Reaction of the title complex with excess [Fe-2(CO)(9)] at room temperature gave the tetranucleat derivative [Fe2Mo2Cp2(mu(4)-P)(mu-PCy2)(mu(3)-PMe)(CO)(9)], following from formal insertion of an Fe(CO)(3) fragment in the P-P bond of the diphosphenyl ligand With formation of a new heterometallic bond (Mo-Fe = 2.935 (1) angstrom), and coordination of an Fe(CO)(4) fragment through the lone electron pair of the resulting phosphide ligand (P-Fe = 2.359(2) angstrom). Reactions of the title complex with excess of the tetrahydrofuran (THF) adducts [MLn(THF)] (MLn = MnCp'(CO)(2), W(CO)(5)) led instead to tetranuclear diphosphenyl-bridged complexes [M2Mo2Cp2(mu-PCy2)(mu-kappa(2):kappa(1):kappa(1):kappa(1)-P2Me)(CO)(2)L-2n] displaying a Mo-Mo double bond (Mo-Mo = 2.760(2) angstrom when M = W), along with the phosphide- and phosphinidene-bridged complex [Mo2W2Cp2(mu(3)-P)(mu-PCy2)(mu(3)-PMe)(CO)(10)], with the latter displaying a Mo-Mo triple bond (Mo-Mo = 2.5542(4) angstrom) and a trigonal planar phosphide ligand. Reaction of the title complex with excess [Mo(CO)(4)(THF)(2)] also resulted in facile P-P bond cleavage of the diphosphenyl ligand to give [Mo4Cp2(mu(4)-P)(mu-PCy2)(mu(3)-PMe)(CO)(9)], a cluster built on a Mo-3 triangular core bridged by phosphinidene and phosphide ligands, with the latter further coordinated to an exocyclic Mo(CO)(5) fragment. The related Mo2W2 complex [Mo2W2Cp2(mu(3)-P) (mu-PCy2)(mu(3)-PMe)(CO)(9)] could be rationally synthesized upon reaction of the trinuclear cluster [Mo2WCp2(mu(3)-P)(mu-PCy2)(mu(3)-PMe)(CO)(6)] with the adduct [W(CO)(5)(THF)]. The title complex reacted photochemically with [M-2(CO)(10)] (M = Mn, Re) to give the 66-electron tetranuclear derivatives [M2Mo2Cp2(mu(4)-P)(mu-PCy2)(mu(3)-PMe)(CO)(9)], after formation of a new Mo-M bond (Mo-Mn = 2.9988(7) angstrom, Mo-Re = 3.1003(4) angstrom) and cleavage of the diphosphenyl P-P bond. In contrast, its room-temperature reaction with [Co-2(CO)(8)] gave the 64-electron square-planar cluster [Co2Mo2Cp2(mu(4)-P)(mu-PCy2)(mu(4)-PMe)(mu-CO)(CO)(6)] resulting from formation of two new Mo-Co bonds (Mo-Co = 2.8812(7) and 2.9067(7) angstrom) and facile P-P bond cleavage in the diphosphenyl ligand.