Acetylene cyclotrimerization with an iron(II) bis(imino)pyridine catalyst

Acetylene oligomerization with an activated iron bis(imino)pyridine complex with low steric hindrance leads to benzene as the major product, in contrast to this reaction with a more sterically encumbered analogue, which leads to polyacetylene. The mechanism of benzene formation was studied and likely occurs via metallacycle intermediates; this process can be interrupted by addition of ZnEt₂ as a chain transfer agent to generate hexadiene instead.