C-F Bond Activation of a Perfluorinated Ligand Leading to Nucleophilic Fluorination of an Organic Electrophile

Article abstract of DOI:10.1021/acs.organomet.0c00176

We report a fluorine transfer reaction in which fluorine from a perfluorinated ligand undergoes C-F bond activation and transfers to an electrophile, resulting in the formation of a new fluorinated product and dimerization of the monodefluorinated complex. Treatment of [(η5,κ2C-C5Me4CH2C6F5CH2NC3H2NMe)-RhCl] with the organic electrophile, toluoyl chloride, resulted in the formation of a rhodium(III) metallocycle via C-F bond activation assisted defluorinative coupling. Fission of the C-F bond liberated nucleophilic fluoride, which converted acyl chloride to acyl fluoride. The overall reaction was monitored using a multivariate analysis approach in real time.

Full text of DOI:10.1021/acs.organomet.0c00176

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Article
C−F Bond Activation of a Perfluorinated Ligand Leading to
Nucleophilic Fluorination of an Organic Electrophile
Patrick J. Morgan, Magnus W. D. Hanson-Heine, Hayden P. Thomas, Graham C. Saunders,*
Andrew C. Marr,* and Peter Licence*
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ABSTRACT: We report a fluorine transfer reaction in which fluorine from
a perfluorinated ligand undergoes C−F bond activation and transfers to an
electrophile, resulting in the formation of a new fluorinated product and
dimerization of the monodefluorinated complex. Treatment of [(η5,κ2C−
C5Me4CH2C6F5CH2NC3H2NMe)−RhCl] with the organic electrophile,
toluoyl chloride, resulted in the formation of a rhodium(III) metallocycle
via C−F bond activation assisted defluorinative coupling. Fission of the C−
F bond liberated nucleophilic fluoride, which converted acyl chloride to
acyl fluoride. The overall reaction was monitored using a multivariate
analysis approach in real time.
C−F activation at a metal center has become a powerful tool
for the introduction of new functionality at the site of C−F
bonds.38−44 This process predominantly proceeds via the
oxidative addition of the fluoroorganic across the metal center
forming a new metal−fluorine bond, followed by the
scavenging of fluorine by thermodynamic sinks such as H−F,
Si−F, or B−F bonds. Transition metal mediated fluorination
routes often rely on the formation of a transition metal−
fluorine bond,45−47 which renders fluorine nucleophilic,
facilitating its reaction with an electrophile. Both of these
routes to activated fluorine rely on the interaction of the
fluorinated precursor with the metal center. The generation of
activated fluorine distant from the metal center within an
organometallic complex is highly unusual, as is the generation
of nucleophilic fluorine from the activation of a C−F bond.48
Ogiwara and Sakai have recently highlighted a metal-based
fluorine transfer reaction where benzoyl fluoride is used as a
nucleophilic fluorination reagent. Oxidative addition across a
palladium center facilitates acyl exchange with anhydrides to
yield acyl fluorides and represents a possible use of the
fluorinated products produced within this work.49 The current
focus of our work revolves around the reactivity of complexes
bearing a poly- or perfluorinated moiety with organic
INTRODUCTION
■
The activation of carbon−fluorine bonds, once thought to be
inert to most chemical manipulations1 in part due to high bond
dissociation energies,2 is gradually becoming synthetically
useful and is no longer the insurmountable challenge it once
represented. The ability to cleave C−F bonds is becoming
increasingly important due to our growing awareness of the
negative environmental impact of organofluorine, and their
persistent nature within the local environment.3−5 The
potential harmful environmental effects of organofluorine has
been highlighted by the bioaccumulation of fluorinated
pharmaceuticals6,7 or the emission of CFCs and the dangers
these hazardous chemicals pose.8 One way of dealing with
issues related to fluorinated waste is to recycle the fluorine.
Some persistent fluorinated pollutants such as SF6 and
fluoroform have already undergone valorization through
fluorine or trifluoromethane transfer.9,10
The field of C−F activation, which started as a series of one-
off transition metal organometallic reactions,11−16 has
developed in recent years into a rapidly expanding field of
research.17−24 This expansion has been driven by the need for
greener fluorination methodologies (as outlined by the ACS
Green Chemistry Institute Pharmaceutical Roundtable)25,26
and the success of fluorinated pharmaceuticals,27,28 the growth
of which can be partially attributed to the greater accessibility
of methodologies available to incorporate a fluorine atom into
their molecular structure. New synthetic pathways and
strategies are constantly being proposed to prepare fluorinated
building blocks, which have been discussed previously.29−37
Received: March 12, 2020
https://dx.doi.org/10.1021/acs.organomet.0c00176
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Figure 1. (a) Previous work on silver-particle-induced cyclometalation of rhodium complex, 1. (b) This work on C−F bond activation induced
defluorinative coupling, forming 2, with fluorine transfer to organic electrophiles.
19
Figure 2. (left, top) Transfer fluorination induced metallocycle formation of 2, including F NMR spectra (left, below) showing four fluorine
environments: −117.43 ppm (red), −131.12 ppm (purple), −135.12 ppm (orange), and −160.86 ppm (green). (right, top) Silver-particle-induced
19
ortho-metalation of [Cp*RhCl(κC2-MeNC3H2NCH2C6F4)], 3, including F NMR spectra (right, below) showing four fluorine environments:
−110.35 ppm (purple), −146.83 ppm (orange), −157.99 ppm (green), and −164.44 ppm (blue).
electrophiles. Reported here is the discovery of a concerted C−
F bond activation and formation reaction, where nucleophilic
fluorine is generated via the activation of a C−F bond from a
noninnocent perfluorinated ligand resulting in the fluorination
of an electrophile and the formation of a new monode-
fluorinated bimetallic rhodacycle.
bond formation in an external substrate initiated by the
treatment of [(η5,κ2C−C5Me4CH2C6F5CH2NC3H2NMe)−
RhCl],50 1, with the organic electrophile toluoyl chloride.
During the course of the reaction, the fluoride liberated
following C−F activation reacted with the electrophile toluoyl
chloride to give the fluorinated product, toluoyl fluoride, and
new complex, 2 (Figure 1). While examples of intramolecular
C−F-activated metallacycle formation are known,16,51−57 to
our knowledge this represents the first account of fluorine
transfer via C−F activation of a perfluorinated ligand resulting
in the fluorination of an external organic substrate, without the
formation of deactivated fluorine bonds such as H−F, Si−F, or
B−F, and without producing fluorine-containing waste.
RESULTS AND DISCUSSION
■
The transfer of fluorine from a perfluorinated moiety of an
organometallic complex onto a nonfluorinated substrate was
demonstrated. The reaction was spontaneous and occurred
under mild conditions. The reaction occurred via the
concurrent C−F bond activation, fluorine transfer, and C−F
B
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Treatment of 1 with a 2 fold excess of toluoyl chloride in
acetonitrile at room temperature resulted in fluorine transfer
from 1 to form toluoyl fluoride, over the course of 1 week.
Subsequent NMR analysis resulted in the detection of a new
rhodium complex with four distinct fluorine environments
within the 19F NMR, with fluorine resonances of equal
integration at δ −117.35, −131.84, −135.31, and −161.06
ppm. The fluorine resonance for toluoyl fluoride at δ 17.43
ppm was in a 1:1 ratio with the newly formed rhodium
complex (see Figure S3).
Following our recent observation of C−F bond activation
induced cyclometalation forming [Cp*IrCl(κC2-
MeNC3H2NCH2C6F4)],51 it was initially thought that a similar
process was occurring for the rhodium analogue, where C−F
bond activation at the C−F bond α to the metal center,
followed by rearomatization of the phenyl ring resulted in the
formation of [Cp*RhCl(κC2-MeNC3H2NCH2C6F4)], 3 (Fig-
ure 2). However, the 19F NMR spectral signature of the new
four-fluorine-environment rhodium complex observed upon
reaction with toluoyl fluoride (Figure 2a) differed from that
observed for [Cp*IrCl(κC2-MeNC3H2NCH2C6F4)]. This
deviation between the 19F NMR spectrum for the new four-
fluorine-environment rhodium complex and the iridium ortho-
metalated complex was larger than expected if C−F bond
activation induced cyclometalation of the rhodium species had
occurred. Subsequent synthesis and characterization of
[Cp*RhCl(κC2-MeNC3H2NCH2C6F4)], 3 (Figure 2b),
proved that 3 was not the identity of the new complex
observed. Therefore, further complementary studies were
required in order to deduce the structure of the new rhodium
complex, 2.
chloride as a substrate. The fluorination of additional
substrates and functional groups has been summarized in
Table 1. As a 10-fold excess of the electrophile was used,
conversion has been calculated with respect to the formation of
2, which is in a roughly 1:1 ratio with the fluorinated organic
product, and the 19F NMR yield of the product against an
internal standard. Of particular interest was the fluorination of
anhydrides upon treatment with 1 resulting in the formation of
acyl fluorides. Transfer fluorination occurred more rapidly
using anhydrides as the substrate compared to acyl chlorides,
with detection of the fluorinated product after only 10 min
(entries 1−3). Acetic anhydride rapidly underwent fluorination
resulting in 11% yield of acetyl fluoride and a 12.5% conversion
to 2 over 10 min. Benzoic anhydride showed similar reactivity
with 47.7% yield of the fluorinated product after 30 min, with
50% conversion from 1 to 2 observed (Table 1, entry 2).
Butyric anhydride underwent fluorination to butyryl fluoride
over the course of 20 h resulting in 28.3% conversion of 2
(Table 1, entry 3). The reactivity of anhydrides is in contrast to
acyl chlorides, for which the fluorinated product was identified
after 4 h leading to 18% conversion of toluoyl fluoride after 72
h (Table 1, entry 4). Similar lower activity was observed for
benzoyl chloride (Table 1, entry 5). Taking toluoyl chloride as
an example, the rate of formation of toluoyl fluoride decreased
after 20 h. Monitoring of the reaction showed 12.5% yield after
20 h with 22.8% yield of toluoyl fluoride after 5 days, clearly
showing a reduction in the rate of formation of the fluorinated
product over time. After 5 days, 1 was not observed in solution.
As the concentration of 1 decreases in solution over time, the
rate of formation of the fluorinated product and 2 also
decreases (Figure S11). This is consistent with the rate of
dimer (2) formation becoming increasingly limited by the
concentration of 1. Other transfer fluorination attempts are
listed in Table S1.
The structure of 2 was solved by single-crystal X-ray
diffraction (Figure 3). Work up by elution of the reaction
In situ monitoring of the reaction (Table 1, entry 1) was
carried out using the in situ infrared technique ReactIR.
ReactIR enables the measurement of reaction profiles and
trends, allowing for changes in the composition of a reaction to
be monitored in real time. The IR probe was added to a
Schlenk tube containing 1, acetic anhydride and dry, degassed
acetonitrile under a nitrogen atmosphere. During the course of
the experiment, the C−O band at 1268 cm−1, corresponding to
acetic anhydride substrate, and a C−F band of 1 at 1386 cm−1
reduced in intensity. Meanwhile, a new C−F band
corresponding to acyl fluorides (1346 cm−1) grew in intensity,
proportional to the loss of the C−F bond of 1 (Figure 4, left).
This correlation shows that the fluorine incorporated within
the acyl fluoride product comes from the perfluorinated ligand
of 1, confirming transfer fluorination between a perfluorinated
moiety and organic substrate is occurring. The use of ReactIR
as an in situ monitoring technique for this reaction confirms
the observation of transfer of the fluoride from one substrate to
the other. Similar reactivity was observed for benzoic
anhydride. The time scale of reactivity for toluoyl chloride
was too long for in situ monitoring to be accessible.
Figure 3. Molecular structure of 2. Thermal ellipsoids for the
anisotropic displacement parameters represent 50% probability.
Hydrogen atoms and solvent molecules have been omitted for clarity.
Selected bond distances (Å) and angles (deg) given in Table S3.
mixture with cold ether resulted in the separation of the metal
complex and organic product. Slow evaporation of a saturated
DCM solution of 2 resulted in the formation of single crystals.
2 comprises a bimetallic metallocycle in which the methylene
group of the Cp* ligand of one complex is attached to the
partially fluorinated phenyl ring of the substituted NHC of
another molecule at the site of C−F activation.
Intermolecular defluorinative coupling results in the
formation of 2, liberating nucleophilic fluoride via C−F
activation, which undergoes nucleophilic attack on the organic
electrophile. The aromatization of the polyfluorocyclohexa-1,4-
diene substituent could be key to the formation of 2, as the
conformational change caused by the conversion of the ring to
planar may pull one of the ligands (Cp* or NHC) from the
metal. The fission of the Rh−Cp* bond of 1 would lead to a
Transfer fluorination resulting in the formation of 2 and a
fluorinated product was not restricted to the use of toluoyl
C
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a
Table 1. Transfer Fluorination of Organic Substrates by Fluorine Transfer
a
b
Reaction conditions: 1 (0.0056 mmol), substrate (0.056 mmol) in CD3CN (0.5 mL) under argon at room temperature. Determined by 19F
NMR spectroscopy using α,α,α-trifluorotoluene as internal standard.
Figure 4. (left) Plot of the rate of change of C−F bond fission (1386 cm−1) and C−F bond formation (1346 cm−1) over the course of the reaction
highlighting the correlation between the two linear regression plots. (right) 3D surface plot for reaction of 1 (20 mg) with acetic anhydride (35 μL)
in acetonitrile (5 mL). The peaks associated with the solvent, acetic anhydride, and 1 have been subtracted from the plot to allow for changes over
time to be observed. The changes that occur over time include (from left to right) (a) the cleavage of a C−F bond of 1 at 1386 cm−1, (b) formation
of a new C−F (COF) bond at 1346 cm−1, (c) cleavage of a C−O bond from acetic anhydride at 1268 cm−1, and (d) formation of a new C−O(H)
group as byproduct at 1130 cm−1.
zwitterionic fragment, which when combined with a second
fragment may form 2 (Figure 5a). Conversely removal of the
NHC could form a 16-electron neutral intermediate, which at
first glance would appear more likely (Figure 5b).
Brubaker and Lee noted in their work on photochemical Cp
exchange59 that while photolysis of the metal−Cp bond readily
occurred, thermal exchange occurred slowly resulting in
roughly 10% formation of the exchange products after 1
week. Given that photoexcitation of toluoyl chloride and 1
gives a 40% conversion to toluoyl fluoride over 30 min
compared to the thermal route which initially gave 13%
conversion to toluoyl fluoride over 2 weeks, we propose that a
similar process is occurring. This supports a mechanism
leading to transfer fluorination and the formation of 2 via Rh−
Cp* bond cleavage (Figure 5a). However, photoactivation of
the Rh−NHC bond cannot be ruled out.
Density functional theory (DFT) geometry optimizations,
NMR shifts, and energy and electron density calculations were
performed for 1 and 2 (see Supporting Information section 1.6
for calculation details). The calculated fluorine interaction
energies (Figure 7) indicated that fluorine atoms attached to
the carbon atoms in 1 that are displaced away from the plane
of the ring (bonds 1 and 4) have interaction energies ca. 50 kJ/
mol lower than those of the fluorine atoms attached to the
While metal−Cp* bonds may be difficult to cleave
thermally,58 photoinitiated M−Cp(*) bond migration is a
known process.58−60 To investigate whether photoactivation
may be occurring, toluoyl chloride and 1 were exposed to high-
intensity filtered UV (308 and 360 nm) in a quartz reactor,
under inert, dry conditions. Sampling of the reaction over time
showed the rapid formation of both toluoyl fluoride and 2
within 30 min. UV/vis analysis of samples during this time
showed the decrease in intensity of the absorption peak at 328
nm, the blueshift of the maximum to 252 nm (associated with
1), and the growth of a band at 408 nm, representing 2 (Figure
6). 19F NMR analysis of the reaction mixture shows the
formation of toluoyl fluoride with 40% conversion after 30
min. The quantity of fluorinated product and 2 formed were in
a 1:1 ratio, consistent with the thermal result.
D
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Figure 5. Reaction of 1 with toluoyl chloride (a) showing dimerization of zwitterion following fission of the Rh−Cp* bond or (b) showing
recombination of free NHC to the neutral 16-electron Rh complex, resulting in the formation of 2.
Figure 6. (a) UV/vis plot of the photolysis of 1 with toluoyl chloride over time. (b) Shift of maximum peak to 252 nm. (c) Reduction in intensity
of 330 nm band. (d) Appearance of a new band at 395 nm.
more coplanar carbon atoms (bonds 2, 3, and 5). The fluorine
attached to the carbon atom connected to the Cp* ring (bond
1) has the weakest calculated interaction overall, ca. 6 kJ/mol
lower than the fluorine attached to the metal bound carbon
(bond 4). The 19F chemical shifts for 1 have also been
calculated for the optimized geometry (Figure S24), which
align closely with those observed experimentally.50 Natural
population analysis was used to calculate the occupancy and
charge distribution of electrons for each fluorine atom within
1. The fluorine atoms displaced away from the plane of the
E
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Figure 7. Optimized geometry of 1 with the polyfluorocyclohexadiene region highlighted. The color of the fluorine atoms has been changed to
correspond with their natural population analysis (NPA) as given in the gradient scale (top right). The calculated fluorine atom interaction energies
and the relative charge from natural population analysis for bonds 1−5 are given in the table (bottom right). Geometries were calculated at the
PBE0/6-31G(d)/LANL2DZ level of theory. Energies and natural populations were calculated at the PBE0/6-311++G(d,p)/SRSC level of theory.
ring (bonds 1 and 4) have the most negative overall atom
charges. Therefore, these fluorine atoms can be considered
more nucleophilic due to the greater electron density found on
the atom.
EXPERIMENTAL SECTION
■
General Information. NMR spectral analysis was carried out
using a Bruker Ascend 400 spectrometer (400 MHz) and Bruker
Ascend 500 spectrometer (500 MHz) at room temperature (≈300
1
The ReactIR data, the crystal structure of 2, the theoretical
calculations, and the 19F NMR tell a coherent story about C−F
bond activation and fluorine dissociation. The reactive C−F
bond in 1 has the lowest calculated fluorine interaction energy,
one of the highest fluorine atom charges (from NPA), and the
most upfield chemical shift in the 19F NMR. The results reveal
the activation of fluorine within a perfluorinated moiety,
rendering it nucleophilic. Multivariate analysis confirms
fluorine transfer from the perfluorinated ligand of 1 to the
organic electrophiles, resulting in the formation of the
fluorinated product and 2.
K). H and 13C NMR spectra were calibrated to the corresponding
solvent signals (CDCl3: 7.26 ppm for 1H, 77.16 ppm for 13C). The 19
F
NMR spectra were calibrated by an internal method of the NMR. The
chemical shifts are reported in ppm, and coupling constants are given
in Hz. Electrospray mass spectra were recorded on a Bruker
micrOTOF II with Agilent technologies 1200 Infinity Series mass
spectrometer. RhCp*(Cl2)(F5Bzmim) and 1 were synthesized as
previously described.50,61,62 3-Methyl-1-(3,4,5,6-tetrafluorobenzyl)-
imidazolium bromide was synthesized using a similar procedure
which has previously been described.61 1-Methylimidazole, silver
oxide, toluoyl chloride, benzoyl chloride, benzoic anhydride, and
butyric anhydride were purchased from Sigma-Aldrich (Merck).
[RhCp*Cl2]2 was purchased from Alfa Aesar. Acetic anhydride was
purchased from VWR. All solvents were purified, degassed, and dried
before use.
CONCLUSIONS
■
In conclusion, we report the reactivity of [(η5,κ2C−
C5Me4CH2C6F5CH2NC3H2NMe)−RhCl], 1, to form dirho-
dium species 2 upon treatment with organic electrophiles. C−
F bond activation was followed by concurrent rhodacycle
formation resulting in up to 1:1 formation of 2 and fluorinated
products. Photoexcitation of 1 with toluoyl chloride resulted in
the rapid formation of 2 and toluoyl fluoride, and on the basis
of this, we propose a mechanism for the formation of 2
involving Cp* migration. The nucleophilic fluorine was
remarkable, as it arose from a perfluorinated ligand’s C−F
bond and not from fluorine attached to the metal center. The
formation of 1 involved nucleophilic attack of a perfluorinated
aryl by a strong nucleophile generate from the deprotonation
of Cp* (Figure 1b), and this appears to have rendered the C−
F bond unusually electron-rich. Fluorine transfer or shuttling
that results in the formation of a new C−F bond is very rare. It
is therefore important to understand the chemical nature of
fluorine in 1 in order to harness the synthetic potential of this
reaction. Toward this end, computational fluorine interaction
energies and natural population analysis gave some insight into
the reactivity of parent complex 1, and this provided a first
understanding of the environment required to initiate a
nucleophilic transfer fluorination.
Procedure for Synthesis of 2. Dichloromethane (5 mL) was
added to a flask containing 1 (25 mg, 0.046 mmol). Once dissolved,
toluoyl chloride (0.10 mmol, 2 equiv) was added, and the stirring was
continued for 1 week. The reaction mixture was removed from the
glovebox, and the solvent was removed in vacuo resulting in an orange
crystalline powder and an orange oil. CDCl3 (0.5 mL) was added, and
the solution was transferred to a Young’s valve NMR tube under
argon. Analysis of the 19F NMR showed up to 30% conversion of 1 to
2. Toluoyl fluoride was extracted with ether, and 2 was recrystallized
from a saturated solution of dichloromethane. Isolated yield: 3.5 mg
(13.7% yield). 1H NMR (400 MHz, chloroform-d1): δ 7.71 (d, JHH
3.3 Hz, HCCH, 1H), 7.70 (d, JHH = 3.3 Hz, HCCH′, 1H), 7.54 (d,
HH = 3.3 Hz, HCCH, 1H), 7.53 (d, JHH = 3.3 Hz, HCCH′, 1H), 5.82
=
J
(d, JHH = 16.5 Hz, CH2, 2H), 5.56 (d, JHH = 16.2 Hz, CH2, 2H), 4.05
(s, CH3, 6H), 1.87 (s, C5−CH2, 4H), 1.77 (s, C5−CH3, 6H), 1.40 (s,
C5−CH3, 6H), 1.25 (s, C5−CH3, 6H), 0.92 (s, C5−CH3, 6H). 19F
NMR (376 MHz, chloroform-d1): δ −117.43 (s, C6−F, 1F), −131.12
(d, JFF = 19.9 Hz, C6−F, 1F), −135.12 (d, JFF = 20.9 Hz, C6−F, 1F),
−160.86 (t, JFF = 22.8 Hz, C6−F, 1F). MS (ESI) of 2: theoretical for
C21H21Cl1F4N2Rh [M/2 − Cl]+ 515.0384. Found [M/2 − Cl]+
515.0389. Theoretical for C42H42Cl3F8N4Rh2 [M − Cl]+ 1065.0457.
Found [M − Cl]+ 1065.0445: The formation of toluoyl fluoride was
also identified: 1 mg (13.3% yield; 97% conversion vs 0.003 mmol of
1
2 formed {Figure S3}). H NMR (400 MHz, chloroform-d1): δ 7.99
(d, JHH = 8.1 Hz, C6−H, 2H), δ 7.27 (d, JHH = 8.1 Hz, C6−H, 2H),
2.43 (s, Me, 3H). 19F NMR (376 MHz, d1-chloroform): δ 17.30 (s,
F
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1F, COF). MS (ESI) of toluoyl fluoride: theoretical [M − F]+
Experimental procedures, characterization of all isolated
compounds, copies of reported spectroscopic data,
details of DFT and reaction performance data (PDF)
[C8H7O]+ 119.0497. Found [C8H7O]+ 119.0498.
General Procedure for the Fluorine Transfer between 1 and
Organic Electrophiles. The organic electrophile (0.056 mmol) was
added to a Young’s tap NMR tube containing 1 (3 mg, 0.0056 mmol)
and dry, degassed CD3CN (0.5 mL) with α,α,α-trifluorotoluene (1
μL) under argon. The contents of the tube were shaken, and the
reaction was monitored via 19F NMR over time. The conversion and
formation of the fluorinated product are highlighted in Table S1; the
substrate specific experimental is given below (sections 1.4.2−1.4.11
of the Supporting Information). Due to the 10 equiv of substrate
Accession Codes
CCDC 1977788 and 1978328 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
1
added H NMR analysis of products proved difficult in some cases
due to overlapping signals. Products have been assigned using 19F
NMR, referenced against literature precedent, where available.
Acetic Anhydride. The acetyl fluoride product was formed using
the general method (section 1.4.1 of the Supporting Information).
Acetic anhydride (6 mg, 0.056 mmol) was added to a Young’s tap
NMR tube containing 1 (3 mg, 0.0056 mmol) in dry, degassed
CD3CN (0.5 mL) with α,α,α-trifluorotoluene (1 μL) under argon.
The contents of the tube were shaken and the reaction monitored via
19F NMR over time. 19F NMR yield versus the internal standard after
10 min: 11.2%. 19F NMR (376 MHz, ACN-d3): δ 48.91 (q, JHF = 7.3
Hz, COF, 1F).63
AUTHOR INFORMATION
Corresponding Authors
■
Graham C. Saunders − School of Science, University of
Waikato, Hamilton 3240, New Zealand; Email: g.saunders@
waikato.ac.nz
Andrew C. Marr − School of Chemistry and Chemical
Engineering, Queen’s University Belfast, Belfast BT9 5AG,
United Kingdom; orcid.org/0000-0001-6798-0582;
Email: a.marr@qub.ac.uk
Peter Licence − GSK Carbon Neutral Laboratory, School of
Chemistry, University of Nottingham, Nottingham NG7 2TU,
United Kingdom; orcid.org/0000-0003-2992-0153;
Email: peter.licence@nottingham.ac.uk
Benzoic Anhydride. The benzoyl product was formed using the
general method (section 1.4.1 of the Supporting Information).
Benzoic anhydride (13 mg, 0.056 mmol) was added to a Young’s tap
NMR tube containing 1 (3 mg, 0.0056 mmol) in dry, degassed
CD3CN (0.5 mL) with α,α,α-trifluorotoluene (1 μL) under argon.
The contents of the tube were shaken, and the reaction was
monitored via 19F NMR over time. 19F NMR yield versus the internal
Authors
1
Patrick J. Morgan − GSK Carbon Neutral Laboratory, School
of Chemistry, University of Nottingham, Nottingham NG7
2TU, United Kingdom
Magnus W. D. Hanson-Heine − GSK Carbon Neutral
Laboratory, School of Chemistry, University of Nottingham,
Nottingham NG7 2TU, United Kingdom
Hayden P. Thomas − School of Science, University of Waikato,
Hamilton 3240, New Zealand
standard after 30 min: 47.7%. H NMR (400 MHz, ACN-d3): δ 8.01
(d, JHH = 7.5 Hz, C6−H, 2H), δ 7.56 (t, JHH = 8.1 Hz, C6−H, 1H),
7.46 (t, JHH = 7.7 Hz, C6−H, 2H). 19F NMR (376 MHz, ACN-d3): δ
16.57 (s, COF, 1F).64
Butyric Anhydride. The butanoyl fluoride product was formed
using the general method (section 1.4.1 of the Supporting
Information). Butyric anhydride (12 mg, 0.056 mmol) was added
to a Young’s tap NMR tube containing 1 (3 mg, 0.0056 mmol) in dry,
degassed CD3CN (0.5 mL) with α,α,α-trifluorotoluene (1 μL) under
argon. The contents of the tube were shaken, and the reaction was
monitored via 19F NMR over time. 19F NMR yield versus the internal
standard after 20 h: 28.3%. 19F NMR (376 MHz, ACN-d3): δ 43.10
(s, COF, 1F).63
Toluoyl Chloride. The toluoyl fluoride product was formed using
the general method (section 1.4.1 of the Supporting Information).
Toluoyl chloride (9 mg, 0.056 mmol) was added to a Young’s tap
NMR tube containing 1 (3 mg, 0.0056 mmol) in dry, degassed
CD3CN (0.5 mL) with α,α,α-trifluorotoluene (1 μL) under argon.
The contents of the tube were shaken, and the reaction was
monitored via 19F NMR over time. 19F NMR yield versus the internal
standard after 72 h: 18.0%. 1H NMR (400 MHz, ACN-d3): δ 7.92 (dt,
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.organomet.0c00176
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We acknowledge the financial support provided by the EPSRC
Centre for Doctoral Training for Sustainable Chemistry (EP/
L015633/1). M.W.D.H.H. thanks the University of Notting-
ham Green Chemicals Beacon for funding toward this
research.
J
HH = 1.9, 8.2 Hz, C6−H, 2H), δ 7.33−7.30 (m, C6−H, 2H), 2.42 (s,
Me, 3H). 19F NMR (376 MHz, ACN-d3): δ 15.85 (s, COF, 1F).65
Benzoyl Chloride. The benzoyl fluoride product was formed using
the general method (section 1.4.1 of the Supporting Information).
Benzoyl chloride (8 mg, 0.056 mmol) was added to a Young’s tap
NMR tube containing 1 (3 mg, 0.0056 mmol) in dry, degassed
CD3CN (0.5 mL) with α,α,α-trifluorotoluene (1 μL) under argon.
The contents of the tube were shaken, and the reaction was
monitored via 19F NMR over time. 19F NMR yield versus the internal
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ASSOCIATED CONTENT
■
sı
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.organomet.0c00176.
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https://dx.doi.org/10.1021/acs.organomet.0c00176
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