Trans-selective insertional dihydroboration of a cis-diborene: synthesis of linear sp3-sp2-sp3-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-3hydrotriboranes, while hydride abstraction affords cationic triboranes, which represent the first doubly base-stabilized B3H4+ analogues.