Experimental and Theoretical Studies of Bis(perfluorovinyl)mercury, Hg(CF=CF2)2: Synthesis, Characterization, and Structure in the Gaseous and Crystalline Phases

• Published in: Inorganic chemistry Vol. 38; no. 25; pp. 5894 - 5900
• Main Authors: Banger, Kulbinder K, Brisdon, Alan K, Brain, Paul T, Parsons, Simon, Rankin, David W. H, Robertson, Heather E, Smart, Bruce A, Bühl, Michael
• Format: Journal Article
• Language: English
• Published: American Chemical Society 13-12-1999
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic991018h

The low-temperature reaction between 2 equiv of (perfluorovinyl)lithium, derived from CF3CH2F and butyllithium, and mercury(II) chloride results in high yields of Hg(CFCF2)2. Complete characterization of the air- and moisture-stable liquid product is afforded by multinuclear (13C, 19F, 199Hg) NMR studies. Crystals of the compound [triclinic, P1̄; a = 4.956(4), b = 5.733(4), c = 6.394(4) Å; α = 104.57(5), β = 109.32(6), γ = 107.16(6)°; Z = 1] were obtained by slow cooling; an X-ray structural determination at 110 K represents the first such report for a (perfluorovinyl)metal complex. The mercury is coordinated linearly [r(Hg−C) = 1.998(5) Å], and π-stacking of the perfluorovinyl groups is observed. There is considerable variation in the C−F bond distances [1.286(6), 1.312(6), 1.362(6) Å] within each perfluorovinyl group. Structural data for the vapor-phase species were obtained by analysis of the electron-diffraction pattern. There appears to be free rotation of the perfluorovinyl groups around the Hg−C bonds, a significantly longer mercury−carbon distance [2.054(3) Å], and a similar, but smaller, variation in the C−F bond lengths. Theoretical optimization of the geometry at the MP2/DZP level predicts a shallow potential-energy minimum when the two perfluorovinyl groups are nearly perpendicular [Φ(CC···CC) = 98.2°] to one another. Analysis of the bonding in the molecule suggests that no significant d(Hg) → π*(CC) interaction is present.