Crystal and Molecular Structures of Trifluoroacrylonitrile, F₂CCF−CN, and Trifluorovinyl Isocyanide, F₂CCF−NC, by Low-Temperature X-ray Crystallography and ab Initio Calculations

Abstract

The structures of trifluoroacrylonitrile, F2C=CF-CN, monoclinic, P2(1/n) (no. 14), a = 8.595(4), b = 8.748(1), c = 5.421(1) A, beta = 102.83(2) degrees, Z = 4, and its thermally unstable isomer trifluorovinyl isocyanide, F2C=CF-NC, monoclinic, P2(1/n), a = 8.501(2), b = 8.828(2), c = 5.599(2) A, beta = 101.11(2) degrees, 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), C...N 1.158(1)/1.167(2) A. 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.

Crystal and Molecular Structures and Experimentally Determined Charge Densities of Fluorinated Ethenes

“…Solid‐state structural information on these compounds based on conventional X‐ray crystal structure determination is very limited. Crystallographic data for small, highly fluorinated alkenes are available only for potassium hydrogen difluorofumarate,19 potassium hydrogen difluoromaleate,19 1,2‐difluorodinitroethene,20 perfluorocyclopropene,21 trifluorovinyl isocyanide,22 trifluorovinyl cyanide,22 hexafluoropropene,23 1,1‐difluoroallene,24 tetrafluoroallene,24 1,1,4,4‐tetrafluorobutadiene,25 tetrafluorobutatriene,25 trifluorobutadiene,26 and octafluoro‐1,2‐dimethylenecyclobutane 27…”

Syntheses of highly unsaturated isocyanidesvia organometallic pathways

“…The product readily polymerizes on further warming. 19 F NMR (376 MHz, CDCl 3 , CFCl 3 intern): (E)-Isomer: d = -138.1 (d, 3 J FF = 117 Hz, 1F, (E)-CF CF-CH CH 2 ), -156.1 (dd, 3 J HF = 25 Hz, 3 J FF = 117 Hz, 1F, (E)-CF CF-CH CH 2 ); (Z)-Isomer: d = -121.2 (s, 1F, (Z)-CF CF-CH CH 2 ), -148.2 (d, 3 J HF = 25 Hz, 1F, (Z)-CF CF-CH CH 2 ); 1 H NMR (400 MHz, CDCl 3 ): (E)-Isomer: d = 6.53-6.38 (dddd, 4 J HF = 3.6 Hz, 3 J HH = 11.5 Hz, 3 J HH = 17.4 Hz, 3 J HF = 26.1 Hz, 1 H, CH= CH 2 ), 5.73 (dd, 2 J HH = 1.8 Hz, 3 J HH = 17.4 Hz, 1 H, CH CH 2 ), 5.47 (ddd, 2 J HH = 1.8 Hz, 4 J HF = 3.6 Hz, 3 J HH = 11.5 Hz, 1 H, CH CH 2 ); (Z)-Isomer: d = 6.36-6.22 (dddd, 4 J HF = 1.8 Hz, 3 J HH = 11.4 Hz, 3 J HH = 17.2 Hz, 3 J HF = 24.6 Hz, 1 H, CH CH 2 ), 5.83 (dd, 2 J HH = 1.8 Hz, 3 J HH = 17.2 Hz, 1 H, CH CH 2 ), 5.58 (dd, 2 J HH = 1.8 Hz, 3 J HH = 11.4 Hz, 1 H, CH CH 2 ); 13…”

“…48-49 • C. 19 F-NMR (CDCl 3 , CFCl 3 intern, 376.0 MHz): (Z)-Isomer: d = -108.5 (s, 1 F, (Z)-CF CF-C), -130.4 (dt, 1 F, 4 J FF = 8.5 Hz, 6 J FF = 2.5 Hz, (Z)-CF CF-C), -133.5 (m, 2 F, 4 J FF = 8.5 Hz, 4 J FF = 3.1 Hz, Ar-F ortho ), -144.7 (dt, 1 F, 3 J FF = 21.0 Hz, 6 J FF = 2.5 Hz, Ar-F para ), -157.6 (m, 2 F, 3 J FF = 21.0 Hz, 3 J FF = 8.7 Hz, Ar-F meta ); (E)-Isomer: d = -124.6 (dt, 3 J FF = 129.7 Hz, 5 J FF = 14.0 Hz, 1 F, (E)-CF CF-C), -133.9 (m, 5 J FF = 14.0 Hz, 4 J FF = 8.3 Hz, 2 F, Ar-F ortho ), -141.5 (ddt, 3 J FF = 129.7 Hz, 4 J FF = 8.3 Hz, 5 J FF = 2.5 Hz, 1 F, (E)-CF CF-C), -145.4 (dt, 3 J FF = 20.8 Hz, 1 F, Ar-F para ), -158.2 (m, 3 J FF = 20.8 Hz, 3 J FF = 9.5 Hz, 5 J FF = 2.5 Hz, 2 F, Ar-F meta ). 13 52 Cr, 15.5%), 419 (M + -CO, 52 Cr, 2.0%), 391 (M + -2 CO, 52 Cr, 6.3%), 363 (M + -3 CO, 52 Cr, 9.6%), 335 (M + -4 CO, 52 Cr, 21.1%), 308 (M + -5 CO, 53 Cr, 20.6%), 307 (M + -5 CO, 52 3i was prepared analogously to 3h. The product was purified by TLC on silica using pentane as eluent.…”

“…105 • C (dec). 53 Cr], 608 (63) [M + , 52 Cr], 496 (13) [M + -4 CO], 469 (19) [M + -5 CO, 53 Cr], 468 (46) [M + -5 CO, 52 Cr], 412 (21) [M + -7 CO, 52 Cr], 385 (27) [M + -8 CO, 53 Cr], 384 (100) [M + -8 CO, 52 Cr], 357 (47), 356 (99.6) [M + -9 CO, 52 Cr], 329 (30) [M + -10 CO, 53 Cr], 328 (94.5) [M + -10 CO, 52 Cr], 238 (43) [M + -(CO) 5 CrCNCFCF, 52 Cr], 149 (15), 148 (30), 142 (26), 141 (23), 52 ( 27 To a solution of 700 mg (1.1 mmol) of (CO) 5 Cr(CNCFCFC 2 C 2 CF-CFNC)Cr(CO) 5 7 in 10 mL of a pentane/dichloromethane mixture (1 : 1) 980 mg (2.9 mmol) of octacarbonyldicobalt was added under argon atmosphere. During stirring of the solution the reaction was observed by TLC.…”

“…The first fluorinated ethenyl isoycanide, F 2 C CF-NC, was synthesized in 1992 12 and its structure was elucidated by low temperature single-crystal X-ray crystallography. 13 on chloroethenyl isocyanides synthesized and stabilized at a pentacarbonyl chromium fragment in 1989. 14 In 1991 we reported on the preparation, microwave spectroscopic study, and structure of the first alkynyl isocyanide, ethynyl isocyanide, H-C C-NC, by vacuum pyrolysis of a suitable organometallic precursor molecule, (CO) 5 Cr(CN-CCl CCl(H).…”