Lithium and Sodium Ion Distributions in A_{2- x}[W₆I₁₄] Structures

Ag₂[W₆I₁₄] and A_{2- 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 A_{2- x}[W₆I₁₄] compounds, because it is the only compound which is soluble in water.