Microwave rotational spectra for six isotopomers of H2Os(CO)4 were measured in the 4-12 GHz range using a Flygare-Balle-type spectrometer. The 18 rotational constants from these isotopomers were used to determine eight structural parameters describing the gas-phase structure of this complex. This near-octahedral complex has C2v symmetry and the dipole moment lies along the c-principal axis for the normal isotopomer. The distance between H atoms, obtained directly from experimental structural parameters, is rHH = 2.40(2) Å. This rather long H-H distance indicates that this is clearly a "dihydride" rather than a "dihydrogen" complex. The Os-H bond lengths are rOsH = 1.72(1) Å. The osmium-carbonyl carbon bond lengths for axial and equatorial carbonyl groups are rOsC1 = 1.96(1) Å and rOsC3 = 1.97(2) Å. Results for other structural parameters obtained using least-squares fitting and the structural parameters obtained using the Kraitchman method are presented and discussed. No evidence for internal motion was observed for this complex.
ASJC Scopus subject areas
- Colloid and Surface Chemistry