Lithium and Sodium Ion Distributions in A 2- x [W 6 I 14 ] Structures.

Ag ₂ [W ₆ I ₁₄ ] and A _{2- x} [W ₆ I ₁₄ ] compounds with A = Na, Li were prepared from binary tungsten iodides (W ₃ I ₁₂ ) and corresponding metal iodides. Their crystal structures are analyzed on the basis of X-ray diffraction data. ⁷ Li and ²³ 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 _x [M ₆ I ₁₄ ] 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 _{2- x} [W ₆ I ₁₄ ] compounds, because it is the only compound which is soluble in water.