Journal of the Chemical Society, Faraday Transactions
Journal of the Chemical Society, Faraday Transactions; was published from 1990 - 1998. In 1999 it merged with a number of European chemical society physical Chemistry journals to become Physical Chemistry Chemical Physics.
Paper
J. Chem. Soc., Faraday Trans., 1997, 93, 2361 - 2365, DOI: 10.1039/a701323j
Identification and geometry of the pre-reactive complex buta-1,3-diene···ClF by rotational spectroscopy
S. A. Cooke, J. H. Holloway and A. C. Legon
The rotational spectra of the two isotopomers C4H6···35ClF and C4H6···37ClF of a complex formed between buta-1,3-diene and chlorine monofluoride were observed by using a fast-mixing nozzle in a Balle–Flygare Fourier-transform microwave spectrometer. Rotational constants, quartic centrifugal distortion constants and Cl nuclear–quadrupole and spin–rotation coupling constants were determined in each case. Diagonalisation of the complete 35Cl nuclear quadrupole coupling tensor (
aa, bb,
cc, ab,
ac and bc) led to
the principal axis values <ii>
(i=x, y and z). A detailed
interpretation of the observed spectroscopic constants for both
isotopomers led to the conclusion that the Cl end of the ClF molecule
interacts with the C3
C4 
bond of
buta-1,3-diene to give a complex in which the ClF molecule is
perpendicular to the plane of buta-1,3-diene. The distance
r(*···Cl) of the Cl atom from the
centre (*) of the C3C4 bond is
2.736(4) Å, the angle
C3–*–Cl=95.0(2)° and the system
*···Cl–F is nearly collinear
(
=177.4°). A comparison of the properties of the prototype
b.a
complexes ethene···ClF,
allene···ClF and
buta-1,3-diene···ClF is presented. Several
similarities are noted but the weaker binding in
buta-1,3-diene···ClF
(k=6.2 N m-1) is consistent with
a weakening of the formal bonds C1C2
and C3C4 by conjugation in
buta-1,3-diene.
