A Homoleptic KrF2 Complex, [Hg(KrF2)8][AsF6]2⋅2 HF

The reaction of Hg(AsF₆ )₂ with a large molar excess of KrF₂ in anhydrous HF has afforded the first homoleptic KrF₂ coordination complex of a metal cation, [Hg(KrF₂ )₈ ][AsF₆ ]₂ ⋅2 HF. The [Hg(KrF₂ )₈ ]²⁺ dication is well-isolated in the low-temperature crystal structure of its HF-solvated [AsF₆ ]^- salt, and consists of eight KrF₂ molecules that are terminally coordinated to Hg²⁺ by means of Hg-F(KrF) bonds to form a slightly distorted, square-antiprismatic coordination sphere around mercury. The Raman spectrum of [Hg(KrF₂ )₈ ]²⁺ was assigned with the aid of calculated gas-phase vibrational frequencies. Computational studies indicate that both electrostatic and orbital interactions are important for metal-ligand bonding and provide insight into the geometry of the [Hg(KrF₂ )₈ ]²⁺ cation and the nature of noble-gas difluoride ligand bonding.