Supramolecular assemblies of [Mo3Se4Clx(H2O)9-x](4-x)+ with cucurbituril;: complementarity control through the variation of x

From solutions of seleno bridged triangular cluster Mo3Se4(aq)(4+) in HCl. crystalline adducts with cucurbituril (Cuc, C36H36N24O12) of different composition, depending on HCl concentration. were isolated. From 2 M HCl, a monosubstituted cationic cluster crystallizes as {[Mo3Se4Cl(H2O)(8)](2)(C36H36O12)}Cl-6.16H(2)O (1), Increase in HCl concentration to 6 M gives a pentasubstituted anionic species, (H3O)(2)[Mo3Se4Cl5(H2O)(4)](2)(C36H36N24O12).15H(2)O (2). The crystal structures of 1 and 2 were determined by X-ray crystallography. Each portal of Cuc in 1 is covered with cluster cations [Mo3Se4Cl(H2O)(8)](3+) like a 'lid' on a 'barrel'. Six water molecules in the trans position to the core mu(2)-Se form complementary hydrogen bonds with oxygen atoms of Cuc (O...O, 2.713-3.067 Angstrom). In 2 the complementarity is lost and the main structure building factor is short Se...Se interactions (Se...Se, 2.96-3.43 Angstrom) between two adjacent anionic clusters. Stereochemistry of halide substitution in the triangular clusters M(3)Q(4) is analyzed. (C) 2002 Elsevier Science B.V. All rights reserved.