Diboron tetrachloride

Diboron tetrachloride is a chemical compound with the formula B₂Cl₄. It is a colorless liquid.[1] The electrical discharge procedure of boron trichloride can be divided into three steps:[2]

Diboron tetrachloride

Names
Preferred IUPAC name Diboron tetrachloride
Systematic IUPAC name Tetrachlorodiborane
Identifiers
CAS Number	13701-67-2
3D model (JSmol)	Interactive image
ChemSpider	123068
PubChem CID	139548
UNII	3KKJ90L3I5
CompTox Dashboard (EPA)	DTXSID40160031
InChI InChI=1S/B2Cl4/c3-1(4)2(5)6 Key: LCWVIHDXYOFGEG-UHFFFAOYSA-N InChI=1S/B2Cl4/c3-1(4)2(5)6 Key: LCWVIHDXYOFGEG-UHFFFAOYAN
SMILES ClB(Cl)B(Cl)Cl
Properties
Chemical formula	B2Cl4
Molar mass	163.433 g/mol
Appearance	colorless liquid
Density	1.5 g/cm^3 (0 °C)
Melting point	−92.6 °C (−134.7 °F; 180.6 K)
Boiling point	65.5 °C (149.9 °F; 338.6 K)
Thermochemistry
Heat capacity (C)	137.7 J/mol K
Std molar entropy (S^o298)	232.3 J/mol K
Std enthalpy of formation (ΔfH^⦵298)	-523 kJ/mol
Gibbs free energy (ΔfG˚)	-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).
Infobox references

Synthesis

The modern synthesis involves dechlorination of boron trichloride using copper.[3] It can also be formed by the electrical discharge procedure of boron trichloride at low temperatures.[1]

BCl₃ → BCl₂ + Cl

Cl + Hg (electrode) → HgCl or HgCl₂

2 BCl₂ → B₂Cl₄

Reactions

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:[2]

3 B₂Cl₄ + 3 H₂ → B₂H₆ + 4 BCl₃

References

1. P. L. Timms (1972). Low Temperature Condensation. Advances in Inorganic Chemistry and Radiochemistry. p. 143. ISBN 0-12-023614-1.
2. 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.
3. Timms, Peter L. (1979). "Tetrachlorodiborane(4) (Diboron Tetrachloride)". Inorganic Syntheses. Inorganic Syntheses. 19. pp. 74–78. doi:10.1002/9780470132500.ch14. ISBN 9780470132500.
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.