Wikipedia

Boron monofluoride

Boron monofluorideorfluoroboryleneis a chemical compound with the formula BF, one atom ofboronand one offluorine.It is an unstable gas, but it is a stableligandontransition metals,in the same way ascarbon monoxide.It is asubhalide,containing fewer than the normal number of fluorine atoms, compared withboron trifluoride.It can also be called aborylene,as it contains boron with two unshared electrons. BF isisoelectronicwith carbon monoxide anddinitrogen;each molecule has 14 electrons.[1]

Boron monofluoride
Names
Other names
Boron fluoride

Boron(I) fluoride
Fluoroboronene

Fluoroborylene
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.033.970Edit this at Wikidata
EC Number
  • 237-383-0
UNII
  • InChI=1S/BF/c1-2checkY
    Key: YFSQMOVEGCCDJL-UHFFFAOYSA-NcheckY
  • [BH0]F
  • [B-]=[F+]
  • [B-2]#[F+2]
Properties
BF
Molar mass 29.81g·mol−1
Thermochemistry
200.48 J K−1mol−1
115.90 kJ mol−1
Related compounds
Carbon monoxide,dinitrogen,nitrosonium,cyanide,acetylide
Related compounds
 aluminium monofluoride
aluminium monochloride
aluminium monoiodide
gallium monofluoride
Except where otherwise noted, data are given for materials in theirstandard state(at 25 °C [77 °F], 100 kPa).

Structure

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The experimental B–Fbond lengthis 1.26267Å.[2][3][4]Despite being isoelectronic to the triple-bonded species CO and N2,computational studies generally agree that the true bond order is much lower than 3. One reported computedbond orderfor the molecule is 1.4, compared with 2.6 for CO and 3.0 for N2.[5]

Lewis dot diagram structures show three formal alternatives for describing bonding in boron monofluoride.

BF is unusual in that the dipole moment is inverted with fluorine having a positive charge even though it is the more electronegative element. This is explained by the 2sp orbitals of boron being reoriented and having a higher electron density.Backbonding,or the transfer of π orbital electrons for the fluorine atom, is not required to explain the polarization.[6]

Preparation

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Boron monofluoride can be prepared by passingboron trifluoridegas at 2000 °C over a boron rod. It can be condensed at liquid nitrogen temperatures (−196 °C).[7]

Properties

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Boron monofluoride molecules have a dissociation energy of 7.8 eV or heat of formation −27.5±3 kcal/mole[1][8]or 757±14 kJ/mol.[2]The first ionization potential is 11.115 eV.[2]Thespectroscopic constantsvibrational frequency ωeof BF+(X2Σ+) is 1765 cm−1and for neutral BF (X1Σ+) it is 1402.1 cm−1.[2][9]The anharmonicity of BF is 11.84 cm−1.[9]

Reactions

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BF can react with itself to form polymers of boron containing fluorine with between 10 and 14 boron atoms. BF reacts withBF3to formB2F4.BF and B2F4further combine to form B3F5.B3F5is unstable above −50 °C and forms B8F12.This substance is a yellow oil.[7]

BF reacts with acetylenes to make the 1,4-diboracyclohexadiene ring system. BF can condense with2-butyneforming 1,4-difluoro-2,3,5,6-tetramethyl-1,4-diboracyclohexadiene. Also, it reacts withacetyleneto make 1,4-difluoro-1,4-diboracyclohexadiene.[7]Propene reacts to make a mix of cyclic and non-cyclic molecules which may contain BF or BF2.[2]

BF hardly reacts withC2F4orSiF4.[2]BF does react witharsine,carbon monoxide,phosphorus trifluoride,phosphine,andphosphorus trichlorideto make adducts like (BF2)3B•AsH3,(BF2)3B•CO, (BF2)3B•PF3,(BF2)3B•PH3,and (BF2)3B•PCl3.[2]

BF reacts with oxygen: BF + O2→OBF+ O; with chlorine: BF + Cl2→ ClBF + Cl; and withnitrogen dioxideBF + NO2→OBF+ NO.[10]

Ligand

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A naïve analysis would suggest that BF is isoelectronic with carbon monoxide (CO) and so could form similar compounds tometal carbonyls.As discussed above (see§ Structure), BF has a much lower bond order, so that thevalence shellaround boron is unfilled. Consequently, BF as a ligand is much moreLewis acidic;it tends to form higher-order bonds to metal centers, and can also bridge between two or three metal atoms (μ2and μ3).[11]

Working with BF as a ligand is difficult due to its instability in the free state.[12]Instead, most routes tend to use derivatives ofBF3that decompose oncecoordinated.

In a 1968 conference report, Kämpferet alclaimed to produce Fe(BF)(CO)4via reaction ofB2F4withFe(CO)5,but modern chemists have not reproduced the synthesis, and the original compound has no crystallographic characterization.[13][14]The first modern demonstration of BFcoordinatedto atransition elementis due to Vidovic and Aldrige, who produced[(C5H5)Ru(CO)2]2(μ2-BF)(with BF bridging bothrutheniumatoms) in 2009.[15]To make the compound, Vidovic and Aldridge reacted NaRu(CO)2(C5H5) with (Et2O)·BF3;the boron monofluoride ligand then formed in-place.[14]

Vidovic and Aldridge also developed a substance with the formula (PF3)4FeBF by reacting iron vapour with B2F4and PF3.[2]Hafnium, thorium, titanium, and zirconium can form a difluoride with a BF ligand at the low temperature of 6K. These come about by reacting the atomic metal with BF3.[2]

The first fully characterized molecule featuring BF as a terminal ligand was synthesized by Drance and Figueroa in 2019, bysterically hinderingthe formation of a dimer. In the molecule, boron isdouble-bondedtoiron.[16]

FBScF2, FBYF2,FBLaF2,and FBCeF2have been prepared in a solid neon matrix by reacting atomic metals with boron trifluoride.[17]

References

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  1. ^abHildenbrand, Donald L.; Murad, Edmond (1965). "Dissociation Energy of Boron Monofluoride from Mass-Spectrometric Studies".The Journal of Chemical Physics.43(4): 1400.Bibcode:1965JChPh..43.1400H.doi:10.1063/1.1696932.
  2. ^abcdefghiVidovic, Dragoslav; Aldridge, Simon (2011). "Coordination chemistry of group 13 monohalides".Chemical Science.2(4): 601.doi:10.1039/C0SC00508H.
  3. ^Nesbet, R. K. (1964). "Electronic Structure of N2, CO, and BF".The Journal of Chemical Physics.40(12): 3619–3633.Bibcode:1964JChPh..40.3619N.doi:10.1063/1.1725063.
  4. ^Cazzoli, G.; Cludi, L.; Degli Esposti, C.; Dore, L. (1989). "The millimeter and submillimeter-wave spectrum of boron monofluoride: Equilibrium structure".Journal of Molecular Spectroscopy.134(1): 159–167.Bibcode:1989JMoSp.134..159C.doi:10.1016/0022-2852(89)90138-0.ISSN0022-2852.
  5. ^Martinie, R. J.; Bultema, J. J.; van der Wal, M. N.; Burkhart, B. J.; van der Griend, D. A. & de Kock, R. L. (2011). "Bond Order and Chemical Properties of BF, CO, and N2".Journal of Chemical Education.88(8): 1094–1097.Bibcode:2011JChEd..88.1094M.doi:10.1021/ed100758t.
  6. ^Fantuzzi, Felipe; Cardozo, Thiago Messias; Nascimento, Marco Antonio Chaer (28 May 2015). "Nature of the Chemical Bond and Origin of the Inverted Dipole Moment in Boron Fluoride: A Generalized Valence Bond Approach".The Journal of Physical Chemistry A.119(21): 5335–5343.Bibcode:2015JPCA..119.5335F.doi:10.1021/jp510085r.PMID25531385.
  7. ^abcTimms, P. L. (1972)."Low Temperature Condensation".Advances in Inorganic Chemistry and Radiochemistry.Academic Press. p. 143.ISBN0-12-023614-1.
  8. ^Eyring, Leroy (1967).Advances in High Temperature Chemistry volume 1.Academic Press. p. 70.ISBN9781483224343.
  9. ^abDyke, John M.; Kirby, Colin; Morris, Alan (1983). "Study of the ionization process BF+(X2Σ+) ← BF(X1Σ+) by high-temperature photoelectron spectroscopy ".J. Chem. Soc., Faraday Trans. 2.79(3): 483–490.doi:10.1039/F29837900483.
  10. ^Light, G. C.; Herm, R. R.; Matsumoto, J. H. (November 1985)."Kinetics of some gas-phase elementary reactions of boron monofluoride"(PDF).The Journal of Physical Chemistry.89(23): 5066–5074.doi:10.1021/j100269a036.Archived(PDF)from the original on June 1, 2022.
  11. ^Xu, Liancai; Li, Qian-shu; Xie, Yaoming; King, R. Bruce; Schaefer, Henry F. (15 March 2010). "Major Difference between the Isoelectronic Fluoroborylene and Carbonyl Ligands: Triply Bridging Fluoroborylene Ligands in Fe3(BF)3(CO)9 Isoelectronic with Fe3(CO)12".Inorganic Chemistry.49(6): 2996–3001.doi:10.1021/ic902511m.PMID20143841.
  12. ^Xu, Liancai; Li, Qian-shu; King, R. Bruce (May 2012). "Fluoroborylene ligands in binuclear ruthenium carbonyls: Comparison with their iron analogues".Polyhedron.38(1): 44–49.doi:10.1016/j.poly.2012.02.003.
  13. ^Drance et al. 2019:"Previously, Vidovic and Aldridge reported that two equivalents of the ruthenium-based nucleophileNa[CpRu(CO)2](Cp,cyclopentadienyl;[C5H5]−) reacts with boron trifluoride diethyl etherate (BF·
    3    Et
    2    O    ) with the formal loss of two equivalents of sodium fluoride (NaF) to produce the bridgingBFcomplex ((μ2-BF)[CpRu(CO)2]2) (20). The latter is the only crystallographically characterized compound in whichBFfunctions as a ligand to a metal center. "
  14. ^abXu, L.; Li, Q.-S.; Xie, Y.; King, R. B.; Schaefer, H. F. III (2010). "Binuclear fluoroborylene manganese carbonyls".Inorganica Chimica Acta.363(13): 3538–3549.doi:10.1016/j.ica.2010.07.013.
  15. ^Vidovic, Dragoslav; Aldridge, Simon (4 May 2009). "Coordination and Activation of the BF Molecule".Angewandte Chemie.121(20): 3723–3726.Bibcode:2009AngCh.121.3723V.doi:10.1002/ange.200901022.PMID19373822.
  16. ^Drance, M. J.; Sears, J. D.; Mrse, A. M.; Moore, C. E.; Rheingold, A. L.; Neidig, M. L.; Figueroa, J. S. (2019)."Terminal Coordination of Diatomic Boron Monofluoride to Iron".Science.363(6432): 1203–1205.Bibcode:2019Sci...363.1203D.doi:10.1126/science.aaw6102.PMID30872521.S2CID78094683.
  17. ^Xu, Bing; Li, Li; Pu, Zhen; Yu, Wenjie; Li, Wenjing; Wang, Xuefeng (18 February 2019). "Fluoroborylene Complexes FBMF 2 (M = Sc, Y, La, Ce): Matrix Infrared Spectra and Quantum Chemical Calculations".Inorganic Chemistry.58(4): 2363–2371.doi:10.1021/acs.inorgchem.8b02801.
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