Cluster Compounds with Oxidised, Hexanuclear [Nb₆ Clⁱ ₁₂ I^a ₆ ]^n- Anions (n=2 or 3)

Four mixed-halide cluster salts with chloride-iodide-supported octahedral Nb₆ metal atoms cores were prepared and investigated. The cluster anions have the formula [Nb₆ Clⁱ ₁₂ I^a ₆ ]^n- with Cl occupying the inner ligand sites and I the outer one. They are one- or two-electron-oxidized (n=2 or 3) with respect to the starting material cluster. (Ph₄ P)⁺ and (PPN)⁺ function as counter cations. The X-ray structures reveal a mixed occupation of the outer sites for only one compound, (PPN)₃ [Nb₆ Clⁱ ₁₂ I^a _5.047(9) Cl^a _0.953 ]. All four compounds are obtained in high yield. If in the chemical reactions a mixture of acetic anhydride, CH₂ Cl₂ , and trimethylsilyl iodide is used, the resulting acidic conditions lead to form the two-electron-oxidised species (n=2) with 14 cluster-based electrons (CBEs). If only acetic anhydride is used, the 15 CBE species (n=3) is obtained in high yield. Interesting intermolecular bonding is found in (Ph₄ P)₂ [Nb₆ Clⁱ ₁₂ I^a ₆ ] ⋅ 4CH₂ Cl₂ with I⋅⋅⋅I halogen bonding and π-π bonding interactions between the phenyl rings of the cations in (PPN)₃ [Nb₆ Clⁱ ₁₂ I^a _5.047(9) Cl^a _0.953 ]. The solubility of (Ph₄ P)₂ [Nb₆ Clⁱ ₁₂ I^a ₆ ] ⋅ 4CH₂ Cl₂ has been determined qualitatively in a variety of solvents, and good solubility in the aprotic solvents CH₃ CN, THF and CH₂ Cl₂ has been found.