| Abstract
| - Electrochemical reduction of the dinuclear [(η5-C5Me5)ClM(μ-L)MCl(η5-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)) proceedsvia the paramagnetic intermediates [(η5-C5Me5)ClM(μ-L)MCl(η5-C5Me5)]+ (L = bpip) or [(η5-C5Me5)M(μ-L)MCl(η5-C5Me5)]2+ (L = bxip) and [(η5-C5Me5)M(μ-L)M(η5-C5Me5)]+. Whereas the first is clearly a radical specieswith 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 thed 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 throughthe bxip ligand for reasons of steric interference.
- The larger g anisotropy of the odd-electron complexes [(η5-C5Me5)M(μ-L)M(η5-C5Me5)]+, L = 2,5-diiminopyrazines, in comparison to chloride-containing species (signal x) indicates metal−metal mixed-valency for the former and a radical ligand situation for the latter compounds.
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