An inelastic neutron scattering study and re-assignment of the vibrational spectrum of [Os3(CO)9(µ2-CO)(µ3-η2-C2H2)], a model compound for chemisorbed ethyne

Abstract

The complex [Os₃(CO)₉(µ₂-CO)(µ₃-η²-C₂H₂)] (1) has been used as a vibrational model compound for the bonding of ethyne on metal single crystal surfaces. The original vibrational assignment of the ethyne ligand in 1 was based on the infrared and Raman spectra of the protonated and deuterated complexes and comparison with the spectra of related compounds. We have now measured the inelastic neutron scattering (INS) spectrum of the complex, and the assignment of the C–H bending and the Os–C stretching modes of 1 has been partially revised in the light of this. Since the revisions largely affect the antisymmetric modes, (A″), the conclusions from previous work regarding the assignment of the type B (di-σ/π) ethyne chemisorption on metal single crystals are still valid.