Synthesis and some reactions of the heterometallic C₇ complex {Cp*(dppe)Ru}C≡CC≡CC≡CC{Co₃(μ-dppm)(CO)₇}

Abstract

The heterometallic carbon-chain complex {Cp*(dppe)Ru} C≡CC≡CC≡CC{Co3(μ-dppm)(CO)7} (1) has been obtained by three routes that involve assembly of the C7 chain by combination of appropriate C1 + C6, C2 + C5, or C3 + C4 precursors. The Cp analogue 2 and Co3(CO)9 cluster analogue 3 were obtained via the C2 + C5 and C1 + C6 routes, respectively. Reaction of 1 with PPh3 gave 4 via substitution of a Co3 cluster-bonded CO group. Addition of MeOTf to the second carbon from the Ru center in 1 afforded the vinylidene [{Cp*(dppe)Ru}=C= CMeC≡CC≡CC{Co3(μ-dppm)(CO)7}]OTf (5), while addition of tcne or tcnq across the central C≡C bond gave {Cp*(dppe)Ru}C≡CC[=C(CN)2]C[=C(CN)2]- C≡CC{Co3(μ-dppm)(CO)7} (6) and {Cp*(dppe)Ru}C≡CC[=C6H4C(CN) 2]C[=C(CN)2]C≡CC{Co3(μ-dppm)(CO) 7} (7), respectively. The reaction between 1 and Fe 2(CO)9 was more complex, the major product being {Cp*(dppe)Ru}C≡CC{Fe3(CO)9}CC≡CC{Co 3(μ-dppm)(CO)7} (8), accompanied by an Fe 2(CO)6 derivative (9) of as yet undetermined structure. {Cp*(dppe)Ru} C≡CC≡CC≡CC {Co2Ni(μ-dppm) (CO)4Cp} (10) was obtained from the reaction with NiCp2. An unstable adduct containing two Co2(CO)6 groups attached to the C7 chain was formed in reactions between 1 and Co 2(CO)8. XRD structural studies of 1, 2, 6-8, and 10 are reported. Electrochemical measurements suggest that there is some interaction between the two end groups, although this cannot presently be quantified. It is concluded that the C7 chain is long enough for the properties of the individual end caps to be preserved, while steric inhibition from the phenyl groups of the dppe and dppm ligands directs addition to the central C≡C triple bond of the C7 chain. © 2008 American Chemical Society.