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

Abstract

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 C 3υ 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 3p π or 3d π nitrogen orbital with a filled 3p π oxygen orbital. The electron‐diffraction analysis led to the following values for the principal parameters: r( N = O ) = 1.158 Å (0.004 0 ), r( N – F ) = 1.431 Å (0.003 0 ), r( O ··· F ) = 2.214 Å (0.013 0 ), r( F ··· F ) = 2.206 Å (0.015 8 ), r( X ··· X ) ( the average of the nonbond distances ) = 2.210 Å (0.002 4 ), l( N = O ) = 0.028 9 Å (0.004 4 ), l( N – F ) = 0.050 7 Å (0.003 2 ), l( O ··· F ) = 0.058 4 Å (0.008 9 ), l( F ··· F ) = 0.055 1 Å (0.007 7 ), ∠ ONF = 117.1° (0.8 9 ) , and ∠ FNF = 100.8° (1.1 2 ) . The distances and amplitudes are r a and l a values; the parenthesized quantities are 2σ . When the rotational constant B 0 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 (+ 0.002 0 , − 0.002 5 ), r( N – F ) = 1.432 Å (+ 0.002 0 , − 0.006 1 ), ∠ ONF = 117.4° (+ 0.6 0 , − 1.1 6 ) , and ∠ FNF = 100.5 Å (+ 1.4 4 , − 0.7 5 ) .