A Structurally Diverse Series of Eight-Coordinate Hg²⁺ Complexes of KrF₂ Derived from Hg(PnF₆)₂ (Pn = As, Sb) and FHg(AsF₆)

Low-temperature (LT) reactions of the strong oxidative fluorinator, KrF₂, with Hg(PnF₆)₂ (Pn = As, Sb) and FHg(AsF₆) in anhydrous HF solvent provide a structurally diverse series of eight-coordinate Hg(II) complexes in which Hg²⁺ is coordinated to KrF₂, [PnF₆]⁻ (Pn = As, Sb), and HF. The complexes, [Hg(FKrF)₅(AsF₆)₂] (1), [Hg(FKrF)₄(FH)₂SbF₆]₂[SbF₆]₂ (2), [Hg(FKrF)₃(FH)(SbF₆)₂] (3), [Hg(FKrF)₂(AsF₆)₂] (4), [Hg(FKrF)(FH)(AsF₆)₂] (5), [Hg(FKrF)₄(FH)(FH---FH)(AsF₆)₂] (6), [μ-FHg(μ₃-FKrF)1.5(FKrF)0.5AsF₆]₂ (7), and [μ₃-FHg(μ₃-FKrF)0.5(FKrF)1.5AsF₆]₂ (8), were characterized by LT single-crystal X-ray diffraction and LT Raman spectroscopy. Complexes 2, 3, 5, and 6 are the only KrF₂ coordination complexes known in which a second neutral donor, HF, is coordinated to the metal center. The series of complexes exhibits three coordination modalities for KrF₂. In addition to Hg²⁺ coordination through a single fluorine atom of KrF₂, complex 7 provides a rare example of a KrF₂ ligand that bridges two Hg²⁺ cations by coordination through both of its fluorine atoms, and complexes 7 and 8 provide unique examples of μ₃-FKrF coordination in which a single fluorine atom of KrF₂ bridges two Hg²⁺ cations. Although quantum-chemical calculations show that electrostatic contributions dominate bonding of Hg²⁺ to μ₃-coordinated KrF₂ in the model cation, [μ-F(HgF)₂(μ₃-FKrF)₂]⁺, orbital contributions are also significant.