The reaction of the 1,2,3-triphosphaferrocene [Cp'"Fe(eta(5)-P3C2(H)Ph)] (1) with the Lewis acidic complex [PtCl2(PEt3)](2) yields the monosubstituted derivative [Cp'"Fe(eta(5)-P3C2(H)Ph){PtCl2(PEt3)}] (2), in which the Pt moiety is located at the P atom adjacent to the C(H) group of the cyclo-P3C2 ring.-Using an excess of the Pt complex no multiple substitution occurs. In contrast, using [W(CO)(5)] units as Lewis acids results in mono-, di-, and tricoordination at the cyclo-P3C2 ring. The products, [Cp'"Fe(eta(5)-P3C2(H)Ph){W(CO)(5)}(n)] (n = 1 (3), 2 (4), 3 (5)), have all been spectroscopically characterized, and the substitution patterns of the experimentally found (mono- and disubstituted) isomers are found to be in accordance with the energetically favored derivatives calculated by DFT methods. For these structures the energetically favored rotational conformers have also been calculated. The energetically favored 2,3-coordinated isomer 4b could be crystallized, and its structure and that of the tricoordinated derivative 5 were deter-mined by X-ray diffraction methods.