Aggregation of organolithium compounds

The degree of aggregation of organolithium compounds (alkyl-, aryl-, and alkynyl-lithium compounds as well as lithium enolates) in dilute tetrahydrofuran solution at —108 °C has been determined by means of cryoscopic [289] and NMR spectroscopic measurements [290] for a review on the solution structure of Hthium enolates and phenolates, see reference [406]. 

The different contributions of Li and Li to the spin-lattice relaxation of neighbouring nuclei also provide, in suitable cases, a means for the determination of Li-C and Li-H distances in aggregates of organolithium compounds through the use of the isotopic substitution method [42], as has... 

Bauer, W., Seebach, D. Determination of the degree of aggregation of organolithium compounds by cryoscopy in tetrahydrofuran. Helv. Chim. Acta 1984, 67, 1972-1988. 

L.M. Pratt, Mixed Aggregates of Organolithium Compounds , p. 209 E. Kawashima and K. Kamaike, Synthesis of Stable-Isotope ( C and N) Labeled Nucleosides and Their Applications , p. 309... 

It has been found that the Li quadrupole parameters x( Li) and /]( Li) are sensitive probes of solid state structures of organolithium compounds, for example with respect to aggregate size, solvation, ion pair structure and the X-Li-X structural angle. These results will be discussed in the following sections. 

Recently, deuterium-induced isotope effects on Li chemical shifts in organolithium compounds have been observed [51] and based on this observation, the isotopic fingerprint method was developed as a tool for structural investigations in the field of organolithium compounds. With this method, typical Li multiplets, which are characteristic of the aggregation state. 

The Restricted Vibrational Space (RVS) decomposition Scheme has been used in a quantitative analysis of the intermolecular forces which account for formation of aggregates/complexes of organolithium compounds the electrostatic contribution is always dominant and outweighs any disadvantage of distortion of the partners in complex formation. " ... 

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