REDUCTION OF IRIDOCENIUM SALTS [IR(ETA(5)-C5ME5)(ETA(5)-L)](- LIGAND-TO-LIGAND DIMERIZATION INDUCED BY ELECTRON-TRANSFER() (L=C5H5, C5ME5, C9H7) )

Redox properties of iridium complexes [Ir(eta(5)-C5Me5)(eta(5)-L)](+) (1(+), L = C5H5; 2(+), L = C5Me5; 3(+), L = C9H7) were studied by cycl ic voltammetry (CV). All three complexes can be reduced to 19-electron radicals 1-3. The stability and reactivity of these radicals depend o n the electronic and steric properties of the ligands. The mixture of dimers Me5)Ir(mu-eta(4):eta(4)-C5H5C5Me5)Ir(eta(5)-C5H5)] (4a) and H5) Ir(mu-eta(4):eta(4)-C5Me5C5Me5)Ir(eta(5)-C5H5)] (4b) was formed as a r esult of reduction of 1(+) with Na/Hg in THF. Both chemical and electr ochemical reduction of 2(+) gave the dimer 5)Ir(mu-eta(4):eta(4)-C5Me5 C5Me5)lr(eta(5)-C5Me5)] (5) in low yield. Reduction of 3(+) gave the t etranuclear complex e5C5Me5)Ir(mu-eta(5):eta(4)-C9H7)Ir(eta(5)-C5Me5)] (6).