Walfort B, Lameyer L, Weiss W, Herbst-Irmer R, Bertermann R, Rocha J, Stalke D
Institut für Anorganische Chemie der Universität Würzburg, Germany.
Chemistry. 2001 Apr 1;7(7):1417-23. doi: 10.1002/1521-3765(20010401)7:7<1417::aid-chem1417>3.0.co;2-q.
Organolithium compounds play the leading role among the organometallic reagents in synthesis and in industrial processes. Up to date industrial application of methyllithium is limited because it is only soluble in diethyl ether, which amplifies various hazards in large-scale processes. However, most reactions require polar solvents like diethyl ether or THF to disassemble parent organolithium oligomers. If classical bidentate donor solvents like TMEDA (TMEDA= N,N,N',N'tetramethyl-1,2-ethanediamine) or DME (DME=1,2-dimethoxyethane) are added to methyllithium, tetrameric units are linked to form polymeric arrays that suffer from reduced reactivity and/or solubility. In this paper we present two different approaches to tune methyllithium aggregation. In [[(MeLi)4(dem)1,5)infinity] (1; DEM = EtOCH2OEt, diethoxymethane) a polymeric architecture is maintained that forms microporous soluble aggregates as a result of the rigid bite of the methylene-bridged bidentate donor base DEM. Wide channels of 720 pm in diameter in the structure maintain full solubility as they are coated with lipophilic ethyl groups and filled with solvent. In compound 1 the long-range Li3CH3...Li interactions found in solid [[(MeLi)4]infinity] are maintained. A different approach was successful in the disassembly of the tetrameric architecture of [((MeLi)4]infinity]. In the reaction of dilithium triazasulfite both the parent [(MeLi)4] tetramer and the [[Li2[(NtBu)3S]]2] dimer disintegrate and recombine to give an MeLi monomer stabilized in the adduct complex [(thf)3Li3Me-[(NtBu)3S]] (2). One side of the Li3 triangle, often found in organolithium chemistry, is shielded by the tripodal triazasulfite, while the other face is mu3-capped by the methanide anion. This Li3 structural motif is also present in organolithium tetramers and hexamers. All single-crystal structures have been confirmed through solid-state NMR experiments to be the same as in the bulk powder material.
有机锂化合物在合成及工业过程中的有机金属试剂中起着主导作用。到目前为止，甲基锂在工业上的应用有限，因为它只溶于乙醚，这在大规模过程中会放大各种危险。然而，大多数反应需要极性溶剂，如乙醚或四氢呋喃，来拆解母体有机锂低聚物。如果将经典的双齿供体溶剂，如四甲基乙二胺（TMEDA = N,N,N',N'-四甲基-1,2-乙二胺）或二甲氧基乙烷（DME = 1,2-二甲氧基乙烷）添加到甲基锂中，四聚体单元会连接形成聚合物阵列，其反应性和/或溶解度会降低。在本文中，我们提出了两种不同的方法来调节甲基锂的聚集。在[[(MeLi)4(dem)1.5]∞]（1；DEM = 乙氧基甲醚，二乙氧基甲烷）中，维持了一种聚合物结构，由于亚甲基桥连双齿供体碱DEM的刚性咬合，形成了微孔可溶性聚集体。结构中直径为720 pm的宽通道保持了完全的溶解性，因为它们被亲脂性的乙基覆盖并充满了溶剂。在化合物1中，在固体[[(MeLi)4]∞]中发现的远程Li3CH3...Li相互作用得以维持。一种不同的方法成功地拆解了[[(MeLi)4]∞]的四聚体结构。在三氮杂亚硫酸盐二锂的反应中，母体[(MeLi)4]四聚体和[[Li2[(NtBu)3S]]2]二聚体都分解并重新组合，生成在加合物[(thf)3Li3Me-[(NtBu)3S]]（2）中稳定的甲基锂单体。有机锂化学中经常发现的Li3三角形的一侧被三脚架状的三氮杂亚硫酸盐屏蔽，而另一面则被甲烷阴离子以μ3-帽的形式覆盖。这种Li3结构单元也存在于有机锂四聚体和六聚体中。所有单晶结构均通过固态核磁共振实验得到证实，与块状粉末材料中的结构相同。
