Dimethylcyclodecyl cations. Evidence for .mu.-hydrido bridging
Dimethylcyclodecyl cations. Evidence for .mu.-hydrido bridging
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二甲基环癸基阳离子。
DOI：
10.1021/ja00393a015
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发表时间：
1981
影响因子：
15
通讯作者：
T. S. Sorensen
中科院分区：
文献类型：
--
作者：
R. P. Kirchen;K. Ranganayakulu;A. Rauk;B. Singh;T. S. Sorensen
假定碳阳离子1, 5-和1, 6-二甲基环十二烷基具有μ-氢桥结构。这项分配基于对 NMR 中单个极高场氢的观察、涉及该氢的异常低耦合常数以及使用桑德斯平衡和共振结构区分标准的非常小的同位素微扰位移。这些桥离子可能发生位置异构化和构象异构化，但没有发现顺反异构化的证据。 μ-氢桥最好被视为“开放”三中心、二电子共振系统，涉及桥接氢的单个电势最小值。桥联氢不具有亲电性，桥联离子不能通过十氢萘中心键质子化来制备，μ-氢也不能作为质子被除去。已经进行了大量的理论计算并将其与实验数据相关联。
The carbocations 1, 5-and1, 6-dimethylcyclododecyl are postulated to have a µ-hydrido-bridged structure. This assignment is based on the observation of a single very high-field hydrogen in the NMR, anomalously low coupling constants involving this hydrogen, and very small isotope perturbation shifts using Saunders’ criterion for equilibrating and resonance structural distinction. Both positionaland conformational isomerization is possible in these bridged ions, but no evidence for cis-trans isomerization was found. The µ-hydrido bridging is best treated as an “open” three-center, two-electron resonance system involving a single potential minimumfor the bridgedhydrogen. The bridging hydrogen is not electrophilic, and the bridged ions cannot be prepared by protonating the central bond of decalins nor can the µ-hydrogen be removed as a proton. Numerous theoretical calculations have been performed and correlated with the experimental data.