Understanding Structure Formation in Organolithium Compounds: An Experimental and Quantum-Chemical Approach
Understanding Structure Formation in Organolithium Compounds: An Experimental and Quantum-Chemical Approach
复制标题
DOI：
10.1002/zaac.201200495
复制
发表时间：
2013-09-01
影响因子：
1.4
通讯作者：
Strohmann, Carsten
中科院分区：
文献类型：
--
作者：
Goetz, Kathrin;Gessner, Viktoria H.;Strohmann, Carsten
由于有机锂化合物的反应性与所涉及物种的结构密切相关，因此结构知识是理解反应机理的前提。以甲基锂为例，我们结合X射线结构分析和量子化学方法，着重讨论了稳定有机锂聚集体中非经典相互作用的问题，以及解聚与极性的关系。一系列Meli加合物的结构分析表明，其中二乙醚加合物(Meli中心点Et2O)(4)的α-氢原子相对于锂有不同的排列。即使在改变二聚体加合物中配体的立体化学时，α-氢取向也不同。计算只证实了Li-H相互作用的微弱稳定效应，这种相互作用与形成的聚集体中空间位置的其他方面相竞争。NPA和QTAIM对具有不同共配体的不同聚集体(如单体、二聚体、四聚体、扩展晶体环境)的分析表明，聚集度与Li-C键极性之间存在复杂的关系，但对锂配位数的依赖关系更为明显。
As the reactivity of organolithium compounds is strongly connected with the structure of the involved species, the structural knowledge is a prerequisite for the understanding of reaction mechanisms. Using the example of methyllithium, we address particularly the issues of stabilizing non-classical interactions in organolithium aggregates and the relations between disaggregation and polarity, using a combination of X-ray structure analysis and quantum-chemical methods. The structure analyses of a series of MeLi adducts, among them the diethyl ether adduct (MeLi center dot Et2O)(4), exhibit varying arrangements of the alpha-hydrogen atoms relative to lithium. alpha-Hydrogen orientations differ even when changing the stereochemistry of the ligand in dimeric adducts. Computations confirm only weak stabilizing effects of agostic Li-H interactions, which compete with other aspects of the spatial situation in the formed aggregates. NPA and QTAIM analyses on different aggregates (e.g. monomer, dimer, tetramer, extended crystal environment) with different co-ligands reveal a complicated relation between the degree of aggregation and Li-C bond polarity but a more clearcut dependence on the lithium coordination number.