Dominant changes in centre Fe atom of decamethyl-ferrocene from ferrocene in methylation

Abstract Staggered decamethyl-ferrocene (*Fc) becomes the lower energy conformer at low temperature, whereas eclipsed of ferrocene (Fc) is more stable. The powerful infrared (IR) spectroscopy which has remarkably provided signatures in and staggered conformers recently employed to investigate methylation Fc. most significant consequences full Fc IR spectra are blue shift band ~ 800 cm −1 1500 *Fc, enhancement C–H stretch 3200 region *Fc. Further analysis reveals large impact on core electron energies centre Fe atom (1 s 2 p 6 3 ). changes can be as 10 kcal mol directional—the z orbitals along *Cp–Fe–*Cp axis (Cp centroids, vertical) change strongly than other electrons x y orbitals. directional inner shell evidenced by larger reorganization energy. Energy decomposition (EDA) indicates that methyl groups *Fc apparently physical components with respect steric evidences closest hydrogens adjacent same *Cp ring crystal structure 0.2–0.4 Å closer nearest-neighbour opposing rings A increase Pauli repulsive contributes