Developing a Hetero-Alkali-Metal Chemistry of 2,2,6,6-Tetramethylpiperidide (TMP): Stoichiometric and Structural Diversity within a Series of Lithium/Sodium, Lithium/Potassium and Sodium/Potassium TMP Compounds
Developing a Hetero-Alkali-Metal Chemistry of 2,2,6,6-Tetramethylpiperidide (TMP): Stoichiometric and Structural Diversity within a Series of Lithium/Sodium, Lithium/Potassium and Sodium/Potassium TMP Compounds
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DOI：
10.1002/chem.201101167
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发表时间：
2011-08-01
影响因子：
4.3
通讯作者：
Robertson, Stuart D.
中科院分区：
文献类型：
--
作者：
Armstrong, David R.;Kennedy, Alan R.;Robertson, Stuart D.
Li（TMP）（TMP= 2，2，6，6-tetramethylpiperidide）作为一种强碱性、弱亲核性的C-H金属化试剂，在溶液和固体状态下得到了广泛的研究。最近，人们对含有大体积TMP阴离子的混合金属衍生物的兴趣激增。在本文中，我们通过报道N，N，N '，N'-四甲基乙二胺（TMEDA）-半溶剂化的钠-锂环杂二聚体[（tmeda）Na（mu-tmp）（2）Li]及其不含TMEDA的变体[{Na（mu-tmp）Li（mu-tmp）}infinity]开始开发杂（碱金属）TMP化学，其提供了晶体学上认证的聚合碱金属酰胺的罕见实例。实验观察表明，前者是一个动力学中间体的路线，后者的热力学产品。此外，第三个修改，混合的富钾锂环杂三聚体[（tmeda）K（mu-tmp）Li（mu-tmp）Li（mu-tmp）]，也已合成和晶体学特征。在移动到体积较大的三齿供体N，N，N '，N“，N”-五甲基二乙二胺（PMDETA）时，额外的连接迫使钠-锂和钾-二锂环物质打开，分别得到无环弧形复合物[（pmdeta）Na（mu-tmp）Li（tmp）]和[（pmdeta）K（mu-tmp）Li（mu-tmp）Li（tmp）]。完成系列，钾-锂和钾-钠衍生物[（pmdeta）K（mu-tmp）（2）M]（M=Li，Na）也被分离为具有明显不对称的中心MN 2K环的封闭结构。总的来说，这七个新的化合物显示出五个不同的结构基序，其中四个从未在TMP化学中见过，其中三个在碱金属酰胺化学的庞大结构库中是前所未有的。
Studied extensively in solution and in the solid state, Li(TMP) (TMP=2,2,6,6-tetramethylpiperidide) is an important utility reagent popular as a strongly basic, weakly nucleophilic tool for C-H metallation. Recently, there has been a surge in interest in mixed metal derivatives containing the bulky TMP anion. Herein, we start to develop hetero (alkali metal) TMP chemistry by reporting the N,N,N',N'-tetramethylethylenediamine (TMEDA)-hemisolvated sodium-lithium cycloheterodimer [(tmeda)Na(mu-tmp)(2)Li], and its TMEDA-free variant [{Na(mu-tmp) Li(mu-tmp)}infinity], which provides a rare example of a crystallographically authenticated polymeric alkali metal amide. Experimental observations suggest that the former is a kinetic intermediate en route to the latter thermodynamic product. Furthermore, a third modification, the mixed potassium-lithium-rich cycloheterotrimer [(tmeda) K(mu-tmp) Li(mu-tmp) Li( mu-tmp)], has also been synthesised and crystallographically characterised. On moving to the bulkier tridentate donor N,N,N',N '',N ''-pentamethyldiethylenediamine (PMDETA), the additional ligation forces the sodium-lithium and potassium-dilithium ring species to open giving the acyclic arc-shaped complexes [(pmdeta)Na(mu-tmp)Li(tmp)] and [(pmdeta)K(mu-tmp)Li(mu-tmp)Li(tmp)], respectively. Completing the series, the potassium-lithium and potassium-sodium derivatives [(pmdeta)K(mu-tmp)(2)M] (M=Li, Na) have also been isolated as closed structures with a distinctly asymmetric central MN2K ring. Collectively, these seven new bimetallic compounds display five distinct structural motifs, four of which have never hitherto been witnessed in TMP chemistry and three of which are unprecedented in the vast structural library of alkali metal amide chemistry.