SYNTHESES AND VIBRATIONAL AND C-13 MAS-NMR SPECTRA OF BIS(CARBONYL)MERCURY(II) UNDECAFLUORODIANTIMONATE(V) ([HG(CO)(2)][SB2F11](2)) AND OF BIS(CARBONYL) DIMERCURY(I) UNDECAFLUORODIANTIMONATE ([HG-2(CO)(2)][SB2F11](2)) AND THE MOLECULAR-STRUCTURE OF [HG(CO)(2)][SB2F11](2)

The synthesis of bis(carbonyl)mercury(II) undecafluorodiantimonate(V), [Hg(CO)(2)][Sb2F11](2), and that of the corresponding mercury(I) salt [Hg-2(CO)(2)][Sb2F11](2) are accomplished by the solvolyses of Hg(SO3 F)(2) or of Hg2F2, treated with fluorosulfuric acid, HSO3F, in liquid antimony(V) fluoride at 80 or 60 degrees C, respectively, in an atmosp here of CO (500-800 mbar). The resulting white solids are the first ex amples of metal carbonyl derivatives formed by a post-transition eleme nt. Both salts are characterized by FT-IR, FT-Raman, and C-13-MAS-NMR spectroscopy. For [Hg(CO)(2)][Sb2F11], unprecedentedly high CO stretch ing frequencies (<(nu)over bar>(av) = 2279.5 cm(-1)) and stretching fo rce constant (f(r) = 21.0 +/- 0.1) x 10(2) Nm(-1)) are obtained. Equal ly unprecedented is the (1)J(C-13-Hg-199) value of 5219 +/- 5 Hz obser ved in the C-13 MAS-NMR spectrum of the C-13 labeled isotopomers at de lta = 168.8 +/- 0.1 ppm. The corresponding values (<(nu)over bar>(av) = 2247 cm(-1), f(r) = (20.4 +/- 0.1) x 10(2) Nm(-1), (1)J(C-13-Hg-199) = 3350 +/- 50 Hz and (2)J(C-13-Hg-199) 850 +/- 50 Hz) are found for [ Hg-2(CO)(2)][Sb2F11](2), which has lower thermal stability (decomposit ion point in a sealed tube is 140 degrees C vs 160 degrees C for the H g(II) compound) and a decomposition pressure of 8 Torr at 20 degrees C . The mercury(I) salt is sensitive toward oxidation to [Hg(CO)(2)][Sb2 F11](2) during synthesis. Both linear cations (point group D infinity h) are excellent examples of nonclassical (sigma-only) metal-CO bondin g. Crystal data for [Hg(CO)(2)][Sb2F11](2): monoclinic, space group P2 (1)/n; Z = 2; a = 7.607(2) Angstrom; b = 14.001(3) Angstrom; c = 9.730 (2) Angstrom; beta = 111.05(2)degrees; V = 957.1 Angstrom(3); T = 195 K; R(F) = 0.035 for 1983 data (I-0 greater than or equal to 2.5 sigma( I-0)) and 143 variables. The Hg atom lies on a crystallographic invers ion center. The Hg-C-O angle is 177.7(7)degrees. The length of the mer cury-carbon bond is 2.083(10) Angstrom and of the C-O bond 1.104(12) A ngstrom respectively. The structure is stabilized in the solid state b y a number of significant secondary interionic Hg---F and C---F contac ts.