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Syntheses and Crystal Structures of Phenyl-Lithium Derivatives

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journal contribution
posted on 16.07.2018 by Alexander Bodach, René Hebestreit, Michael Bolte, Lothar Fink
Although organolithium compounds have been studied and applied for ∼100 years, only few crystal structures of pure, unsolvated organolithium compounds have been reported so far. Therefore, several phenyl-lithium derivatives were synthesized by lithium–halogen exchange reactions, yielding fairly soluble polymers in the cases of 4- and 2-methylphenyl-lithium (p-TolLi and o-TolLi). Their crystal structures have been determined by X-ray powder diffraction. Remarkably, o-TolLi crystallizes in the noncentrosymmetric space group P212121 with two independent monomers, whereas the crystal structure of p-TolLi is described in spacegroup P21/a. In contrast, no polymer of 5-m-XyLi (3,5-dimethyl-phenyl-lithium) could be observed, but single crystals of a [(5-m-XyLi)3­(MTBE)3LiBr] adduct were isolated (MTBE = methyl-tert-butylether). This gives hints on the nature of lithium–halogen exchange reactions. Steric and electronic effects of the phenyl-lithium substitution are further discussed in conjunction with related compounds.