Structure of solvated Fe(CO)5: XANES and EXAFS measurements using ultrafast laser plasma and conventional X-ray sources

Abstract

The structures of solvated iron pentacarbonyl, Fe(CO)5, have been measured by X-ray absorption near edge structure and extended X-ray absorption fine structure spectroscopy. Cyclohexane and benzene have been used as solvents. The results were analyzed in conjunction with theoretical molecular structures based on density functional theory calculations. The calculations as well as previously published infrared absorption data showed that between 60% and over 90% of iron pentacarbonyl molecules have C2v symmetry in aromatic solvents at room temperature. Typically, one solvent molecule interacts with the iron atom trans to the apical CO-ligand. This publication presents, to our knowledge, the first X-ray absorption fine structure measurements of chemical solutions ever performed with a laser plasma X-ray source. The results were found to be in good agreement with measurements using a micro-focus X-ray tube as well as with theoretical X-ray absorption spectra of solvated Fe(CO)5.