The alkynylphosphines Ph2P(C≡CR) (R = H, C(O)OMe) react with [PPh4][HFe3(CO)11] to give, in a first step, complexes containing the Ph2PC═CHR ligands. When R = C(O)OMe, the structure of the complex 3 isolated was determined by a single-crystal X-ray diffraction study. The anionic part consists of a Ph2PC═CHC(O)OMe ligand in which the phosphorus atom is bonded to an Fe(CO)4 group and in which the C═CHC(O)OMe fragment is η1,η2-bonded and η1(O)-bonded to an anionic Fe2(CO)6 unit. When R = H, the structure of complex 5 was deduced from spectroscopic data. It consists of a Ph2PCCH2 ligand bonded to each iron atom of an [Fe3(CO)9]- triangle through the P, C, and C═CH2 atoms, respectively. Complexes 3 and 5 evolved in boiling acetone and ethyl acetate, respectively, to [PPh4] [Fe3(CO)6(μ-CO)2(μ-PPh2)(μ-CCHR)] compounds, resulting from the breaking of the phosphorous-carbon bond. © 1990, American Chemical Society. All rights reserved.