Understanding Structure Formation in Organolithium Compounds: An Experimental and Quantum‐Chemical Approach

Abstract

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·Et 2 O) 4 , exhibit varying arrangements * Dr. M. Kaupp

The Reactivity of Benzyl Lithium Species is Regulated by Intermediate Structures

“…Communications calculations of the NMR chemical shifts were performed using DFT-methods at the B3LYP/6-311 + G(2d,p)//B3LYP/ 6-31 + G(d) level. [10] Fort he monomeric species a 7 Li chemical shift of d = 1.2 ppm was calculated, and fits well to the measured data. Forthe dimeric species the calculations result in chemical shifts of d = 0.7 and À5.7 ppm.…”

“…It is the first known example of an alkyl lithium compound having one lithium-aryl sandwich complex and one lithium coordinated by ac arbanionic center. [10] Scheme 4. Carbolithiation of the piperidinoallylamine and further reaction with trimethylchlorostannane in THF.…”

“…The 7 Li NMR spectrum shows two different signals,o ne broad signal from d = À1.3 to À4.2 ppm in the benzylic region as well as one sharp signal at d = À7.3 ppm, which is indicative of alithium cation in between two p-systems. [10] This data suggests that in solution ad imer is formed, where two different lithium cations exist, one in between the two phenyl groups,and one in abenzylic environment.…”

The Reactivity of Benzyl Lithium Species is Regulated by Intermediate Structures

“…[10] This data suggests that in solution ad imer is formed, where two different lithium cations exist, one in between the two phenyl groups,and one in abenzylic environment. In the 7 Li NMR spectrum, with THF as as olvent, only one signal at d = 0.8 ppm was observed.…”

“…[10] Fort he monomeric species a 7 Li chemical shift of d = 1.2 ppm was calculated, and fits well to the measured data. [10] Fort he monomeric species a 7 Li chemical shift of d = 1.2 ppm was calculated, and fits well to the measured data.…”