Rhodium vibrational spectra

The rhodium binding energy is 0.5 eV higher in the case of the bis-isocyanide derivative. This is in favor of the effective ji back donation from metal to ligand that is also reflected by the energy of the isocyanide stretching vibration in the IR spectrum of the complex. 

The adsorption of ethylene on the Rh(lll) surface provides a typical example. The high-resolution electron-energy-loss (HREEL) spectrum at 77 K in Figure 2.25 has been attributed to ethylene adsorbed molecularly intact on the Rh(lll) surface [101]. However, vibrational frequencies measured are markedly different from those for gas-phase ethylene, indicating a strong interaction between ethylene and the rhodium surface. 

Under syn gas pressure the rhodium acac precursors were converted to the catalytically active hydride complexes HRh(CO)2(L-L). The complexes are generally assmned to have a trigonal bipyramidal structure and two isomeric structures of these complexes are possible, containing the diphosphite coordinated in a bisequatorial (ee) or an equatorial-apical (ea) fashion. The structure of the complexes can be elucidated by (high pressure) IR and NMR data (Table 3). In the carbonyl region of the infrared spectrum the vibrations of the ee and ea complex can be easily distinguished. The ee complexes typically show absorptions around 20 15 and 2075 cm [24, 26,... 

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