Structure of Solvated Fe(CO)5: A Concerted XAFS, FTIR, and DFT Study of Solvation in Fluorinated Arenes

The structures of iron pentacarbonyl, Fe(CO) 5, solvated in benzene and its fluorinated derivatives have been investigated by X-ray absorption fine structure (XAFS) spectroscopy and infrared (IR) spectroscopy as well as density functional theory (DFT) calculations. As discussed previously (Jiang, Y.; Lee, T.; Rose-Petruck, C. J. Phys. Chem. A 2003, 107, 7524−7538), 60−90% of iron pentacarbonyl (IPC) molecules are distorted to C 2 v symmetry in aromatic solvents at room temperature. Typically one solvent molecule interacts with the iron atom of IPC trans to the apical CO ligand forming an IPC···solvent complex. In substituted benzene several IPC···solvent complex conformations coexist. The relative conformer populations were determined by IR spectroscopy. These populations were subsequently used to determine the equilibrium structures of each conformer through the analysis of XAFS spectra in combination with DFT structural data for the IPC···solvent complexes.