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.