Diboron tetrachloride
Preferred IUPAC name
Diboron tetrachloride
Systematic IUPAC name
3D model (JSmol)
  • InChI=1S/B2Cl4/c3-1(4)2(5)6
  • InChI=1S/B2Cl4/c3-1(4)2(5)6
  • ClB(Cl)B(Cl)Cl
Molar mass 163.42 g·mol−1
Appearance colorless liquid
Density 1.5 g/cm3 (0 °C)
Melting point −92.6 °C (−134.7 °F; 180.6 K)
Boiling point 65.5 °C (149.9 °F; 338.6 K)
137.7 J/mol K
232.3 J/mol K
-523 kJ/mol
-468.8 kJ/mol
Related compounds
Related compounds
Diboron tetrafluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Diboron tetrachloride is a chemical compound with the formula B2Cl4. It is a colorless liquid.[1]


The modern synthesis involves dechlorination of boron trichloride using copper.[2]

It can also be formed by the electrical discharge procedure of boron trichloride at low temperatures:[1][3]

BCl3 → BCl2 + Cl
Cl + Hg (electrode) → HgCl or HgCl2
2 BCl2 → B2Cl4


The compound is used as a reagent for the synthesis of organoboron compounds. For instance, diboron tetrachloride reacts with ethylene:[4]

CH2=CH2 + B2Cl4 → Cl2B–CH2–CH2–BCl2

The compound absorbs hydrogen quickly at room temperature:[3]

3 B2Cl4 + 3 H2 → B2H6 + 4 BCl3


  1. ^ a b P. L. Timms (1972). Low Temperature Condensation. Academic Press. p. 143. ISBN 0-12-023614-1. ((cite book)): |work= ignored (help)
  2. ^ Timms, Peter L. (1979). "Tetrachlorodiborane(4) (Diboron Tetrachloride)". Inorganic Syntheses. Vol. 19. pp. 74–78. doi:10.1002/9780470132500.ch14. ISBN 9780470132500.
  3. ^ a b Urry, Grant; Wartik, Thomas; Moore, R. E.; Schlesinger, H. I. (1954). "The Preparation and Some of the Properties of Diboron Tetrachloride, B2Cl4". Journal of the American Chemical Society. 76 (21): 5293–5298. doi:10.1021/ja01650a010. ISSN 0002-7863.
  4. ^ Urry, Grant; Kerrigan, James; Parsons, Theran D.; Schlesinger, H. I. (1954). "Diboron Tetrachloride, B2Cl4, as a Reagent for the Synthesis of Organo-boron Compounds. I. The Reaction of Diboron Tetrachloride with Ethylene". Journal of the American Chemical Society. 76 (21): 5299–5301. doi:10.1021/ja01650a011. ISSN 0002-7863.