Oxidation of [Rh-2(O2CEt)(4)(PR3)(2)] (R : cy = cyclohexyl and Pr-i = iso-propyl) with ferrocenium ion gave stable salts of their cationic radicals. Their X-ray structures showed ca. 0.048 Angstrom longer Rh-Rh and ca. 0.12 Angstrom shorter Rh-P bonds than those of the diamagnetic neutral complexes. The pyramids of the phosphine ligands of these cationic complexes are more flattened than those of the neutral complexes. These observations and ESR data indicate that the sigma(RhRh) singly occupied molecular orbital (SOMO) of these complexes is extensively mixed with the phosphine lone-pair orbitals in the Rh-P sigma antibonding phase. X-ray crystallographic structures of [Rh-2(mhp)(4)](+) (mhp = anion of 2-hydroxy-6-methylpyridine) and [Rh-2(form)(4)](+) (form = N,N＇-di-p-tolylformamidinate anion) showed that the removal of a delta(RhRh)* electron results in 0.017-0.043 Angstrom decreases of their Rh-Bh bond distances, where Eq is the ligation atom in the bridging Ligand. These results are consistent with the delocalization of the delta(RhRh)* orbital (the SOMO of these cationic radicals) onto the bridging ligands in the it antibonding phase. B3LYP DFT calculations of Rh-2(4+) and Rh-2(5+) model complexes reproduced the ligand dependence oi. the electron configuration of Rh-2(5+) complexes and geometrical changes accompanying the ionization and showed that the relatively rigid arrangement of the bridging ligands retards the dependence of the Rh-Rh bond length on the electron configuration. Also, the spin population in [Rh-2(O2CH)(4)(PH3)(2)](+) is extensively delocalized onto the axial ligands, that in [Rh-2(HNCHNH)(4)](+) and [Rh-2(HNCHO)(4)(H2O)(2)](+) moderately onto the bridging ligands and that in [Rh-2(O2CH)(4)(H2O)(2)](+) rather localized on the metal atoms.