Electronic structure and spectra of rhodium(II) tetracarboxylate complexes

The DFT B3LYP geometry optimization was carried out and the IR spectra were calculated for rhodium(II) tetracarboxylate complexes Rh2(O2CR)4 (R = H, CH3, CF3, C6H5) and for the compound Rh2(O2CH)4(H2O)2 with two axially coordinated water molecules. A minor influence of the substituent R on the electronic structure and geometric and spectral characteristics of the cage was noted. From the calculation results, it was concluded that the Rh(II)-Rh(II) stretching vibrations should be attributed to about 300 cm−1. The results obtained for rhodium(II) dimers were compared with analogous data for Mo2(O2CH)4. Analysis of the electronic structure including consideration of the natural bond orbitals indicates the presence of a strong Rh(II)-Rh(II) single bond and a quadruple Mo(IV)-Mo(IV) bond. The electronic spectra of Rh2(O2CR)4 (R = H, C6H5) and Rh2(O2CH)4(H2O)2 were simulated by the TDDFT technique.