Synthesis and structures of alkali metal salts of bis[(trifluoromethyl)sulfonyllimide

A series of alkali metal salts of the bis[(trifluoromethyl)sulfonyl]imide anion have been prepared and structurally characterized. Despite very similar crystallization conditions, the salts exhibit a variety of solvent inclusion behavior. The potassium and cesium salts are anhydrous, the lithium and rubidium salts crystallize as monohydrates, and the sodium salt includes both water and methanol molecules in the lattice (1:1:1). In all but the rubidium salt, the anion has a cisoid conformation with the trifluoroalkyl groups lying to the same side of the S-N-S plane. Interestingly, the rubidium salt which has a three-dimensional network structure with tunnels running parallel to the c-axis is the only one that does not have a layered structure. However, fluorine segregation resulting in formation of hydrophilic and hydrophobic domains is a dominant feature in the crystal packing of the entire series.