Borohydride Anions as Terminal Ligands on a Fe/Mo/S Cluster. Synthesis, Structure, and Characterization of the [(Cl₄-cat)(PPr₃)MoFe₃S₄(BH₄)₂]₂(Bu₄N)₄ Double-Fused Cubane

The synthesis and structure of the first Mo/Fe/S/BH4 cluster is reported. Reaction of (Cl4-cat)2Mo2Fe6S8(PPr3)6 with 4 equiv of Bu4NBH4 results in the formation of [(Cl4-cat)(PPr3)MoFe3S4(BH4)2]2(Bu4N)4 (Cl4-cat = tetrachloro-catecholate) which has been fully characterized. X-ray structural determination of this double-fused cubane reveals four BH4- ligands bound to four Fe atoms in a bidentate fashion. A synopsis of the solution characterization as well as the reactivity of this cluster is also presented.