[MoFe3S4]3+ and [MoFe3S4]2+ cubane clusters containing a pentamethylcyclopentadienyl molybdenum moiety

A series of organometallic molybdenum/iron/sulfur clusters of the general formula [Cp∗MoFe3S4Ln]m (Cp∗ = η5-C5Me5; L = StBu, SPh, Cl, I, n = 3, m = 1−; Ln = I2(PtBu3), m = 0; L = 2,6-diisopropylphenylisocyanide (ArNC), n = 7, m = 1+) have been synthesized. A cubane cluster (PPh4)[Cp∗MoFe3S4(StBu)3] (2) was isolated from a self-assembly reaction of Cp∗Mo(StBu)3 (1), FeCl3, LiStBu, and S8 followed by cation exchange with PPh4Br in CH3CN, while an analogous cluster (PPh4)[Cp∗MoFe3S4(SPh)3] (3) was obtained from the Cp∗MoCl4/FeCl3/LiSPh/PPh4Br reaction system or from a ligand substitution reaction of 2 with PhSH. Treatment of 2 with benzoyl chloride gave rise to (PPh4)[Cp∗MoFe3S4Cl3] (4), which was in turn converted to (PPh4)[Cp∗MoFe3S4I3] (5) by the reaction with NaI. A neutral cubane cluster Cp∗MoFe3S4I2(PtBu3) (6) was generated upon treating 5 with PtBu3. Although reduction of 4 by cobaltocene under the presence of ArNC resulted in a disproportionation of the cubane core to give Fe4S4(ArNC)9Cl (7), a similar reduction reaction of 5 produced [Cp∗MoFe3S4(ArNC)7]I (8), where the MoFe3S4 core was retained. The crystal structures of 4–6, and 8 were determined by the X-ray analysis.

Graphical abstractA series of [MoFe3S4]n+ (n = 2 and 3) clusters were synthesized, which consists of a common Cp∗ (=η5-C5Me5) fragment. The self-assembly reactions of Cp∗Mo(StBu)3 (1) with FeCl3 in the presence of LiStBu (or LiSPh) and elemental sulfur (S8), followed by cation exchange with PPh4Br, generated (PPh4)[Cp∗MoFe3S4(StBu)3] (2) and (PPh4)[Cp∗MoFe3S4(SPh)3] (3). The tert-butyl thiolate ligands of 2 were readily replaced by benzenethiolate, chloride, and iodide to give (PPh4)[Cp∗MoFe3S4X3] (X = SPh (3), Cl (4), I (5)), while the reactions of 5 with PtBu3 and ArNC/cobaltocene gave rise to Cp∗MoFe3S4I2(PtBu3) (6) and [Cp∗MoFe3S4(ArNC)7]I (7, ArNC = 2,6-diisopropylphenylisocyanide), respectively.Figure optionsDownload full-size imageDownload as PowerPoint slide