Vibrational spectra of buta-1,3-diene iron tricarbonyl: comparison to surface species

Abstract

Abstract Butadiene potentially exhibits many different modes of bonding to a surface, the aim of this work is to fully characterise how the spectrum of the s-cis conformer changes on coordination. A model complex, C4H6Fe(CO)3 and its deuterated isotopomer, was studied with infrared, Raman and inelastic neutron scattering (INS) spectroscopies and has provided a definitive set of assignments for the ligand. These differ in many respects from previous work that was solely based on empirical correlations. The use of INS spectroscopy has allowed observation of several of the low energy modes for the first time, the most significant of which is the C1–C1′ torsion at 485 cm−1. The comparison of observed and calculated infrared spectra for butadiene on silica confirms the surprising assignment that the molecule is adsorbed as the gauche form.