Abstract
Vibrational and H-NMR spectroscopic studies on di-μ-chlorobis(1,5-cyclooctadiene) of iridium(I) and rhodium (I) complexes have been carried out. In addition, the two D2h and D2 structures for both complexes have been fully optimized. It was expected from the single-molecule vapor-phase density functional theory (DFT) calculation that the D2 structure is more stable by 5 - 6 kcal/mol. While spectroscopic analysis study confirms that in the solid phase, the two complexes retain the higher D2h symmetry. The vibrational wavenumbers of certain modes associated to free 1,5-cyc- looctadiene were observed to be shifted to lower values upon coordination with rhodium or iridium metals. It was also found theoretically that the metal-olefin interaction is slightly more pronounced for iridium metal.
Highlights
Di-μ-chlorobis(1,5-cyclooctadiene) of iridium (I) and rhodium (I) ions are popular complexes which are employed in several homogenous catalytic reactions
The D2 symmetry is obtained from the Ci COD, while the D2h complex is associated with C2 COD [7] [8]
C1, sp2.59; H1, s C2, sp2.59; H2, s C1, sp2.02; C2, sp2.02 C1, sp2.73; H1, s C2, sp2.73; H2, s C1, sp2.15; C2, sp2.15 C1, sp2.79; H1, s C2, sp2.79; H1, s is more electropositive than Rh and as such it populates carbon with more electron than Rh, decreasing the bond order which in return increases the bond length. This resulted in shift to lower wavenumbers for such vibrational modes for coordinated olefinic C=C with Ir than Rh. Both vibrational and H-NMR spectroscopic investigation reveals complex of di-μ-chlorobis(1,5-cyclooctadiene) of iridium (I) and rhodium (I) to be of the same geometry
Summary
Di-μ-chlorobis(1,5-cyclooctadiene) of iridium (I) and rhodium (I) ions are popular complexes which are employed in several homogenous catalytic reactions They are mostly used as precursor catalysts in the development of catalytic systems for applications in different reactions well-reported in the literature [1]-[3]. An infrared study on the assignments of ν(C=C), ν(M-Cl) and ν(M-olefin) vibrations [7] as well as the strength of metal-olefin bond interaction was reported [8] These studies showed that the molecular symmetry plays a role in understanding the electronic, structural properties as well as the catalytic activity. In this paper we highlight some of our findings which will be detailed in future in another article
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