Edge-bridged Mo-Fe-S double cubanes are versatile precursors for the synthesis of other clusters of the same nuclearity. Thus, the double cubane [(Tp)(2)Mo2Fe6S8(PEt3)(4)] sustains terminal ligand substitution with retention of the Mo2Fe6(mu(3)-S)(6)(mu(4)-S)(2) core structure and rearrangement to the Mo2Fe6(mu(2)-S)(2)(mu(3)-S)(6)(mu(6)-S) topology of the nitrogenase ION cluster upon reaction with certain nucleophiles. Four distinct processes for the conversion of double cubanes to p(N)-type clusters are documented, affording the products [(Tp)(2)Mo2Fe6S9(SR)(2)](3-), [(Tp)(2)Mo2Fe6S8(OMe)(3)](3-), and [(Tp)(2)Mo2Fe6S7(OMe)(4)](2-). In the latter clusters, two methoxides are terminal ligands and one or two are mu(2)-bridging ligands. The reverse transformation of a pN-type cluster to an edge-bridged double cubane has been demonstrated by the reaction of [(Tp)(2)Mo2Fe6S8(OMe)(3)](3-) with Me3SiX to afford [(Tp)(2)Mo2Fe6S8X4](2-) (X = Cl-, Br-). Edge-bridged double cubanes have been obtained in the oxidation states [Mo2Fe6S8](2+,3+.4+). The stable oxidation state of p(N)-type clusters is [Mo2Fe6S9](+). Structures of five double cubanes and four P-N-type clusters are reported. The P-N-type clusters are synthetic representations of the biologically unique topology of the native p(N) cluster. Best-fit superpositions of the native and synthetic cluster cores gives weighted rms deviations in atom positions of 0.20-0.38 Angstrom. This study and an earlier investigation (Zhang, Y.; Holm, R. H. J. Am. Chem. Soc. 2003, 125, 3910-3920) provide a comprehensive account of the synthesis of structural analogues of the native P-N cluster and provide the basis for continuing investigation of the synthesis of weak-field Mo-Fe-S clusters related to nitrogenase. (Tp = tris(pyrazolyl)hydroborate(1-).).