Rotational and hyperfine spectra for a sandwich titanium complex, C5H5TiC7H7

Microwave spectroscopy measurements and density functional theory calculations are reported for the cyclopentadienyl cycloheptatrienyl titanium complex, C5H5TiC7H7. Rotational transition frequencies for this symmetric-top complex were measured in the 4-13 GHz range using a Flygare-Balle-type pulsed beam spectrometer. The spectroscopic constants obtained for the normal C5H548TiC7H7 isotopomer are B = 771.78907(38), DJ = 0.0000295(41), and DJK = 0.001584(73) MHz. The quadrupole hyperfine splittings for C5H547TiC7H7 were clearly observed and the measured constants are B = 771.79024(32) MHz, DJ = 0.0000395(33), DJK = 0.001646(24), and eQqaa = 8.193(40) MHz. Analysis of the experimental and theoretical rotational constants indicates that the η7-C7H7Ti and η5-C5H5Ti bond lengths in the gas phase are about 0.02 Å longer than those reported for the solid-state X-ray structure. The calculated Ti-C bond lengths are shorter for the C7H7 ligand (r(Ti-C) = 2.21 Å) than for the C5H5 ligand (r(Ti-C) = 2.34 Å), and the C7H7 H atoms are displaced 0.15 Å out of the C7 plane, toward the Ti atom.