Reduction of iridocenium salts [Ir(η5-C5Me5)(η5-L)]+ (L = C5H5, C5Me5, C9H7); ligand-to-ligand dimerisation induced by electron transfer

Abstract Redox properties of iridium complexes [Ir( η 5 -C 5 Me 5 )( η 5 -L)] + ( 1 + , L = C 5 H 5 ; 2 + , L = C 5 Me 5 ; 3 + , L = C 9 H 7 ) were studied by cyclic voltammetry (CV). All three complexes can be reduced to 19-electron radicals 1–3 . The stability and reactivity of these radicals depend on the electronic and steric properties of the ligands. The mixture of dimers [( η 5 -C 5 Me 5 )Ir( μ - η 4 : η 4 -C 5 H 5 C 5 Me 5 )Ir( η 5 -C 5 H 5 )] ( 4a ) and [( η 5 -C 5 H 5 )Ir( μ - η 4 : η 4 -C 5 Me 5 C 5 Me 5 )Ir( η 5 -C 5 H 5 )] ( 4b ) was formed as a result of reduction of 1 + with Na Hg in THF. Both chemical and electrochemical reduction of 2 + gave the dimer [( η 5 -C 5 Me 5 )Ir( μ - η 4 : η 4 -C 5 Me 5 C 5 Me 5 )Ir( η 5 -C 5 Me 5 )] ( 5 ) in low yield. Reduction of 3 + gave the tetranuclear complex [( η 5 -C 5 Me 5 )Ir( μ - η 4 : η 5 -C 9 H 7 ) Ir( μ - η 4 : η 4 -C 5 Me 5 C 5 Me 5 ) Ir( μ - η 5 : η 4 -C 9 H 7 )Ir( η 5 -C 5 Me 5 )] ( 6 ).