The molecular structure of cyclopentadienyl vanadium tetracarbonyl determined by gas-phase electron diffraction

The molecular structure of cyclopentadienyl vanadium tetracarbonyl, C5H5V(CO)(4), has been determined by gas-phase electron diffraction at 95 degrees C assuming local C-4 upsilon symmetry for the V-(CO)(4) moiety and C-5 upsilon symmetry for the C5H5-V group. The relative positions of these two groups could not be determined unequivocally. Models with an eclipsed (torsion angle, tau (C-V-X-C) = 0 degrees where X is the centre of the cyclopentadienyl ring) or staggered configuration (tau = 9 degrees) fit the experimental data equally as well as a model which allows for free rotation of the C5H5 ring with respect to the V-(CO)(4) group. The C-H bonds were allowed to bend out of the plane of the ring and angle V-C-O was allowed to be non-linear. For both the staggered and the eclipsed models angle X-C-H = 171(19)degrees (C-H bent away from the metal) and angle V-C-O = 177(11)degrees (C-O bent slightly towards the ring). The remaining parameter values are almost identical for both models and for the staggered model are: r(g)(V-C-(ring)) = 2.281(13) Angstrom, r(g)(V-C-(CO)) = 1.963(7) Angstrom, r(g)(C-C) = 1.405(6) Angstrom, r(g)(C-O) = 1.135(4) Angstrom, angle(OC-V-CO) = 75.4(2.0)degrees, R = 11.4%.