An Iodido‐Bridged Dimer of Cubane‐Type RuIr3S4 Cluster: Structural Rearrangement to New Octanuclear Core and Catalytic Reduction of Hydrazine

Nitrogen‐fixing enzymes contain octanuclear metal–sulfur clusters at the active site, which are constructed on the basis of combined two cubic M4S3C skeletons. In this study, the dimer of cubane‐type RuIr3S4 cluster [{(Cp*Ir)3(µ3‐S)4Ru}2(µ2‐I)3]I (2: Cp* = η5‐C5Me5) was synthesized via oxidation of [(Cp*Ir)3(µ3‐S)4(CymRu)] (Cym = η6‐p‐iPrC6H4Me) with I2 followed by ligand exchange. Two cubane cores are bridged by three iodido ligands in 2, while these cubes are fused into a unique Ru2Ir6S8 framework by 2e‐reductuion to give [(Cp*Ir)6Ru2(µ3‐S)8][I]2. Addition of excess PhNHNH2 to 2 cleaved the dimer structure to form the hydrazine adduct of single cubane [(Cp*Ir)3(µ3‐S)4{RuI(NH2NHPh)2}]I. Reduction of N2H4 with Cp2Co and [HNEt3][BF4] was catalyzed by 2 in much higher rate than disproportionation of N2H4. The molecular structures of all new cluster compounds were characterized by X‐ray diffraction studies. Cubane‐type RuIr3S4 cluster forms a dimer in which two Ru centers are triply bridged by iodido ligands each other. Two‐electron reduction induces fusion of two RuIr3S4 units accompanied by deformation of one cubane core to give a unique sulfido‐bridged octanuclear framework. The cubane dimer is catalytically active in reduction of N2H4 with Cp2Co and [HNEt3][BF4].