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

The [(CF3SO2)(2)N](-) anion has low basicity and it does not form strong io n pairs with the lithium cation as shown by the absence of lithium coordina tion to [(CF3SO2)(2)N](-) in the crystal structures of [Li subset of 2.2.2] [(CF3SO2)(2)N] and [Li subset of (12-C-4)(2)][(CF3SO2)(2)N]. The structure of [Li subset of 2.2.2][(CF3SO2)(2)N] consists of a lithium cation encapsul ated by the large 2.2.2-cryptand macrocycle. In the complex [Li subset of ( 12-C-4)(2)][(CF3SO2)(2)N], the lithium cation is sandwiched between two 12- C-4 macrocycles. Correlations between these structures and the previously r eported [Li subset of 12-C-4][CF3SO2N-(CH2)(3)OCH3] structures are describe d. (C) 2000 Published by Elsevier Science B.V.