Crystal and Molecular Structures of Trifluoroacrylonitrile, F2C=CF-CN, and Trifluorovinyl Isocyanide, F2C=CF-NC, by Low-Temperature X-ray Crystallography and ab Initio Calculations

Inorg. Chem., 39 (13), 2807 -2812, 2000. 10.1021/ic000264m S0020-1669(00)00264-0
Web Release Date: June 2, 2000

Crystal and Molecular Structures of Trifluoroacrylonitrile, F₂C=CF-CN, and Trifluorovinyl Isocyanide, F₂C=CF-NC, by Low-Temperature X-ray Crystallography and ab Initio Calculations

Jürgen Buschmann, Sven Kleinhenz, Dieter Lentz,* Peter Luger, Krishnan V. Madappat, Dagmar Preugschat, and Joseph S. Thrasher

Institut für Chemie-Anorganische und Analytische Chemie, Freie Universität Berlin, Fabeckstr. 34-36, D-14195 Berlin, Germany, Institut für Chemie-Kristallographie, Freie Universität Berlin, Takustr. 6, D-14195 Berlin, Germany, and Department of Chemistry, the University of Alabama, Tuscaloosa, Alabama 35487-0336

Received March 8, 2000

Abstract:

The structures of trifluoroacrylonitrile, F₂C=CF-CN, monoclinic, P2₁/n (no. 14), a = 8.595(4), b = 8.748(1), c = 5.421(1) Å, = 102.83(2), Z = 4, and its thermally unstable isomer trifluorovinyl isocyanide, F₂C=CF-NC, monoclinic, P2₁/n, a = 8.501(2), b = 8.828(2), c = 5.599(2) Å, = 101.11(2), Z = 4 were determined by X-ray crystal structure analysis at 113 and 128 K, respectively, from single crystals grown by partial melting and gradient cooling in small glass capillaries. Selected experimental bond lengths of F₂C=CF-CN/F₂C=CF-NC are as follows: C=C 1.326(1)/1.304(2), CN 1.158(1)/1.167(2) Å. The C-F bond lengths of the CF₂ group are significantly shorter than those of the CF(NC) and CF(CN) units, respectively. The vibrational frequencies and molecular geometries of this cyanide/isocyanide pair were also calculated by ab initio methods for comparison with the experimental results, which were found to be in general agreement.