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 IrFn (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 C4v symmetry, which was spectroscopically detected in solid argon and neon matrices.