Selective Inclusion of Cu + and Ag + Electron‐Rich Metallic Cations within Supramolecular Polyoxometalates Based on {AsW 9 O 33 }{Mo 3 S 4 } Combinations

Coordination of the [Mo 3 S 4 (H 2 O) 9 ] 4+ cluster with the trivacant [AsW 9 O 33 ] 9− ion gives the supramolecular complex [{(H 4 AsW 9 O 33 ) 4 (Mo 3 S 4 {H 2 O} 5 )} 2 ] 12− ( 1 ) in good yield. The structure of 1 shows that two [H 4 AsW 9 O 33 ] 5− subunits sandwich a single central [Mo 3 S 4 (H 2 O) 5 ] 4+ ion to give a basic monomeric unit [(H 4 AsW 9 O 33 ) 2 {Mo 3 S 4 (H 2 O) 5 }] 6− . In the solid sate, a supramolecular dimeric association is evidenced that consists of two [(H 4 AsW 9 O 33 ) 2 {Mo 3 S 4 (H 2 O) 5 }] 6− units held together by twelve hydrogen bonds and four S⋅⋅⋅S contacts. Complex 1 reacts with NaAsO 2 , AgNO 3 and CuI to give compounds 2 , 3 and 4 , respectively. X‐ray structural analysis reveals that the molecular arrangements of 2 to 4 are closely related to the parent structure of 1 . {AsOH} 2+ , Ag + and Cu + ions are located on three distinct pairs of sites. Two hanging {AsOH} 2+ groups in 2 are symmetrically attached to two opposite {AsW 9 O 33 } subunits. Complex 3 is the first example of an Ag/{Mo 3 S 4 } combination in which the environment of the two equivalent Ag + cations is remarkable for containing two sulfur atoms belonging to {Mo 3 S 4 }, two oxygen and one central arsenic atom of the {AsW 9 O 33 } subunits. Potentiometric titration shows that the addition of Ag + ions is quantitative and occurs in two successive steps ( K 1 =4.1×10 6 and K 2 =2.3×10 5  L mol −1 ), which is consistent with the retention of the supramolecular cluster in solution. The structure of 4 reveals a single copper atom embedded in the central part of the dimer. The Cu + cation is bound to four sulfur atoms to complete a cuboidal moiety. UV/Vis studies in solution indicate that the stability of the dimeric assemblies of 2 , 3 and 4 is significantly enhanced by the presence of Cu + or Ag + ions, which act as additional coordination linkers within the supramolecular cluster. The anions 1 to 4 were characterised by 183 W NMR spectroscopy in solution. The 10‐line spectra recorded for each of them are consistent with an averaged C 2 h molecular symmetry in solution.