Spectroscopic and theoretical evaluation of the metal-olefin interaction in di-μ-chlorobis (1,5-cyclooctadiene) complexes of Ir and Rh

sThe complexes of di-μ-chlorobis(1,5-cyclooctadiene) of rhodium(I); [Rh(μ-Cl)(COD)]2 and iridium(I); [Ir(μ-Cl)(COD)]2 have shown prominent activities in a number of catalytic reactions. In the solid packing form these two complexes were shown to adopt D2h and C2v symmetries for iridium and rhodium, respectively. In this work vibrational spectroscopic techniques assisted with density functional theory (DFT) calculations have been employed to assess the metal-olefin interaction and to provide thorough assignments of the infrared and Raman spectra for both complexes. The wavenumber shifts associated with the CH2 bending modes have been established as a potential tool to access the σ and π components in the metal-olefin interaction for the two complexes. Examination of the catalytic activity based on calculated reactivity parameters, natural bond orbital (NBO) analysis and coordination energy was also carried out.