The microwave spectrum and structure of the argon trifluoroacetonitrile complex

The rotational spectrum of argon trifluoroacetonitrile complex has been studied by pulsed-nozzle, Fourier transform microwave spectroscopy. Both a-type and b-type transitions have been observed. The rotational constants are A = 3053.0903(2) MHz, B = 1039.9570(2) MHz, and C = 895.5788(1) MHz. The ¹⁴N nuclear quadrupole hyperfine components of the rotational transitions have been resolved, the ¹⁴N nuclear quadrupole coupling constants are χ_aa = 1.746(1) MHz, and χ_bb − χ_cc = −6.426(2) MHz. The complex is T-shaped, with the argon atom located 3.73 Å from the center of mass of the trifluoroacetonitrile molecule.     

Reactions of quadricyclane with fluorinated nitrogen-containing compounds. Synthesis of 3-aza-4-perfluoroalkyl-tricyclo[4.2.1.0]non-3,7-dienes

The cycloaddition reactions of quadricyclane (1) and polyfluorinated imines and nitriles were studied. Both (CF₃)₂CNH and (CF₃)₂CN(2-FC₆H₄) were found to have low reactivity towards 1, giving the corresponding [2 + 2 + 2] cycloadducts in a low yield. C₂F₅NCFCF₃ however, reacts with 1 rapidly, giving a mixture of two isomeric cycloadducts in a high yield. Perfluoroalkyl nitriles R_fCN (R_f = CF₃, C₂F₅, n-C₃F₇) were found to have surprisingly high reactivity to 1 producing exo-3-aza-4-(fluoroalkyl)-tricyclo[4.2.1.0^2,5]non-3,7-dienes in 56-81% yields at elevated temperature. Exo-3-aza-4-(perfluoroalkyl)-tricyclo[4.2.1.0^2,5]non-3,7-dienes rapidly react with CF₃Si(CH₃)₃ in the presence of CsF catalyst. The reaction results in addition of CF₃Si(CH₃)₃ across the CN bond of the azadienes with selective formation of only one stereoisomer of exo-3-aza-3-(trimethylsilyl)-4,4-bis(perfluoroalkyl)-tricyclo[4.2.1.0^2,5]non-7-enes. Silyl group in this compounds can be removed either by the action of tetrabutylammonium fluoride hydrate, leading to the formation of the corresponding amine after hydrolysis, or by reaction with HCl resulting in the formation of the corresponding amine hydrochloride.