Knowledge Bank

Microwave spectra of seven isotopomers of tetracarbonyldihydroiron were measured in the 4-16 GHz range using a Flygare-Balle type microwave spectrometer. Measured transitions were fit using a rigid rotor Hamiltonian with five independent distortion constants. Structural parameters from a least squares fit to the rotational constants are; $r(Fe-H)=1.576(64)$ {\AA}, $r(Fe-Cl)=1.815(54)$ {\AA}, $r(Fe-C3)=1.818(65)$ {\AA}, $r(C1-O1)=1.123(80)$ {\AA}, $r(C3-O3)=1.141$ {\AA}, $\angle (H-Fe-H)=88.0(2.8),\angle (Cl-Fe-C2)=154.2(4.2),\angle (C3-Fe-C4)=99.4(4.3),\angle (Fe-Cl-Ol)=172.5(5.6)$ and $\angle (Fe-C3-O3)=177.8(6.8)$. The oxygen atoms in the equatorial plane and the axial oxygen atoms are bent slightly toward the hydrogen atoms. These parameters are in excellent agreement with the substitution coordinates determined from Kraitchmann's equations, the density functional theoretical geometry, and the previously published electron diffraction data.