Diboron tetrachloride

Diboron tetrachloride
Names
	Preferred IUPAC name Diboron tetrachloride
	Systematic IUPAC name Tetrachlorodiborane(4)
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	163.42 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)
Thermochemistry
Heat capacity (C)	137.7 J/mol K
Std molar; entropy (S⦵298)	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

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

Synthesis

The modern synthesis involves dechlorination of boron trichloride using copper.^[2]^{[better source needed]}

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 most efficient synthesis technique uses no dechlorinating metal, instead passing radio-frequency AC current through gaseous boron trichloride.^[4]

Reactions

The compound is used as a reagent for the synthesis of organoboron compounds. For instance, diboron tetrachloride adds to ethylene:^[5]

CH₂=CH₂ + B₂Cl₄ → Cl₂B–CH₂–CH₂–BCl₂

Diboron tetrachloride absorbs hydrogen quickly at room temperature:^[3]

3 B₂Cl₄ + 3 H₂ → B₂H₆ + 4 BCl₃

With boranes, it replaces a hydrogen to form dichloroborane(3) and a polyhedral dichloroborane. Heat induces disproportionation back to boron trichloride and a polyhedral boron(I) chloride.^[4]

References

^ ^a ^b P. L. Timms (1972). Low Temperature Condensation. Academic Press. p. 143. ISBN 0-12-023614-1. {{cite book}}: |work= ignored (help)
^ Timms, Peter L. (1979). "Tetrachlorodiborane(4) (Diboron Tetrachloride)". Inorganic Syntheses. Vol. 19. pp. 74–78. doi:10.1002/9780470132500.ch14. ISBN 9780470132500.
^ ^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.
^ ^a ^b Morrison, John A. (1991-01-01). "Chemistry of the polyhedral boron halides and the diboron tetrahalides". Chemical Reviews. 91 (1): 35–48. doi:10.1021/cr00001a003. ISSN 0009-2665.
^ 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.

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[AICR-1] 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.

[Urry2-3] 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.

[:0-4] Morrison, John A. (1991-01-01). "Chemistry of the polyhedral boron halides and the diboron tetrahalides". Chemical Reviews. 91 (1): 35–48. doi:10.1021/cr00001a003. ISSN 0009-2665.

[Urry1-5] 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.

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