Alkyne-Induced Facile C–C Bond Formation of Two η2-Alkynes on Dinuclear Tantalum Bis(alkyne) Complexes To Give Dinuclear Tantalacyclopentadienes

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• 作者：Keishi Yamamoto ; Hayato Tsurugi ; Kazushi Mashima
• 刊名：Organometallics
• 出版年：2016
• 出版时间：May 23, 2016
• 年：2016
• 卷：35
• 期：10
• 页码：1573-1581
• 全文大小：550K
• 年卷期：0
• ISSN：1520-6041

文摘

The dinuclear tantalum–alkyne complexes [(η²-RC≡CR)TaCl₂]₂(μ-OMe)₂(μ-thf) (2a, R = Et; 2b, R = ⁿPr) were synthesized by treating the mononuclear tantalum–alkyne complexes (η²-RC≡CR)TaCl₃(dme) (1a, R = Et; 1b, R = ⁿPr) with 1 equiv of NaOMe in THF. We found that adding a catalytic amount (20 mol %) of 3-hexyne to 2a induced the spontaneous formation of Ta₂Cl₄(OMe)₂(μ-C₄Et₄)(thf) (4a). Similarly, Ta₂Cl₄(OMe)₂(μ-C₄ⁿPr₄)(thf) (4b) was obtained by treatment of 2b with a catalytic amount (20 mol %) of 4-octyne. Reaction of 4a,b with 4-dimethylaminopyridine gave 4-dimethylaminopyridine-coordinated complexes 6a,b, whose structures were elucidated by the X-ray structure of 6a. We conducted a control experiment in which 10 equiv of 4-octyne was added to 2a to give Ta₂Cl₄(OMe)₂(μ-C₄-2,3-ⁿPr₂-4,5-Et₂)(thf) (7) in 90% yield, indicating that free 4-octyne reacted with the tantalacyclopropene moiety of 2a to form a dissymmetric tantalacyclopentadiene, followed by the release of 3-hexyne. The catalytic activity of 4a–6a for [2 + 2 + 2] cyclotrimerization of 3-hexyne was examined, and we found that their activities were in the order 5a > 4a ≫ 6a.