Diboron tetrafluoride

Diboron tetrafluoride is the inorganic compound with the formula (BF₂)₂, classed as a tetrahalodiborane. A colorless gas, the compound has a halflife of days at room temperature. It is the most stable of the diboron tetrahalides,^[1] and does not appreciably decompose under standard conditions.^[2]

Diboron tetrafluoride

Names
Preferred IUPAC name Diboron tetrafluoride
Systematic IUPAC name Tetrafluorodiborane(4)
Identifiers
CAS Number	13965-73-6
3D model (JSmol)	Interactive image
ChemSpider	123165
PubChem CID	139653
CompTox Dashboard (EPA)	DTXSID80161143
InChI InChI=1S/B2F4/c3-1(4)2(5)6 Key: WUWOPJNIAKTBSJ-UHFFFAOYSA-N
SMILES FB(F)B(F)F
Properties
Chemical formula	B2F4
Molar mass	97.61 g·mol−1
Appearance	Colorless gas
Density	4.3 kg/m3 (gas)
Melting point	−56 °C (−69 °F; 217 K)
Boiling point	−34 °C (−29 °F; 239 K)
Thermochemistry
Heat capacity (C)	79.1 J/mol K
Std molar entropy (S⦵298)	317.3 J/mol K
Std enthalpy of formation (ΔfH⦵298)	−1440.1 kJ/mol
Gibbs free energy (ΔfG⦵)	−1410.4 kJ/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Structure and bonding

Diboron tetrafluoride is a planar molecule with a B-B bond distance of 172 pm.^[1] Although it is electron-deficient, the unsaturated boron centers are stabilized by pi-bonding with the terminal fluoride ligands. The compound is isoelectronic with oxalate.

Synthesis and reactions

Diboron tetrafluoride can be formed by treating boron monofluoride with boron trifluoride at low temperatures, taking care not to form higher polymers.^[3] Alternatively, diboron tetrachloride can be fluorinated with antimony trifluoride.^[2]

Addition of diboron tetrafluoride to Vaska's complex was employed to produce an early example of a transition metal boryl complex:^[4]

2 B₂F₄ + IrCl(CO)(PPh₃)₂ → Ir(BF₂)₃(CO)(PPh₃)₂ + ClBF₂

Historical literature

• Louis Trefonas and William N. Lipscomb (1958). "Crystal and Molecular Structure of Diboron Tetrafluoride, B₂F₄". J. Chem. Phys. 28 (1): 54–55. Bibcode:1958JChPh..28...54T. doi:10.1063/1.1744079.
• Gayles, J. N.; Self, J. (1964). "Infrared Spectrum of Diboron Tetrafluoride in the Gaseous and Solid States". Journal of Chemical Physics. 40 (12): 3530–3539. Bibcode:1964JChPh..40.3530G. doi:10.1063/1.1725048.
• A. K. Holliday; F. B. Taylor (1964). "Diboron tetrafluoride. Part II. Reactions with some oxides and organometallic compounds". J. Chem. Soc.: 2731–2734. doi:10.1039/JR9640002731.
• Vernon H. Dibeler; Susan K. Liston (1968). "Mass-spectrometric study of photoionization. XII. Boron trifluoride and diboron tetrafluoride". J. Chem. Soc. 7 (9): 1742–1746. doi:10.1021/ic50067a010.