Diisopinocampheylborane was originally prepared by hydroboration of excess α-pinene with borane,
but it is now more commonly generated from borane-methyl sulfide (BMS). 
The compound can be isolated as a solid, but because it is quite sensitive to water and air, it is often generated in situ and used as a solution.  The synthesis is complicated by a number of factors, including the tendency of the compound to eliminate pinene.
Diisopinocampheylborane is often represented as a monomer (including in this article), but X-ray crystallography establishes a dimeric structure.