The anionic oxophosphinidene complexes (H-DBU)[MCp{P(O)R-star}(CO)(2)] (M = Mo, W; R-star = 2,4,6-(C6H2Bu3)-Bu-t; CP = eta(5)-C5H5, DBU = 1,8-diazabicyclo [5.4.0] undec-7-ene) displayed multisite reactivity when faced with different electrophilic reagents. The reactions with the group 14 organochloride compounds ER4-xClx, (E = Si, Ge, Sn, Pb) led to either phosphide-like, oxophosphinidene-bridged derivatives [MCp{P(OE')R-star)(CO)(2)](E'=SiMe3, SiPh3, GePh3, GeMe2Cl) or to terminal oxophosphinidene complexes [MCp{P(O)R-star}(CO)(2)(E')] (E' = SnPh3, SnPh2Cl, PbPh3; Mo-Pb = 2.8845(4) angstrom for the MoPb compound). A particular situation was found in the reaction with SnMe3Cl, this giving a product existing in both tautomeric forms, with the phosphide-like complex [MCp{P(OSnMe3)R-star}(CO)(2)] prevailing at room temperature and the tautomer [MCp{P(O)R-star}(CO)(2)(SnMe3)] being the unique species present below 203 K in dichloromethane solution. The title anions also showed a multisite behavior when reacting with transition-metal based electrophiles. Thus, the reactions with the complexes [M'Cp2Cl2] (M' = Ti, Zr) gave phosphide-like derivatives [MCp{P(OM')R-star}(CO)(2)] (M = Mo, M' = TiCp2Cl, ZrCp2Cl; M = W, M' = ZrCp2Cl), displaying a bridging kappa(1),kappa(1)-P O-oxophosphinidene ligand connecting MCp(CO)(2) and M'Cp2Cl metal fragments (W-P = 2.233(1) angstrom, O-Zr = 2.016(4) angstrom for the WZr compound]. In contrast, the reactions with the complex [AuCl{P(p-tol)(3)}] gave the metal-metal bonded derivatives trans-[MCp{P(O)R*}(CO)(2){AuP(p-tol)(3)}] (M = Mo, W; Mo-Au = 2.7071(7) angstrom). From all the above results it was concluded that the terminal oxophosphinidene complexes are preferentially formed under conditions of orbital control, while charge-controlled reactions tend to give derivatives with the electrophilic fragment bound to the oxygen atom of the oxophosphinidene ligand (phosphide-like, oxophosphinidene-bridged derivatives).