Alkyne-Induced Carbyne-Carbyne Coupling in the Trinuclear Bis(carbene) Iron Cluster Fe3(CO)9(μ3-CO2C2H5)(μ3-CCH3). X-ray Structures of Fe3(CO)6(μ-CO)2-μ3-η4 and Fe3(CO)6(μ-CO)2-μ3-η4

Article abstract of DOI:10.1021/ja00292a032

The reaction of alkynes R₁CCR₂ with the trinuclear bis (carbyne) iron cluster Fe3(CO)9(μ₃-COC2H5)(μ₃-CCH3) produces comlexes in which coupling of the entering alkynes with the carbyne ligands has occured.X-ray structure determinations of the resulting Fe3(CO)6(μ-CO)2(R₁CCR₂)(C(CH3)) complexes in the cases where R₁ = R₂ = C6H5 or Si(CH3)3 show the presence of Fe-C(C6H5)-C(C6H5)-C(CH3)-C-(OC2H5) and Fe-C(Si(CH3)3)-C(Si(CH3)3)-C(OC2H5)-C(CH3) ferracyclopentadiene rings.Extension to other alkynes like acetylene and phenylacetylene or tert-butylacetylene revealed a third situation in which the ferracyclopentadiene rings result from the insertion of the alkynes between the two carbyne ligands.Spectroscopic data also suggest that in the case of phenyl- and tert-butylacetylene, the ferracyclopentadiene ring results from the carbon-carbon breaking alkynes and coupling of the resulting carbyne fragments.Mechanisms for these observations are proposed and discussed.