Reaction of Cp(CO) 2RuCHCCH 2 with Fe 2(CO) 9 in hexane at reflux affords four iron-ruthenium products: Cp(CO) 2 Ru(μ 3-η 1,η 2,η 3- C(O)CHCCH 2) Fe 2( CO) 6( 3), CO) 3 Fe(μ 2- CO) RuCp(μ 2- CO) Fe( CO) 3(μ 3-η 1- CCHCH 2) ( 4), Cp(CO) 2Ru( μ 4- η 1, η 3, η 3 η 1-CH 2CCHC(CH)CH 2)(CO) 3FeFe(CO) 2( μ 2-CO) Ru(CO)Cp ( 5) and (CO) 3FeRu(CO)CpFe(CO) 3( μ 3- η 1, η 1, η 3-CCHCH 2) ( 6), which were isolated and characterized. Complex 3 reacts with PPh 3 to yield the monosubstitution derivative Cp(CO) 2Ru( μ 3- η 1, η 3, η 3-C(O)-CHCCH 2)Fe 2(CO) 5(PPh 3) ( 10); both 3 and 10 were characterized spectroscopically and are thought to contain a Ru-bonded allenylcarbonyl ligand, which is attached to Fe 2(CO) 5L (L=CO,PPh 3) through the oxygen atom and the two CC double bonds. The trinuclear 4 is structurally analogous to the previously prepared (C.E. Shuchart, A. Wojcicki, M. Calligaris, P. Faleschini and G. Nardin, Organometallics, 13 (1994) 1999), from Cp(CO) 2RuCH 2CCPh and Fe 2(CO) 9, (CO) 3Fe( μ 2-CO)RuCp( μ 2-CO)Fe(CO) 3( μ 3- η 1-CCHCHPh) ( 1) and contains a μ 3- η 1-CCHCH 2 ligand capping an Fe 2Ru metal core. In solution, 4 and 1 undergo partial conversion to 6 and (CO) 3FeRu(CO)CpFe(CO) 3( μ 3- η 1, η 1, η 3-CCHCHPh) ( 2), respectively, in which the CCHCHR (R = H, Ph) ligand bridges the Fe 2Ru triangle in a μ 3- η 1, η 1, η 3 mode. Complexes 6 and 2 also equilibrate to mixtures of 6 and 4 and of 2 and 1, respectively, upon storage in solution. 1 reacts with 2 equiv. of PEt 3 in the presence of Me 3NO to afford the disubstituted (CO)(PEt 3) 2Fe( μ 2-CO)RuCp( μ 2-CO)Fe(CO) 3( μ 3- η 1-CCHCHPh) (4 bd9), in which the bridging CCHCHPh ligand retains its μ 3- η 1 bonding mode. In contrast, reactions of 1 and 4 with PPh 3 yield (CO) 2(PPh 3)Fe( μ 2-CO)RuCp( μ 2-CO)Fe(CO) 3( μ 3- η 1, η 1, η 3-CCHCHPh) ( 8) and (CO) 2(PPh 3)Fe( μ 2-CO)RuCp( μ 2-CO)Fe(CO) 3( μ 3- η 1, η 1, η 3-CCHCH 2) ( 7), respectively, which contain μ 3- η 1, η 1, η 3-CCHCHR ( R= H, Ph). The tetranuclear Fe 2Ru 2 complex 5 results from the coupling of two FeRu allenyl or related species between a terminal and a central carbon atom of their C 3 fragments. The structures of 4 and 8 (as 8·0.5CH 2Cl 2) were determined by X-ray diffraction analysis. 4: monoclinic, P2 1/n, a = 9.038(1) A ̊ , b = 15.062(6) A ̊ , c = 13.485(4) A ̊ , β = 99.16(1)°, Z = 4, R = 2.8%, R w = 2.9% ; 8·0.5CH 2Cl 2: monoclinic, C2/c, a = 39.851(9) A ̊ , b = 9.319(2) A ̊ , c = 21.156(5) A ̊ , β = 112.91(2)°, Z = 8, R = 4.02%, R w = 4.81% .