Boron monofluoride

Boron monofluoride  Names

Other names

Boron fluoride

Boron(I) fluoride
Fluoroboronene

Fluoroborylene

Identifiers

CAS Number

* 13768-60-0 Y

3D model (JSmol)

* Interactive image
* Interactive image
* Interactive image

ChemSpider |

* 4891729 Y

ECHA InfoCard | 100.033.970
EC Number |

* 237-383-0

PubChem CID

* 6336604

UNII |

* N01K2O1ZJH Y

CompTox Dashboard (EPA)

* DTXSID501317099

InChI

* InChI=1S/BF/c1-2 Y

Key: YFSQMOVEGCCDJL-UHFFFAOYSA-N Y

SMILES

* [BH0]F

* [B-]=[F+]

* [B-2]#[F+2]

Properties

Chemical formula

| BF
Molar mass | 29.81 g·mol−1
Thermochemistry

Std molar
entropy (S⦵298)

| 200.48 J K−1 mol−1

Std enthalpy of
formation (ΔfH⦵298)

| 115.90 kJ mol−1
Related compounds

Related isoelectronic 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 their standard state (at 25 °C [77 °F], 100 kPa).

Infobox references

Chemical compound

Boron monofluoride or fluoroborylene is a chemical compound with the formula BF, one atom of boron and one of fluorine. It is an unstable gas, but it is a stable ligand on transition metals, in the same way as carbon monoxide. It is a subhalide, containing fewer than the normal number of fluorine atoms, compared with boron trifluoride. It can also be called a borylene, as it contains boron with two unshared electrons. BF is isoelectronic with carbon monoxide and dinitrogen; each molecule has 14 electrons.[1]

## Structure

[edit]

The experimental B-F bond length is 1.26267 Å.[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 computed bond order for 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

[edit]

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

## Properties

[edit]

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] The spectroscopic constants vibrational frequency ωe of BF+ (X 2Σ+) is 1765 cm−1 and for neutral BF (X 1Σ+) it is 1402.1 cm−1.[2][9] The anharmonicity of BF is 11.84 cm−1.[9]

## Reactions

[edit]

BF can react with itself to form polymers of boron containing fluorine with between 10 and 14 boron atoms. BF reacts with BF3 to form B2F4. BF and B2F4 further combine to form B3F5. B3F5 is 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 with 2-butyne forming 1,4-difluoro-2,3,5,6-tetramethyl-1,4-diboracyclohexadiene. Also, it reacts with acetylene to 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 with C2F4 or SiF4.[2] BF does react with arsine, carbon monoxide, phosphorus trifluoride, phosphine, and phosphorus trichloride to 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 with nitrogen dioxide BF + NO2 → OBF \+ NO.[10]

## Ligand

[edit]

A naïve analysis would suggest that BF is isoelectronic with carbon monoxide (CO) and so could form similar compounds to metal carbonyls. As discussed above (see § Structure), BF has a much lower bond order, so that the valence shell around boron is unfilled. Consequently, BF as a ligand is much more Lewis acidic; it tends to form higher-order bonds to metal centers, and can also bridge between two or three metal atoms (μ2 and 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 of BF3 that decompose once coordinated.

In a 1968 conference report, Kämpfer et al claimed to produce Fe(BF)(CO)4 via reaction of B2F4 with Fe(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 BF coordinated to a transition element is due to Vidovic and Aldrige, who produced [(C5H5)Ru(CO)2]2(μ2-BF) (with BF bridging both ruthenium atoms) 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 B2F4 and 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, by sterically hindering the formation of a dimer. In the molecule, boron is double-bonded to iron.[16]

FBScF2, FBYF2, FBLaF2, and FBCeF2 have been prepared in a solid neon matrix by reacting atomic metals with boron trifluoride.[17]

## References

[edit]

1. ^ a b Hildenbrand, 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. ^ a b c d e f g h i Vidovic, 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. ISSN 0022-2852.
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. PMID 25531385.
7. ^ a b c Timms, P. L. (1972). "Low Temperature Condensation". Advances in Inorganic Chemistry and Radiochemistry. Academic Press. p. 143\. ISBN 0-12-023614-1.
8. ^ Eyring, Leroy (1967). Advances in High Temperature Chemistry volume 1. Academic Press. p. 70\. ISBN 9781483224343.
9. ^ a b Dyke, John M.; Kirby, Colin; Morris, Alan (1983). "Study of the ionization process BF+ (X 2Σ+ ) ← BF(X 1Σ+ ) 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. PMID 20143841.
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 nucleophile Na[CpRu(CO)2] (Cp, cyclopentadienyl; [C5H5]−) reacts with boron trifluoride diethyl etherate (BF·
3Et
2O) with the formal loss of two equivalents of sodium fluoride (NaF) to produce the bridging BF complex ((μ2-BF)[CpRu(CO)2]2) (20). The latter is the only crystallographically characterized compound in which BF functions as a ligand to a metal center."
14. ^ a b Xu, 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. PMID 19373822.
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. PMID 30872521. S2CID 78094683.
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.

* v
* t
* e

Boron compounds

Boron pnictogenides|

* BAs
* BN
* BP

Boron halides|

* BBr3
* BCl3
* BF
* BFO
* BF3
* BI3
* B2F4
* B2Cl4

Acids|

* B(NO3)3
* B(OH)3
* BPO4
* B2(OH)4
* BH3O

Boranes|

* BH3
* B2H4
* B2H6
* BH3NH3
* B4H10
* B5H9
* B5H11
* B6H10
* B6H12
* B10H14
* B18H22

Boron oxides and sulfides|

* BO
* B2O3
* B2S3
* B6O

Carbides|

* B4C

Organoboron compounds|

* (BH2Me)2
* BMe3
* BEt3
* Ac4(BO3)2
* COBH3

* v
* t
* e

Fluorine compounds

* v
* t
* e

Salts and covalent derivatives of the fluoride ion

| HF |  |  |  | ?HeF2

|
|
|
|

LiF | BeF2 | BF
BF3
B2F4
+BO3 | CF4
CxFy
+CO3 | NF3
FN3
N2F2

N2F4
NF2
?NF5

+NO3 | OF2
O2F2

O3F2
O4F2
?OF4 | F2 | Ne
NaF | MgF2 | AlF
AlF3 | SiF4 | P2F4
PF3
PF5
+PO4 | S2F2
SF2
S2F4
SF3
SF4
S2F10
SF6
+SO4 | ClF
ClF3
ClF5 | ?ArF2
?ArF4
KF | CaF
CaF2 |  | ScF3 | TiF2
TiF3
TiF4 | VF2
VF3
VF4
VF5 | CrF2
CrF3
CrF4
CrF5
?CrF6 | MnF2
MnF3
MnF4
?MnF5 | FeF2
FeF3
FeF4 | CoF2
CoF3
CoF4 | NiF2
NiF3
NiF4 | CuF
CuF2
?CuF3 | ZnF2 | GaF2
GaF3 | GeF2
GeF4 | AsF3
AsF5 | Se2F2
SeF4
SeF6
+SeO3 | BrF
BrF3
BrF5 | KrF2
?KrF4
?KrF6
RbF | SrF
SrF2 |  | YF3 | ZrF2
ZrF3
ZrF4 | NbF4
NbF5 | MoF4
MoF5
MoF6 | TcF4
TcF

TcF6 | RuF3
RuF

RuF5
RuF6 | RhF3
RhF4
RhF5
RhF6 | PdF2
Pd[PdF6]
PdF4
?PdF6 | Ag2F
AgF
AgF2
AgF3 | CdF2 | InF
InF3 | SnF2
SnF4 | SbF3
SbF5 | TeF4
?Te2F10
TeF6
+TeO3 | IF
IF3
IF5
IF7
+IO3 | XeF2
XeF4
XeF6
?XeF8
CsF | BaF2 |  | LuF3 | HfF4 | TaF5 | WF4
WF5
WF6 | ReF4
ReF5
ReF6
ReF7 | OsF4
OsF5
OsF6
?OsF

?OsF
8 | IrF2
IrF3
IrF4
IrF5
IrF6 | PtF2
Pt[PtF6]
PtF4
PtF5
PtF6 | AuF
AuF3
Au2F10
?AuF6
AuF5•F2 | Hg2F2
HgF2
?HgF4 | TlF
TlF3 | PbF2
PbF4 | BiF3
BiF5 | ?PoF2
PoF4
PoF6 | AtF
?AtF3
?AtF5 | RnF2
?RnF

?RnF

FrF  | RaF2 |  | LrF3 | Rf  | Db  | Sg  | Bh  | Hs  | Mt  | Ds  | Rg  | Cn  | Nh  | Fl  | Mc  | Lv  | Ts  | Og
| ↓  |  |
| LaF3 | CeF3
CeF4 | PrF3
PrF4 | NdF2
NdF3
NdF4 | PmF3 | SmF
SmF2
SmF3 | EuF2
EuF3 | GdF3 | TbF3
TbF4 | DyF2
DyF3
DyF4 | HoF3 | ErF3 | TmF2
TmF3 | YbF2
YbF3
AcF3 | ThF3
ThF4 | PaF4
PaF5 | UF3
UF4
UF5
UF6 | NpF3
NpF4
NpF5
NpF6 | PuF3
PuF4
PuF5
PuF6 | AmF2
AmF3
AmF4
?AmF6 | CmF3
CmF4
?CmF6 | BkF3
BkF
4 | CfF3
CfF4 | EsF3
EsF4
?EsF6 | Fm  | Md  | No

PF−6, AsF−6, SbF−6 compounds|

* AgPF6
* KAsF6
* LiAsF6
* NaAsF6
* HPF6
* HSbF6
* NH4PF6
* LiSbF6
* KPF6
* KSbF6
* LiPF6
* NaPF6
* NaSbF6
* TlPF6

AlF2−5, AlF3−6 compounds|

* (NH4)3[AlF6]
* Cs2AlF5
* Li3AlF6
* K3AlF6
* Na3AlF6

chlorides, bromides, iodides
and pseudohalogenides|

* BaClF
* SiIBrClF
* CFN
* ClFO2

SiF2−6, GeF2−6 compounds|

* BaSiF6
* BaGeF6
* (NH4)2SiF6
* Na2[SiF6]
* K2[SiF6]
* Li2GeF6
* Li2SiF6

Oxyfluorides|

* BrOF3
* BrO2F
* BrO3F
* LaOF
* ThOF2
* VOF

* TcO

* WOF

* YOF
* ClOF3
* ClO2F3

Organofluorides|

* CBrF3
* CBr2F2
* CBr3F
* CClF3
* CCl2F2
* CCl3F
* CF2O
* CF3I
* CHF3
* CH2F2
* CH3F
* C2Cl3F3
* C2H3F
* C6H5F
* C7H5F3
* C15F33N
* C3H5F
* C6H11F

with transition metal,
lanthanide, actinide, ammonium|

* VOF3
* CrOF4
* CrF2O2
* NH4F
* (NH4)3CrF6
* (NH4)3GaF6
* (NH4)2GeF6
* (NH4)3FeF6
* (NH4)3InF6
* NH4NbF6
* (NH4)2SnF6
* NH4TaF6
* (NH4)3VF6
* (NH4)2ZrF6
* CsXeF7
* Li2SnF6
* Li2TiF6
* LiWF6
* Li2ZrF6
* K2TiF6
* Rb2TiF6
* Na2TiF6
* Na2ZrF6
* K2NbF7
* K2TaF7
* K2ZrF6
* UO2F2

nitric acids|

* FNO
* FNO2
* FNO3

bifluorides|

* KHF2
* NaHF2
* NH4HF2

thionyl, phosphoryl,
and iodosyl|

* F2OS
* F3OP
* PSF3
* IOF3
* IO3F
* IOF5
* IO2F
* IO2F3

Chemical formulas
*[CID]: Compound ID
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