Cluster Compounds with Oxidised, Hexanuclear [Nb₆Clⁱ₁₂I^a₆]ⁿ⁻ Anions (n=2 or 3)

Abstract

Four mixed‐halide cluster salts with chloride‐iodide‐supported octahedral Nb 6 metal atoms cores were prepared and investigated. The cluster anions have the formula [Nb 6 Cl i 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. (Ph 4 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 [Nb 6 Cl i 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, CH 2 Cl 2 , 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 (Ph 4 P) 2 [Nb 6 Cl i 12 I a 6 ] ⋅ 4CH 2 Cl 2 with I⋅⋅⋅I halogen bonding and π‐π bonding interactions between the phenyl rings of the cations in (PPN) 3 [Nb 6 Cl i 12 I a 5.047(9) Cl a 0.953 ]. The solubility of (Ph 4 P) 2 [Nb 6 Cl i 12 I a 6 ] ⋅ 4CH 2 Cl 2 has been determined qualitatively in a variety of solvents, and good solubility in the aprotic solvents CH 3 CN, THF and CH 2 Cl 2 has been found.

Hexanuclear Niobium Cluster Alcoholates – First Representatives with Isopropanolato Ligands

“…The starting compound (Ph 4 P) 2 [Nb 6 Cl 12 I 6 ] is prepared according to a literature known procedure and intensively dried in a high vacuum (10 À 6 mbar) at 60 °C. [39] Single-Crystal X-ray Diffraction Structure Studies: Diffraction data of single-crystals of all four cluster compounds were measured on a Bruker-Nonius Apex Kappa II diffractometer with fine focus X-ray tube, monochromator, Oxford-Cryosystem Cooler, and a CCD detector. MoKα radiation, λ = 0.71073 Å, was used.…”

“…The starting compound (Ph 4 P) 2 [Nb 6 Cl 12 I 6 ] is prepared according to a literature known procedure and intensively dried in a high vacuum (10 −6 mbar) at 60 °C [39] …”

“…The title compounds, which are mixed niobium halide-alkoxides, are accessible by ligand exchange reactions starting from (Ph 4 P) 2 [Nb 6 Cl 12 I 6 ]. [39] The substitution of halide (Cl and I) by alcoholate anions requires strong Brønsted basic conditions, which are achieved by Mg(OR) 2 (R = CH 3 , C 2 H 5 ) for 1 and 2 or Li(OC 3 H 7 ) solutions for 3 and 4. [26][27] Under these conditions Nb 6 cluster units are easily oxidized and decompose such that strict anaerobic conditions are required.…”