Reactivity of Terminal Iron Borylenes and Bis(borylenes) with Carbodiimides: Cycloaddition, Metathesis, Insertion and C?H Activation Pathways

The reactions of carbodiimides with the iron arylborylene complex [Fe=BDur(CO)3(PMe3)] (Dur=2,3,5,6-Me4C6H) and bis(borylene) [Fe{=BDur}{=BN(SiMe3)2}(CO)3] yield a wide variety temperature-dependent products, including known FeBNC novel FeBNB metallacycles, complexes N-heterocyclic boracarbene spiro-boracarbene ligands unique 1,3,2,4-diazadiborolyl pianostool complex, characterized by NMR spectroscopy X-ray crystallography. product distributions can be rationalized considering sequences cycloaddition, metathesis, insertion, C?H activation pathways mainly governed sterics.