Gravar-mail: Bis(1,2-dimethoxyethane)-1κ(2) O,O′;3κ(2) O,O′-tetra­kis­(μ-1,1,1,3,3,3-hexa­fluoro-2-methyl­propan-2-olato)-1:2κ(4) O:O;2:3κ(4) O:O-1,3-dilithium-2-magnesium