Abstract
Gaseous di-t-butylamine, NHBu t 2, has been studied by electron diffraction at a nozzle temperature of ca. 293 K. The diffraction data reveal that this amine is exceedingly hindered. Repulsive steric interactions between the Bu t groups are mainly relieved by an opening of the CNC valence angle to 135(3)°. Evidence of steric strain may also be found in the non-zero tilts (2–3°) of the Bu t groups, defining the angle of rotation of these groups about axes through the N-bonded carbon atoms orthogonal to the NC 2 plane. The NC and CC bonds, 1.467(13) and 1.561(6) Å, respectively, are on the other hand relatively unstrained. Other principal geometrical parameters are unexceptional: CH = 1.103(10) Å, ∠NCC = 111.3(1.5)° (mean value) and ∠CCH = 106(2)°. The position of the N-bonded hydrogen atom relative to the NC 2 plane could not be determined. The torsional positions of the Bu t groups, with respect to the NC bonds, could not be derived from least-squares refinements. A large number of models with Bu t groups in various fixed positions were considered; the best fit between the observed and theoretical intensity data was obtained with one Bu t group being twisted 19° away from the position typified by one CC bond of this group being anti to the remote NC bond, and the other Bu t group similarly twisted by 30°. When viewed along the NC bonds, the Bu t groups are twisted in the same direction. Viewed along the C(N)C axis, these groups come close to being staggered with respect to each other. The values of the above bond distances are those of r a parameters. Parenthesized values denote error limits, being least-squares standard deviations multiplied by a factor of three.
Published Version
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