Phosphine‐Stabilized Borylenes and Boryl Anions as Ligands? Redox Reactivity in Boron‐Based Pincer Complexes

Stabilized borylenes (L 2 BH:) with weakly π‐accepting substituents L, such as phosphines, were previously believed to be unstable. In the current manuscript, we describe a series of complexes formally containing a phosphine‐stabilized borylene or boryl anion. In contrast to common trivalent boron compounds, the boron‐based ligands in this study act as electron‐donating ligands. The reported iron hydride complexes exhibit a unique reactivity pattern, undergoing a reversible B−H reductive elimination concomitant with oxidation of the boron(I) center.