Recent work has shown that cyanide ligation increases the redox potentials of Fe4S4 clusters, enabling the isolation of [Fe4S4(CN)(4)](4-), the first synthetic Fe4S4 cluster obtained in the all-ferrous oxidation state ( Scott, T. A.; Berlinguette, C. P.; Holm, R. H.; Zhou, H.-C. Proc. Natl. Acad. Sci. U. S. A. 2005, 102, 9741). The generality of reduced cluster stabilization has been examined with MoFe3S4 clusters. Reaction of single-cubane [(Tp) MoFe3S4(PEt3)(3)](1+) and edge-bridged double-cubane [(Tp)(2)Mo2Fe6S8(PEt3)(4)] with cyanide in acetonitrile affords [(Tp) MoFe3S4(CN)(3)](2-) (2) and [(Tp)(2)Mo2Fe6S8(CN)(4)](4-) ( 5), respectively. Reduction of 2 with KC14H10 yields [(Tp) MoFe3S4(CN)(3)](3-) ( 3). Clusters were isolated in similar to 70 - 90% yields as Et4N+ or Bu4N+ salts; clusters 3 and 5 contain all-ferrous cores, and 3 is the first [MoFe3S4](1+) cluster isolated in substance. The structures of 2 and 3 are very similar; the volume of the reduced cluster core is slightly larger (2.5%), a usual effect upon reduction of cubane-type Fe4S4 and MFe3S4 clusters. Redox potentials and Fe-57 isomer shifts of [(Tp) MoFe3S4L3](2-,3-) and [(Tp)(2)Mo2Fe6S8L4](4-,3-) clusters with L = CN-, PhS-, halide, and PEt3 are compared. Clusters with pi-donor ligands (L = halide, PhS) exhibit larger isomer shifts and lower (more negative) redox potentials, while pi-acceptor ligands (L = CN, PEt3) induce smaller isomer shifts and higher (less-negative) redox potentials. When the potentials of 3/2 and [(Tp) MoFe3S4(SPh)(3)](3-/2-) are compared, cyanide stabilizes 3 by 270 mV versus the reduced thiolate cluster, commensurate with the 310 mV stabilization of [Fe4S4(CN)(4)](4-) versus [Fe4S4(SPh)(4)](4-) where four ligands differ. These results demonstrate the efficacy of cyanide stabilization of lower cluster oxidation states. (Tp = hydrotris( pyrazolyl) borate(1 -)).