Synthesis and Reactivity of Low-Valent f‑Element Iodide Complexes with Neutral Iminophosphorane Ligands

The coordination and reactivity of simple iodide salts of low-valent f elements [YbI₂, SmI₂, TmI₂, and UI₃(THF)₄, where THF = tetrahydrofuran] with iminophosphorane (R₃PNR′) ligands are reported. The studied chelates were observed to adapt their geometry and effectively bind divalent ytterbium and samarium centers, as well as the trivalent uranium cation. The reactivity of the ytterbium adducts with benzophenone was found to be dependent on the steric demand of the supporting iminophosphorane ligand. In particular, a rare example of a stable charge-separated ketyl radical species is reported with ytterbium. Additionally, divalent thulium was observed to induce a reductive coupling at the ligand’s central pyridine ring.