The methyl/trifluoromethyl substitution effect in boranes. A gas-phase electron diffraction and vibrational study of bis(dimethylamino)-(trifluoromethyl)borane and dimethylaminobis(trifluoromethyl)borane
- 1 January 1987
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 8,p. 1839-1845
- https://doi.org/10.1039/dt9870001839
Abstract
The gas-phase structures of CF3B(NMe2)2 and (CF3)2BNMe2 have been determined by electron diffraction. The vibrational spectra have been recorded by i.r. (gas) and Raman (liquid) and valence force fields have been derived. The following skeletal geometric parameters (ra values with 3σ uncertainties) have been obtained: for CF3B(NMe2)2, B–C = 164.8(8), B–N = 142.2(9), C–N = 145.3(4), C–F = 135.2(3) pm, NBN = 125.5(31), FCF = 105.3(4), and τBN= 24(3)°(τBN is the torsional angle around the B–N bond from the planar configuration); for (CF3)2BNMe2, B–C = 162.3(4), B–N = 142.5(18), C–N = 145.3(7), C–F = 134.3(2) pm, CBC = 122.2(15), FCF = 106.5(2)°. The B–C bonds in the trifluoromethyl compounds are considerably longer than in the analogous methyl derivatives and this CH3/CF3 substitution effect is confirmed by the force constants.Keywords
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