Reactions of [{Mo(O)(DMF)3}2(μ2-S)2]I2 (1) with an equimolar amount of [(Cp*MCl)2(μ2-SH)2] (M = Ir, Rh; Cp* = η5-C5Me5) and excess [Me4N]Cl in DMF at room temperature afforded cubane-type clusters with a terminal oxo ligand, [{Mo(O)Cl2}{MoCl2(DMF)}(Cp*M)2(μ3-S)4] (M = Ir (5), Rh (6)), while treatment of 1 with [(Cp‘RuCl)2(μ2-SH)2] (Cp‘ = Cp*, Cp°; Cp° = η5-C5EtMe4) under analogous conditions gave cubane-type clusters without oxo ligands, [{MoCl2(DMF)}2(Cp‘Ru)2(μ3-S)4] (Cp‘ = Cp*, Cp° (7‘)). Cluster 5 reacted with MePhNNH2 in DMF at room temperature, yielding the methylphenylhydrazido(2−) cluster [{Mo(NNMePh)Cl2}{MoCl2(DMF)}(Cp*Ir)2(μ3-S)4] (9), which upon treatment with lutidinium chloride (Lut·HCl) as the source of protons and cobaltocene as the source of electrons produced PhNHMe in considerable yield. Catalytic conversion of MePhNNH2 into PhNHMe through the reductive cleavage of the N−N bond by a Lut·HCl/cobaltocene mixture was attained by the use of the cubane-type clusters as catalyst precursors, which include 5, 6, and their mixed-chalcogenido analogues [{Mo(O)Cl2}{MoCl2(DMF)}(Cp*M)2(μ3-S)2(μ3-Se)2] (M = Ir, Rh). X-ray analyses have been undertaken for 5, 7‘, and 9 to determine their detailed structures.

Metal-sulfur cubane-type clusters have been attracting significant attention owing to their unique structures and properties. 1 Recent X-ray crystallographic studies on nitrogenase have revealed the structure of the FeMo cofactor cluster, which consists of two incomplete cubane-type units connected by three bridging sulfides {(MoFe 3 S 3 )(µ-S) 3 (Fe 4 S 3 )}. 2 This has spurred on particularly the syntheses of the cuboidal clusters relevant to this active site core, including those with {(MoFe 3 S 4 )(µ-S)(Fe 4 S 4 )} or related Mo/Fe/S chromophores. 3 However, cuboidal metal-sulfides with a N 2 ligand are still unknown, 4 and even those with nitrogenous ligands relevant to N 2 reduction are unexplored except for a few examples having coordinated hydrazines. 3d,5 Our research interest has focused recently on the exploitation of the rational pathways for preparing the metal-sulfido clusters, particularly the cubane-type clusters containing noble metals. 6 Now we have found that a new cubane-type Mo 2 Ir 2 S 4 cluster with a terminal oxo ligand can be obtained from the reaction of a sulfido-bridged dioxo dimolybdenum complex with a hydrosulfido-bridged diiridium complex. Importantly, this cluster has been shown to undergo the condensation reaction with PhMeNNH 2 at its ModO site to afford a novel cluster with a hydrazido(2-) ligand. Although mononuclear hydrazido(2-) complexes of Mo and W with tertiary phosphine coligands have been studied extensively in relevance to the mechanism of biological and industrial N 2 fixation, 7 cubane-type metal-sulfido clusters containing a hydrazido ligand are yet unknown 8 in spite of their potential to give some insight into the biological N 2 -reducing system.