trans ‐Selective Insertional Dihydroboration of a cis ‐Diborene: Synthesis of Linear sp 3 ‐sp 2 ‐sp 3 ‐Triboranes and Subsequent Cationization

The reaction of aryl- and amino(dihydro)boranes with dibora[2]ferrocenophane 1 leads to the formation 1,3-trans-dihydrotriboranes by formal hydrogenation and insertion of a borylene unit into the B=B bond. The aryltriborane derivatives undergo reversible photoisomerization to the cis-1,2-μ-H-3-hydrotriboranes, while hydride abstraction affords cationic triboranes, which represent the first doubly base-stabilized B3 H4+ analogues.