The redox behavior and electronic spectra of Rh2(II)(OAc)4 were studied in 14 nonaq. solns. The oxidation potentials of the axial solvation complexes Rh2(OAc)4.L2 for weak s-donor ligands (L) such as CH2Cl2, (CH2Cl)2, propylene carbonate (PC), MeCN(AN), THF, DMF, PrCN, acetone (AC), PhCN, and MeNO2 are essentially invariant. Observable cathodic shifts of the oxidation potentials occur for the stronger s-donor ligands such as pyridine (Py), DMSO, P(OEt)3 and PPh3. This is explained in terms of 2 types of electronic configuration. Based on these electrochem. and spectra data of the neutral and cation radical of Rh2(OAc)4.L2, the HOMO orbital of Rh2(OAc)4.L2 was confirmed experimental to be dRhRh* in the weak s-donor ligands. In axial Rh2(OAc)4 complexes with stronger s-donor ligands, the HOMO orbital is considered to be sRhRh-L,* which has an electronic transition in the electronic absorption spectra (n1) and electron-transfer in the electrochem. oxidation of the Rh2(OAc).L2. This differs from the case in the weak s-donor ligands, in which n1 results from pRhRh* ?sRhRh* electronic transition, and an electron is removed from the HOMO dRhRh* in electrochem. oxidation The donor power of these solvents is in the order: CH2Cl2~(CH2Cl)2

Key words: ELECTRON TRANSFER, WAVE LENGTH, ELECTRONIC STRUCTURE, MOLECULAR ORBITAL THEORY, ACETIC ACID P, DINUCLEAR COMPLEX, ELECTROCHEMICAL ANALYSIS, ELECTRON TRANSITION, RHODIUM COMPLEX, POLYCARBOXYLIC ACID