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
Preferred IUPAC name
Octamethyl-2,2′-bi-1,3,2-dioxaborolane
Identifiers
3D model (JSmol)
Abbreviations B2pin2
ChEBI
ChemSpider
ECHA InfoCard 100.111.245
UNII
  • InChI=1S/C12H24B2O4/c1-9(2)10(3,4)16-13(15-9)14-17-11(5,6)12(7,8)18-14/h1-8H3 ☒N
    Key: IPWKHHSGDUIRAH-UHFFFAOYSA-N ☒N
  • InChI=1/C12H24B2O4/c1-9(2)10(3,4)16-13(15-9)14-17-11(5,6)12(7,8)18-14/h1-8H3
    Key: IPWKHHSGDUIRAH-UHFFFAOYAV
  • B1(OC(C(O1)(C)C)(C)C)B2OC(C(O2)(C)C)(C)C
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 treating tetrakis(dimethylamino)diboron with pinacol in acidic conditions.[1] The B-B bond length is 1.711(6) Å.

Dehydrogenation of pinacolborane provides an alternative route:[2]

2 (CH3)4C2O2BH → (CH3)4C2O2B-BO2C2(CH3)4 + H2

Reactions
Pinacolborane is a closely related reagent.

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. Bis(pinacolato)diboron can also be used as reducing agent for example in transition metal catalyzed hydrogenations of alkenes and alkynes. [4]

References
  1. Tatsuo Ishiyama; Miki Murata; Taka-aki Ahiko & Norio Miyaura (2004). "Bis(pinacolato)diboron". Organic Syntheses.; Collective Volume, vol. 10, p. 115
  2. Neeve, Emily C.; Geier, Stephen J.; Mkhalid, Ibraheem A. I.; Westcott, Stephen A.; Marder, Todd B. (2016). "Diboron(4) Compounds: From Structural Curiosity to Synthetic Workhorse". Chemical Reviews. 116 (16): 9091–9161. doi:10.1021/acs.chemrev.6b00193. PMID 27434758.
  3. Xinyu Liu "Bis(pinacolato)diboron" Synlett 2003, pp 2442–2443. doi:10.1055/s-2003-43344
  4. "Bis(pinacolato)diboron, B2pin2".
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