The role of Li⋯F interactions in lithium and heterobimetallic lithium–magnesium complexes of the hexafluoroisopropoxide anion

As part of ongoing investigations of battery electrolytes and additives based on derivatives of 1,1,1,3,3,3-hexafluoroisopropanol, the solvent-free hexameric precursor [Li(μ 3 -OCH(CF 3 ) 2 )] 6 ( 1 ) was isolated and characterised by single-crystal X-ray diffraction and found to possess a ring-stacked hexagonal prismatic Li 6 arrangement supported by Li⋯F interactions. To explore the behaviour of this fluoroalkoxide ligand further, the lithium magnesiate complexes [Li 2 (thf) 4 Mg(μ 2 -OCH(CF 3 ) 2 ) 4 ] ( 2 ) and [Li 3 (thf) 2 ( n BuMg)(μ 3 -OCH(CF 3 ) 2 ) 4 ] ( 3 ) were also obtained; 2 from the reaction of the fluorinated alcohol with a 2:1 mixture of n BuLi: n Bu 2 Mg, and 3 from the reaction of the alcohol with a 1:1 mixture of n BuLi: n Bu 2 Mg. The structure of 3 is of particular interest, being based on a Li 3 MgO 4 heterocubane arrangement which possesses a highly unusual 3:1 Li:Mg stoichiometry. The solid-state structures of 1 – 3 illustrate some of the range of vastly different geometries possible for s -block metal alkoxides and highlight the potential importance of Li⋯F interactions in molecular stabilisation.