Borylene transfer from an iron bis(borylene) complex: synthesis of 1,4-diboracyclohexadiene and 1,4-dibora-1,3-butadiene complexes.

Diene to be made: By tuning the size of acetylenic substituents, 1,4-diboracyclohexadiene and unprecedented 1,4-dibora-1,3-butadiene complexes were generated in a controlled manner by borylene transfer from an iron bis(borylene) complex to alkynes (see scheme).