Bis(pinacolato)diboron

Bis(pinacolato)diboron is a covalent compound containing two boron atoms and two pinacolato ligands. It has the formula [(CH3)4C2O2B]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.[1]

Bis(pinacolato)diboron
Names
IUPAC name
4,4,4′,4′,5,5,5′,5′-Octamethyl-2,2′-bi(1,3,2-dioxaborolane)
Identifiers
3D model (JSmol)
Abbreviations B2pin2
ChemSpider
ECHA InfoCard 100.111.245
UNII
Properties
C12H24B2O4
Molar mass 253.94 g·mol−1
Melting point 137 to 140 °C (279 to 284 °F; 410 to 413 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Preparation and structure

This compound may be prepared by reacting tetrakis(dimethylamino)diboron with pinacol in acidic conditions.[1] The B-B bond length is 1.711(6) Å.[2]

Reactions

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:[3]

CH3(CH2)6CH3 + [pinB]2 → pinBH + CH3(CH2)7Bpin

These reactions proceed via boryl complexes.

References
  1. Tatsuo Ishiyama; Miki Murata; Taka-aki Ahiko & Norio Miyaura (2004). "Bis(pinacolato)diboron". Organic Syntheses.; Collective Volume, 10, p. 115
  2. C.Kleeberg, A.G.Crawford, A.S.Batsanov, P.Hodgkinson, D.C.Apperley, Man Sing Cheung, Zhenyang Lin, T.B.Marder "Spectroscopic and Structural Characterization of the CyNHC Adduct of B2pin2 in Solution and in the Solid State" J. Org. Chem. 2012, vol. 77, pp. 785. doi:10.1021/jo202127c
  3. Xinyu Liu "Bis(pinacolato)diboron" Synlett 2003, pp 2442–2443. doi:10.1055/s-2003-43344
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