Lithium and Sodium Ion Distributions in A2- x[W6I14] Structures.

Ag2[W6I14] and A2- x[W6I14] compounds with A = Na, Li were prepared from binary tungsten iodides (W3I12) and corresponding metal iodides. Their crystal structures are analyzed on the basis of X-ray diffraction data. 7Li and 23Na solid-state NMR measurements reveal that Li+ and Na+ ions are distributed over two sites in the respective structures. These results shed some new light on A x[M6I14] with A = alkali and M = Mo, W compounds being reported with x = 1 and 2, which exhibit photophysical properties. The lithium compound is an exception in the series of A2- x[W6I14] compounds, because it is the only compound which is soluble in water.