Isolobal Zwitterionic Niobium and Tantalum Imido and Zirconium Monocyclopentadienyl Complexes: Theoretical and Methyl Methacrylate Polymerization Studies

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• 作者：Rocí ; o Arteaga-M&#xfc ; ller ; Javier Sá ; nchez-Nieves ; Javier Ramos ; Pascual Royo ; Marta E. G. Mosquera
• 刊名：Organometallics
• 出版年：2008
• 出版时间：April 14, 2008
• 年：2008
• 卷：27
• 期：7
• 页码：1417 - 1426
• 全文大小：443K
• 年卷期：v.27,no.7(April 14, 2008)
• ISSN：1520-6041

文摘

The trichloro derivatives [MCl₃(NR)(py)₂] reacted with LiOAr to give the imido aryloxo complexes [MCl₂(NR)(OAr)(py)₂] (M = Nb, R = tBu (1a), Ar (1b); M = Ta, R = tBu (2a); Ar = 2,6-iPr₂C₆H₃) and were alkylated with [BzMgCl], affording the tribenzyl derivatives [NbBz₃(NR)] (R = tBu (3a), Ar (3b)). Similar alkylations of the aryloxo derivatives 1 and 2 gave the dibenzyl complexes [MBz₂(NR)(OAr)(THF)] (M = Nb, R = tBu (5a); M = Ta, R = tBu (6a), Ar (6b)). The zwitterionic imido complexes [MBz₂(NtBu){η⁶-C₆H₅CH₂E(C₆F₅)₃}] (M = Nb, E = B (7a-B), Al (7a-Al); M = Ta, E = Al (8a-Al)) were obtained upon addition of 1 equiv of E(C₆F₅)₃ (E = B, Al) to the tribenzyl derivatives [MBz₃(NtBu)] (M = Nb (3a), Ta (4a)). The aryloxo compound 6a reacted with 2 equiv of the Lewis acids E(C₆F₅)₃ (E = B, Al) to give the corresponding zwitterionic imido complexes [TaBz(NtBu)(OAr){η⁶-C₆H₅CH₂E(C₆F₅)₃}] (E = B (11a-B), Al (11a-Al)) and the adduct (THF)·E(C₆F₅)₃, through two different intermediates, the ionic [TaBz(NtBu)(OAr)(THF)][BzB(C₆F₅)₃] (9a) for E = B and the neutral [TaBz₂(NtBu)(OAr)] (10a) for E = Al. The related monocyclopentadienyl complex [ZrCpBz₂{η⁶-C₆H₅CH₂Al(C₆F₅)₃}] (12-Al) was also isolated by reaction of [ZrCpBz₃] with Al(C₆F₅)₃. DFT calculations were carried out to further understand this type of zwitterionic imido derivative in comparison with the isolobal zirconium cyclopentadienyl compound [ZrCpBz₂{η⁶-C₆H₅CH₂B(C₆F₅)₃}]. MMA polymerization was investigated for the [MBz₂X(NtBu)]/E(C₆F₅)₃ (X = Bz, OAr) and [ZrCpBz₃]/E(C₆F₅)₃ (E = B, Al) systems.