Investigation of Molecular Iridium Fluorides IrFn (n=1-6): A Combined Matrix-Isolation and Quantum-Chemical Study.

Abstract

The photo‐initiated defluorination of iridium hexafluoride (IrF6) was investigated in neon and argon matrices at 6 K, and their photoproducts are characterized by IR and UV‐vis spectroscopies as well as quantum‐chemical calculations. The primary photoproducts obtained after irradiation with λ=365 nm are iridium pentafluoride (IrF5) and iridium trifluoride (IrF3), while longer irradiation of the same matrix with λ=278 nm produced iridium tetrafluoride (IrF4) and iridium difluoride (IrF2) by Ir−F bond cleavage or F2 elimination. In addition, IrF5 can be reversed to IrF6 by adding a F atom when exposed to blue‐light (λ=470 nm) irradiation. Laser irradiation (λ=266 nm) of IrF4 also generated IrF6, IrF5, IrF3 and IrF2. Alternatively, molecular binary iridium fluorides IrF n (n=1–6) were produced by co‐deposition of laser‐ablated iridium atoms with elemental fluorine in excess neon and argon matrices under cryogenic conditions. Computational studies up to scalar relativistic CCSD(T)/triple‐ζ level and two‐component quasirelativistic DFT computations including spin‐orbit coupling effects supported the formation of these products and provided detailed insights into their molecular structures by their characteristic Ir−F stretching bands. Compared to the Jahn‐Teller effect, the influence of spin‐orbit coupling dominates in IrF5, leading to a triplet ground state with C 4v symmetry, which was spectroscopically detected in solid argon and neon matrices.