Alkyllithium compounds, crystal

Alkyldiazenido complexes, mechanisms of formation, 27 223-225 Alkylfluorophosphines, 13 367-378 Alkyl ftillerides, 44 38 Alkylidiboranes cyclic, 16 215, 216 electron diffiaction studies of, 16 216 NMR of, 16 216 preparation of, 16 214, 215 Alkyllithium compounds, crystal structures, 37 83-85... 

When bidentate solvents are present, the clusters may crystallize forming linear polymers by linking clusters together, as in complexes 292-295. This further diminishes solubility and reactivity of the alkyllithium compound, making the unassociated RLi species the most probable reactive form in synthetic processes. MeLi dissolved in diethoxymethane shows at room temperature a single Li NMR peak, that resolves into four distinct peaks at —80°C, pointing to temperature-dependent monomer/oligomer/polymer equilibria . 

Stable homoleptic tetraorganyldielement compounds characterized by crystal structure determinations are summarized in Table III. Their syntheses succeeded by three methods (i) Reduction of element(III) compounds by alkali metals (ii) treatment of subhalides with the corresponding alkyllithium compounds (iii) reactions of particular silanides... 

In the absence of Lewis bases, i.e., crystallized in pure form or dissolved in hydrocarbons, alkyllithium compounds occur as hexamers or tetramers, depending on the alkyl substituent (Figure 10.1). 

Alkyllithium compounds normally crystallize in the form of amine-complexed tetramers (alkyllithium NRj)4 l55). 

Moreover, in deprotonation reactions with common alkyllithium bases (e.g. butyl-lithium), no side-products are formed, that increase the solubility of the polylithium compound. Also, product mixtures are only rarely observed with this method. Thus, the resulting polylithium compound can be isolated or crystallized more easily. This is why—in addition to Section II. E—only this section presents many visualizations of successful X-ray structural analyses of polylithiated compounds. 

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