PREPARATION, CHARACTERIZATION, AND CRYSTAL-STRUCTURE OF THE ADDUCTS WF6.F-PY AND WOF4.F-PY (F-PY = 2-FLUOROPYRIDINE)

The adducts of tungsten(VI) WF6.F-py and WOF4.F-py have been prepared from the reaction of WF6 or WOF4 with 2-fluoropyridine (F-py) in dichloromethane. The two adducts were characterized by X-ray powder data and vibrational spectroscopy. The adduct of WOF4 is only slightly volatile at room temperature, whereas that of WF6 has a dissociation pressure of 26.5 mmHg at 21-degrees-C. Solutions of these adducts in CD2Cl2 were studied by F-19, H-1, and C-13 NMR spectroscopy. In WOF4.F-py, the fluorine atoms bonded to the tungsten atom are magnetically equivalent, and their coupling with the fluorine atom of F-py was observed at 25-degrees-C (delta(F(W)) = 66.8 ppm/CFCl3, JFF = 14.3 Hz). The labile character of F-py in WF6.F-py did not permit such observations. The crystal structures of WF6.F-py and WOF4.F-py have been determined by X-ray diffraction methods. In WF6.F-py, the tungsten atom is surrounded by a capped trigonal prism of ligands with the nitrogen atom of the organic ligand occupying the capping site. In WOF4.F-py, the tungsten atom is surrounded by a distorted octahedron of ligands with the nitrogen atom of the organic ligand trans to the oxygen atom and the equatorial plane made up of four fluorine atoms located at the corners of a square. The space groups, unit cell parameters, and R factors are as follows. WF6-F-py: monoclinic, P2(1)/c (No. 14), a = 7.008(9) angstrom, b = 15.373(3) angstrom, c = 8.023(3) angstrom, beta = 101.62(4)-degrees, V = 846(1) angstrom3, Z = 4, R = 0.028. WOF4.F-py: monoclinic, P2(1)/c (No. 14), a = 8.742(3) angstrom, b = 9.349(8) angstrom, c = 10.737(4) angstrom, beta = 106.85(3)-degrees, V = 840(1) angstrom3, Z = 4, R = 0.033.