Syntheses and Structures of the Homoleptic [Hg(OSOClF)6]2+ and [Hg(N≡CR)5]2+ (R = Me, Et) Salts of [Sb(OTeF5)6]−; Examples of Cl(−1)---F σ-Hole (Halogen) Bonding in [Hg(OSOClF)6][Sb(OTeF5)6]2

Abstract

The strong oxidant source of the weakly coordinating [Sb(OTeF5)6]− anion, [XeOTeF5][Sb(OTeF5)6], was used to synthesize the room-temperature stable salt, [Hg(OSOClF)6][Sb(OTeF5)6]2 (1), in the weak Lewis base solvent, SO2ClF, by displacement of Hg(OTeF5)2 with [XeOTeF5][Sb(OTeF5)6] to yield 1 and Xe(OTeF5)2 and by the redox reaction of HgCl2 with [XeOTeF5][Sb(OTeF5)6] to yield 1, ClOTeF5, and Xe. The low-temperature (LT) single-crystal X-ray diffraction (SCXRD) structure of 1 consists of the homoleptic [Hg(OSOClF)6]2+ dication (S6) in which the SO2ClF ligands form bifurcated F---Cl---F σ-hole (halogen) bonds with the F5TeO-groups of [Sb(OTeF5)6]−. Reactions of [Hg(OSOClF)6]2+ with RC≡N (R = Me, Et) in SO2ClF solvent resulted in SO2ClF ligand displacement and isolation of [Hg(N≡CMe)5][Sb(OTeF5)6]2·SO2ClF (2) and [Hg(N≡CEt)5][Sb(OTeF5)6]2·2SO2ClF (3), which were characterized by LT SCXRD. The Hg---N-bonded, trigonal bipyramidal [Hg(N≡CR)5]2+ dications and [Sb(OTeF5)6]− anions are well-isolated. Compounds 1–3 were also characterized by LT Raman spectroscopy and quantum-chemical calculations, which were used to aid in vibrational assignments and to assess bonding in the gas-phase dications. Thermochemical calculations show SO2ClF is significantly less strongly bound to Hg2+ than RC≡N and is readily displaced by RC≡N in SO2ClF solvent to give [Hg(N≡CR)5]2+.