Reaction of ferrocene with acetylene to generate methylferrocene. An unusual labeling result

Article abstract of DOI:10.1021/om00017a007

Heating a gaseous mixture of ferrocene and acetylene (1:6.3 mol ratio) at 450°C results in the formation of methylferrocene. When ¹³C₂H₂ is the substrate, GC/MS analysis reveals that the methylferrocene fraction consists of predominately two compounds: methylferrocene-¹³C₁ and methylferrocene-¹³C₆ in a 1:2.5 ratio. A mechanism involving initial addition of the alkyne C-H bond across the Fe-Cp bond to generate an (ethynyl-η⁴-cyclopentadiene)iron hydride is proposed to explain both products.