Studies on Organometallic Oxidants: Structure, Redox Properties, and Magnetism of (C₅H₅)VBr₃ and (C₅H₅)VI₃

The preparation and properties of CpVBr₃ and CpVI₃ (Cp = η⁵-C₅H₅) are described. The compound CpVBr₃ exhibits an E_1/2 of 510 mV (vs Ag/AgCl) and is able to oxidize ferrocene. The salt [Cp₂Fe][CpVBr₃] was characterized by infrared spectroscopy (v_CH(Cp₂Fe) = 857 cm^-1), ⁵⁷Fe Mössbauer spectroscopy at 295 K (δ₁ = 0.35, δ₂ = 0-421 mm/s) and 150 K, variable-temperature magnetic susceptibility (μ_eff(300 K) = 3.75 μ_B), and ¹H NMR spectroscopy. While CpVBr₃ is more oxidizing than CpVCl₃, we find that CpVI₃ is less oxidizing (E_1/2 = 425 mV). In solution CpVI₃ exists as two distinct species as shown by ¹H NMR spectroscopy. The structure of CpVI₃ was solved in the orthorhombic space group Pn2₁a (no. 33, alternate setting) with the lattice constants a = 11.847 (4) Å, b = 11.304 (3) Å, c = 7.532 (1) Å, and Z = 4.