Isomers of Manganese Tetracarbonyl Hydride: A Density Functional Study of Structure and Vibrational Spectra

Abstract

Density functional theory (DFT) calculations have been used to find and characterize various isomers of HMn(CO)4, a coordinatively unsaturated complex. For comparison, its saturated parent compound HMn(CO)5 has been included in the study. Optimized geometries and vibrational spectra were calculated for each species. For the pentacarbonyl, the theoretical geometry allows a critical discussion of various experimental results. Its calculated vibrational spectrum agrees with experiment within an average error of less than 10 cm-1 and maximum deviation of ∼30 cm-1. In a search for isomeric forms of the tetracarbonyl complex, two minima have been found on the potential surface. The most stable form is a Cs structure, with a second isomer of C4v symmetry lying about 3 kcal/mol higher in energy. The existence of these two structures is in agreement with the conclusions of a sophisticated matrix isolation photolysis study by Church et al.18 The calculated vibrational spectrum supports the interpretation of the CO ...