Lithium and Sodium Ion Distributions in A[WI] Structures.

Ag[WI] and A[WI] compounds with A = Na, Li were prepared from binary tungsten iodides (WI) and corresponding metal iodides. Their crystal structures are analyzed on the basis of X-ray diffraction data. Li and Na 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 [MI] 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 A[WI] compounds, because it is the only compound which is soluble in water.