\/jats:sup> is <jats:italic>p<\/jats:italic>\u2010<jats:italic>tert<\/jats:italic>\u2010butylhexahomotrioxacalix[3]areneH<jats:sub>3<\/jats:sub>, affords, after work\u2010up, the trimeric complexes [{M(<jats:italic>t<\/jats:italic>Bu\u2010L<jats:sup>2<\/jats:sup>)(\u03bc\u2010O)}<jats:sub>3<\/jats:sub>] (M=Nb (<jats:bold>6<\/jats:bold>), Ta (<jats:bold>7<\/jats:bold>)). The behaviour of <jats:bold>1<\/jats:bold> to <jats:bold>7<\/jats:bold> (not <jats:bold>3<\/jats:bold>), as well as the known complexes [{(MCl)<jats:italic>p<\/jats:italic>\u2010<jats:italic>tert<\/jats:italic>\u2010butylcalix[4]arene}<jats:sub>2<\/jats:sub>] (M=Nb (<jats:bold>8<\/jats:bold>), Ta (<jats:bold>9<\/jats:bold>)) and [(MCl<jats:sub>2<\/jats:sub>)<jats:italic>p<\/jats:italic>\u2010<jats:italic>tert<\/jats:italic>\u2010butylcalix[4]arene(OMe)] (M=Nb (<jats:bold>10<\/jats:bold>), Ta (<jats:bold>11<\/jats:bold>)), as pro\u2010catalysts for the polymerisation of ethylene has been investigated. In the presence of dimethyl (or diethyl)aluminium chloride, methylaluminoxane or trimethylaluminium, these niobium and tantalum procatalysts are all active (&lt;35\u2005g\u2009mmol<jats:sup>\u22121<\/jats:sup>\u2009h<jats:sup>\u22121<\/jats:sup>\u2009bar<jats:sup>\u22121<\/jats:sup>), for the polymerisation of ethylene affording high\u2010molecular\u2010weight linear polyethylene. The dimethyleneoxa\u2010bridged systems (derived from <jats:bold>6<\/jats:bold> and <jats:bold>7<\/jats:bold>) are more active (84 and 46\u2005g\u2009mmol<jats:sup>\u22121<\/jats:sup>\u2009h<jats:sup>\u22121<\/jats:sup>\u2009bar<jats:sup>\u22121<\/jats:sup>, respectively) than the methylene\u2010bridged systems. The molecular structures of <jats:bold>1<\/jats:bold>\u2013<jats:bold>6<\/jats:bold> and <jats:bold>10<\/jats:bold> (acetonitrile solvate) are reported.<\/jats:p>","DOI":"10.1002\/chem.200700893","type":"journal-article","created":{"date-parts":[[2007,10,4]],"date-time":"2007-10-04T10:20:30Z","timestamp":1191493230000},"page":"10129-10139","source":"Crossref","is-referenced-by-count":35,"title":["Niobium\u2010 and Tantalum\u2010Based Ethylene Polymerisation Catalysts Bearing Methylene\u2010 or Dimethyleneoxa\u2010Bridged Calixarene Ligands"],"prefix":"10.1002","volume":"13","author":[{"given":"Carl","family":"Redshaw","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael","family":"Rowan","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Damien\u2005M.","family":"Homden","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mark\u2005R.\u2005J.","family":"Elsegood","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Takehiko","family":"Yamato","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carol","family":"P\u00e9rez\u2010Casas","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2007,12,7]]},"reference":[{"key":"e_1_2_6_1_2","unstructured":"\u00a0"},{"key":"e_1_2_6_2_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0022-328X(99)00279-X"},{"key":"e_1_2_6_3_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0014-3057(00)00248-2"},{"key":"e_1_2_6_4_2","doi-asserted-by":"publisher","DOI":"10.1039\/b010248m"},{"key":"e_1_2_6_5_2","doi-asserted-by":"crossref","first-page":"1026","DOI":"10.1139\/v01-079","volume":"79","author":"Long G. 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