This colourless solid is used in organic chemistry as a hydroboration reagent.

The compound exists as a hydride-bridged dimer, which easily cleaves in the presence of reducible substrates.

[3][better source needed] 9-BBN is prepared by the reaction of 1,5-cyclooctadiene and borane usually in ethereal solvents, for example:[4][5]

[6][7][8] Its highly regioselective addition on alkenes allows the preparation of terminal alcohols by subsequent oxidative cleavage with H2O2 in aqueous KOH.

The steric demand of 9-BBN greatly suppresses the formation of the 2-substituted isomer compared to the use of borane.