Bis(pinacolato)diboron

Bisdiboron is a covalent compound containing two boron atoms and two pinacolato ligands. It has the formula ₂; the pinacol groups are sometimes abbreviated as "pin", so the structure is sometimes represented as B₂pin₂. It is a colourless solid that is soluble in organic solvents. It is a commercially available reagent for making pinacol boronic esters for organic synthesis. Unlike some other diboron compounds, B₂pin₂ is not moisture-sensitive and can be handled in air.

Preparation and structure

This compound may be prepared by treating tetrakisdiboron with pinacol in acidic conditions. The B-B bond length is 1.711 Å.
Dehydrogenation of pinacolborane provides an alternative route:

file:Pinacolborane.svg|thumb|left|Pinacolborane is a closely related reagent.|110px
The B-B bond adds across alkenes and alkynes to give the 1,2-diborylated alkanes and alkenes. Using various organorhodium or organoiridium catalysts, it can also be installed onto saturated hydrocarbons:
These reactions proceed via boryl complexes.
Bisdiboron can also be used as reducing agent for example in transition metal catalyzed hydrogenations of alkenes and alkynes.