Tetrahydroxydiboron
Names
IUPAC name
Hypoboric acid[1]
Other names
(Dihydroxyboranyl)boronic acid
Hypoboric acid
Hypodiboric acid
Sub-boric acid (Unterborsäure in German)
1,1,2,2-Tetrahydroxydiborane
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.222.662
UNII
  • InChI=1S/B2H4O4/c3-1(4)2(5)6/h3-6H
    Key: SKOWZLGOFVSKLB-UHFFFAOYSA-N
  • B(B(O)O)(O)O
Properties
B2H4O4
Molar mass 89.65 g·mol−1
Appearance White powder
Density 1.657
Melting point 143–148 °C (289–298 °F; 416–421 K)
very soluble
Solubility ethanol, DMF, DMSO, DMA
Structure
monoclinic P21/c
Thermochemistry
125.46 J K−1 mol−1
−1410.43 kJ mol−1
Hazards
GHS labelling:
H302, H315, H319, H332, H335
P261, P264, P270, P271, P280, P301+P312, P302+P352, P304+P312, P304+P340, P305+P351+P338, P312, P321, P330, P332+P313, P337+P313, P362, P403+P233, P405, P501
Related compounds
Related compounds
 Diborane
Diboron tetrafluoride
Bis(pinacolato)diboron
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Tetrahydroxydiboron is a chemical reagent which can be used to prepare boronic acids.[2]

Synthesis

The reaction of boron trichloride with alcohols was reported in 1931, and was used to prepare dimethoxyboron chloride, B(OCH3)2Cl.[3] Egon Wiberg and Wilhelm Ruschmann used it to prepare tetrahydroxydiboron by first introducing the boron–boron bond by reduction with sodium and then hydrolysing the resulting tetramethoxydiboron, B2(OCH3)4, to produce what they termed sub-boric acid.[4] The methanol used in this process can be recycled:

BCl3     B(OCH3)2Cl     B2(OCH3)4     B2(OH)4

Overall: 2 BCl3 + 2 Na + 4 H2O → B2(OH)4 + 2 NaCl + 4 HCl

Reactions

When heated to over 90 °C, tetrahydroxydiboron dehydrates to a polymeric boron(II) oxide. The temperature must rise to 220 °C to be totally free from water.[5]

Tetrahydroxydiboron is a reducing agent. A water solution slowly gives off hydrogen gas.[4]

References

  1. ↑ "Hypodiboric acid". IUPAC.
  2. ↑ Little, Sarah; Trice, Jane (2001). "Tetrahydroxydiboron". Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. doi:10.1002/047084289x.rn01181. ISBN 9780470842898.
  3. ↑ Wiberg, Egon; Sütterlin, Walther (1931). "Zur Kenntnis einiger Verbindungen vom Typus BCl3−n(OR)n. (Über alkoxyl-substituierte Borchloride)" [Notes on some compounds of type BCl3−n(OR)n. (Via alkoxy-substituted boron chlorides)]. Z. anorg. allg. Chem. (in German). 202 (1): 1–21. doi:10.1002/zaac.19312020102.
  4. 1 2 Wiberg, Egon; Ruschmann, Wilhelm (1937). "Über eine neue Borsäure ('Unterborsäure'︁) der Formel H4B2O4 und ihre Ester" [On a new boric acid ('Sub-boric acid') of the formula H4B2O4 and its esters]. Ber. Dtsch. Chem. Ges. A/B (in German). 70 (6): 1393–1402. doi:10.1002/cber.19370700636.
  5. ↑ Wartik, Thomas; Apple, Eugene F. (1955). "A New Modification of Boron Monoxide". J. Am. Chem. Soc. 77 (23): 6400–6401. doi:10.1021/ja01628a116.
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