Synthesis of a Sulfido-Capped Trinuclear Cluster [{(η5-C5Me5)Ir}2{Mo(CO)3}(μ3-S)2] and Its Reactions at the Molybdenum Site Forming a Series of Ir2MoS2 Clusters

Treatment of a hydrosulfido-bridged diiridium complex, [(Cp*IrCl)2(μ-SH)2] (1; Cp* = η5-C5Me5), with [Mo(η6-toluene)(CO)3] in the presence of NEt3 gave the sulfido-bridged Ir2Mo cluster [(Cp*Ir)2{Mo(CO)3}(μ3-S)2] (3). Detailed studies on the reactivity of its Mo site have resulted in the isolation of a series of new Ir2Mo(μ3-S)2 clusters. Thus, 3 reacted with Ph2PCH2CH2PPh2 (dppe) to afford [(Cp*Ir)2{Mo(CO)(dppe)}(μ3-S)2] (4), which underwent the oxidation by I2 at the molybdenum site to give [(Cp*Ir)2{MoI(CO)(dppe)}(μ3-S)2]I (5). On the other hand, oxidation of 3 with [Cp2Fe][PF6] in THF−MeCN resulted in the elimination of one CO ligand and concomitant coordination of two MeCN molecules at the Mo center, yielding [(Cp*Ir)2{Mo(CO)2(MeCN)2}(μ3-S)2][PF6]2 (6). Further oxidation of 6 using O2 gas led to the elimination of all the remaining CO ligands to give an oxo-dichloro cluster, [(Cp*Ir)2(MoOCl2)(μ3-S)2] (7). The ligation of diphosphines to the molybdenum site in 7 formed the cationic oxo-chloro cluster [(Cp*Ir)2{MoOCl(R2PC2H4PR2)}(μ3-S)2]X (8a, R = Me (dmpe), X = Cl; 8b, R = Et, X = Cl; 8c, R = Ph, X = PF6) with concurrent dissociation of one of the Cl ligands, and the following deoxygenation from 8a with BCl3 gave [(Cp*Ir)2{MoCl3(dmpe)}(μ3-S)2][BCl4] (9). Reduction of 9 with Cp2Co afforded a paramagnetic Mo(III) cluster, [(Cp*Ir)2{MoCl2(dmpe)}(μ3-S)2][BCl4] (11), whereas reduction of 8c with NaBH4 resulted in the formation of a Mo(II) dihydrido cluster, [(Cp*Ir)2{MoH2(dppe)}(μ3-S)2] (12). X-ray analyses have been undertaken to determine the detailed structures for 3, 4, 5, 6, 7, 8b, 9, and 12.