Correlation between the electrochemical response and main components structure in solutions for rechargeable Mg batteries based on THF and the reaction products of tBuMgCl and AlCl3

•We explore here the products of the reaction of the Grignard reagent t-BuMgCl with AlCl3 (1:1) in THF, and how their presence in solutions affect their electrochemical behavior.•Two complex products were isolated from the precipitated part of the reaction and the counter solution part, which exhibit two distinct single-crystal structures.•Crystallization from precipitated part (compound I) has the molecular structure [MgCl·THF5]+ [AlCl4]– and it is electrochemically inactive in terms of reversible Mg dissolution/deposition.•The molecular structure of the second compound (II), obtained from solution part is [Mg2(μ-Cl)3·THF6]+ [t-BuAlCl3]- and its solutions in THF exhibit reversible Mg dissolution/deposition behavior.•This study demonstrates the possibility of tuning judiciously the electrochemical response of ethereal solutions of magnesium organohaloaluminate complexes through their structural modifications.