Morphological plasticity of LiCl clusters interacting with Grignard reagent in tetrahydrofuran

Ab initio molecular dynamics simulations are used to explore tetrahydrofuran (THF) solutions containing pure LiCl, and LiCl with CH3MgCl, as model constituents of the turbo Grignard reagent. Solvated LiCl aggregates as Li4Cl4, which preferentially assumes compact cubane-like conformations. In particular, an open-edge pseudo tetrahedral frame is promoted by solvent-assisted Li-Cl bond cleavage. Among the various Grignard species produced by the Schlenk equilibrium, LiCl shows clear preference for MgCl2, combining with it through μ2-Cl bridges. Using a 1:1 Mg:Li ratio, the highly plastic tetranuclear LiCl cluster decomposes to a highly solvated mixed LiCl:MgCl2 aggregate with prevalent Li-(μ-Cl)2-Mg rings and linear LiCl entities. The MgCl2 assisted disaggregation of Li4Cl4 occurs through transient structures analogous to those detected for pure LiCl in THF, which also correspond to various moieties observed in the solid state. This study identifies a synergistic role of LiCl for the determination of the compounds present in turbo Grignard solutions, in a scenario where LiCl shifts the Schlenk equilibrium promoting a higher concentration of strongly reactive dialkylmagnesium, meanwhile decomposing into smaller, more soluble, and putatively more active mixed Mg:Li:Cl clusters.