Microwave measurements of the gas-phase molecular structure of cobalt tetracarbonyl hydride

Microwave rotational spectra for six isotopomers of HCo(CO)₄ were measured using a Flygare-Balle type spectrometer. Transitions were measured in the 4-10 GHz range. The data were analyzed to obtain rotational constants, ⁵⁹Co quadrupole coupling strengths, distortion constants and spin-rotation interaction strengths. The common isotopomer is clearly a symmetric top, with C_3v symmetry. For the common isotopomer 5 = 1131.7212(9) MHz and eQq(⁵⁹Co)=116.62(3) MHz. The rotational constants were used to determine the complete, three-dimensional structure of this complex. The measured H-Co bond length of 1.52(2) Å is significantly shorter than the previous value from electron diffraction work. Other structural parameters for this complex are reported and discussed.