Synthesis of copper(I) thiolate complexes in the thioetherification of aryl halides

Article abstract of DOI:10.1021/om300711c

The copper(I) thiophenolato complexes 1-3 containing 1,10-phenanthroline (phen) and 2,9-dimethyl-1,10-phenanthroline (Me₂phen) were isolated in excellent yields from reactions of [CuOtBu]₄ with the dative ligands and subsequent addition of 1 equiv of arenethiol. These complexes were characterized spectroscopically and crystallographically. X-ray structural analysis of a single crystal of [(phen)Cu(μ-SC₆H ₅)]₂ (1) revealed that this complex adopts a neutral dimeric form with a weak Cu-Cu bonding interaction. These complexes were found to react with iodoarenes to form aryl sulfide products. The intermediacy of such complexes in copper-catalyzed thioetherification of aryl halides was demonstrated by the reactivity with p-tolyl iodide and o-tolyl iodide to form two aryl thioethers with selectivities similar to those of catalytic reactions conducted with the same two iodoarenes.

Full text of DOI:10.1021/om300711c

Article
pubs.acs.org/Organometallics
Synthesis of Copper(I) Thiolate Complexes in the Thioetherification
of Aryl Halides
Chaohuang Chen,† Zhiqiang Weng,*,† and John F. Hartwig*,‡
†Department of Chemistry, Fuzhou University, Fujian 350108, People's Republic of China
‡Department of Chemistry, University of California, Berkeley, California 94720, United States.
S
* Supporting Information
ABSTRACT: The copper(I) thiophenolato complexes 1−3
containing 1,10-phenanthroline (phen) and 2,9-dimethyl-1,10-
phenanthroline (Me2phen) were isolated in excellent yields
from reactions of [CuOtBu]4 with the dative ligands and
subsequent addition of 1 equiv of arenethiol. These complexes
were characterized spectroscopically and crystallographically.
X-ray structural analysis of a single crystal of [(phen)Cu(μ-
SC6H5)]2 (1) revealed that this complex adopts a neutral
dimeric form with a weak Cu−Cu bonding interaction. These complexes were found to react with iodoarenes to form aryl sulfide
products. The intermediacy of such complexes in copper-catalyzed thioetherification of aryl halides was demonstrated by the
reactivity with p-tolyl iodide and o-tolyl iodide to form two aryl thioethers with selectivities similar to those of catalytic reactions
conducted with the same two iodoarenes.
Liebeskind and Musaev et al. reported a density functional
theory study on the mechanism of the CuI-templated aerobic
cross-coupling of thiol esters with boronic acids to form
ketones in which the nature of the active oxidized species
[LC(O)R1]Cu−(O2)−Cu[LC(O)R1]2+ in these reactions was
assessed.40 In addition, Punniyamurthy and co-workers
suggested that the C−S cross-coupling of thiols with aryl
halides occurs by oxidative addition of RX to form the
intermediate LnRCuX followed by reductive elimination of
LnRCuSAr.41 However, the composition of the species that
undergo these steps has not been established.
Recent contributions from our laboratory include the
synthesis, characterization, and reactivity of a series of
copper(I) imidate, amidate, amido, and phenoxide complexes
that are chemically and kinetically competent to be
intermediates in Ullmann reactions.42−44 This information
has clarified several mechanistic questions about copper-
catalyzed coupling reactions. In brief, the phenoxide and
amidate complexes adopt ionic structures consisting of a copper
cation containing two bidentate dative ligands and a copper
anion containing two of the anionic ligands. These structures
were shown to be the most stable form of these complexes in
the solid state and in solution. Here, we report the preparation
and isolation of copper(I) thiophenolato complexes, the
structures of these species, and their reactions with aryl iodides.
The structures of these species are distinct from those of the
analogous copper(I) phenoxide complexes.
INTRODUCTION
■
Much research has focused on the development of copper
catalysis in organic synthesis during the past decade.1−12 When
simple ligands are used, the catalysts are inexpensive and less
toxic than those based on precious metals. Copper-catalyzed
coupling reactions to form C(aryl)−C, C(aryl)−N, and
C(aryl)−O bonds starting from aryl halides and suitable
reagents have been a particular focus of this work. Given the
importance of aryl sulfides and their derivatives in numerous
biologically and pharmaceutically active compounds,13−19
copper-catalyzed C(aryl)−S bond-forming reactions (eq
1)20−30 have been developed. However, this reaction has
been studied much less than other copper-catalyzed cou-
plings.31 Most relevant to the work described here, no studies
on the mechanism of copper-catalyzed coupling of thiol
nucleophiles by ligated copper systems have been reported.
A series of ligands have been used with different copper
precursors for the coupling of thiols with aryl halides, including
ethylene glycol,32 neocuproine,33 1,2-diamine derivatives,34
1,1,1-tris(hydroxymethyl)ethane,35 amino acids,36 and β-keto
esters.37,38 These ligands have been proposed to increase the
catalyst solubility or stability and prevent aggregation of the
metal, but the identity of thiolate complexes containing these
ligands and the reactions of these complexes with haloarenes
have not been reported.
Special Issue: Copper Organometallic Chemistry
Liebeskind and co-workers proposed that the coupling of
boronic acids and N-thioimides proceeded through a
combination of CuI and CuIII species.39 More recently,
Received: July 31, 2012
Published: October 4, 2012
© 2012 American Chemical Society
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RESULTS AND DISCUSSION
■
Synthesis of Copper(I) Thiophenolato and Alkane-
thiolate Complexes. A series of copper(I) thiophenolato
complexes containing 1,10-phenanthroline (phen) and 2,9-
dimethyl-1,10-phenanthroline (Me2phen) were prepared by the
methods outlined in Scheme 1. Treatment of [CuOtBu]4 with
Scheme 1
the dative ligand and subsequent addition of 1 equiv of
arenethiol resulted in the formation of complexes 1−3,
containing phen and Me2phen as the ancillary dative ligand.
These complexes were isolated in excellent yields (81−86%
yield). All these Cu(I) thiophenolates are diamagnetic and were
characterized by NMR spectroscopy and elemental analysis.
The reaction of CuCl with KSBn, followed by addition of
Me2phen, produced complex 4, containing two K+ ions ligated
by six Me2phen groups and an anionic tetranuclear copper(I)
cluster ligated by six thiolates (Scheme 2). This Cu(I) alkylthio
Figure 1. ORTEP drawing of 1 showing 40% probability thermal
ellipsoids. The hydrogen atoms are omitted for clarity.
Table 1. Selected Bond Lengths and Angles of Complex 1
Bond Lengths (Å)
Cu(1)−Cu(1A)
Cu(1)−S(2)
Cu(1)−N(2)
2.7207(4)
2.3400(5)
2.0710(14)
Cu(1)−S(1)
Cu(1)−N(1)
2.2913(5)
2.0923(13)
Bond Angles (deg)
S(1)−Cu(1)−S(2)
N(2)−Cu(1)−N(1)
N(2)−Cu(1)−S(2)
108.011(14) Cu(1)−S(1)−Cu(1A)
72.84(2)
Scheme 2
80.69(5)
N(1)−Cu(1)−S(1)
122.30(4)
114.31(4)
pseudotetrahedral. Both Cu atoms are ligated by one phen
ligand and bridged by the S atoms of the thiophenolato to form
a planar Cu2S2 ring.
The Cu−Cu distance in 1 (2.7207(4) Å) is slightly longer
than that observed in the related thiolato complexes [(phen)-
Cu(μ-SC6H4CH3-o)]2 (2.613(3) Å)46 and [(Me2phen)Cu(μ-
SC6H4CH3-o)]2 (2.613 Å)45 but is short enough to suggest that
the complex contains a weak Cu−Cu bonding interaction.
These Cu−Cu distances are much shorter than that in the
complex (Ph3P)2Cu(μ-SPh)2Cu(PPh3)2 (3.662(2) Å).47 The
Cu−S distances are 2.2913(5) and 2.3400(5) Å, and these
distances are slightly shorter than those found in (Ph3P)2Cu(μ-
SPh)2Cu(PPh3)2 (2.344(4) and 2.415(4) Å) and a thiolate-
bridged polymeric copper(I) compound, [(Me2phen)Cu-
(SC6H5)]n (average 2.319 Å).48 However, all of these bond
lengths are longer than those observed in the monomeric Cu(I)
complex (tmphen)Cu(SAr) (2.1470(8) and 2.1687(14) Å).49
The Cu−S−Cu angle in 1 is only 72.84(2)°, and this angle is
much smaller than that the 102.75(4) and 98.63(4)° Cu−S−
Cu angles in (Ph3P)2Cu(μ-SPh)2Cu(PPh3)2. This small angle
in 1 leads to the short Cu−Cu distance. The Cu−N distances
(2.0923(13) and 2.0710(14) Å) are similar to those in the
neutral and ionic compounds of phen-ligated copper(I)
imidate, amidate, and aryloxide complexes.
complex was obtained after crystallization from the reaction
mixture in 92% yield. This result highlights that the site for
binding of the dative ligand can be the countercation, as well as
the copper reaction site.
To assess whether the arene thiolate complexes adopt ionic
forms in solution or maintain the neutral forms observed in the
solid state (vide infra), we measured the conductivity of 0.01
mM solutions containing complexes 1−4 in DMSO. The small
values for the conductivity of solutions of 1−3 (2.55, 2.07, 7.89
Ω−1 cm2 mol−1, respectively) versus those of [NBu4]Br (30.0
Ω−1 cm2 mol−1) imply that the neutral structure is the major
form of the thiophenolato in solution, even in polar solvents.
For reference, the conductivity of ferrocene was 0.09 Ω−1 cm2
mol−1. The higher conductivity value of 15.7 Ω−1 cm2 mol−1 for
4 is consistent with a structure in solution that is similar to the
structure in the solid state.
X-ray Structure of [(phen)Cu(μ-SC6H5)]2 (1). Crystals of
1 suitable for X-ray diffraction were grown from CH2Cl2 at −30
°C. An ORTEP diagram of 1 is shown in Figure 1, and selected
bond lengths and angles are summarized in Table 1. Related
structures of ortho-substituted copper thiolates ligated by
substituted phenanthrolines were reported previously.45 In
sharp contrast to the ionic phenoxide complexes of
phenanthroline we isolated and characterized previously,42−44
complex 1 adopts a neutral dimeric structure in the solid state.
The coordination geometry about the copper atom is
X-ray Structure of [(Me2phen)3K]2[Cu4(μ-SCH2C6H5)6]
(4). Single crystals of the tetranuclear copper complex 4 were
grown by the diffusion of pentane into a THF solution of 4 at
−30 °C. An ORTEP diagram is shown in Figure 2, and selected
geometric parameters are given in Table 2. In contrast to the
copper(I) thiophenolato complexes, complex 4 exists as an
ionic form in the solid state. The anion cluster comprises a
tetrahedral array of copper(I) centers ligated by six SBn ligands.
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containing the less sterically hindered phen ligand, reacts more
quickly than complex 3, containing the more sterically hindered
o,o′-dimethyl-disubstituted Me2phen ligand. This observation
parallels the relative reactions of aryl halides with copper(I)
phenoxide complexes containing the same two ligands,43
despite the difference in the ground-state structures. Complex
4 reacted with 5 equiv of p-tolyl iodide after 16 h at 110 °C in
DMSO to afford the coupled product in 95% yield (eq 3).
Figure 2. ORTEP drawing of the dianion 4 showing 50% probability
thermal ellipsoids. The hydrogen atoms are omitted for clarity.
Table 2. Selected Bond Lengths and Angles of Complex 4
To evaluate the intermediacy of the thiophenolato complexes
in the copper-catalyzed etherification, we conducted the
reactions of 2 with two iodoarenes and compared the ratio of
the products of this reaction to that from a catalytic reaction
between the arenethiol and the same two aryl halides. If
complexes 1−3 are intermediates in the catalytic reaction, then
the ratios of products from a single-turnover experiment and a
catalytic reaction should be similar.
Bond Lengths (Å) .
Cu(1)−Cu(2)
Cu(1)−Cu(1B)
Cu(2)−Cu(1A)
Cu(2)−S(1)
2.7126(8)
2.7273(7)
2.7126(8)
2.2651(8)
2.2706(8)
Cu(1)−Cu(1A)
Cu(2)−Cu(1B)
Cu(1)−S(1)
Cu(1)−S(2)
Cu(1)−S(2A)
2.7273(7)
2.7126(8)
2.2848(10)
2.3044(8)
2.2706(8)
Cu(1A)−S(2)
Bond Angles (deg)
S(1)−Cu(1)−S(2)
S(2A)-Cu(1)−S(2)
S(2)−Cu(1)−Cu(2)
110.06(3)
125.13(4)
103.69(2)
S(2A)−Cu(1)−S(1)
S(1)−Cu(1)−Cu(2)
124.57(3)
53.07(3)
59.80(1)
Isolated complex 2 reacted with a mixture of p-tolyl iodide
and o-tolyl iodide to produce a 57:43 ratio of bis(4-
methylphenyl) sulfide and o-tolyl(p-tolyl)sulfide (eq 4). The
Cu(2)−Cu(1)−
Cu(1B)
Cu(2)−Cu(1)−
59.821(11) Cu(1B)−Cu(1)−
60.0
Cu(1A)
Cu(1A)
Cu(2)−S(1)−Cu(1)
73.20(3)
Cu(1B)−S(2)−Cu(1)
73.18(3)
Each copper atom is surrounded by three ligands to form a
nearly trigonal planar geometry.
The Cu−Cu distances in 4 range from 2.7126(8) to
2.7273(7) Å and are comparable to the observed bond
distances in 1 and the related thiolato tetranuclear Cu(I)
complex (Ph4P)2[Cu4(SPh)6] (a mean Cu−Cu distance of 2.76
(2) Å)50 and also shows a weak bonding interaction. The Cu−S
distances (average 2.2812 Å) are marginally shorter than those
found in 1. The Cu−S−Cu angles (73.20(3) and 73.18(3)°)
are also similar to those of complex 1.
reaction of NaSC6H4Me-p with a 1:1 mixture of the two
iodoarenes catalyzed by Cu/phen formed the same two aryl
sulfides in a similar ratio (eq 5; Cu:phen = 1:1, (56 1):44;
Reactivity of 1−4 with Aryl Iodides. These copper(I)
thiophenolato complexes react with haloarenes to form aryl
thioethers. The results of these experiments are summarized in
eq 2. Reaction of the phen-ligated complex 2 with 5 equiv of p-
iodotoluene in DMSO-d6 produced bis(4-methylphenyl)
sulfide in 99% yield after 3 h at 110 °C, and reaction of the
Me2phen-ligated complex 3 with 5 equiv of p-iodotoluene in
DMSO-d6 formed bis(4-methylphenyl) sulfide in 83% yield
after 6 h at 110 °C. These results indicate that complex 2,
Cu:phen = 1:2, (57 1):43; Cu:phen = 1:4, (57 1):43). The
presence of the phen ligand affects the selectivity of the metal
for the two haloarenes, although the effect was subtle. The
reaction of a 1:1 ratio of the two iodoarenes catalyzed by CuI
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alone gave a (51 2):49 ratio of the two aryl sulfides, rather
than a (56−62):(38−44) ratio, and formed the two products in
a lower combined yield (eq 5). In sharp contrast, in the absence
of copper catalyst, the reaction afforded the two aryl sulfide
products in a decreased yield with a (36 3):64 ratio.51 Thus,
these data are at least consistent with the intermediacy of the
isolated copper(I) thiophenolato complexes in the couplings of
thiols with iodoarenes in the presence of CuI and phenanthro-
line as ligand.
of p-toluenethiol with o-(allyloxy)iodobenzene, in the presence
of 10 mol % CuI and 20 mol % phen in DMSO solvent at 110
°C, produced 7 and 8 in 62% and 5% yields, respectively (eq
8). No cyclized product 3-methyl-2,3-dihydrobenzofuran was
The mechanism of the reactions of these complexes with
iodoarenes was evaluated by conducting experiments that probe
the potential for initial electron transfer and the potential
intermediacy of free aryl radical intermediates. To probe the
potential of an initial, outer-sphere electron-transfer mecha-
nism, we compared the reactivity of the copper(I) thiopheno-
lato with 4-chlorobenzonitrile to the reactivity of this complex
with 1-bromonaphthalene. The chloroarene is more easily
reduced than the bromoarene, and the resulting aryl radical
anions undergo dissociation of halide at the same fast rates.52,53
However, concerted oxidative additions of chloroarenes are
typically much slower than concerted oxidative additions of
bromoarenes.
In the event, the reaction of 2 in DMSO at 110 °C with 4-
chlorobenzonitrile and 1-bromonaphthalene in separate vessels
for 12 h produced the corresponding aryl sulfides 5 and 6 in 0%
and 69% yields, respectively. Consistent with this observation,
the reaction of 2 with a mixture of 4-chlorobenzonitrile and 1-
bromonaphthalene in DMSO at 110 °C after 12 h generated 5
and 6 in 0% and 32% yields, respectively (eq 6). This lack of
reaction with the chloroarene but reaction with the less readily
reduced bromoarene argues against a mechanism involving
initial, outer-sphere electron transfer.
formed in either of these reactions. This absence of products
from cyclization in the stoichiometric or catalytic reactions
implies that the C−S coupling process occurs without the
intermediacy of aryl radicals.
CONCLUSION
■
In conclusion, we have prepared copper(I) thiophenolato
complexes that are kinetically and chemically competent to be
intermediates in the copper-catalyzed thioetherification of aryl
halides. The arenethiolate complexes exist in a neutral dimeric
form in the solid state, whereas the benzenethiolate complex
adopts a tetranuclear ionic structure with the dative
phenanthroline ligand bound to the potassium cation and the
tetranuclear copper species possessing a dianionic charge. The
reactivity of the complexes with two haloarenes that probe for
electron transfer processes and the reactivity of an aryl iodide
that probes for the intermedicy of aryl radicals provide evidence
against electron transfer to form free or caged aryl radicals.
Further investigations on the mechanisms of copper-catalyzed
coupling reactions are currently being conducted.
EXPERIMENTAL SECTION
■
General Experimental Procedure and Reagent Availability.
All manipulations were carried out under an inert atmosphere using a
nitrogen-filled glovebox or standard Schlenk techniques. All glassware
was oven- or flame-dried immediately prior to use. Solvents were
freshly dried and degassed according to the procedures in ref 56 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
without further purification. Copper tert-butoxide ([CuO-tBu]4) was
prepared using the reported procedures.54,55 The 1H and 13C{1H}
NMR spectra were obtained at 293 K on a Bruker Avance 400
spectrometer, and chemical shifts were recorded relative to the solvent
resonance. GC-MS measurements were conducted on a Shimadzu
QP2010SE instrument. GC measurement was conducted on a
Shimadzu 2010Plus with an FID detector. Elemental analyses were
performed at the Microanalytical Laboratory of the Fujian Institute of
Research on the Structure of Matter.
Preparation of [(phen)Cu(μ-SC6H5)]2 (1). A solution of 1,10-
phenanthroline (18.0 mg, 0.100 mmol) in 1 mL of THF was added
dropwise to a solution of [CuOtBu]4 (13.6 mg, 0.0250 mmol) in 5 mL
of THF. The resulting reddish brown solution was stirred at room
temperature for 30 min. To this mixture was added a solution of
thiophenol (11.0 mg, 0.100 mmol) in 1 mL of THF. The product
precipitated from the reaction mixture immediately as a red-brown
precipitate. The mixture was stirred for an additional 1 h at room
temperature, at which time pentane (12 mL) was added to precipitate
the remaining product. The product was separated by filtration
through a fine-fritted funnel and washed with pentane to afford 28.5
mg (81% yield) of 1 that was analytically pure after recrystallization
from CH2Cl2/Et2O. 1H NMR (400 MHz, DMSO-d6): δ 9.09 (s, 2H),
8.48 (s, 4H), 7.96 (s, 4H), 7.65 (s, 4H), 6.90 (s, 4H), 6.46 (s, 2H),
6.34 (s, 4H). 13C{1H} (101 MHz, DMSO-d6): δ 149.69, 142.91,
The intermediacy of an aryl radical formed by another
mechanism was probed by conducting reactions with o-
(allyloxy)iodobenzene. This aryl radical corresponding to this
iodoarene is known to undergo cyclization to yield the 2,3-
(dihydrobenzofuranyl)methyl radical with a rate constant of 9.6
× 109 s−1 in DMSO with subsequent formation of 2-
methyldihydrobenzofuran. Thus, if the copper complex led to
generation of a free aryl radical from the iodoarene, the reaction
of 2 with o-(allyloxy)iodobenzene would generate cyclized
products.
The reaction of 2 with o-(allyloxy)iodobenzene in DMSO-d6
at 110 °C 28 h gave the product 7 from C−S coupling at the
aryl group in 54% yield, along with phenyl allyl ether 8 in 1%
yield from hydrodehalogenation (eq 7). The catalytic reaction
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1
136.58, 131.88, 129.93, 128.07, 127.73, 127.03, 124.96, 122.14. Anal.
Calcd for C36H26Cu2N4S2·0.25CH2Cl2: C, 59.88; H, 3.67; N, 7.71.
Found: C, 60.24; H, 3.71; N, 8.03. Conductivity (34 °C, 0.01 mM in
DMSO): 2.55 Ω cm2 mol−1.
NMR tube was removed at regular intervals, and H NMR spectra
were acquired at 25 °C until the yield did not change. The yield of the
p-tolyl phenyl sulfide was calculated to be 99%.
Representative Procedure for Measuring the Yield of
[(Me2phen)Cu(μ-SC6H4CH3-p)]2 (3) with p-Iodotoluene. Com-
plex 3 (7.9 mg, 0.020 mmol) and 1,3,5-trimethoxybenzene (3.4 mg,
0.020 mmol) as internal standard were weighed into a vial and
dissolved in 0.6 mL of DMSO-d6. The contents of the vial were
agitated and then transferred to an NMR tube containing a septum-
lined screw cap. An initial 1H NMR spectrum was acquired. p-
Iodotoluene (21.8 mg, 0.100 mmol, 5.0 equiv) was then added as a
DMSO-d6 solution (0.1 mL), and the resulting mixture was heated at
110 °C in an oil bath. The NMR tube was removed at regular intervals,
Preparation of [(phen)Cu(μ-SC6H4CH3-p)]2 (2). A solution of
1,10-phenanthroline (18.0 mg, 0.100 mmol) in 1 mL of THF was
added dropwise to a solution of [CuOtBu]4 (13.6 mg, 0.0250 mmol)
in 5 mL of THF. The resulting reddish brown solution was stirred at
room temperature for 30 min. To this mixture was added a solution of
p-thiocresol (12.4 mg, 0.100 mmol) in 1 mL of THF. The product
precipitated from the reaction mixture immediately as a red-brown
precipitate. The mixture was stirred for an additional 1 h at room
temperature, at which time pentane (12 mL) was added to precipitate
the remaining product. The product was separated by filtration
through a fine-fritted funnel and washed with pentane to afford 31.5
mg (86% yield) of 2 that was analytically pure after recrystallization
from CH2Cl2/Et2O. 1H NMR (400 MHz, DMSO-d6): δ 9.07 (s, 4H),
8.51 (s, 4H), 7.99 (s, 4H), 7.71 (s, 4H), 6.76 (s, 4H), 6.18 (s, 4H),
1.91 (s, 6H). 13C{1H} (101 MHz, DMSO-d6): δ 149.78, 143.42,
139.41, 131.69, 130.58, 128.79, 127.75, 126.91, 124.79, 20.70. Anal.
Calcd for C38H30Cu2N4S2·CH2Cl2·Et2O: C, 57.84; H, 4.74; N, 6.27.
Found: C, 57.91; H, 4.28; N, 6.09. Conductivity (34 °C, 0.01 mM in
DMSO): 2.07 Ω cm2 mol−1.
Preparation of [(Me2phen)Cu(μ-SC6H4CH3-p)]2 (3). A solution
of 2,9-dimethyl-1,10-phenanthroline (21.7 mg, 0.100 mmol) in 1 mL
of THF was added dropwise to a solution of [CuOtBu]4 (13.6 mg,
0.0250 mmol) in 5 mL of THF. The resulting reddish brown solution
was stirred at room temperature for 30 min. To this mixture was added
a solution of p-thiocresol (12.4 mg, 0.100 mmol) in 1 mL of THF. The
product precipitated from the reaction mixture immediately as a red-
brown precipitate. The mixture was stirred for an additional 1 h at
room temperature, at which time pentane (12 mL) was added to
precipitate the remaining product. The product was separated by
filtration through a fine-fritted funnel and washed with pentane to
afford 33.0 mg (83% yield) of 3 that was analytically pure after
recrystallization from CH2Cl2/Et2O. 1H NMR (400 MHz, DMSO-d6):
δ 8.75 (d, J = 8.3 Hz, 4H), 8.21 (s, 4H), 7.96 (d, J = 8.3 Hz, 4H), 7.00
(s, 4H), 6.44 (s, 4H), 2.39 (s, 12H), 2.06 (s, 6H). 13C{1H} (101 MHz,
DMSO-d6): δ 158.18, 147.74, 137.95, 136.97, 132.45, 128.04, 127.69,
126.43, 126.20, 125.79, 25.70, 20.89. Anal. Calcd for
C42H38Cu2N4S2·0.5CH2Cl2: C, 61.32; H, 4.72; N, 6.73. Found: C,
61.12; H, 5.00; N, 6.62. Conductivity (34 °C, 0.01 mM in DMSO):
7.89 Ω cm2 mol−1.
1
and H NMR spectra were acquired at 25 °C until the yield did not
change. The yield of the p-tolyl phenyl sulfide was calculated to be
83%.
Representative Procedure for Measuring the Yield of
[(Me2phen)3K]2[Cu4(μ-SCH2C6H5)6] (4) with p-Iodotoluene. Into
a small vial was placed 4 (7.7 mg, 0.0033 mmol), p-iodotoluene (21.8
mg, 0.100 mmol), and 0.6 mL of DMSO. The vial was sealed with a
Teflon-lined screw cap, and the mixture was stirred at 110 °C for 16 h.
The resulting solution was warmed to room temperature, and 100 μL
of diphenyl disulfide (0.20 mmol/mL in DMSO) was added as internal
standard. The mixture then was filtered through a layer of Celite. The
filtrate was analyzed by GC/MS. The yield was calculated to be 95%.
Competition Reaction of [(phen)Cu(μ-SC6H4CH3-p)]2 (2) with
p-Iodotoluene and o-Iodotoluene. Into a small vial was placed 2
(7.3 mg, 0.020 mmol), p-iodotoluene (21.8 mg, 0.100 mmol), o-
iodotoluene (21.8 mg, 0.100 mmol), and 0.6 mL of DMSO-d6. The
vial was sealed with a Teflon-lined screw cap, and the mixture was
stirred at 110 °C for 3 h. The resulting solution was warmed to room
temperature, and 100 μL of a solution of 1,3,5-trimethoxybenzene
(0.20 mmol/mL in DMSO-d6) was added as internal standard. The
mixture then was filtered through a layer of Celite. The filtrate was
analyzed by 1H NMR spectroscopy. The yields of p-tolyl phenyl sulfide
and o-tolyl phenyl sulfide were calculated to be 57% and 43%,
respectively.
Competition Reaction of NaSC6H4Me-p with p-Iodotoluene
and o-Iodotoluene Catalyzed by CuI/phen (1:2). Into a small vial
was placed CuI (1.0 mg, 0.0050 mmol, 10 mol %), 1,10-
phenanthroline (1.8 mg, 0.010 mmol, 20 mol %), NaSC6H4Me-p
(7.3 mg, 0.050 mmol), p-iodotoluene (54.5 mg, 0.250 mmol), o-
iodotoluene (54.5 mg, 0.250 mmol), and 0.6 mL of DMSO-d6. The
vial was sealed with a Teflon screw cap, and the reaction mixture was
stirred at 110 °C for 24 h. The resulting mixture was warmed to room
temperature, and 100 μL of 1,3,5-trimethoxybenzene (0.20 mmol/mL
in DMSO-d6) was added as internal standard. The mixture then was
filtered through a layer of Celite. The filtrate was analyzed by 1H NMR
spectroscopy. The yields of p-tolyl phenyl sulfide and o-tolyl phenyl
sulfide were calculated to be 54% and 34%, respectively.
Competition Reaction of NaSC6H4Me-p with p-Iodotoluene
and o-Iodotoluene Catalyzed with CuI/phen (1:1). Into a small
vial was placed CuI (1.0 mg, 0.0050 mmol, 10 mol %), 1,10-
phenanthroline (0.9 mg, 0.005 mmol, 10 mol %), NaSC6H4Me-p (7.3
mg, 0.050 mmol), p-iodotoluene (54.5 mg, 0.250 mmol), o-
iodotoluene (54.5 mg, 0.250 mmol), and 0.6 mL of DMSO. The
vial was sealed with a Teflon-lined screw cap, and the reaction mixture
was stirred at 110 °C for 24 h. The resulting mixture was warmed to
room temperature, and 100 μL of diphenyl disulfide (0.20 mmol/mL
in DMSO) was added as internal standard. The mixture then was
filtered through a layer of Celite. The filtrate was analyzed by GC/MS.
The yields of p-tolyl phenyl sulfide and o-tolyl phenyl sulfide were
calculated to be 54% and 41%, respectively.
Competition Reaction of NaSC6H4Me-p with p-Iodotoluene
and o-Iodotoluene Catalyzed with CuI/phen (1:4). Into a small
vial was placed CuI (1.0 mg, 0.0050 mmol, 10 mol %), 1,10-
phenanthroline (3.6 mg, 0.020 mmol, 40 mol %), NaSC6H4Me-p (7.3
mg, 0.050 mmol), p-iodotoluene (54.5 mg, 0.250 mmol), o-
iodotoluene (54.5 mg, 0.250 mmol), and 0.6 mL of DMSO. The
vial was sealed with a Teflon-lined screw cap, and the reaction mixture
Preparation of [(Me2phen)3K]2[Cu4(μ-SCH2C6H5)6] (4). A
solution of KSCH2C6H5 (16.2 mg, 0.100 mmol) in 1 mL of THF
was added to a suspension of CuCl (9.9 mg, 0.10 mmol) in 5 mL of
THF. The resulting mixture was stirred at room temperature for 1 h.
To this yellow mixture was added a solution of 2,9-dimethyl-1,10-
phenanthroline (21.7 mg, 0.100 mmol) in 1 mL of THF. The resulting
solution turned reddish brown immediately and was further stirred at
room temperature for 30 min. The resulting reaction mixture was
filtrated through a layer of Celite. Pentane (12 mL) was added to the
filtrate to precipitate the product. The product was separated by
filtration through a fine-fritted funnel and washed with pentane to
1
afford 35.6 mg (92% yield) of 4. H NMR (400 MHz, DMSO-d6): δ
8.35 (d, J = 8.2 Hz, 12H), 7.87 (s, 12H), 7.63 (d, J = 8.2 Hz, 12H),
7.43 (d, J = 7.2 Hz, 12H), 7.14 (t, J = 7.2 Hz, 12H), 7.05 (t, J = 6.7 Hz,
6H), 3.90 (s, 12H), 2.80 (s, 36H). 13C{1H} (101 MHz, DMSO-d6): δ
157.57, 142.14, 137.35, 128.07, 127.33, 127.09, 125.84, 125.61, 124.94,
124.01, 37.01, 25.11. Conductivity (34 °C, 0.005 mM in DMSO): 15.7
Ω cm2 mol−1.
Representative Procedure for Measuring the Yield of
[(phen)Cu(μ-SC6H4CH3-p)]2 (2) with p-Iodotoluene. Complex 2
(7.3 mg, 0.020 mmol) and 1,3,5-trimethoxybenzene (3.4 mg, 0.020
mmol) as internal standard were weighed into a vial and dissolved in
0.6 mL of DMSO-d6. The contents of the vial were agitated and then
transferred to an NMR tube containing a septum-lined screw cap. An
initial 1H NMR spectrum was acquired. p-Iodotoluene (21.8 mg, 0.100
mmol, 5.0 equiv) was then added as a DMSO-d6 solution (0.1 mL),
and the resulting mixture was heated at 110 °C in an oil bath. The
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Article
was stirred at 110 °C for 24 h. The resulting mixture was warmed to
room temperature, and 100 μL of diphenyl disulfide (0.20 mmol/mL
in DMSO) was added as internal standard. The mixture then was
filtered through a layer of Celite. The filtrate was analyzed by GC/MS.
The yields of p-tolyl phenyl sulfide and o-tolyl phenyl sulfide were
calculated to be 56% and 41%, respectively.
diluted with ethyl acetate, and the resulting solution was filtered
through a layer of Celite. The mixture was analyzed by GC/MS. The
yields determined by GC/MS of phenyl allyl ether and the p-tolyl aryl
thioether versus the 1,3,5-trimethoxybenzene internal standard were
calculated to be 1% and 54%, respectively.
Procedure for the Reaction of NaSC6H4Me-p with o-
(Allyloxy)iodobenzene Catalyzed by CuI/phen. Into a small
vial was placed CuI (1.0 mg, 0.0050 mmol, 10 mol %), 1,10-
phenanthroline (1.8 mg, 0.010 mmol, 20 mol %), NaSC6H4Me-p (7.3
mg, 0.050 mmol), o-(allyloxy)iodobenzene (130.0 mg, 0.2500 mmol),
and 0.6 mL of DMSO-d6. The mixture was agitated and transferred to
a Teflon-lined screw-capped NMR tube. The NMR tube was heated at
110 °C in a constant-temperature bath for 24 h. The resulting solution
was warmed to room temperature, and 100 μL of a solution of 1,3,5-
trimethoxybenzene (0.20 mmol/mL in DMSO-d6) was added as
internal standard. A 0.1 mL aliquot of the solution was withdrawn and
diluted with ethyl acetate, and the resulting solution was filtered
through a layer of Celite. The mixture was analyzed by GC/MS. The
yields determined by GC/MS of phenyl allyl ether and the p-tolyl aryl
thioether versus the 1,3,5-trimethoxybenzene internal standard were
calculated to be 5% and 62%, respectively.
Competition Reaction of NaSC6H4Me-p with p-Iodotoluene
and o-Iodotoluene Catalyzed by CuI. Into a small vial was placed
CuI (1.0 mg, 0.0050 mmol, 10 mol %), NaSC6H4Me-p (7.3 mg, 0.050
mmol), p-iodotoluene (54.5 mg, 0.250 mmol), o-iodotoluene (54.5
mg, 0.250 mmol), and 0.6 mL of DMSO-d6. The vial was sealed with a
Teflon-lined screw cap, and the reaction mixture was stirred at 110 °C
for 24 h. The resulting mixture was warmed to room temperature, and
100 μL of 1,3,5-trimethoxybenzene (0.20 mmol/mL in DMSO-d6)
was added as internal standard. The mixture then was filtered through
1
a layer of Celite. The filtrate was analyzed by H NMR spectroscopy.
The yields of p-tolyl phenyl sulfide and o-tolyl phenyl sulfide were
calculated to be 42% and 37%, respectively.
Competition Reaction of NaSC6H4Me-p with p-Iodotoluene
and o-Iodotoluene without CuI/phen. Into a small vial was placed
NaSC6H4Me-p (7.3 mg, 0.050 mmol), p-iodotoluene (54.5 mg, 0.250
mmol), o-iodotoluene (54.5 mg, 0.250 mmol), and 0.6 mL of DMSO.
The vial was sealed with a Teflon-lined screw cap, and the reaction
mixture was stirred at 110 °C for 24 h. The resulting mixture was
warmed to room temperature, and 100 μL of diphenyl disulfide (0.20
mmol/mL in DMSO) was added as internal standard. The mixture
then was filtered through a layer of Celite. The filtrate was analyzed by
GC/MS. The yields of p-tolyl phenyl sulfide and o-tolyl phenyl sulfide
were calculated to be 23% and 40%, respectively.
ASSOCIATED CONTENT
* Supporting Information
■
S
CIF files giving details of the X-ray structures of 1 and 4. This
material is available free of charge via the Internet at http://
pubs.acs.org.
Procedure for the Reaction of [(phen)Cu(μ-SC6H4CH3-p)]2 (2)
with 4-Chlorobenzonitrile. Into a small vial was placed 2 (7.3 mg,
0.020 mmol), 4-chlorobenzonitrile (14.0 mg, 0.100 mmol), and 0.6
mL of DMSO. The vial was sealed with a Teflon-lined screw cap, and
the mixture was stirred at 110 °C for 48 h. The resulting solution was
warmed to room temperature, and 100 μL of 1,3,5-trimethoxybenzene
(0.20 mmol/mL in DMSO) was added as internal standard. The
mixture then was filtered through a layer of Celite. The filtrate was
analyzed by GC/MS. Formation of p-tolyl thiophenyl benzonitrile
product was not detected.
Procedure for the Reaction of [(phen)Cu(μ-SC6H4CH3-p)]2 (2)
with 1-Bromonaphthalene. Into a small vial was placed 2 (7.3 mg,
0.020 mmol), 1-bromonaphthalene (21 mg, 0.10 mmol), and 0.6 mL
of DMSO. The vial was sealed with a Teflon-lined screw cap, and the
mixture was stirred at 110 °C for 48 h. The resulting solution was
warmed to room temperature, and 100 μL of 1,3,5-trimethoxybenzene
(0.20 mmol/mL in DMSO) was added as internal standard. The
mixture then was filtered through a layer of Celite. The filtrate was
analyzed by GC/MS. The yield of the 1-p-tolyl thiophenyl
naphthalene was calculated to be 69%.
Competition Reaction of [(phen)Cu(μ-SC6H4CH3-p)]2 (2) with
4-Chlorobenzonitrile and 1-Bromonaphthalene. Into a small vial
was placed 2 (7.3 mg, 0.020 mmol), 4-chlorobenzonitrile (14 mg, 0.10
mmol), 1-bromonaphthalene (21 mg, 0.10 mmol), and 0.6 mL of
DMSO. The vial was sealed with a Teflon-lined screw cap, and the
mixture was stirred at 110 °C for 48 h. The resulting solution was
warmed to room temperature, and 100 μL of a solution of 1,3,5-
trimethoxybenzene (0.20 mmol/mL in DMSO) was added as internal
standard. The mixture then was filtered through a layer of Celite. The
filtrate was analyzed by GC/MS. The yield of 1-p-tolyl thiophenyl
naphthalene was calculated to be 32%. The p-tolyl thiophenyl
benzonitrile product was not detected.
AUTHOR INFORMATION
Corresponding Author
*E-mail: jhartwig@berkeley.edu (J.F.H.).
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the NIH (GM-55382) for funding and Z.W.
acknowledges financial support from the National Natural
Science Foundation of China (21072030) and Fuzhou
University (022318).
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