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| Names | |||
|---|---|---|---|
| Preferred IUPAC name Diboron tetrachloride | |||
| Systematic IUPAC name Tetrachlorodiborane(4) | |||
| Identifiers | |||
3D model (JSmol) | |||
| ChemSpider | |||
| UNII | |||
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| Properties | |||
| 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 | |||
| 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 theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Diboron tetrachloride is atetrahalodiboranechemical compound with theformula B2Cl4. It is a colorless liquid.[1]
The modern synthesis involves the chlorination ofdiboron tetrabromide bygallium(III) chloride.[2]
It can also be formed by the electricaldischarge procedure of boron trichloride at low temperatures:[1][3]
The most efficient synthesis technique uses no dechlorinating metal, instead passingradio-frequencyAC current through gaseous boron trichloride.[4]
The molecular structure of diboron tetrachloride, B2Cl4, was determined bygas electron diffraction.[5] The molecules haveD2dsymmetry, i.e. the two planar BBCl2 units are perpendicular to each other (torsion angle Cl-B-B-Cl 90°). The B-B distance is 1.70(4) Å, the B-Cl distance is 1.750(5) Å, the Cl-B-Cl angle is 118.7(3)°. B2Cl4 thus differs significantly fromB2F4, which is a planar molecule overall.
The compound is used as areagent for the synthesis oforganoboron compounds. For instance, diboron tetrachlorideadds toethylene:[6]
Diboron tetrachloride absorbshydrogen quickly atroom temperature:[3]
Withboranes, it replaces a hydrogen to form dichloroborane(3) and a polyhedral dichloroborane. Heat inducesdisproportionation back toboron trichloride and a polyhedral boron(I) chloride.[4]
