The Difluoromethylated Organogold(III) Complex cis-[Au(PCy3)(4-F-C6H4)(CF2H)(Cl)]: Preparation, Characterization, and Its C(sp2)-CF2H Reductive Elimination

Article abstract of DOI:10.1021/acs.organomet.8b00579

The preparation of the difluoromethylated organogold(III) complex cis-[Au(PCy₃)(4-F-C₆H₄)(CF₂H)(Cl)] (3) and its Ar-CF₂H reductive elimination are described. In the presence of 1.0 equiv of AgSbF₆ or AgPF₆, compound 3 underwent a quantitative Ar-CF₂H reductive elimination in less than 1.0 min at 25 °C, while the lack of silver salt resulted in Ar-CF₂H reductive elimination from complex 3 in 1,1,2,2-tetrachloroethane (CCl₂HCCl₂H) after 80 min at 115 °C to afford the elimination product p-F-PhCF₂H (4) and (Cy₃P)Au(Cl) in quantitative yields. On the basis of the mechanistic studies of the kinetics of the reaction and DFT calculation, a concerted Ar-CF₂H bond-forming pathway for the Ar-CF₂H reductive elimination from organogold(III) complex 3 is proposed.

Full text of DOI:10.1021/acs.organomet.8b00579

Article
pubs.acs.org/Organometallics
Cite This: Organometallics XXXX, XXX, XXX−XXX
The Difluoromethylated Organogold(III) Complex cis-[Au(PCy3)(4-
F‑C6H4)(CF2H)(Cl)]: Preparation, Characterization, and Its C(sp2)−
CF2H Reductive Elimination
Shuanshuan Liu,† Kai Kang,‡ Shihan Liu,§ Decai Wang,† Ping Wei,*,† Yu Lan,*,§,∥
and Qilong Shen*,‡
†Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, Jiangsu Province 210009, People’s Republic of
China
‡Key Laboratory of Organofluorine Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic
Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032,
People’s Republic of China
§School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030, People’s Republic of China
∥College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450001, People’s Republic of China
S
* Supporting Information
ABSTRACT: The preparation of the difluoromethylated organogold-
(III) complex cis-[Au(PCy3)(4-F-C6H4)(CF2H)(Cl)] (3) and its Ar−
CF2H reductive elimination are described. In the presence of 1.0
equiv of AgSbF6 or AgPF6, compound 3 underwent a quantitative Ar−
CF2H reductive elimination in less than 1.0 min at 25 °C, while the
lack of silver salt resulted in Ar−CF2H reductive elimination from
complex 3 in 1,1,2,2-tetrachloroethane (CCl2HCCl2H) after 80 min
at 115 °C to afford the elimination product p-F-PhCF2H (4) and
(Cy3P)Au(Cl) in quantitative yields. On the basis of the mechanistic
studies of the kinetics of the reaction and DFT calculation, a concerted Ar−CF2H bond-forming pathway for the Ar−CF2H
reductive elimination from organogold(III) complex 3 is proposed.
the understanding of the fundamentals of the Ar−CF2H bond-
forming process. Nevertheless, the preparation of difluorome-
thylated transition-metal complexes and studies of their
elementary reactions are still imperatively needed.
INTRODUCTION
■
Due to their exceptional properties that may bring favorable
changes in the molecule’s performance, fluoroalkyl groups
including trifluoromethyl (−CF3), difluoromethyl (−CF2H),
and trifluoromethylthio (−SCF3) have attracted substantial
interest from the pharmaceutical/agrochemical industry as well
as academia.1 Consequently, numerous efforts from many
teams around the world have resulted in the development of a
variety of efficient methods for the strategic incorporation of
these functional groups.2 One general approach accessing the
fluoroalkylated compounds involves the tranistion-metal-
mediated/-catalyzed fluoroalkylation of the corresponding
substrates under mild conditions.3,4 Despite this widespread
interest, the fundamental organometallic chemistry of the
transition-metal-catalyzed fluoroalkylation reactions is much
less developed than that of hydrocarbons.5−9 In particular,
reports of isolated complexes bearing the difluoromethyl
group, which is considered as a biostere of a hydroxy or
thiol group10 in drug molecule design, are rare11 and very few
elementary reactions of difluoromethylated transition-metal
complexes have been reported previously. To the best of our
knowledge, the only report for Ar−CF2H reductive elimination
from a well-characterized [(DPPF)Pd(Ar)(CF2H)] complex
was reported previously by Shen’s group,12 which shed light on
Herein, we report the preparation of the stable difluor-
omethylated gold(III) complex cis-[Au(PCy3)(4-F-C6H4)-
(CF2H)(Cl)] (3) and its Ar−CF2H bond-forming reductive
elimination in 1,1,2,2-tetrachloroethane in the absence and
presence of silver salt.13,14 In the presence of 1.0 equiv of
AgSbF6 or AgPF6, which is presumably to abstract the chloride,
complex 3 underwent a quantitative Ar−CF2H reductive
elimination in less than 1.0 min at 25 °C. In the absence of
silver salt, Ar−CF2H reductive elimiantion from complex 3 in
1,1,2,2-tetrachloroethane (CCl2HCCl2H) occurred after 80
min at 115 °C to afford the elimination product p-F-PhCF2H
(4) and (Cy3P)Au(Cl) in quantitative yields. Kinetic studies
and investigation on the effects of the temperature and added
free phosphine ligand and chloride, as well as DFT
calculations, let us conclude that a concerted carbon−carbon
bond-forming pathway is preferred for the Ar−CF2H reductive
elimination from cis-[Au(PCy3)(4-F-C6H4)(CF2H)(Cl)] (3),
Received: August 13, 2018
© XXXX American Chemical Society
A
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which differed significantly from the mechanism for Ar−CF3
reductive elimination from the trifluoromethylated complex cis-
[Au(PPh3)(4-F-C6H4)(CF3)(Cl)] that was proposed to
proceed via a phosphine ligand dissociation pathway.
example, there is a peak at 6.68 ppm (triplet of doublets with
coupling constants J = 52.0 and 20.0 Hz, respectively) in the
1H NMR spectrum and a triplet peak at −97.61 ppm with the
coupling constant J = 50.8 Hz in the 19F NMR spectrum,
which represent two characteristic splitting patterns for a
difluoromethyl group. In addition, the peak in the proton
NMR spectrum shows a doublet with the coupling constant J =
20.0 Hz, which indicates that the difluoromethyl group is trans
to PCy3 in complex 3, as shown in Figure 1A.
Single crystals of complex 3 were obtained by diffusion of n-
pentane vapors into a CH2Cl2 solution of complex 3, and its X-
ray structure is shown in Figure 1B. Likewise, its trifluor-
omethylated analogue cis-[Au(PCy3)(4-F-C6H4)(CF3)(Cl)]
(3a) was synthesized following a similar procedure, and its
single-crystal structure is shown in Figure 1C. In both
complexes, the phosphines are located trans to the
difluoromethyl or trifluoromethyl group. As found in Table
1, the sums of the four bond angles surrounding the gold metal
center in complexes 3 and 3a are 360.08 and 359.97°,
respectively, which is consistent with the NMR data which
suggest that the configuration of complexes 3 and 3a is square
planar. The Au−C(Ar) and Au−C(CF3) bond distances in cis-
[Au(PCy3)(4-F-C6H4)(CF3)(Cl)] (3a) are longer than the
Au−C(Ar) and Au−C(CF2H) bond distances in cis-[Au-
(PCy3)(4-F-C6H4)(CF2H)(Cl)] (3), presumably because the
trifluoromethyl group is more sterically hindered than the
difluoromethyl group.
RESULTS AND DISCUSSION
■
Preparation of cis-[Au(PCy3)(4-F-C6H4)(CF2H)(Cl)] (3)
and Its X-ray Structure. The difluoromethylated
organogold(III) complex cis-[Au(PCy3)(4-F-C6H4)(CF2H)-
(Cl)] 3 was prepared via a two-step process from the readily
available starting material [(Cy3P)AuCl] (1), as shown in
Scheme 1. Initially, cis-[Au(PCy3)(4-F-C6H4)(Cl)2] (2) was
Scheme 1. Synthesis of Difluoromethylgold(III) Complexes
3
prepared in 48% yield by oxidative addition of 4-
fluorobenzenediazonium chloride to [(Cy3P)Au(Cl)] in
CH3CN at 25 °C under irradiation of blue LED light,
following the general procedure developed by Hashmi.15
Treatment of a solution of complex 2 in dichloromethane with
1.5 equiv of (SIPr)Ag(CF2H) (SIPr = 1,3-bis(2,6-diisopropyl-
phenylimidazolin-2-ylidene),12,16 gave the difluoromethylated
gold(III) complex cis-[Au(PCy3)(4-F-C6H4)(CF2H)(Cl)] (3)
after 15 min at room temperature in 87% yield. Complex 3 is a
shelf-stable, air- and moisture-insensitive white crystalline solid
that could be purified by column chromatography.
In general, the trans influence of a phosphine ligand is
stronger than that of an aryl group.17 Therefore, the gold−
chloro bond trans to a phosphine ligand in cis-[Au(PCy3)(4-F-
C6H4)Cl2] (2) is more easily transmetalated than the gold−
chloro bond trans to an aryl group. As a result, complex 3 is
thought to have a cis configuration. The NMR spectra of
complex 3 are consistent with the proposed structure. For
C(sp2)−CF2H Bond Reductive Elimination. Having
successfully synthesized stable difluoromethylated organogold-
(III) complex 3, we then studied its Ar−CF2H reductive
elimination in the presence/absence of silver salt. Addition of
1.0 equiv of AgSbF6 or AgPF6 to a solution of complex 3 in
1,1,2,2-tetrachloroethane (CCl2HCCl2H) resulted in an
immediate reductive elimination to give p-F-PhCF2H (4) in
quantitative yield (Scheme 2). Presumably, the cationic Y-
shaped intermediate [Au(PCy3)(4-F-C6H4)(CF2H)] is
formed, which undergoes a fast reductive elimination to give
compound 4. In the absence of silver salt, complex 3 is stable
in 1,1,2,2-tetrachloroethane at room temperature and the
formation of reductive elimination product 4 was not observed.
On the other hand, full conversion of complex 3 and the
quantitative formation of the elimination product p-F-PhCF2H
1
Figure 1. (A) H (top) and 19F NMR (bottom) spectra for the difluoromethyl group of complex 3 (CDCl3, 298 K, 400 MHz). (B) ORTEP
diagram of complex 3. (C) ORTEP diagram of complex 3a. Thermal ellipsoids are shown at the 50% probability level.
B
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Table 1. Selected Bond Distances (Å) and Bond Angles (deg) for Complexes 3 and 3a
cis-[Au(PCy3)(4-F-C6H4)(CF2H)(Cl)] (3)
bond distance (Å) bond angles (deg)
cis-[Au(PCy3)(4-F-C6H4)(CF3)(Cl)] (3a)
bond distance (Å) bond angle (deg)
Au−C(CF2H)
Au−C(Ar)
Au−P
2.071(4)
2.020(4)
2.3964(9)
2.3459(10)
1.337(5)
1.328(5)
1.00(4)
Cl−Au−C(CF2H)
C(CF2H)−Au−C(Ar)
C(Ar)−Au−P
87.17(13)
87.36(16)
95.57(10)
89.98(3)
Au−C(CF3)
Au−C(Ar)
Au−P
2.093(5)
2.048(5)
2.3855(12)
2.3487(13)
1.343(6)
1.337(6)
1.343(6)
Cl−Au−C(CF3)
C(CF3)−Au−C(Ar)
C(Ar)−Au−P
92.18(15)
85.1(2)
93.74(14)
88.95(4)
103.7(4)
104.6(5)
105.7(4)
Au−Cl
P−Au−Cl
Au−Cl
P−Au−Cl
C(CF2H)−F(1)
C(CF2H)−F(2)
C(CF2H)−H
F(2)−C(CF2H)−F(1)
H−C(CF2H)−F(2)
H−C(CF2H)−F(1)
105.0(4)
103(2)
111.7(3)
C(CF3)−F(1)
C(CF3)−F(2)
C(CF3)−F(3)
F(2)−C(CF3)−F(3)
F(2)−C(CF3)−F(4)
F(3)−C(CF3)−F(4)
(4) and (Cy3P)Au(Cl) was observed after 80 min at 115 °C in
1,1,2,2-tetrachloroethane (CCl2HCCl2H) (Scheme 2). The
yields for the formation of the compound 4 in other solvents
were much lower. For example, thermolysis of complex 3 in
solvents such as diglyme, acetonitrile, DMF, and DMSO
occurred to roughly 90% conversion after 2.0 h at 120 °C for 2
h to to give compound 4 in 39%, 50%, 62%, and 64% yields,
respectively.
Scheme 2. Reductive Elimination from Complex 3 in
CHCl2CCl2H in the Presence or Absence of Silver Salt
To gain some insight into the thermal reductive elimination
process, we investigated the kinetics of the Ar−CF2H bond-
forming process from complex 3. Experimentally, a solution of
complex 3 with the internal standard 1-fluoronaphthalene in
Figure 2. (A) Thermolysis of complex 3 in CCl2HCCl2H at 115 °C and the kinetic profile of the product complex 4. (B) Rate constant of reductive
elimination of complex 3 in CCl2HCCl2H at different initial concentration at 115 °C. (C) Effect of the concentration of nBu4NCl on reductive
elimination of complex 3. (D) Eyring plot for the thermolysis of complex 3 over the temperature range 90−120 °C in CCl2HCCl2H.
C
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Scheme 3. Possible Pathways for the Ar−CF2H Reductive Elimination from Complex 3
Figure 3. Calculated activation free energies for the Ar−CF2H reductive elimination of cis-[Au(PCy3)(4-F-C6H4)(CF2H)(Cl)] (3). Optimized
structures for all the transition states are shown. Selected bond distances (Å) are provided.
1,1,2,2-tetrachloroethane was placed in a NMR tube. The
solution was heated at 115 0.1 °C, and periodically, a 19F
NMR spectrum of the reaction mixture was acquired. The
change in concentration of complex 3 vs time was then plotted,
and it showed that the decay of the concentration followed
first-order kinetics (Figure 2A). Further studies showed that
the rate constants did not change with different initial
concentrations of complex 3 (Figure 2B), consistent with the
first-order kinetic behavior of the reductive elimination
process.
Previously, Komiya reported that the rate of the C(sp2)−
CH3 bond-forming process from complexes cis-[(Ar3P)Au-
(Me)2(Ar)] was significantly suppressed by the addition of
even a small amount of free tertiary phosphine.18 Likewise,
D
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Toste reported that the addition of small amount of free
phosphine ligand inhibited the C(sp2)−CF3 bond-forming
process from the complex [(Ph3P)Au(4-F-C6H4)(CF3)(I)].19
In both cases, a ligand dissociation pathway was proposed for
these reductive elimination processes. To probe whether Ar−
CF2H reductive elimination from complex 3 proceeds via a
similar ligand dissociation pathway (Scheme 3), we studied the
reaction in the presence/absence of 1.0 equiv of PCy3 at 115
°C. As shown in Figure 2A, reaction in the presence of 1.0
equiv of PCy3 occurred to full conversion after 80 min to
generate p-F-PhCF2H in 78% yield and the unidentified side
product with chemical shifts at −85.43 and −76.97 ppm in 19F
NMR spectroscopy in 18% yield. Nevertheless, kinetic studies
disclosed that the reaction in the presence of PCy3 followed
the first-order decay. Interestingly, the rate was 1.36 times
faster than that in the absence of phosphine ligand (6.99 ×
10−4 vs 5.13 × 10−4 s−1, respectively). These results differed
greatly from the previous observations by Komiya and Toste
for the reductive elimination from [(Ar3P)Au(Me)2(Ar)] or
[(Ph3P)Au(4-F-C6H4)(CF3)(I)], thus clearly ruling out the
phosphine ligand dissociation pathway (pathway A in Scheme
3).
An alternative mechanistic pathway for the Ar−CF2H bond-
forming process from complex 3 would be a rate-determining
chloride dissociation to form the Y-shaped ionic species
[Au(PCy3)(4-F-C6H4)(CF2H)]+, followed by a fast Ar−CF2H
bond-forming elimination from this intermediate (pathway B
in Scheme 3). If this is the case, addition of a small amount of
n-Bu4NCl would significantly retard the reductive elimination
process. Experimentally, thermolysis of complex 3 with 0.01−
0.5 equiv of n-Bu4NCl in 1,1,2,2-tetrachloroethane at 115 °C
for 80 min gave the elimination product in 73−99% yield and
an unknown side product with a chemical shift at −90.69 ppm
in 19F NMR spectroscopy in 1−24% yields. Kinetic studies
showed the rate constants changed slightly with the increase of
the amount of n-Bu4NCl, even though the magnitude of
difference is small (Figure 2C). More specifically, the reaction
was 1.4 times slower when it conducted in absence of n-
Bu4NCl than that with n-Bu4NCl (5.13 × 10−4 s−1vs 7.37 ×
10−4 s−1, respectively). Thus, it is clear that the addition of n-
Bu4NCl did not inhibit the Ar−CF2H bond forming process
and the increase in the rate constant in the presence of n-
Bu4NCl might due to a kinetic salt effect. Overall, these results
suggest a chloride dissociation pathway for Ar−CF2H bond-
forming process from complex 3 is unlikely (pathway B in
Scheme 3).
Computational Investigation. To further deepen our
understanding of the Ar−CF2H reductive elimination from
complex 3, we conducted density functional theory (DFT)
calculations of three possible pathways shown in Scheme 3. cis-
[Au(PCy3)(4-F-C6H4)(CF2H)(Cl)] (3) was chosen as a
starting point, and the free energy profiles of three pathways
are shown in Figure 3. It was found that, in pathway A, the
dissociation of the tricyclohexylphosphine from complex 3 is
an endothermic process (28.2 kcal/mol), while reduction
elimination of the resulting tricoordinated intermediate 4 via
the three-membered-ring transition state 6-ts requires over-
coming an additional barrier of 10.5 kcal/mol. Overall, the
total energy barrier of pathway A (38.7 kcal/mol) is 11.4 kcal/
mol greater than that of pathway C, suggesting that pathway A
is unfavorable. Likewise, in path B, the dissociation of chloride
from complex 3 requires overcoming a barrier of 28.9 kcal/
mol, while the barrier for the Ar−CF2H bond-forming process
from the resulting cationic tricoodinated intermediate 11 via
the three-membered-ring transition state 12-ts is 8.6 kcal/mol.
The activation energy barrier of pathway B is 10.2 kcal/mol
greater than that from pathway C (37.5 kcal/mol vs 27.3 kcal/
mol), which rules out a chloride dissociation pathway. Overall,
DFT calculations also support that the Ar−CF2H bond-
forming process from complex 3 proceeds via a classic
concerted pathway with the three-membered-ring transition
state 14-ts, as illustrated in pathway C in Scheme 3.
Comparison with C(sp2)−CF3 Reductive Elimination
from Complex 3a. Interestingly, the proposed concerted Ar−
CF2H bond-forming process from complex 3 is different from
that for the Ar−CF3 bond-forming process from the analogous
trifluoromethylated complex [(Ph3P)Au(4-F-C6H4)(CF3)(I)],
where a mechanism of rate-limiting phosphine dissociation and
then elimination from the resulting Y-shaped cationic complex
was proposed by Toste and co-workers.19
As a comparison, we prepared the trifluoromethyl-sub-
stituted organogold(III) complex cis-[Au(PCy3)(4-F-C6H4)-
(CF3)(Cl)] (3a), which bears an phosphine ligand (PCy3)
identical with that of complex 3 and studied its C(sp2)−CF3
reductive elimination. As shown in Scheme 4, thermolysis of a
Scheme 4. Thermolysis of Complex 3a in CCl2HCCl2H at
150 °C
To further elucidate the mechanism of the process, we
studied the effect of reaction temperature on the reaction of
complex 3. Experimentally, we investigated the kinetics of the
Ar−CF2H bond-forming process at a temperature from 90 to
120 °C. These results revealed that the rates constants were
linearly dependent on the reaction temperature, as shown in
Figure 2D. The activation parameters of ΔH⧧ = 28.40 1.86
kcal/mol and ΔS⧧ = −0.68 0.07 eu were then extracted, and
the small negative entropy change suggests a pathway that
involves a rate-determining phosphine ligand dissociation or
chloride dissociation followed by a fast Ar−CF2H reductive
elimination from the three-coordinated intermediate is highly
unlikely. Instead, the observed experimental results indicate
that reductive elimination might proceed via a direct carbon−
carbon bond-forming pathway involving a three-centered
transition state (pathway C in Scheme 3).
solution of complex 3a in 1,1,2,2-tetrachloroethane
(CCl2HCCl2H) occurred in >90% conversion after 6.0 h at
150 °C to generate p-F-PhCF3 (15) in 34% yield, while the
formation of p-F-PhCl was not observed, as monitored by GC-
MS and 19F NMR spectroscopy. In addition, the yield
decreased significantly to less than 10% upon addition of 1.0
equiv of tricyclohexylphosphine or nBu4NCl. These exper-
imental results suggest that reductive elimination from
trifluoromethylated complex 3a is significantly slower than
that from difluoromethylated complex 3 and the underlying
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Preparation of cis-[Au(PCy3)(4-F-C6H4)(CF2H)(Cl)] (3). In a
glovebox, cis-[Au(PCy3)(4-F-C6H4)(Cl)2] (2; 320 mg, 0.486 mmol,
1.00 equiv) and (SIPr)Ag(CF2H)2 (399 mg, 0.729 mmol, 1.50 equiv)
were placed in a 10 mL Schlenk tube that was equipped with a stirrer.
Then 4.0 mL of freshly distilled CH2Cl2 was added and the reaction
mixture was stirred at room temperature for 15 min. The mixture was
then filtered through a short plug of Celite. The solvent was removed
under vacuum. The residue was purified by flash chromatography on
silica gel (n-pentane/dichloromethane = 5/1 to 3/1) to give cis-
[Au(PCy3)(4-F-C6H4)(CF2H)(Cl)] (3) as a white solid (278 mg,
87%). 1H NMR (400 MHz, CDCl3, 298 K, TMS): δ 7.34−7.26 (m, 2
H), 6.99−6.86 (m, 2 H), 6.84−6.50 (m, 1 H), 2.19 (d, J = 12.3 Hz, 3
H), 1.80 (dt, J = 14.3, 7.6 Hz, 12 H), 1.72−1.64 (m, 3 H), 1.52 (dt, J
= 12.7, 3.5 Hz, 6 H), 1.28−1.19(m, 3 H), 1.19−0.93 (m, 6 H). 19F
NMR (376 MHz, CDCl3, 298 K): δ −97.61 (t, J = 50.5 Hz), −117.58
(ddd, J = 8.8, 6.1, 2.6 Hz). 31P NMR (162 MHz, CDCl3, 298 K): δ
29.19 (t, J = 49.4 Hz) ppm. Anal. Calcd for C25H38AuClF3P: C, 45.57;
H, 5.81. Found: C, 45.56; H, 5.83.
mechanisms for the two carbon−carbon reductive elimination
processes might be different. A comparison of the X-ray
structures of complexes 3 and 3a showed that the Au−C(Ar)
and Au−C(CF3) bond distances in complex 3a are 0.028 and
0.022 Å, respectively, longer than the Au−C(Ar) and Au−
C(CF2H) bond distances in complex 3. The longer Au−C(Ar)
and Au−C(CF3) bond distances in complex 3a suggest that
the formation of the three-membered-ring transition state is
much more difficult than that from complex 3, even though a
detailed mechanism for the Ar−CF3 bond-forming process
from complex 3a is unclear at this stage.
CONCLUSION
■
In summary, we have systematically studied the Ar−CF2H
bond-forming reductive elimination from the PCy3-ligated
difluoromethylated organogold(III) complex cis-[Au(PCy3)(4-
F-C6H4)(CF2H)(Cl)] (3). These investigations suggest that
the Ar−CF2H bond-forming process proceeds through a
classic concerted pathway with a three-membered-ring
transition state. A comparative study of thermolysis of its
analogous trifluoromethyl-substituted organogold(III) com-
plex cis-[Au(PCy3)(4-F-C6H4)(CF3)(Cl)] (3a) disclosed that
Ar−CF3 reductive elimination from the trifluoromethylated
complex 3a is significantly slower than that from the
difluoromethylated complex 3 and the underlying mechanisms
for the two carbon−carbon reductive elimination processes
differ greatly.
Preparation of cis-[Au(PCy3)(4-F-C6H4)(CF3)(Cl)] (3a). In a
glovebox, AgF (40 mg, 0.31 mmol), TMSCF3 (92 μL, 0.62 mmol),
and MeCN (2.0 mL) were placed in a 4 mL Schlenk tube that was
equipped with a stirring bar. The reaction mixture was stirred in the
dark for 3 h. The complex cis-[Au(PCy3)(4-F-C6H4)(Cl)2] (2; 200
mg, 0.310 mmol) was added, and the reaction mixture was stirred at
room temperature in the dark for 12 h. The mixture was then filtered
through a short plug of Celite. The solvent was removed under
vacuum. The residue was purified by flash chromatography on silica
gel (n-pentane/dichloromethane = 5/1) to give the complex cis-
[Au(PCy3)(4-F-C6H4)(CF3)(Cl)] (3a) as a white solid (162 mg,
1
77%). H NMR (400 MHz, chloroform-d): δ 7.24 (dd, J = 8.2, 6.1
Hz, 2 H), 6.98 (dd, J = 10.2, 7.8 Hz, 2 H), 5.32 (s, 2 H), 2.18 (dd, J =
13.6, 10.7 Hz, 3 H), 1.85 (dd, J = 10.9, 5.9 Hz, 12 H), 1.79−1.68 (m,
3 H), 1.54 (dtd, J = 12.8, 9.6, 9.1, 3.5 Hz, 6 H), 1.35−1.19 (m, 3 H),
1.18−1.01 (m, 6 H). 19F NMR (376 MHz, CDCl3, 298 K): δ −32.19
(d, J = 65.2 Hz), −116.65 (m, 1 F). 31P NMR (162 MHz, CDCl3, 298
K): δ 28.43 (q, J = 64.7 Hz) ppm. Anal. Calcd for C25H37AuClF4P: C,
44.36; H, 5.51. Found: C, 44.19; H, 5.38.
EXPERIMENTAL SECTION
■
General Information. All glassware was oven or flame-dried
immediately prior to use. Solvents were freshly degassed according to
the procedures in Purification of Laboratory Chemicals prior to use.
Deuterated solvents were purchased from Cambridge Isotope
Laboratories, Inc., and were degassed and stored over activated 4 Å
molecular sieves. Unless otherwise noted, all other reagents and
starting materials were purchased from commercial sources and used
ASSOCIATED CONTENT
■
S
* Supporting Information
1
without further purification. The H, 19F, 31P, and 13C NMR spectra
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.8b00579.
were obtained at 293 K on a 400 or 500 MHz spectrometer, and
chemical shifts were recorded relative to the solvent resonance. 19F
shifts were determined relative to CFCl3 as an outside standard, and
low field is positive. Coupling constants are reported in hertz. The
following abbreviations were used to explain the multiplicities: s =
singlet; d = doublet; t = triplet; q = quartet; m = multiplet; br = broad.
Preparation of cis-[Au(PCy3)(4-F-C6H4)(Cl)2] (2). cis-[Au-
(PCy3)(4-F-C6H4)(Cl)2] (2) was synthesized by oxidative addition
of 4-fluorobenzenediazonium chloride to [(Cy3P)Au(Cl)] in CH3CN
at room temperature under blue LED irradiation, following a
procedure developed by the Hashmi group. 4-Fluoroaniline (44.4
mg, 0.400 mmol) and acetonitrile (0.4 mL) were placed in a Schlenk
tube equipped with a magnetic stir bar. A solution of concentrated
HCl (60 mg, 0.60 mmol) in CH3CN (0.4 mL) was added at 0 °C, and
X-ray diffraction data of complexes 3 and 3a, data for
kinetics, and DFT calculation of Ar−CF2H bond
formation from complex 3 (PDF)
Accession Codes
CCDC 1848595−1848596 contain the supplementary crys-
tallographic 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.
t
the mixture was stirred for 5 min. BuONO (60 μL, 0.44 mmol) was
added dropwise. The mixture was stirred for another 15 min at 0 °C.
The resulting mixture was then frozen with liquid nitrogen and
Cy3PAuCl (102 mg, 0.200 mmol) was added. The mixture was
degassed with freeze−pump−thaw for three cycles and was then
irradiated with blue LEDs for 18 h at room temperature. A 10 mL
portion of diethyl ether was added, and the precipitate were filtered as
AUTHOR INFORMATION
■
Corresponding Authors
*E-mail for P.W.: weiping@njtech.edu.cn.
*E-mail for Y.L.: lanyu@cqu.edu.cn.
*E-mail for Q.S.: shenql@sioc.ac.cn.
1
a white solid (50 mg, 48%). H NMR (400 MHz, chloroform-d): δ
ORCID
7.28 (dd, J = 8.5, 5.5 Hz, 2 H), 6.94 (t, J = 8.7 Hz, 2 H), 2.48 (d, J =
12.2 Hz, 3 H), 1.92 (t, J = 9.2 Hz, 6 H), 1.85−1.77 (m, 6 H), 1.68
(dtd, J = 13.7, 9.7, 9.3, 5.1 Hz, 9 H), 1.24 (dt, J = 13.2, 3.7 Hz, 3 H),
1.13−1.01 (m, 6 H). 19F NMR (376 MHz, CDCl3, 298 K): δ −103.61
to −135.72 (m, 1 F). 31P NMR (162 MHz, CDCl3, 298 K): δ 29.20
ppm.
Yu Lan: 0000-0002-2328-0020
Qilong Shen: 0000-0001-5622-153X
Notes
The authors declare no competing financial interest.
F
DOI: 10.1021/acs.organomet.8b00579
Organometallics XXXX, XXX, XXX−XXX

Organometallics
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ACKNOWLEDGMENTS
■
We acknowledge financial support from the Strategic Priority
Research Program of the Chinese Academy of Sciences
(XDB20000000) and National Natural Science Foundation
of China (21625206, 21632009, 21421002).
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