Copper(I) trifluoromethylthiolate complex bearing triphenylphosphine ligand for nucleophilic trifluoromethylthiolation of allylic bromides

Article abstract of DOI:10.1016/j.jorganchem.2013.08.008

Copper(I) trifluoromethylthiolate complex (PPh₃) ₂Cu(SCF₃) (1) has been synthesized from a convenient reaction of CuF₂ with CF₃SiMe₃ and S ₈ in the presence of triphenylphosphine. The crystal structure of complex 1 has been determined by X-ray crystallography. In the solid state, complex 1 exists as a monomeric copper(I) species with a three-coordinated trigonal planar geometry. Complex 1 reacted with a wide range of allylic bromides to afford corresponding allylic trifluoromethyl thioethers in moderate to good yields. Several functional groups, including alkyl, alkoxy, nitro, halides and geranyl groups, are tolerated.

Full text of DOI:10.1016/j.jorganchem.2013.08.008

Journal of Organometallic Chemistry 751 (2014) 830e834
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Note
Copper(I) trifluoromethylthiolate complex bearing
triphenylphosphine ligand for nucleophilic trifluoromethylthiolation
of allylic bromides
*
Zhiyuan Wang, Qiqi Tu, Zhiqiang Weng
College of Chemistry and Chemical Engineering, Fuzhou University, Fujian 350108, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Copper(I) trifluoromethylthiolate complex (PPh3)2Cu(SCF3) (1) has been synthesized from a convenient
reaction of CuF2 with CF3SiMe3 and S8 in the presence of triphenylphosphine. The crystal structure of
complex 1 has been determined by X-ray crystallography. In the solid state, complex 1 exists as a
monomeric copper(I) species with a three-coordinated trigonal planar geometry. Complex 1 reacted with
a wide range of allylic bromides to afford corresponding allylic trifluoromethyl thioethers in moderate to
good yields. Several functional groups, including alkyl, alkoxy, nitro, halides and geranyl groups, are
tolerated.
Received 10 June 2013
Received in revised form
2 August 2013
Accepted 5 August 2013
Keywords:
Copper(I) trifluoromethylthiolate
Trifluoromethylthiolation
Allylic bromides
Ó 2013 Elsevier B.V. All rights reserved.
Allylic trifluoromethyl thioether
1. Introduction
stereogenicity [10], in particular for the direct selective incorpora-
tion of a eSCF3 group on an allylic position remains a significant
In recent years, the trifluoromethylthio group (-SCF3) containing
compounds have gained considerable attention in pharmaceutical,
agricultural, and advanced materials industries [1]. This interest
derives from their high lipophilicity, hydrophobicity, and the
recognized potential to have positive influence on biological
activity.
Numerous methods have been reported for the synthesis of this
important class of compounds including the nucleophilic and
radical trifluoromethylation of aryl sulfides and disulfides, thiocy-
anates, and thiols and electrophilic trifluoromethylation of thio-
lates [2e5]. However, most of these reactions require harsh
reaction conditions and the use of expensive and/or toxic reagents.
Recently, transition metal-catalyzed trifluoromethythiolation or
metal-free oxidative trifluoromethylthiolation have provided a
useful method to access these compounds [6e11]. A number of
metal catalysts, including palladium, copper and nickel, have been
exploited for these processes, providing access to various aryl tri-
fluoromethyl thioethers in moderate to excellent yields. Despite the
utility of this approach, the construction of Csp3eSCF3 bonds
challenge.
Trifluoromethylthiocopper (CuSCF3) is well known as a prom-
ising trifluoromethylthiolation reagent for the introduction of e
SCF3 group into arenes [3b,12]. However, there are only two types of
structurally characterized copper trifluoromethylthiolate com-
plexes that have been reported in literature. Examples include
acetonitrile-solvated copper(I) trifluoromethylthiolate complex
[Cu(SCF3)]10(CH3CN)8 [13] and the monomeric alkyne-stabilized
Cu(SCF3) complex [14].
In the context of our interest in the Cu-mediated tri-
fluoromethylation [15] and trifluoromethythiolation chemistry
[16], we have recently isolated and structurally characterized a
series of the dinitrogen-ligated copper(I) trifluoromethylthiolate
complexes [16a]. These complexes were prepared from readily
available, inexpensive materials and reacted with a variety of aryl
and heteroaryl halides to afford aryl trifluoromethyl thioethers in
good to excellent yields. Encouraged by these results, we then
described the first nucleophilic trifluoromethylation of allylic ha-
lides using this copper reagent to prepare allylic trifluoromethyl
thioethers [17]. In view of the wide applicability of phosphine li-
gands as strong s-donor ligands in metal-mediated reactions, we
wish to explore the synthesis of phosphine-ligated copper(I) tri-
fluoromethylthiolate complexes and examine their reactivity to-
wards nucleophilic trifluoromethylthiolation of allylic halides.
* Corresponding author. Tel./fax: þ86 594 22866121.
E-mail address: zweng@fzu.edu.cn (Z. Weng).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.08.008

Z. Wang et al. / Journal of Organometallic Chemistry 751 (2014) 830e834
831
Table 2
Selected bond lengths and angles of complex 1.
ꢀ
Bond lengths (A)
Cu(1)eS(1)
Cu(1)eP(2)
Bond angles (ꢁ)
P(1)eCu(1)eP(2)
S(1)eCu(1)eP(2)
2.2233(13)
2.2546(12)
Cu(1)eP(1)
C(1)eS(1)
2.2703(12)
1.745(5)
Scheme 1.
119.16(4)
126.39(5)
S(1)eCu(1)eP(1)
C(1)eS(1)eCu(1)
114.45(5)
110.53(16)
2. Results and discussion
2.1. Synthesis and characterization of the trifluoromethylthiolate
complex containing triphenylphosphine ligand, (PPh3)2Cu(SCF3) (1)
ꢀ
(bpy)Cu(SCF3) (2.2729(6) A) and significantly shorter than those
found in the dimeric trifluoromethylthiolate complex [(phen)
The reaction of CuF2, sulfur, with CF3SiMe3 (RuppertPrakash
reagent) in CH3CN, followed by the addition of phosphine ligands,
yielded the copper(I) trifluoromethylthiolate complex containing
triphenylphosphine, (PPh3)2Cu(SCF3) (1), as orange solids in 32%
yields (Scheme 1). This method is similar to that used to prepare
copper(I) trifluoromethylthiolate complexes ligated by chelating
nitrogen ligands [16a].
ꢀ
Cu(SCF3)]2 (2.3303(10) A) [16a]. The CueP bond lengths [2.2703(12)
and 2.2546(12) A] are comparable with those observed in other
ꢀ
ꢀ
(PPh3)2Cu(X) (X ¼ Cl, Br and I) complexes (2.260e2.282 A) [18].
ꢀ
Moreover, the copper atom in complex 1 is displaced 0.086 A from
the plane of the sulfur and phosphorus atoms.
2.2. Trifluoromethylthiolation of allylic bromides by 1
Complex 1 is stable in solution toward air and moisture up to
24 h and is indefinitely stable in the solid state. Complex 1 has been
characterized by 1H, 13C, 31P and 19F NMR spectroscopies, as well as
elemental analysis. The 19F NMR spectrum is consistent with the
assignment of 1 with a single resonance appearing at ꢀ18.76 ppm.
The structure of complex 1 was determined by X-ray crystal-
lography (Table 1). Selected bond lengths and angles of complex 1
are given in Table 2.
Having established the crystal structure of copper(I) tri-
fluoromethylthiolate complex 1, we sought to evaluated the
reactivity of this complex towards trifluoromethylthiolation with
allylic bromides. Under our previously reported optimized con-
ditions, a range of allylic bromides were subsequently examined
to study the feasibility of the present reaction (Table 3). We were
gratified to find that treatment of 1 with 2 in CH3CN at 70 ꢁC for
15 h did indeed furnish trifluoromethylthiolated products in
reasonable yields, albeit in some cases somewhat inferior to the
yields by employing the bi-pyridine ligated (phen)Cu(SCF3) as
reagent [17]. Cinnamyl bromide 2a and 4- and 3-methyl and tert-
butyl-substituted cinnamyl bromides (2b, 2c and 2e) reacted with
1 to afford the corresponding allylic trifluoromethyl thioethers
3ae3c and 3e in 75e86% yields based on 1 (entries 1e3 and 5). In
the case of i-propyl-substituted cinnamyl bromides 2d, the
desired trifluoromethylthiolate product 3d was obtained in
moderate yield (44%; entry 4). The electron-rich, 2-methoxy and
3-methoxy-substituted cinnamyl bromides 2f and 2g reacted in
the moderate to good yields (75% and 65%, respectively; entries 6
and 7), whereas the electron-poor, 2-nitro-substituted cinnamyl
The copper atom in complex 1 is bonded to two neutral tri-
phenylphosphine ligands and one anionic SCF3 group (Fig. 1). The
geometry around the copper atom is three-coordinated trigonal
planar with a PeCueP angle of 119.16(4)ꢁ and larger SeCueP angles
of 114.45(5)ꢁ and 126.39(5)ꢁ. The CF3 group is almost in the PeCue
P plane pointing towards P(2), resulting in a large difference be-
tween P(1)eCueS and P(2)eCueS angles of 11.94ꢁ. The PeCueP
angle in 1 is smaller than those found in the [(PPh3)2]CuX com-
pounds (the value for the PeCueP angle in a range 120e130ꢁ) [18].
ꢀ
The CueS bond length of 2.2233(13) A in complex 1 is similar to
that found in the monomeric trifluoromethylthiolate complex
Table 1
Selected crystal data, data collection and refinement parameters of complex 1.
Complex
1e
Formula
C37H30CuF3P2S
689.15
Formula weight
Crystal size/mm
Temperature/K
Crystal system
Space group
0.20 ꢂ 0.13 ꢂ 0.08
173(2)
Monoclinic,
P2(1)/n
11.5342(4)
19.8189(6)
13.9964(4)
90
93.638(3)
90
3193.06(17)
4
ꢀ
a/A
ꢀ
b/A
ꢀ
c/A
ꢁ
ꢁ
a
/
b
/
ꢁ
g
/
3
ꢀ
V/A
Z
Dc/g cmꢀ3
Radiation used
1.434
Mo-K
0.893
a
m
/mmꢀ1
range/ꢁ
q
2.92e25.00
No. of unique reflections measured
5621
Max., min. transmission
1.0000 and 0.92353
R1 ¼ 0.0554, wR2 ¼ 0.1531
R1 ¼ 0.0741, wR2 ¼ 0.1714
0.822
Final R indices [I > 2
R indices (all data)
s
(I)]a,b
Goodness-of-fit on F2 c
ꢀꢀ3
Large diff peak and hole, e A
1.227 and ꢀ0.621
a
R ¼ (SjFoj ꢀ jFcj)SjFoj.
b
2
wR2 ¼ [(S
u
jFoj ꢀ jFcj)2/S
u
jFoj ]1/2
.
Fig. 1. ORTEP diagram of (PPh3)2Cu(SCF3) (1) with thermal ellipsoids at the 40%
probability level. Hydrogen atoms omitted for clarity.
c
GoF ¼ [(S
u
jFoj ꢀ jFcj)2/(Nobs ꢀ Nparam)]1/2
.

832
Z. Wang et al. / Journal of Organometallic Chemistry 751 (2014) 830e834
Table 3
Trifluoromethylthiolation of allylic bromides.a
Entry
1
Allylic bromides
Products
Yield (%)b
83
2
3
75
79
4
5
6
44
86
75
7
8
65
25
9
37
10
11
35
45
12
70
a
Reaction conditions: 1 (0.30 mmol), allylic bromides 2 (0.60 mmol), CH3CN (5.0 mL), 70 ꢁC, 15 h, under N2 atmosphere.
Isolation yield.
b
bromide 2h gave lower yield (25%; entry 8). It is especially
scaffold of 3k can be used for further palladium-catalyzed
transformation. Reactions of the geranyl bromide 2l bearing
no conjugated aromatic rings also occurred to give the corre-
sponding allylic trifluoromethyl thioether 3l in a yield of 70%
(entry 12).
noteworthy that the process readily transformed cinnamyl bro-
mides bearing halogens substituents (2iek) in moderate yields
(35e45%; entries 9e11). Since the aryl bromide 2k is compatible
with the reaction conditions, the allylic trifluoromethyl thioether

Z. Wang et al. / Journal of Organometallic Chemistry 751 (2014) 830e834
833
3. Conclusion
tube equipped with a magnetic stir bar. The tube was sealed and the
solution was placed into a preheated 70 ꢁC oil bath for 15 h. The
tube was removed from the oil bath and allowed to cool. The re-
action mixture was then filtered through Celite to remove metal
salts. Water (10.0 mL) was added to the mixture at 0 ꢁC. The
resulting mixture was extracted with diethyl ether (6.0 mL ꢂ 3),
and the combined organic layers were dried over magnesium sul-
fate. The solvent was removed by rotary evaporation in an ice bath
and the resulting product was purified by column chromatography
on silica gel with pentane.
In conclusion, we have synthesized
a
copper(I) tri-
fluoromethylthiolate complex (PPh3)2Cu(SCF3) (1) from a conve-
nient reaction of CuF2 with CF3SiMe3 and S8 in the presence of
triphenylphosphine. The X-ray crystal structure of 1 shows a three-
coordinated trigonal planar geometry at the copper atom with two
neutral triphenylphosphine ligands and one anionic SCF3 group.
The reactions of complex 1 with a variety of allylic bromides gave
the corresponding allylic trifluoromethyl thioethers in moderate to
good yields. This procedure is compatible with several functional
groups including alkyl, alkoxy, nitro, halides and geranyl groups.
4.4. Crystal structure analyses
4. Experimental
Crystals suitable for X-ray diffraction of 1 were obtained by
allowing n-hexanes to diffuse into a saturated solution of complex in
CH2Cl2 at ꢀ30 ꢁC. The suitable crystal of 1 was mounted on quartz
fibers and X-ray data collected on a Bruker AXS APEX diffractometer,
4.1. General methods and materials
1H NMR, 19F NMR and 13C NMR spectra were recorded using
Bruker AVIII 400 spectrometer. 1H NMR and 13C NMR chemical shifts
were reported in parts per million (ppm) downfield from tetrame-
thylsilane and 19F NMR chemical shifts were determined relative to
CFCl3 as the external standard and low field is positive. Coupling
constants (J) are reported in Hertz (Hz). The residual solvent peak
equipped with a CCD detector at ꢀ100 ꢁC, using MoK
a radiation (l
ꢀ
0.71073 A). The data was corrected for Lorentz and polarization ef-
fect with the SMART suite of programs [20] and for absorption ef-
fects with SADABS [21]. Structure solution and refinement were
carried out with the SHELXTL suite of programs [22]. The structure
was solved by direct methods to locate the heavy atoms, followed by
difference maps for the light non-hydrogen atoms. The data
collection and processing parameters are given in Table 1.
was used as an internal reference: 1H NMR (chloroform
13C NMR (chloroform
77.0). The following abbreviations were used
d 7.26) and
d
to explain the multiplicities: s ¼ singlet, d ¼ doublet, t ¼ triplet,
q ¼ quartet, m ¼ multiplet, br ¼ broad. Allylic bromides 2bek [19]
were prepared according to the published procedures. Other re-
agents were received from commercial sources. Solvents were
freshly dried and degassed according to the purification handbook
Purification of Laboratory Chemicals prior to use. Column chroma-
tography purifications were performed by flash chromatography
using Merck silica gel 60. GCeMS measurements were conducted on
a Shimadzu QP2010SE. GC measurement was conducted on a Shi-
madzu 2010Plus with an FID detector. Elemental analyses were
performed at the Microanalytical Laboratory of Fujian Institute of
Research on the Structure of Matter.
Acknowledgments
Project supported by the National Science Foundation for
Fostering Talents in Basic Research of the National Natural Science
Foundation of China (No. J1103303), National Natural Science
Foundation of China (21072030) and Fuzhou University (022318
and 022494).
Appendix A. Supplementary materials
CCDC 942430 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
4.2. Synthesis of (PPh3)2Cu(SCF3) (1)
In a glovebox, CuF2 (51 mg, 0.50 mmol), S8 (16 mg, 0.50 mmol)
and 10 mL CH3CN were added to an oven-dried resealable Schlenk
tube possessing a Teflon screw valve. CF3SiMe3 (213 mg, 1.50 mmol)
was added into this tube and the tube was sealed. The mixture was
stirred in a preheated (80 ꢁC) oil bath for 8 h. The reaction mixture
was then allowed to cool to room temperature and filtered through
Celite. The volatiles were removed under reduced pressure and the
resulting dark-brown solid was washed with Et2O (3 ꢂ 4 mL). The
solid was re-dissolved in 5 mL CH3CN and to this solution was
added triphenylphosphine (263 mg, 1.0 mmol) in 4 mL of CH3CN.
The resulting orange mixture was stirred at room temperature for
20 min and then was added 8 mL of Et2O. The resulting solution was
then cooled at ꢀ25 ꢁC for 48 h. The resulting orange crystals were,
washed with 4 ꢂ 3 mL of Et2O, and dried to give 110 mg of 1 (32%).
Appendix B. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2013.08.008.
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