Iron-catalyzed intermolecular [2π + 2π] cycloaddition

Article abstract of DOI:10.1021/ja202992p

The bis(imino)pyridine iron dinitrogen compounds, (^iPrPDI) Fe(N₂)₂ and [(^MePDI)Fe(N₂)] ₂(μ₂-N₂) (^RPDI = 2,6-(2,6-R ₂-C₆H₃N=CMe)₂C₅H ₃N; R = ⁱPr, Me), promote the catalytic intermolecular [2π + 2π] cycloaddition of ethylene and butadiene to form vinylcyclobutane. Stoichiometric experiments resulted in isolation of a catalytically competent iron metallocycle intermediate, which was shown to undergo diene-induced C-C reductive elimination. Deuterium labeling experiments establish competitive cyclometalation of the bis(imino)pyridine aryl substituents during catalytic turnover.