Internally versus Externally Solvated Derivatives of Doubly Bridged 1,4-Dilithio-2-butene: Structures and Dynamic Behavior. A 鈥淭鈥?Shaped Dimeric Cluster in the Solid State

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• 作者：Gideon Fraenkel ; Xiao Chen ; Albert Chow ; Judith Gallucci
• 刊名：The Journal of Organic Chemistry
• 出版年：2013
• 出版时间：February 1, 2013
• 年：2013
• 卷：78
• 期：3
• 页码：1149-1156
• 全文大小：455K
• 年卷期：v.78,no.3(February 1, 2013)
• ISSN：1520-6904

文摘

X-ray crystallographic NMR and calculational modeling studies using B3LYP/6-311G* of selected dilithium derivatives of the 1,3-butadiene dianion including cis-dilithio-1,4-bis(TMS)-2-butene路(TMEDA)₂2, internally solvated cis-dilithio-1,4-bis[bis(2-methoxyethyl)aminomethyldimethylsilyl]-2-butene 5, and using only modeling, 1,4-dilithio-2-butene路(TMEDA)₂9 reveal remarkably similar structural and NMR parameters. In the solid, 5 consists of unusual 鈥淭鈥?shaped dynamic clusters. In all three bridging lithiums are sited between 1.8 and 1.9 脜 normal to the centroids of opposite faces of the near coplanar of the 2-butene component. Typical bond lengths of the latter are 1.458 卤 0.004, 1.385 卤 0.006, and 1.459 卤 0.003 脜, for C1鈥揅2, C2鈥揅3, and C3鈥揅4, respectively. The ¹³C chemical shifts lie within the ranges 未 21 卤 0.5, 99 卤 0.7, 99 卤 0.7 and 21 卤 0.5 for C1, C2 and C3 together, and C4, respectively. Dynamic ¹³C NMR provides activation parameters for nitrogen inversion in 2 and 5, overall molecular inversion of 5, and conformational interconversion of 2.