Electron-Diffraction Investigation of the Molecular Structure of Trifluoramine Oxide, F3NO

The molecular structure of trifluoramine oxide has been investigated by gaseous electron diffraction at a nozzle temperature of 20°C. The results verify the expected C3υ symmetry for the molecule. The N–F bond is slightly longer than the sum of the single-bond radii corrected for electronegativity difference, but the N–O bond is very much shorter and must be regarded as essentially a double bond. The bond angles are not in themselves unusual. However, the positions of the four ligands correspond with remarkable accuracy to the corners of a regular tetrahedron, a fact which strongly emphasizes the importance of nonbonded interactions. The five covalent bonds formed by the nitrogen atom may be understood in terms of a σ system of four bonds comprising 2s–2p hybrids and a π bond obtained by utilizing an empty 3pπ or 3dπ nitrogen orbital with a filled 3pπ oxygen orbital. The electron-diffraction analysis led to the following values for the principal parameters: r(N=O) = 1.158 Å (0.0040), r(N–F) = 1.431 Å (0.0030), r(O···F) = 2.214 Å (0.0130), r(F···F) = 2.206 Å (0.0158), r(X···X) (the average of the nonbond distances) = 2.210 Å (0.0024), l(N=O) = 0.0289 Å (0.0044), l(N–F) = 0.0507 Å (0.0032), l(O···F) = 0.0584 Å (0.0089), l(F···F) = 0.0551 Å (0.0077), ∠ONF = 117.1° (0.89), and ∠FNF = 100.8° (1.12). The distances and amplitudes are ra and la values; the parenthesized quantities are 2σ. When the rotational constant B0 from microwave spectroscopy is taken as a constraint on the diffraction results, the following set of distance and angle values, which differ only very slightly from those above, is obtained: r(N=O) = 1.159 Å (+ 0.0020, − 0.0025), r(N–F) = 1.432 Å (+ 0.0020, − 0.0061), ∠ONF = 117.4° (+ 0.60, − 1.16), and ∠FNF = 100.5 Å (+ 1.44, − 0.75).