Electron paramagnetic resonance and spectroscopic characteristics of electrogenerated mixed-valent systems [(η5-C5Me5)M(μ-L)M(η5-C5Me5)]+ (M = Rh, Ir;: L=2,5-diiminopyrazines) in relation to the radicals [(η5-C5Me5)ClM(μ-L)MCl(η5-C5Me5)]+ and [(η5-C5Me5)M(μ-L)MCl(η5-C5Me5)]2+

Electrochemical reduction of the dinuclear [(eta(5)-C5Me5)ClM(mu-L)MCl(eta(5)-C5Me5)(2+) ions (M = Rh, Ir; L = 2,5-bis(1-phenyliminoethyl)pyrazine (bpip) and 2,5-bis[1-(2,6-dimethylphenyl)iminoethyl]pyrazine (bxip)) proceeds via the paramagnetic intermediates [(eta(5)-C5Me5)ClM(mu-L)MCl(eta(5)-C5Me5)](+) (L = bpip) or [(eta(5)-C5Me5)M(mu-L)MCl(eta(5)-C5Me5)(2+) (L = bxip) and [(eta(5)-C5Me5)M(mu-L)M(eta(5)-C5Me5)](+). Whereas the first is clearly a radical species with a small g anisotropy, the chloride-free cations are distinguished by structured intervalence charge transfer (IVCT) bands in the near-infrared region and by rhombic electron paramagnetic resonance features between g 1.9 and g = 2.3, which suggests considerable metal participation at the singly occupied MO. Alternatives for the d configuration assignment and for the role of the bisbidentate-conjugated bridging ligands will be discussed. The main difference between bpip and bxip systems is the destabilization of the chloride-containing forms through the bxip ligand for reasons of steric interference.