- Electronic structure of the Rh-Rh bond in dirhodium tetracarboxylates from a study of electronic spectra of neutral molecules and their cation radicals
-
Electronic absorption spectra of Rh2(O2CR)4L2 [R = Et, CF3; L = H2O, HC(CH2CH2)3N, PPh3, P(c-C6H11)3, P(OPh)3, P(OMe)3] and some of their cation radicals are examined. The intense absorption band in the near-ultraviolet region (ν? = (25-46) × 103 cm-1 and log ∈ = 4.0-4.7 for neutral complexes and ν = (17-23) × 103 cm-1 and log ∈ = 4.0-4.3 for cationic complexes) is assigned to the intermetallic σ → σ* transition. Ligand dependences of the transition energy and the intensity of this absorption band are interpreted with a bonding model constructed from a hypothesis that metal-ligand interactions are larger than intermetallic interactions. This valence model can also account qualitatively for the ligand dependences of the intermetallic bond distance and the stretching frequency of the intermetallic bond in dirhodium tetracarboxylates and the odd-electron distribution in their cation radicals. The odd electron of Rh2(O2CMe)4(H2O)2 +. is suggested not to be accommodated in the σRhRh MO. The CO stretching frequency of Rh2(O2CCF3)4(CO)2 is 7 cm-1 higher than that of the free carbon monoxide, showing that there is practically no π-type interactions between the metal and the carbonyl in this complex.
- Sowa, Takayoshi,Kawamura, Takashi,Shida, Tadamasa,Yonezawa, Teijiro
-
-