Selenium-centered, undecanuclear silver cages surrounded by iodo and dialkyldiselenophosphato ligands. Syntheses, structures, and photophysical properties

Three clusters [Ag₁₁(μ₉-Se)(μ₃-I) ₃{Se₂P(OR)₂}₆] (R = Et, 1; ⁱPr, 2; ²Bu, 3) were isolated from the reaction of [Ag(CH₃CN)₄](PF₆), NH₄[Se ₂P(OR)₂], and Bu₄NI in a molar ratio of 4:3:1 in CH₂Cl₂ in 47-55% yield. Compounds 1 and 2 can also be synthesized with high yield from the reaction of Ag₁₀(Se)[Se ₂P(OR)₂]₈ with 8 equiv of Bu₄NI. In the positive fast atom bombardment mass spectra of 1-3, two major peaks that correspond to the intact molecule with the loss of an iodide ion, [Ag ₁₁(μ₉-Se)(μ₃-I)₂{Se ₂P(OR)₂}₆]⁺, and a diselenophosphate ligand, [Ag₁₁(μ₉-Se)-(μ₃-I) ₃{Se₂P(OR)₂}₅]⁺, were identified. Single-crystal X-ray analyses of 2 and 3 reveal an Ag₁₁Se core stabilized by three iodide anions and six diselenophosphato ligands in a tetrametallic tetraconnective (μ₂,μ₂) coordination mode. The central core adopts the geometry of a 3,3,4,4,4-pentacapped trigonal prism with a selenium atom in the center. In addition, weak intermolecular Se⋯I interactions exist in 2 and form a one-dimensional polymeric chain structure. Furthermore, all compounds exhibit orange-red luminescence in both the solid state and solution.