Interest in the activation of carbon ± fluorine bonds by transition metal centers has been increasing dramatically over the last decade. [1] Recent discoveries include the stochiometric and catalytic 4] derivatization of aromatic compounds localized in the p orbital perpendicular to the ring plane, while in 1 the highest spin density is in the ring plane.
Photolysis of 4-iodo-2,3,5,6-tetrafluoroazidobenzene (7) offers an access to the until now unknown C 6 F 4 N potential energy surface and to the unusual high-spin nitrene radical 1. The influence of different topologies and substituents on the spin state of nitrene radicals will be investigated in future studies.
Experimental Section
Matrix experiments were carried out according to standard techniques using a Sumitomo Heavy Industries RDK-408D closed-cycle cryostat. The lowest temperature available with this system is 2.7 K. Matrices were produced by codeposition of a large excess of neon or argon (Messer-Griesheim, 99.9999 %) and the substance to be isolated on top of a cold CsI window. During deposition of argon matrices the temperature of the window was maintained at 30 K. Argon matrices for ESR spectroscopy were deposited at 13 K on a 2 mm OFHC-copper rod, cooled by an APD-HC2 closed-cycle cryostat. IR spectra were recorded with a Bruker Equinox 55 FTIR spectrometer with a resolution of 0.5 cm À1 in the range of 400 ± 4000 cm À1 . ESR spectra were recorded with a Bruker Elexsys E500 spectrometer. Irradiations were carried out with a Gr‰ntzel low-pressure mercury lamp (254 nm) and an Osram HBO-500-W/2 high-pressure mercury arc lamp in an Oriel housing with quartz optics, a dichroic mirror, and a Schott cutoff filter (320 nm). DFT calculations were performed with the Gaussian 98 suite of programs. 4-Iodo-2,3,5,6-tetrafluoroaniline: Yellow HgO (12.8 g, 59.1 mmol) was added to a solution of 2,3,5,6-tetrafluoroaniline (12.8 g, 77.6 mmol) in ethanol (200 mL). The solution was vigorously stirred and iodine (19.8 g, 78.0 mmol) added. The mixture was stirred overnight and filtered over celite. After addition of Na 2 SO 3 (1 g) the solution was concentrated to a residual volume of 50 mL using a rotary evaporator. Water (200 mL) was added and the precipitate was filtered off. Recrystallization from 25 % ethanol in water and subsequent drying in vacuo yielded 4-iodo-2,3,5,6tetrafluoroaniline (16.2 g, 55.7 mmol, 72 %) as dark crystals. MS: m/z(%): 291 (M , 100), 164 (50), 144 (25), 137 (60), 127 (30), 117 (25), 69 (20). 4-Iodo-2,3,5,6-tetrafluoroazidobenzene (7): 4-Iodo-2,3,5,6-tetrafluoroaniline (3.0 g, 10.3 mmol) was dissolved in trifluoroacetic acid (30 mL) and cooled to 0 8C. A solution of sodium nitrite (0.81 g, 11.7 mmol) in water (15 mL) was slowly added while stirring and cooling with an ice bath. The solution was stirred for further 15 min at 0 8C. A solution of sodium azide (0.75 g, 11.5 mmol) in water (15 mL) was added to the stirred solution, which was subsequently stirred for 1 h at room temperature. After addition of ether (100 mL) the organic phase was washed with water and dilute aqueous NaOH, dried (Na 2 SO 4 ), and evaporated. Chromatography (silica/ pentane) yielded 7 (2.18 g, 67 %) as a colorless oil. MS: m/z (%): 317 (M , 10), 289 (30), 162 (100), 127 (30), 117 (20), 112 (10), 98 (25), 69 (25). 13 C NMR (CDCl 3 , 50 MHz): d 66.3 (t, J 28.0 Hz), 120.5 (tt, J 2.9 Hz, 12.3 Hz), 140.0 (dm, 256.4 Hz), 147.2 ppm (dm, 248.1 Hz). IR (Ar, 3 K): n Ä (%): 2229.9 (5)