Simple synthetic procedures for accessing novel metal-substituted tungstosulfates [SMW11O39]4− (M = Mn2+, Co2+, Ni2+, and Cu2+) with Keggin-type structures were developed.

Invited for the cover of this issue are Tadaharu Ueda, Kochi University, and co‐workers from Okayama University and Hiroshima University, Japan. The cover image shows the synthesis of metal‐substituted tungstosulfates via [(S2W14O54)3]32− with a unique cavity structure from (S2W18O62)4−].

Currently, a large number of metal‐substituted tungstophosphates and tungstosilicates have been prepared with well‐controlled systematic procedures, and many of them have been applied to various fields, such as catalysis and materials, because of their fascinating chemical properties. In addition, the diverse structures of metal‐substituted polyoxometalates (POMs) are quite interesting as molecular architectures. However, there have been fewer reports on the synthesis of metal‐substituted POMs with other hetero atoms. In the present study, controlled and systematic synthetic procedures for Wells–Dawson‐type metal‐substituted tungstosulfates, [S2MW17O61]6– (M = Mn, Co, Ni, Cu), were developed via a ring‐shaped lacunary tungstosulfate, [(S2W14O54)3]32– prepared from the weak base treatment of K4[S2W18O62] in aqueous solution. [(S2W14O54)3]32– and [S2MW17O61]6– were structurally characterized by elemental analysis, X‐ray crystallography and ESI‐MS. [(S2W14O54)3]32– has a different type of structure with a cavity than Preyssler‐type POMs, [X5W30O110]n–, and the other POMs, [X8W48O184]40– (X = P, As). In addition, IR, Raman and UV/Vis spectra as well as cyclic voltammograms of all of the POMs isolated in the present study were obtained and compared with the corresponding Wells–Dawson‐type metal‐substituted tungstophosphates. The synthetic procedures for [S2MW17O61]6– from [S2W18O62]4– via [(S2W14O54)3]32– could open a new path for tungstosulfate chemistry, such as widespread tungstophosphate and tungstosilicate chemistry.

The Front Cover shows the procedure for the controlled synthesis of Wells‐Dawson‐type metal‐substituted tungstosulfates via [(S2W14O54)3]32– with a unique cavity structure derived from [S2W18O62]4–. The shining light symbolizes the opening of a new avenue in polyoxometalate chemistry. More information can be found in the Full Paper by T. Ueda et al. For more on the story behind the cover research, see the Cover Profile.