Monomerizing Alkali-Metal 3,5-Dimethylbenzyl Salts with Tris(N, N-dimethyl-2-aminoethyl)amine (Me6TREN): Structural and Bonding Implications
Monomerizing Alkali-Metal 3,5-Dimethylbenzyl Salts with Tris(N, N-dimethyl-2-aminoethyl)amine (Me6TREN): Structural and Bonding Implications
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DOI：
10.1021/ic401777x
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发表时间：
2013-10-21
影响因子：
4.6
通讯作者：
Robertson, Stuart D.
中科院分区：
文献类型：
--
作者：
Armstrong, David R.;Davidson, Matthew G.;Robertson, Stuart D.
由1,3,5-三甲苯（甲三苯）衍生的取代苯阴离子3,5-二甲基苄基（Me2C6H3CH2-）的碱金属（Li, Na， K）配合物通过三足四齿路易斯供体三（N，N-二甲基-2-氨基乙基）胺，[N(CH2CH2NMe2)(3)， Me6TREN]被胁迫成单体形式。x射线晶体学分子结构分析表明，正负离子相互作用随碱金属的变化而变化，碳离子与锂的结合主要是sigma型，与钾的结合主要是pi型，与钠的相互作用介于这两个极端之间。这种区别是由于较重的碱金属强迫和利用负电荷的离域进入芳香环以获得与其尺寸一致的较高配位数。Me6TREN在任何时候都以eta(4)模式结合金属。这种配位异构现象通过多核核磁共振波谱也可以扩展到溶液中的结构，并得到模型系统密度泛函理论（DFT）计算的进一步支持。一种Me6TREN稳定的苄基钾配合物通过与tBu(2)Zn的络合反应制备了一种混合金属酸盐配合物，苄基配体作为两种金属之间的异位sigma/pi桥接配体，并且小锌原子将负电荷重新定位到CH2侧臂上，从而得到一种最佳描述为接触离子对锌酸钾的配合物。
The series of alkali-metal (Li, Na, K) complexes of the substituted benzyl anion 3,5-dimethylbenzyl (Me2C6H3CH2-) derived from 1,3,5-trimethylbenzene (mesitylene) have been coerced into monomeric forms by supporting them with the tripodal tetradentate Lewis donor tris(N,N-dimethyl-2-aminoethyl)amine, [N(CH2CH2NMe2)(3), Me6TREN]. Molecular structure analysis by X-ray crystallography establishes that the cation-anion interaction varies as a function of the alkali-metal, with the carbanion binding to lithium mainly in a sigma fashion, to potassium mainly in a pi fashion, with the interaction toward sodium being intermediate between these two extremes. This distinction is due to the heavier alkali-metal forcing and using the delocalization of negative charge into the aromatic ring to gain a higher coordination number in accordance with its size. Me6TREN binds the metal in a eta(4) mode at all times. This coordination isomerism is shown by multinuclear NMR spectroscopy to also extend to the structures in solution and is further supported by density functional theory (DFT) calculations on model systems. A Me6TREN stabilized benzyl potassium complex has been used to prepare a mixed-metal ate complex by a cocomplexation reaction with tBu(2)Zn, with the benzyl ligand acting as an unusual ditopic sigma/pi bridging ligand between the two metals, and with the small zinc atom relocalizing the negative charge back on to the lateral CH2 arm to give a complex best described as a contacted ion pair potassium zincate.