Darstellung und spektroskopische Charakterisierung von Fluoro-Chloro-Iridaten(V)

Preparation and Spectroscopic Characterization of Fluoro-Chloro-Iridates(V) By careful oxidation of the pure fluoro-chloro iridates(IV) with BrF₃ in dichloromethane the corresponding pentavalent complexes [IrF₅Cl]^?, cis-[IrF₄Cl₂]^?, and fac-[IrF₃Cl₃]^? are formed without replacements of Cl ligands. The vibrational spectra of these mixed ligand complexes are assigned according to point groups C_4v, C_2v, and C_3v. The increased bond strength compared with the corresponding Ir^IV compounds is indicated by a significant shift to higher energy by about 5–15%. The anomalous intensities of some of the Raman active fundamentals are attributed to the resonance Raman effect. The electronic absorption spectra are measured on the solid tetraethylammonium salts of the fluoro-chloro iridates(V) at 10 K. The strong bands in the UV/VIS region are assigned to charge transfer transitions from π(t_1u, t_2u) and σ(t_1u) Cl orbitals into the π(t)Ir^V level. The intraconfigurational transitions within the t configuration of Ir^V are split by spin orbit coupling and lowered symmetry, observed in the ranges 3000, 5100–6400, 10900–13000, and 18200 cm^?1. The O? O transitions are deduced from the vibrational fine structure; in some cases they are confirmed by electronic Raman bands. With increasing number of F ligands all absorption bands are shifted systematically to higher energies.