Morphological Plasticity of LiCl Clusters Interacting with Grignard Reagent in Tetrahydrofuran

Ab initio molecular dynamics simulations are used toexplore tetrahydrofuran(THF) solutions containing pure LiCl and LiCl with CH3MgCl,as model constituents of the turbo Grignard reagent. LiCl aggregatesas Li4Cl4, which preferentially assumes compactcubane-like conformations. In particular, an open-edge pseudotetrahedralframe is promoted by solvent-assisted Li-Cl bond cleavage.Among the Grignard species involved in the Schlenk equilibrium, LiClprefers to coordinate MgCl2 through & mu;(2)-Cl bridges. Using a 1:1 Li:Mg ratio, the plastic tetranuclear LiClcluster decomposes to a highly solvated mixed LiCl & BULL;MgCl2 aggregate with prevalent Li-(& mu;(2)-Cl)(2)-Mg rings and linear LiCl entities. The MgCl2-assisted disaggregation of Li4Cl4 occurs throughtransient structures analogous to those detected for pure LiCl inTHF, also corresponding to moieties observed in the solid state. Thisstudy identifies a synergistic role of LiCl for the determinationof the compounds present in turbo Grignard solutions. LiCl shiftsthe Schlenk equilibrium promoting a higher concentration of dialkylmagnesium,while decomposing into smaller, more soluble, mixed Li:Mg:Cl clusters.

Automated summary

Ab initio molecular dynamics simulations are performed to study THF solutions containing LiCl and LiCl with CH3MgCl, as model compounds of the turbo Grignard reagent. LiCl aggregates as compact cubane-like Li4Cl4 structures, with an open-edge pseudotetrahedral frame promoted by solvent-assisted Li-Cl bond cleavage. LiCl prefers to coordinate MgCl2 through μ(2)-Cl bridges. The study identifies the role of LiCl in the determination of compounds present in turbo Grignard solutions.