Syntheses and Vibrational and13C MAS-NMR Spectra of Bis(carbonyl)mercury(II) Undecafluorodiantimonate(V) ([Hg(CO)2][Sb2F11]2) and of Bis(carbonyl)dimercury(I) Undecafluorodiantimonate ([Hg2(CO)2][Sb2F11]2) and the Molecular Structure of [Hg(CO)2][Sb2F11]2

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Abstract
The synthesis of bis(carbonyl)mercury(II) undecafluorodiantimonate(V), [Hg(CO)2][Sb2F11]2, and that of the corresponding mercury(I) salt [Hg2(CO)2][Sb2F11]2 are accomplished by the solvolyses of Hg(SO3F)2 or of Hg2F2, treated with fluorosulfuric acid, HSO3F, in liquid antimony(V) fluoride at 80 or 60 °C, respectively, in an atmosphere of CO (500−800 mbar). The resulting white solids are the first examples of metal carbonyl derivatives formed by a post-transition element. Both salts are characterized by FT-IR, FT-Raman, and 13C-MAS-NMR spectroscopy. For [Hg(CO)2][Sb2F11], unprecedentedly high CO stretching frequencies (ν̄av = 2279.5 cm-1) and stretching force constant (fr = 21.0 ± 0.1) × 102 Nm-1) are obtained. Equally unprecedented is the 1J(13C−199Hg) value of 5219 ± 5 Hz observed in the 13C MAS-NMR spectrum of the 13C labeled isotopomers at δ = 168.8 ± 0.1 ppm. The corresponding values (ν̄av = 2247 cm-1, fr = (20.4 ± 0.1) × 102 Nm-1, 1J(13C−199Hg) = 3350 ± 50 Hz and 2J(13C−199Hg) 850 ± 50 Hz) are found for [Hg2(CO)2][Sb2F11]2, which has lower thermal stability (decomposition point in a sealed tube is 140 °C vs 160 °C for the Hg(II) compound) and a decomposition pressure of 8 Torr at 20 °C. The mercury(I) salt is sensitive toward oxidation to [Hg(CO)2][Sb2F11]2 during synthesis. Both linear cations (point group D∞h) are excellent examples of nonclassical (σ-only) metal−CO bonding. Crystal data for [Hg(CO)2][Sb2F11]2: monoclinic, space group P21/n; Z = 2; a = 7.607(2) Å; b = 14.001(3) Å; c = 9.730(2) Å; β = 111.05(2)°; V = 967.1 Å3; T = 195 K; RF = 0.035 for 1983 data (Io ≥ 2.5σ(Io)) and 143 variables. The Hg atom lies on a crystallographic inversion center. The Hg−C−O angle is 177.7(7)°. The length of the mercury−carbon bond is 2.083(10) Å and of the C−O bond 1.104(12) Å respectively. The structure is stabilized in the solid state by a number of significant secondary interionic Hg- - -F and C- - -F contacts.

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