[(η2-C2H4)Os(CO)4] as a vibrational model for type I′ ethene chemisorbed as a metallacyclopropane on metal surfaces

Abstract

A comprehensive vibrational assignment of the hydrocarbon features in the infrared and Raman spectra of (η²-C₂H₄)Os(CO)₄ has been achieved with the help of data from the (¹³C₂H₄) and (C₂D₄) isotopologues. Close analogies with the vibrational spectra of thiirane (ethene sulfide) assist in the assignment and emphasize the metallacyclopropane nature of the (C₂H₄Os) group. Comparisons are made with analogous spectra from (η²-C₂H₄)Fe(CO)₄ and from Zeise's salt, K[(η²-C₂H₄)PtCl₃].

Taking into account the metal–surface selection rule associated with on-specular vibrational electron energy loss or reflection–absorption infrared spectra, good agreement is found between the wavenumber/intensity pattern from the a₁ modes of the complex and from ethene chemisorbed on metal surfaces previously designated Type I′.