Microwave Spectroscopy Measurements of the Gas-Phase Structure of Cyclopentadienyltungsten Tricarbonyl Hydride

• Published in: Organometallics 2005-06, Vol.24 (12), p.2848-2853
• Main Authors: Tanjaroon, Chakree, Karunatilaka, Chandana, Keck, Kristen S, Kukolich, Stephen G
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om049060u

High-resolution microwave spectra for 13C isotopomers of cyclopentadienyltungsten tricarbonyl hydride were measured using a pulsed-beam Fourier transform microwave spectrometer system. The new rotational constants for the 13C isotopomers are combined with the previously obtained rotational constants for normal and deuterium isotopomers to obtain the gas-phase structure of cyclopentadienyltungsten tricarbonyl hydride. The new frequencies for the five unique 13C isotopomers were measured in the 5−7 GHz range for C5H5W(CO)3H. Kraitchman analysis and least-squares structure-fitting procedures were used to determine the structural parameters. The results from the structural fit yielded the W−H bond length, r 0(W−H) = 1.79(2) Å, which agrees very well with the previously reported value, r s(W−H) = 1.79(4) Å, obtained with a much smaller data set. The present study also yielded the distance from tungsten to the C5H5 ring, r(W−Cp) = 2.03(1) Å, which corresponds to an average W−C (of Cp) bond length of 2.37(2) Å. The experimental ring radius for Cp of r(Cp) = 1.20(2) Å corresponds to an average cyclopentadienyl C−C bond length of 1.423(4) Å. Deviations of near 0.02 Å from C 5 symmetry for the W−C bond lengths for the Cp ligand and smaller deviations for the C−C bond lengths were obtained from the DFT calculations, and incorporating these deviations into the least-squares fit improved the standard deviation by a factor of 5. The average bond length from tungsten to the carbonyl carbons is r(W−CO) = 1.97(2) Å. Results obtained from the structural fit are in very close agreement with the experimental, Kraitchman analysis values. Results from new DFT calculations are given, with heavy-atom coordinates in very good agreement with experimental values, and a slightly shorter calculated W−H bond length, r e(W−H) = 1.73 Å.