The title complex (Cp =eta(5)-C5H5) reacted with the labile carbonyl complexes [M(CO)(5)(THF)] (M = Cr, Mo, W) and [MnCp'(CO)(2)(THF)] (Cp' = eta(5)-C5H4Me) to give phosphinidene-bridged trimetallic compounds of formula [Fe2MCp2(mu(3)-PCy)(mu-CO)-(CO)(7)] (Cr-P = 2.479(1) angstrom) and [Fe2MnCp2Cp'(mu(3)-PCy) (mu-CO)-(CO)(4)], respectively, after formation of a new M-P bond in each case, and related heterometallic complexes [Fe2MClCp2(mu(3)-PCy)(mu-CO)-(CO)(2)] (M = Cu, Au; Au-P = 2.262(1) angstrom) were cleanly formed upon reaction with CuCl or the labile tetrahydrothiophene (THT) complex [AuCl(THT)]. The reaction with [Fe-2(CO)(9)] proceeded analogously to give the triiron derivative [Fe3Cp2(mu(3)-PCy)(mu-CO)(CO)(6)] in high yield (new Fe-P bond =2.318(1) angstrom), along with a small amount of the pentanuclear compound [{Fe(CO)(3)}{(mu(3)-PCy)Fe2Cp2(mu-CO)-(CO)(2)}(2)], the latter displaying a central Fe(CO)(3)P-2 core with a distorted bipyramidal geometry (P-Fe-P = 164.2(1)degrees). In contrast, the reaction with [Co-2(CO)(8)] resulted in a full disproportionation process to give the salt [{Co(CO)(3)}{(mu(3)-PCy)Fe2Cp2(mu-CO)(CO)(2)}(2)][Co(CO)(4)], having a pentanuclear Fe4Co center dot cation comparable to the above Fe-5 complex (P-Co-P = 165.3(2)degrees). The attempted photochemical decarbonylation of the above trinuclear complexes gave results strongly dependent on the added metal fragment. Thus, the irradiation with visible or visible-UV light of the new Fe-3 and Fe2Cr species caused no decarbonylation but a tautomerization of the metal framework to give the corresponding isomers [Fe2MCp2(mu(3)-PCy)(mu-CO)(CO)(n)] now exhibiting a dangling FeCp(CO)(2) moiety (M = Cr, n = 7, Cr-Fe = 2.7370(3) angstrom; M = Fe, n = 6, new Fe-Fe bond = 2.6092(9) angstrom) as a result of the cleavage of the Fe-Fe bond in the precursor and subsequent formation of a new M-Fe bond. These processes are reversible, since the new isomers gave back the starting complexes under low (Cr) or moderate (Fe) thermal activation. In contrast, the manganese diiron complex [Fe2MnCp2Cp'(mu(3)-PCy)(mu-CO)(CO)(4)] could be decarbonylated stepwise, to give first the tetracarbonyl complex [Fe2MnCp2Cp'(mu(3)-PCy)(mu-CO)(2)(CO)(2)] and then the tricarbonyl cluster [Fe2MnCp2Cp'(mu(3)-PCy)(mu-CO)(3)], the latter having a closed triangular metal core (Fe-Fe = 2.568(7) angstrom; Mn-Fe = 2.684(8) and 2.66(1) angstrom).