Rotational spectrum of vinyl fluoride center dot center dot center dot ClF: Are the pi-bonding or nonbonding electrons the most nucleophilic region of vinyl fluoride?
Jb. Davey et al., Rotational spectrum of vinyl fluoride center dot center dot center dot ClF: Are the pi-bonding or nonbonding electrons the most nucleophilic region of vinyl fluoride?, PCCP PHYS C, 1(10), 1999, pp. 2415-2420
The ground-state rotational spectra of C2H3F ...(ClF)-Cl-35 and C2H3F ...(C
lF)-Cl-37 have been observed with a pulsed-nozzle, Fourier-transform microw
ave spectrometer. Rotational constants (A(0), B-0, C-0), centrifugal distor
tion constants (Delta(J), Delta(JK), delta(J), delta(K)) and the Cl nuclear
quadrupole coupling tensor chi(alpha beta) (alpha, beta = a, b, c) Were de
termined in each case. A detailed interpretation of the chi(alpha beta) ten
sor leads to the conclusion that the complex is nearly planar and that the
interaction between the vinyl fluoride and CIF subunits is weak. The direct
ion cosines Phi(alpha z) (alpha = a, b or c) associated with the CIF z axis
and the principal inertial axes were determined together with the principa
l components chi(zz), chi(xx), chi(gamma gamma) Of the Cl nuclear quadrupol
e coupling tensor. The geometry of the complex was obtained by fitting the
rotational constants of the two isotopomers under the constraint that the r
esulting geometry must reproduce the Phi(alpha z). The CIF molecule was fou
nd to form a nearly linear 'chlorine' bond F ... Cl-F (deviation from colli
nearity theta = 0.6 degrees) to the F atom of vinyl fluoride, with r(F ...
Cl) = 2.719(5) Angstrom and the angle C(1)F ... Cl = 125.7(3)degrees. A com
parison with the geometry of vinyl fluoride ... HCl, determined in the same
way, revealed the angular geometries of the Cl and HCl complexes of vinyl
fluoride to be isomorphous, except for a significant deviation (theta = 18.
3 degrees) of the hydrogen bond in C2H3F ... HCl from collinearity.