Structural comparisons of fast ion conductors consisting of Li[(CF3SO2)2N] complexes with cryptands or crown ether

The [(CF3SO2)2N]− anion has low basicity and it does not form strong ion pairs with the lithium cation as shown by the absence of lithium coordination to [(CF3SO2)2N]− in the crystal structures of [Li⊂2.2.2][(CF3SO2)2N] and [Li⊂(12-C-4)2[(CF3SO2)2N]. The structure of [Li⊂2.2.2][(CF3SO2)2N] consists of a lithium cation encapsulated by the large 2.2.2-cryptand macrocycle. In the complex [Li⊂(12-C-4)2][(CF3SO2)2N], the lithium cation is sandwiched between two 12-C-4 macrocycles. Correlations between these structures and the previously reported [Li⊂12-C-4][CF3SO2N(CH2)3OCH3] structures are described.