[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^*MoFe₃S₄L_n]^m (Cp^* = η⁵-C₅Me₅; L = S^tBu, SPh, Cl, I, n = 3, m = 1-; L_n = I₂(P^tBu₃), m = 0; L = 2,6-diisopropylphenylisocyanide (ArNC), n = 7, m = 1+) have been synthesized. A cubane cluster (PPh₄)[Cp^*MoFe₃S₄(S^tBu)₃] (2) was isolated from a self-assembly reaction of Cp^*Mo(S^tBu)₃ (1), FeCl₃, LiS^tBu, 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(P^tBu₃) (6) was generated upon treating 5 with P^tBu₃. 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.