Copper(i) 5-phenylpyrimidine-2-thiolate complexes showing unique optical properties and high visible light-directed catalytic performance

Article abstract of DOI:10.1039/c6dt03721f

Solvothermal reactions of 5-phenylpyrimidine-2-thiol (5-phpymtH) with equimolar CuBr afforded one hexanuclear cluster [Cu₆(μ₃-5-phpymt)₆] (1) along with a tetranuclear by-product [{(Cu₂Br)(μ-5-phpymtH)}(μ₃-5-phpymt)]₂ (2). A two dimensional (2D) polymer [Cu₄(μ₅-5-phpymt)₂(μ-Br)₂]_n (3) was isolated from the reaction of 5-phpymtH with two equiv. of CuBr. Analogous reactions of 5-phpymtH with one or four equiv. of CuI produced one tetranuclear cluster [{Cu₂(μ-5-phpymtH)(μ-5-phpymt)}(μ₃-I)]₂ (4) and one 2D polymer [Cu₆I₂(μ₄-I)₂(μ₄-5-phpymt)₂]_n (5). Compound 1 possesses a water-wheel-shaped hexameric structure. Compound 2 has an H-shaped tetrameric structure. Compound 3 possesses a 2D network in which unique 1D [Cu₈(μ-Br)₂(μ₅-5-phpymt)₄]_n chains are connected by μ-Br^- ions. Compound 4 has another tetrameric structure in which two {Cu₂(μ-5-phpymtH)₂(μ-5-phpymt)} fragments are linked by a pair of μ₃-I^- ions. Compound 5 contains another 2D network in which hexanuclear {Cu₆I₂(μ₄-I)₂} units are linked by μ₄-5-phpymt bridges. The 5-phpymt ligand shows four coordination modes: μ-κ¹(S)-κ¹(N) (4), μ₃-κ²(S)-κ¹(N) (1 and 2), μ₄-κ¹(N)-κ²(S)-κ¹(N′) (5) and μ₅-κ¹(N)-κ³(S)-κ¹(N′) (3). Complex 1 shows strong solvatochromic behaviour and displays reversible luminescence switching upon alternate addition of CF₃COOH and Et₃N into its CHCl₃ solution. Complexes 1-5 exhibit a high photocatalytic activity towards the aerobic oxidative hydroxylation of arylboronic acids to phenols under visible light irradiation. Catalyst 5 can be reused in several cycles without any obvious decay of the catalytic efficiency. These results offer an interesting insight into how the CuX/5-phpymtH molar ratios and X^- ions exert great impacts on the coordination modes of the 5-phpymt^- ligand, the structures of the final complexes, and the luminescence and catalytic properties.

Full text of DOI:10.1039/c6dt03721f

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Copper(I) 5-phenylpyrimidine-2-thiolate complexes
showing unique optical properties and high visible
light-directed catalytic performance†
Cite this: DOI: 10.1039/c6dt03721f
a
a
a
a,b
Meng-Juan Zhang, Hong-Xi Li,* Hai-Yan Li and Jian-Ping Lang*
Solvothermal reactions of 5-phenylpyrimidine-2-thiol (5-phpymtH) with equimolar CuBr afforded one
hexanuclear cluster [Cu
6
2
(μ
3
-5-phpymt)
6
]
(1) along with
a
tetranuclear by-product [{(Cu
2
Br)(μ-5-
phpymtH)}(μ -5-phpymt)]
3
(2). A two dimensional (2D) polymer [Cu
4
(μ -5-phpymt) (μ-Br) (3) was iso-
5
2
2 n
]
lated from the reaction of 5-phpymtH with two equiv. of CuBr. Analogous reactions of 5-phpymtH with
one or four equiv. of CuI produced one tetranuclear cluster [{Cu (μ-5-phpymtH)(μ-5-phpymt)}(μ -I)] (4)
and one 2D polymer [Cu (μ -I) (μ -5-phpymt) (5). Compound 1 possesses a water-wheel-shaped
hexameric structure. Compound 2 has an H-shaped tetrameric structure. Compound 3 possesses a 2D
network in which unique 1D [Cu (μ-Br) (μ -5-phpymt)
chains are connected by µ-Br− ions. Compound
has another tetrameric structure in which two {Cu (μ-5-phpymtH) (μ-5-phpymt)} fragments are linked
-I− ions. Compound 5 contains another 2D network in which hexanuclear {Cu
(μ -I)
-5-phpymt bridges. The 5-phpymt ligand shows four coordination modes:
2
3
2
6
I
2
4
2
4
2 n
]
8
2
5
4 n
]
4
2
2
by a pair of µ
3
6
I
2
4
2
}
units are linked by μ
4
2
1
1
1
1
2
1
1
3
1
μ–κ (S)–κ (N) (4), μ
Complex 1 shows strong solvatochromic behaviour and displays reversible luminescence switching upon
alternate addition of CF COOH and Et N into its CHCl solution. Complexes 1–5 exhibit a high photo-
3
–κ (S)–κ (N) (1 and 2), μ
4
–κ (N)–κ (S)–κ (N’) (5) and μ
5
–κ (N)–κ (S)–κ (N’) (3).
3
3
3
catalytic activity towards the aerobic oxidative hydroxylation of arylboronic acids to phenols under visible
Received 25th September 2016,
Accepted 9th October 2016
light irradiation. Catalyst 5 can be reused in several cycles without any obvious decay of the catalytic
efficiency. These results offer an interesting insight into how the CuX/5-phpymtH molar ratios and X− ions
DOI: 10.1039/c6dt03721f
exert great impacts on the coordination modes of the 5-phpymt− ligand, the structures of the final com-
www.rsc.org/dalton
plexes, and the luminescence and catalytic properties.
strong need to screen out more acceptable catalytic approaches
Introduction
1
1–14
using visible light-promoted transformation.
Some homo-
2
+
11
Phenol derivatives are important synthetic intermediates and geneous catalysts such as [Ru(bpy) ] (bpy = 2,2′-bipyridine),
3
1
2
13
14
widely used in the synthesis of pharmaceuticals, agrochem- methylene blue (MB), rose bengal (RB), and eosin Y have
1
–3
icals, natural products and polymeric forms.
The synthetic been used as visible light-mediated photoredox catalysts to
routes to phenols include metal-catalysed hydroxylation of aryl facilitate aerobic oxidative hydroxylation. However, these
4
–6
halides, and the hydroxylation or oxidative hydroxylation of approaches suffer from inherent problems in the separation
7
–10
arylboronic acids using oxidants and/or metal catalysts.
and recycling of the catalysts from the products. To date, there
From both practical and environmental viewpoints, there is a are only a few examples of visible light-promoted oxidative
hydroxylation of arylboronic acids to phenols by using hetero-
1
5–17
geneous catalysts.
Cohen et al. demonstrated that
a
State and Local Joint Engineering Laboratory for Novel Functional Polymeric
18
2+
α-UiO-67 incorporated with the [Ru(bpy)3] group showed
efficient and recyclable catalytic activity for the aerobic oxi-
dation of arylboronic acids under near-UV and visible light
irradiation. On the other hand, the majority of transition
metal complex photosensitizers are based on expensive, non-
earth abundant noble metals including Ru(II), Pt(II), Re(I),
Materials, College of Chemistry, Chemical Engineering and Materials Science,
Soochow University, Suzhou 215123, Jiangsu, People’s Republic of China.
E-mail: lihx@suda.edu.cn, jplang@suda.edu.cn
b
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences, Shanghai 200032, People’s Republic of
China
1
13
†
Electronic supplementary information (ESI) available: The H and C NMR
spectra of phenol derivatives. CCDC 1474574 (1·2MeCN), 1474575 (2), 1474577
3), 1474573 (4), 1474576 (5) and 1474578 ([Cu(5-phpyms) ). For ESI and crys-
1
9–24
Os(II) and Ir(III).
Copper(I) complexes used in solar energy
technologies are an attractive alternative, because they are less
(
2 n
]
2
5–27
tallographic data in CIF or other electronic format see DOI: 10.1039/c6dt03721f
expensive and environmentally more benign.
Homoleptic
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or heteroleptic Cu(I) photosensitizers with two phenanthroline complex suggests that the aforementioned reaction using CuX
N^N ligands or one bidentate P^P and one N^N chelate and 5-phpymtH should be performed under an inert gas atmo-
ligand have been known as efficient visible-light photoredox sphere in order to yield the desired Cu(I)/5-phpymt complexes.
2
8
29
catalysts for alkene azidation, benzylic azidation, atom Thus we ran the solvothermal reactions of the same com-
3
0,31
transfer radical addition and allylation reactions,
α-amino C–H bond functionali- one yellow hexanuclear cluster [Cu
zation, cross-dehydrogenative coupling reactions and oxi- yield) coupled with red blocks of a tetranuclear cluster
hydrogen ponents in MeCN and DMF at 120 °C under N and obtained
2
3
2–34
generation from water,
6
(μ
3 6
-5-phpymt) ] (1) (in 58%
3
5
36
3
7
dative C–N coupling of anilines with terminal alkynes. In [{(Cu Br)(μ-5-phpymtH)}(μ -5-phpymt)] (2) (in 17% yield).
2
3
2
addition, copper(I) complexes with N-heterocyclic thiolates Addition of triethylamine (Et
3
N) into this reaction only gave 1
possess high stability, visible light absorption, intense lumine- with a higher yield (85%). An analogous reaction of CuBr with
3
8–41
scence and long fluorescence lifetime,
which may lead to 5-phpymtH in a 2 : 1 molar ratio under similar reaction conditions
high photocatalytic activity under visible light irradiation. To afforded a 2D polymer [Cu
4
(μ -5-phpymt) (μ-Br) (3) in 67%
5
2
2 n
]
our knowledge, there are virtually no examples of such copper(I) yield. If the CuBr/5-phpymtH molar ratio was increased to 3 : 1 or
thiolates that are used as an efficient visible light-driven 4 : 1, the reaction always generated a yellow precipitate that was in-
photoredox catalyst. Recently, we have been interested in the soluble in common solvents and uncharacterizable. These results
syntheses and properties of metal/pyrimidine-2-thiolate com- suggested that the molar ratio of the two components did play an
4
2,43
plexes,
and found that they do exhibit high catalytic important role in the formation of 1–3 (Scheme 1).
When CuI was reacted with equimolar 5-phpymtH in MeCN
In this paper, we delicately choose 5-phenyl- and DMF at 120 °C, one tetranuclear complex [{Cu (μ-5-
pyrimidine-2-thiol (5-phpymtH) to react with different equiva- phpymtH)(μ-5-phpymt)}(μ -I)] (4) was isolated in 89% yield
activity towards organic reactions such as C–C, or C–N bond
4
4–47
formation.
2
3
2
lents of CuX (X = Br, I) under solvothermal conditions. One (Scheme 1). In the presence of Et
hexanuclear cluster [Cu (μ -5-phpymt) ] (1), two tetranuclear with CuI also produced 1 in a high yield. An analogous reac-
(2) and tion of 5-phpymtH with two equiv. of CuI at 120 °C afforded
(4), and two 2D poly- orange red blocks of [Cu (μ -I) (μ -5-phpymt) (5) in ca.
(μ -I) (μ -5- 18% yield along with some uncharacterizable yellow powder.
phpymt) ] (5) are isolated therefrom. Complex 1 shows strong The higher CuI/5-phpymtH molar ratios (from 3/1 to 6/1) also
3
N, the mixture of 5-phpymtH
6
3
6
clusters [{(Cu Br)(μ-5-phpymtH)}(μ -5-phpymt)]
2
3
2
[
{Cu
2
(μ-5-phpymtH)(μ-5-phpymt)}(μ
3
-I)]
2
6
I
2
4
2
4
2 n
]
mers [Cu
4
(μ
5
-5-phpymt)
2
(μ-Br)
2
]
n
(3) and [Cu
6
I
2
4
2
4
2
n
solvatochromic behavior and reversible luminescence switch- gave 5 as the only product and did increase the yield of 5 (up
ing upon alternately adding CF COOH and Et N into its CHCl to 82%). Again the molar ratio of the two components dictated
solution. More interestingly, complexes 1–5 display high the outcomes (4 and 5) of the above two reactions. Notably, the
3
3
3
−
−
photocatalytic activity toward aerobic oxidative hydroxylation halide (Br or I ) ion seems to exert a significant effect on the
−
−
of arylboronic acids to generate phenols under irradiation of formation of 1–5. In 2 and 4, half of the Br or I anion in CuX
−
visible light. The catalytic system modelled by 5 can also be (X = Br, I) is replaced by a 5-phpymt ligand. The other ligands
recycled several times without evident decay of its catalysis coordinate to the Cu(I) atom in a 5-phpymtH neutral form. As
efficiency. Herein we describe their synthesis, structural described later in this article, the bromide in 2 and 3 serves as
characterization, luminescence and photocatalytic properties.
a terminal (2) or μ-Br (3) ligand while the iodide in 4 and 5
1
takes a μ
3
-I (4) or μ -I/κ (I) (5) coordination mode. The differ-
4
ences in halide coordination modes are probably due to the
shorter radius of the Br atom than that of the I atom. The
different coordination modes of 5-phpymt also contribute to
the formation of 1–5. Each 5-phpymt in 2 and 3 binds more
Results and discussion
Synthesis and characterization aspects of 1–5
At the beginning, we carried out the solvothermal reactions of Cu(I) atoms than the corresponding one in 4 and 5. For 5-
1
1
CuBr with equimolar 5-phpymtH in MeCN and DMSO at phpymt, four coordination modes are observed: μ–κ (S)–κ (N)
2
1
1
2
1
1
20 °C in air. However, we did not isolate any expected Cu(I)/ (4), μ
3
–κ (S),κ (N) (1 and 2), μ –κ (N),κ (S)–κ (N′) (5) and
4
5
-phpymt complexes. Only an unexpected Cu(II) complex [Cu
(5-phpyms)
2 n
] (5-phpymsH = 5-phenyl-pyrimidine-2-sulfonic
acid) was obtained as blue octahedral crystals in 46% yield
(
(
see the ESI†). X-ray analysis revealed that it has a 1D chain
extending along the b axis) in which each Cu adopts an octa-
hedral geometry defined by four O and two N from four
5
μ
-phpyms ligands, while each 5-phpyms takes
a
1
1
1
3
–κ (N)–κ (O)–κ (O′) chelating/bridging mode to bind at two
Cu atoms (Fig. S1†). Such a copper-catalyzed oxidation of pyri-
4
8
midine-2-thiol is similar to that of pyridine-2-thiol. In this
reaction, Cu(I) was evidently oxidized into Cu(II) and the SH
group of 5-phpymtH was in situ oxidized into a sulfo group,
−
forming a new 5-phpyms anion. The formation of this Cu(II) Scheme 1 Synthesis of complexes 1–5.
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1
3
1
μ –κ (N),κ (S)–κ (N′) (3). Each 5-phpymtH in 2 or 4 exhibits a
5
1
1
bridging bidentate μ–κ (S)–κ (N) fashion. Of course, other
factors that may have effects on the formation of 1–5, such as
reaction temperature and pH value, could not be ruled out.
Compounds 1–5 are stable toward oxygen and moisture.
i
Compounds 1, 2, and 4 are slightly soluble in EtOH, PrOH,
3 2 2
CHCl , CH Cl , DMSO and DMF but insoluble in toluene,
hexane, MeOH, Et O and H O. Compounds 3 and 5 are in-
2
2
soluble in common organic solvents. Their elemental analyses
are consistent with their chemical formula. The powder X-ray
diffraction (PXRD) patterns for each of them match well with
those simulated from their corresponding single crystal data,
suggesting its bulk phase homogeneity (Fig. S2–S7†). The
thermal stability of 1–5 is investigated by thermogravimetric
analysis. They are thermally stable up to 240 °C (Fig. S8†).
Compound 1 continuously decomposes in the range of
3
00–964 °C and the final residue amounts to Cu S. In the
2
Fig. 1 View of the molecular structure of 1 with a labeling scheme and
range of 246–300 °C, 2 has a weight loss of 13.39% (calcd 50% probability. All hydrogen atoms are omitted for clarity.
1
3.72%), which corresponds to the loss of bromide. The final
residue at 995 °C is equal to CuS. Compound 3 has a weight
loss of 9.7% (calcd 10.04%) in the temperature range of
[
{(Cu Br)(5-phpymtH)}(5-phpymt)] . It may be viewed as having
2
2
3
32–358 °C, which agrees well with the total loss of bromide.
an H-shaped structure with the crystallographic center of sym-
metry located on the midpoint of Cu2 and Cu2A (Fig. 2). The
The final residue is assumed to be Cu S. For 4, the weight loss
2
1
1
of 20.52% from 254 °C to 322 °C amounts to the loss of all co-
ordinated iodide atoms (calcd 20.16%). The final residue is
assumed to be CuS. Compound 5 has a weight loss of 10.2%
5
-phpymtH or 5-phpymt ligand adopts a μ–κ (S),κ (N) and
2
1
μ–κ (S),κ (N) mode, respectively. In 2, two {Cu(CuBr) (μ-5-
2
phpymtH)} fragments are connected by a pair of μ -5-phpymt
3
(calcd 10.04%) (amounting to two iodides) in the range of 326
ligands. Each Cu adopts a trigonal planar geometry, co-
and 385 °C. A further loss of 30.30% (calcd 30.12%) (amount-
ing to other iodides) appears in the range of 385–703 °C.
A final residue of Cu S is formed at 966 °C.
2
ordinated by one S from one μ-5-phpymtH molecule, one N
and one S of one μ -5-phpymt (Cu1 and Cu1A) or by one N
3
−
from one μ-5-phpymtH, one S of μ -5-phpymt and one Br
3
(
Cu2 and Cu2A). The Cu1–N1 bond length is shorter than the
Crystal structures of 1·2MeCN
Cu2–N3 distance. The Cu1–S2 and Cu2–S1 bond lengths are
shorter than the Cu2–S2A length. The mean Cu–S bond dis-
tance in 2 is longer than that of 1. The Cu1–Br1 bond distance
is longer than those found in [Cu(SN-Ph)Br] (2.3410(3) Å;
Compound 1·2MeCN crystallizes in the triclinic space group
P ˉ1 and its asymmetric unit consists of half of one discrete
[
Cu (5-phpymt) ] molecule and one MeCN solvent molecule.
6 6
Six Cu(I) atoms in 1 are connected by six 5-phpymt ligands to
form a water-wheel-shaped structure. Such a Cu core struc-
SN-Ph
= N-(2-pyridinyl)amino-diphenylphosphine sulfide),
i
i
6 6
S
[Cu(SN- Pr)Br] (2.327 Å, SN- Pr = N-(2-pyridinyl)amino-diisopropyl-
5
6
ture is similar to those observed in other hexanuclear Cu(I)
clusters with derivatives of pyridine-2-thiolate and pyrimidine-
phosphine sulfide) and [(tpypo)CuBr] (2.344(1) Å; tpypo = tris
5
7
(
2-pyridyl)phosphine oxide),
but shorter than those in
and 2.643(4) Å; mpy
4
9–54
2
-thiolate.
Each 5-phpymt binds to three Cu(I) atoms in a
[
MoS Cu (mpy) Br (2.496(3)
4
4
5
2
]
Å
=
1
2
5
8
μ –κ (N)–κ (S) coordination mode. Each Cu(I) is coordinated
3
α-methylpyridine). The Cu1⋯Cu2 separation (2.6444(8) Å) is
by two bridging S atoms of two 5-phpymt ligands and one N
atom of the third 5-phpymt ligand, forming an approximate
trigonal planar coordination environment (Fig. 1). The Cu–μ -S
3
bond distances (Table S1†) in 1 are comparable to the corres-
ponding ones observed in [Cu
3
(pymt)
thiolate). The Cu–N bond distances are close to those
observed in [Cu (dmpymt) ] (dmpymt = 4,6-dimethyl-pyrimi-
dine-2-thiolate). The Cu⋯Cu distances vary in the range of
.7758(4)–3.0335(4) Å, which are close to the sum of the van
der Waals radii (2.80 Å) of Cu(I) centers, suggesting the exist-
3 n
] (pymt = pyrimidine-2-
5
5
6
6
5
1
2
5
5
ence of weak Cu(I)–Cu(I) interactions.
Crystal structures of 2
Compound 2 crystallizes in the triclinic space group P ˉ1 , and
Fig. 2 View of the molecular structure of 2 with a labeling scheme and
its asymmetric unit has half an independent molecule of 50% probability. All hydrogen atoms are omitted for clarity.
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shorter than that of 1, implying relatively stronger Cu(I)–Cu(I) on the basal plane while Br1 (or S2) occupies the apical posi-
interactions. The Cu1⋯Cu2A, Cu1⋯Cu1A and Cu2⋯Cu2A sep- tion. The Cu–Br bond lengths in 3 are comparable to those in
5
9
arations are 3.781 Å, 5.325 Å, 3.770 Å, respectively, which [Cu
excludes any metal–metal interaction. Notably, the H-bonding [Cu
2
Br
Br
2
(bpe)
2
]
n
(bpe
=
1,2-bis(4-pyridyl)ethane)
and
6
0
4
4
(PPh
2
py)
2
] (PPh py = 2-(diphenylphosphino)pyridine).
2
interaction between N2 and N4 [N2–H2⋯N4 with x, 1 + y, z, The mean Cu–N bond distance is close to that of 1. In 3, the
.793 Å] leads to the formation of a 1D chain extended along Cu1–S1 and Cu3–S2 bond distances are much longer than
2
the a axis (Fig. S9†).
those of the Cu1–S1A, Cu2–S2 and Cu3–S1A bonds. The
elongated distance is ascribed to the steric hindrance of the
two face-to-face 5-phpymt ligands.
Crystal structures of 3
Compound 3 crystallizes in the triclinic space group P ˉ1 , and
its asymmetric unit holds half a discrete [(5-phpymt) Cu Br ]
Crystal structures of 4
4
8
4
unit. The six Cu atoms in 3 are bridged by one pair of bro- Compound 4 crystallizes in the monoclinic space group P21/c,
mides and two pairs of 5-phpymt ligands to form a [(5- and its asymmetric unit contains half a discrete molecule
phpymt) Cu Br ] fragment (Fig. 3). Such a fragment is inter- [Cu
2
(μ-5-phpymtH)(μ-5-phpymt)(μ
connected by Cu ions through one Cu–N bond and one Cu–S phpymtH) (μ-5-phpymt)} units in 4 are connected by two µ
bond, generating 1D chain [Cu (μ -5-phpymt) (μ-Br)
forming a tetranuclear structure (Fig. 4). The crystallographic
extended along the b axis. This chain is further connected center of symmetry is located on the midpoint of Cu2 and
to its equivalent ones via bromides to form a 2D layer Cu2A atoms. Each 5-phpymtH or 5-phpymt adopts
3
-I)]
2
. Two dimeric {Cu
2
(μ-5-
4
6
2
+
-I,
2
3
a
8
5
4
2 n
]
a
1
1
extending along the ab plane. Each 5-phpymt in 3 takes a μ–κ (S),κ (N) bridging mode to bind two Cu atoms via one Cu–
1
3
1
μ –κ (N)–κ (S)–κ (N′) mode to bind five Cu atoms. Cu1 and
N
bond and one Cu–S bond. In such
a
2
{Cu (μ-5-
5
Cu4 adopt a trigonal planar geometry, coordinated by one N phpymtH) (μ-5-phpymt)} fragment, two Cu atoms are bridged
2
and two S atoms from three 5-phpymt ligands (Cu1) or by one by one μ-5-phpymtH ligand and one μ-5-phpymt ligand
N and one S from two 5-phpymt ligands and one Br (Cu4). through two Cu–S bonds and two Cu–N bonds. Cu1 or Cu1A
Based on the bond angles listed in Table S1,† Cu2 (or Cu3) in atom adopts a trigonal planar geometry, coordinated by one N
3
3
may be viewed as having a triangle pyramidal coordination of one μ-5-phpymtH, one S from μ-5-phpymt and one µ -I,
geometry in which N1, S2, and Br2 (or Br1, S1A, and N3I) lie while Cu2 and Cu2A in 4 adopt a distorted tetrahedral coordi-
nation geometry, coordinated by one N of μ-5-phpymtH, one S
of μ-5-phpymt and two µ -I atoms. Cu1–N1, Cu1–S2A and Cu1–
3
I1 bond lengths are shorter than those of the corresponding
ones of Cu2–N3, Cu2–S1, Cu2–I1 and Cu2–I1A bonds. The
shorter bond distances are likely due to the fact that Cu1 has a
lower coordination number than Cu2. The Cu2–N3 bond
5
5
length is slightly longer than that found in [Cu (pymt) ] .
3
3 n
The Cu–S bond distances are comparable with those in
Cu (pymt) . The Cu1⋯Cu2A separation (2.5678(12) Å) in 4 is
shorter than those in Cu1⋯Cu1B (2.9539(18) Å), Cu2⋯Cu2A
2.997(2) Å) and Cu1⋯Cu2 in 2, implying stronger Cu(I)–Cu(I)
[
3
3 n
]
(
Fig. 3 (a) View of a portion of the 1D chain of 3 (extending along the b
axis). (b) View of the 2D network of 3 (extending along the ab plane).
Fig. 4 View of the molecular structure of 4 with a labeling scheme and
50% probability. All hydrogen atoms are omitted for clarity.
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interactions. A two-dimensional H-bonded network (Fig. S10†) Cu1⋯Cu1A (2.741(2) Å) and Cu2⋯Cu2B (2.665(3) Å)
extended bc plane is further generated from the intermolecular separations are slightly longer than that of Cu1⋯Cu2A in 4.
hydrogen bonding interaction between N2 and N4 [N2–
Optical properties
H2⋯N4 with −x, −1/2 + y, 3/2 − z, 2.083 Å].
Complexes 1–5 exhibit a strong and broad absorption with the
maxima values ranging from 240 to 450 nm and a long absorp-
Crystal structures of 5
Compound 5 crystallizes in the monoclinic space group C2/m, tion tail to ca. 750 nm (Fig. S11†). The UV-vis spectra of 1 in
and its asymmetric unit contains one-fourth of the [Cu
phpymt) ] unit. 5 consists of a 2D sheet structure (extended CHCl , 1,4-dioxane and DMF solutions of 1 exhibit similar
along the ab plane) in which hexanuclear {Cu I (μ-I) } frag- absorption bands. The two absorption bands at λ < 290 nm
6 4
2 2
I (5- different solvents are also measured (Fig. S12†). The CH Cl ,
2
3
6
2
2
ments are interconnected to the adjacent ones by three pairs and at 290 nm–400 nm (λmax = 325 nm) are likely derived from
of μ -5-phpymt ligands (Fig. 5). Each 5-phpymt takes a the π → π* or n → π* electron transitions. In addition, 1 in
4
1
2
1
i
μ –κ (N)–κ (S)–κ (N′) mode to coordinate to four Cu atoms of EtOH or PrOH exhibits two absorption bands centred at λ
=
max
4
three {Cu
6
I
2
(μ-I)
2
} cores. In {Cu
6
I
2
2
(μ-I) }, two Cu atoms are 260 nm and 390 nm. The red shift in protic solvents is prob-
−
i
linked by two μ-I atoms, which are further connected by a ably due to the weak interaction between 1 and EtOH or PrOH
pair of {CuI} fragments via four Cu–μ -I bonds. Cu1, Cu1A, molecule. The absorption of 1 at λmax = 325 nm in CHCl3
4
Cu1B and Cu1C are located in the same plane, while the two is gradually red-shifted with the increased addition of
{
CuI} units stand above or below the Cu
adopts a trigonal planar geometry, coordinated by one S and
one N from two μ -5-phpymt ligands and one μ -I (Cu1) or by erature. Being excited at 380 nm in the solid state, compound
one I and two μ -I atoms (Cu2). Cu1–μ -I1 and Cu2–μ -I1 bond 1 exhibits an efficient emission at 583 nm with 12.96%
lengths are longer than that of the Cu2–μ -I2 bond, but close quantum yield (Fig. S14†). Complexes 2–5 do not show lumine-
4 2
3
I plane. Each Cu in 5 CF COOH (Fig. S13†).
The emission spectra of 1–5 are investigated at room temp-
4
4
4
4
4
3
to those in {[Cu(mtz)]
3
(CuI)}
n
(Hmtz = 3,5-dimethyl-1,2,4-tri- scence in the solid state. The luminescence properties of 1 are
6
1
azole). Cu2–μ
3
-I2 and Cu1–N1 bond distances are shorter also examined in various solvents. As shown in Fig. 6, the
than those of the corresponding ones in 4. The Cu1–S1A bond emission spectra reveal very substantial but different solvent
distance is close to those in 4. Cu1⋯Cu2 (2.6508(14) Å), effects. Excited at 380 nm, the solution of 1 in aprotic solvents
3 2 2
such as CHCl , or CH Cl , toluene, acetone, THF, 1,4-dioxane
and DMF emits at a maximum of 815–830 nm. The emissions
appear at a much lower energy with a large Stokes shift of
about 540 nm. The emission of 1 does not get shifted greatly
in aprotic solvents and may be originated from the triplet
states of ligand-to-metal charge-transfer (LMCT) and/or metal-
to-ligand charge-transfer (MLCT) characters, mixed with
3
8,55
metal-centered (ds/dp) states
while the solution of 1 in a
i
protic solvent (EtOH, PrOH) emits at a shorter wavelength
with a maximum at about 720 nm. The reason for the strong
blue-shift of emission maxima is probably due to the weak
hydrogen-bonding interactions of S and N atoms from the pyri-
6 2 2 6
Fig. 5 (a) View of one {Cu I (μ-I) (μ-5-phpymt) } fragment in 5. (b) View
of the 2D network along the ab plane. All H atoms are omitted for
Fig. 6 Emission spectra of 1 (1 × 10− mol L−1) in various solvents at
5
clarity.
room temperature (at λex = 380 nm).
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midyl ring with the protic solvent molecules. At room tempera- resonance of the proton of CF
ture, the quantum yield of 1 is 23.61% in PrOH or 18.45% in upfield shift from δ 8.14 to 5.30. After the further addition of
3
COOH shows a remarkable
i
CH
CHCl
.7 μs, respectively.
A dramatic change in the fluorescence emission intensity is action with CF
2
Cl
2
. Moreover, the photoluminescence lifetimes of 1 in Et
and in the solid state are measured to be 10.0 and 8.81 ppm (Fig. S16–S19†). These results suggest that the N
atoms of 5-phpymt are involved in the hydrogen bonding inter-
COOH.
3
N into the solution, the signal at δ 8.95 ppm comes back to
3
8
3
i
observed in the CHCl
sion maximum of 1 in CHCl / PrOH is blue-shifted from 838
to 727 nm along with the increasing amount of PrOH. Such a The band gap energy (E ) of 1–5 was determined by the
3
– PrOH mixture (Fig. S15†). The emis-
i
Photocatalytic properties
3
i
g
6
2
blue-shift is gradually accompanied by a remarkable enhance- Kubelka–Munk method based on the diffuse reflectance
ment of the emission intensity when the volume ratio of spectra (Fig. S20†). The energy band gaps obtained by extrapol-
i
CHCl
3
/ PrOH is changed from 100 : 0 to 1 : 2. Upon increasing ation of the linear portion of the absorption edges are 1.97 eV
i
the PrOH content from 67% to 80%, the emission intensity (1 and 2), 2.26 eV (3), 1.60 eV (4) and 2.17 eV (5). The narrow
gets decreased and the maximum at 818 nm vanishes with the band gaps of these compounds encouraged us to investigate
formation of a new emission peak at 763 nm. The emission their visible light photocatalytic activity, which can be evalu-
maximum is blue-shifted from 763 nm to 727 nm and the ated by the aerobic oxidative hydroxylation of arylboronic acids
emission intensity increases gradually when the volume ratio into phenol derivatives at room temperature. We chose 5 as a
i
of CHCl
3
/ PrOH is changed from 1 : 4 to 1 : 14. These results catalyst and phenylboronic acid (6a) as the model substrate to
i
show that the interactions between 1 and PrOH do exert a investigate suitable reaction conditions.
great impact on the emission. Afterwards, the emission and
As shown in Table 1, incubating a mixture of 6a, Et N as a
3
i
the emission intensity remain unchanged when the PrOH sacrificial reducing agent and 5 as a catalyst in 3 mL H O
2
fraction is increased up to higher than 93%. Intriguingly, the under visible light afforded phenol (7a) in 55% yield after
luminescence of 1 is also influenced by an acid, which may 24 h. When this reaction was carried out in organic solvents
interact with 1 via stronger intermolecular H-bonding inter-
3
actions. The addition of CF COOH leads to the loss of lumine-
scence. This can be ascribed to the protonation of S and/or N
atom of the 5-phpymt ligand in this complex. It is uncommon
that the hydrogen-bonding interaction leads to the fluo-
rescence quenching (Fig. 7). Moreover, this process is revers-
Table 1 Optimizing the reaction conditions for the oxidative hydroxy-
lation of phenylboronic acids
3
ible when Et N is added in this system and can be shuttled
several times with no loss of emission intensity. Clearly, the
solution of 1 might be used as a luminescence-based on–off
switch upon alternate addition of an acid and a base at room
b
Yield (%)
Cat. ([Cu]
mol%)
Time
Additive (h)
a
1
Entry
Solvent
7a 8a
55
temperature. The H NMR spectrum of 1 reveals some useful
information about the interaction of CF COOH with 5-phpymt
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
5 (2)
5 (2)
5 (2)
5 (2)
5 (2)
5 (2)
5 (2)
5 (2)
5 (2)
5 (2)
5 (2)
5 (2)
5 (2)
5 (2)
5 (2)
5 (1)
5 (5)
5 (2)
—
H O
Et N
24
24
24
24
24
24
24
24
24
24
24
24
48
72
48
48
48
48
48
48
48
48
48
48
—
3
2
3
MeCN
EtOH
MeOH
THF
MeCN/H
MeOH/H
EtOH/H
MeCN/H
MeCN/H
MeCN/H
MeCN/H
MeCN/H
MeCN/H
MeCN/H
MeCN/H
MeCN/H
MeCN/H
MeCN/H
MeCN/H
MeCN/H
MeCN/H
MeCN/H
MeCN/H
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
3
3
3
3
3
3
3
3
3
3
3
3
3
N
N
N
N
N
N
N
N
N
N
N
N
N
36 11
20
27 38
3 3
in CDCl . The addition of CF COOH can lead to a downshift of
the proton signal of the pyrimidyl ring from δ 8.81 to 8.95. The
8
—
75
35
3
2
O (1/1)
2
O (1/1)
O (1/1)
44 Trace
36 Trace
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
O (2/1)
O (1/2)
O (1/4)
50
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
65 Trace
62 Trace
O (1/10) Et
63
—
O (1/1)
O (1/1)
O (1/1)
O (1/1)
O (1/1)
O (1/1)
O (1/1)
O (1/1)
O (1/1)
O (1/1)
O (1/1)
O (1/1)
Et
95 Trace
95 Trace
94 Trace
84 Trace
Et
i
2
Pr NEt
Et
Et
3
N
N
3
94
—
—
—
87
91
89
93
2
—
—
—
7
—
Et
Et
Et
Et
Et
Et
3
N
N
N
N
N
N
c
5 (2)
1 (2)
2 (2)
3 (2)
4 (2)
3
3
3
3
3
5
4
1
a
Reaction conditions: phenylboronic acid (1.0 mmol), solvent
Fig. 7 Emission spectra of 1 (1 × 10− mol L−1) in CHCl
6
at room temp-
3
(
3.0 mL), Et N (1.0 equiv.), 45 W fluorescence lamp irradiation
3
b
erature (blue line), CF
black line).
3
COOH added (red line), and then Et
3
N added (610 nm, 540 nm, 430 nm) and in air. Yields are based on HPLC
c
(
results. Without irradiation.
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such as MeCN, EtOH or MeOH, the yield of 7a became lower Table 2 Oxidative hydroxylation of arylboronic acids catalyzed by 5
under visible light irradiation
(
36% (MeCN); 8% (EtOH); 27% (MeOH)) (Table 1 entries 2–4)
coupled with a byproduct biphenyl (8a) (11%–38%). When the
reaction was performed in a H O–MeCN (v/v = 1/1) mixture,
the yield of 7a was increased significantly within 24 h in air
entry 6). The catalyst showed lower activity in aqueous MeOH
or EtOH (entries 7 and 8). The optimal ratio of H O and MeCN
a
b
Entry
Boronic acid
Product
Yield %
2
c
1
2
3
4
95/93%
(
97
96
93
2
was determined to be 1 : 1 (entries 6, 9–11). Almost complete
conversion of the phenylboronic acid into phenol was achieved
when the reaction time was extended to 48 h in H
2
O–MeCN
(entry 13). Et N was necessary for such aerobic oxidative
3
hydroxylation of arylboronic acid (entry 18). No product was
observed in the absence of the catalyst, and 6a remained
unreacted (entry 19) in contrast to those run in the dark,
where no product was formed, indicating that the formation of
phenol from phenylboronic acid was truly induced by visible
light irradiation (entry 20). Therefore, suitable conditions for
the photosynthesis of phenols from arylboronic acids are sum-
5
6
91
88
7
8
81
75
3
marized as follows: Et N as the sacrificial electron donor,
MeCN–H O (1 : 1) as a solvent system, and air as an oxidant in
2
the presence of visible light at room temperature for 48 h.
With these optimized conditions, the catalytic performances
of 1–4 were also investigated. Compound 2 or 4 as a homo-
geneous catalyst also exhibited excellent activity toward the oxi-
dative hydroxylation of phenylboronic acid to phenol.
Complexes 1 and 3 exhibited relatively poor catalytic perform-
ance and lower selectivity than that of 5.
The scope of the visible light-induced photoredox catalytic
aerobic oxidative hydroxylation of arylboronic acids using 5 as
a photocatalyst is examined (Table 2). When arylboronic acids
are electron-rich, electron-poor, or sterically bulky, they are all
smoothly transformed into the corresponding phenol deriva-
tives in good to excellent yields under the optimized reaction
conditions. The m-, p-methyl, m-, p-methoxyphenylboronic
9
74
1
1
0
1
81
86
1
1
2
3
70
86
acids are converted smoothly to their corresponding phenols 14
in 91%, 96%, 93% and 97% yields, respectively (entries 2–5).
Phenylboronic acids with electron-withdrawing substituents 15
like –NO , –COCH and –F can proceed conveniently, in 81%,
75
74
2
3
8
6%, and 70% yields (entries 10–12), respectively. The steric
1
6
95
94
hindrance of arylboronic acids has influence on the catalytic
activity of the transformation from arylboronic acids to
phenols. Substrates with higher steric hindrance such as
17
(2-methoxyphenyl)boronic acid, o-tolylboronic acid, (2,6-di-
methylphenyl)boronic acid, mesitylboronic acid are also con-
verted into their corresponding phenols in good yields (74%–
a
Reaction conditions: 6 (0.50 mmol), 5 (2 mol%), Et
3
N (1.0 equiv.),
8
8%; entries 6–9). Notably, naphthalen-2-ylboronic acid, 1,4- acetonitrile/water (1.5 mL/1.5 mL), 45 W fluorescence lamp irradiation
b
(
610 nm, 540 nm, 430 nm) for 48 h, in air. Yield of isolated products.
Under irradiation of a 300 W Xe lamp with a 420 nm cut-off filter
420 nm ≤ λ ≤ 760 nm) for 24 h.
phenylenediboronic acid and 1,3-phenylenediboronic acid can
also be oxidatively hydroxylated with satisfactory yields (entries
c
(
1
3–15). The substrate scope of this methodology has been
extended to the use of arylboronic pinacol esters. The desired
products are isolated in 95% and 94% yields under the same
reaction conditions (entries 16 and 17).
3
second cycle by adding phenylboronic acid, Et N and solvent.
The reusability of 5 was also examined for the oxidative As indicated in Fig. 8, no significant loss of catalytic activity
hydroxylation of phenylboronic acid to phenol. After the first was observed after the catalytic system was re-used for five
reaction cycle, the catalyst was separated by centrifugation and times. After 5 cycles, about 79% of 6a was converted to 7a.
then washed with H O. The isolated catalyst was used for the After the catalytic reaction, solid 5 was collected by filtration,
2
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Conclusions
In summary, the solvothermal reactions of CuX (X = Br, I) with
-phpymtH in different molar ratios under N generated one
5
2
hexanuclear cluster 1, two tetranuclear clusters 2 and 4, and
two 2D coordination polymers 3 and 5. In 1–5, the halide and
the molar ratio of the two reactants do have a significant effect
on the coordination modes of 5-phpymt, and the structures
and properties of the resulting Cu(I)/5-phpymt complexes.
Addition of Et N into the reaction results in the formation of
3
hexanuclear cluster 1 in a higher yield. When the reaction was
carried out in air, the SH group of 5-phpymtH could be oxi-
dized in situ into a sulfo group by O
2
from air, forming a 1D
Cu(II) polymer [Cu(5-phpyms) ] . Reactions of 5-phpymtH with
2
n
equimolar CuX resulted in the formation of tetra-, or hexa-
nuclear clusters 1, 2 and 4. When 5-phpymtH reacted with two
or more equiv. of CuX, 5-phpymt could bind more Cu(I) atoms
to yield 2D coordination polymers 3 and 5. In the structures of
Fig. 8 Recycling tests for oxidative hydroxylation of phenylboronic acid
using 5 under visible light irradiation.
washed with MeCN and Et
2
O, dried in air and then character-
1
1
1
–5, 5-phpymt takes four coordination modes: μ–κ (S)–κ (N)
ized by PXRD. The PXRD patterns were in good agreement
with the simulated ones generated from the single crystal data
of 5, suggesting that the original framework structure of 5 was
retained during the catalysis (Fig. S21†).
1
2
1
2
1
(
4), μ –κ (N),κ (S) (1 and 2), μ –κ (N),κ (S)–κ (N′) (5) and
3
4
1
3
1
μ
4
5
–κ (N),κ (S)–κ (N′) (3), while the 5-phpymtH ligand in 2 and
only exhibits a bridging bidentate μ–κ (S)–κ (N) fashion. The
1
1
solvent-dependent photoluminescence of 1 may allow the
development of a luminescent probe that can detect the hydro-
gen-bond-donating species in aprotic solvents. Compound 1
also works as an acid/base-induced “on–off” luminescence
switch material. Compound 5 displays high photocatalytic
activity toward the oxidative hydroxylation of various arylboro-
nic acids under visible light irradiation at ambient tempera-
ture to produce the corresponding phenols in high yields.
Furthermore, this heterogeneous catalyst can be simply
recycled and reused without significant loss of activity.
Compounds 1 and 5 as two representative examples demon-
strate that the Cu(I) complexes of S,N-donor ligands have a
large scope of fascinating applications in advanced materials
such as photoelectronic devices and photocatalysts. Currently,
we are investigating the design and synthesis of other Cu(I)
complexes of pyrimidine-2-thiolate ligands that show visible
light-promoted and more efficient catalytic activity towards
C–C, C–O and C–N bond formation.
−
Electrons (e ) in the valence band (VB) are excited to the
conduction band (CB), generating an equal amount of concei-
+
vable holes (h ) in the VB under the light irradiation. The
+
resulting hole (h ) can react with H
2
O to yield a hydroxyl
molecule to get
•
−
radical ( OH). The electron (e ) binds one O
2
•
−
reduced to O2 . To obtain some insight into the potential
photocatalytic reaction pathway, the experiments with phenyl-
boronic acid are carried out in the presence of tert-butyl
alcohol (TBA) or 1,4-benzoquinone (PBQ) under the optimized
•
•−
catalytic conditions. TBA and PBQ are used as OH and O
2
6
3
scavengers, respectively. The addition of TBA has little effect
on the oxidative hydroxylation of phenylboronic acid. The cata-
lytic efficiency of the system is found to decrease from 95% to
3
8% in the presence of PBQ (Scheme 2). Thus the oxidative
hydroxylation process with 5 as the catalyst predominantly
•
−
depends on O
possible photocatalytic mechanism
hydroxylation of arylboronic acids is also proposed
2
radicals to attack the arylboronic acid. The
1
1–18
for the above oxidative
(
(
Scheme S1†). Under the irradiation of visible light, electrons
−
e ) in the valence band (VB) are excited to the conduction
+
Experimental
band (CB), and holes (h ) are left in the VB. The interaction of
the hole with Et
tron reduction of O
which reacts with the boronic acid to form the intermediate I.
The radical anion I then abstracts a hydrogen atom from
•
+
3
N produces an Et
3
N
radial cation. One elec- Materials and methods
•
−
2
in air generates the superoxide ion (O
2
),
General procedure. Ligand 5-phpymtH was prepared accord-
ing to the literature method. All other reagents were used as
obtained from commercial sources without further purifi-
cation. The analytical instruments for the characterization of
the compounds described in this article are the same as those
64
•
+
Et
3
N
to form intermediate II. The rearrangement of II may
yield the intermediate III. The hydrolysis of III gives phenol as
the product.
65
employed in our previous work unless otherwise mentioned.
The fluorescence spectra were measured on
spectrometer.
a FLS980
Synthesis of [Cu
6
(μ
3
-5-phpymt)
(2). Under N
2
6
] (1·2MeCN) and [{(Cu
2
Br)
(
μ-5-phpymtH)}(μ -5-phpymt)]
3
2
, to a pressure
Scheme 2 The oxidative hydroxylation of phenylboronic acids.
bottle (15 mL) were added CuBr (10.8 mg, 0.075 mmol),
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5
-phpymtH (14.1 mg, 0.075 mmol), 4 mL of MeCN and 0.2 mL materials in 4 mL of MeCN and 0.2 mL of DMF. Yield: 21 mg
of DMF. The mixture was sealed. The tube was heated in an (89%). Anal. Calcd (%) for C H Cu I N S : C 38.16, H 2.40, N
4
0
30
4 2 8 4
−
1
oven at 120 °C for 48 h and then cooled to room temperature 8.90. Found: C 37.63, H 2.45, N 9.13. IR (KBr pellet, ν/cm ):
at the rate of 5 °C h− to form a large amount of yellow crystals 3032 (w), 1602 (m), 1622 (s), 1553 (w), 1526 (w), 1507 (w),
of 1 coupled with red blocks of 2, which were separated 1443 (w), 1397 (s), 1385 (s) 1367 (s), 1164 (s), 1151 (m), 754
mechanically under a microscope. Complex 1: Yield: 11.7 mg (m), 762 (m), 693 (m).
1
(
1
58%). Anal. Calcd (%) for C64
H
48Cu
6
N
14
S
6
: C 48.44, H 3.05, N
Synthesis of [Cu
6
I
2
(μ
4
-I)
2
(μ
4 2 n
-5-phpymt) ] (5). Compound 5
1
2.36. Found: C 48.76, H 3.25, N 11.55. H NMR (400 MHz, was produced as orange red crystals using a similar route to
3
CDCl , ppm): δ 8.81 (s, 2H), 7.52–7.44 (m, 5H). IR (KBr pellet, that described for 1, using CuI (57 mg, 0.30 mmol),
−
1
ν/cm ): 1629 (w), 1578 (m), 1524 (w), 1445 (w), 1393 (s), 1171 5-phpymtH (14.1 mg, 0.075 mmol) as starting materials in
m), 1035 (w), 768 (m), 693 (m), 509 (w). Complex 2: Yield: MeCN (4 mL) and DMF (0.2 mL). Yield: 39 mg (82%). Anal.
.3 mg (17%). Anal. Calcd (%) for C40 Cu : C 41.24, Calcd (%) for C40 : C 19.01, H 1.12, N 4.43.
H 2.60, N 9.62. Found: C 41.32, H 2.65, N 9.68. IR (KBr pellet, Found: C 18.88, H 1.32, N 4.36. IR (KBr pellet, ν/cm ): 3031
(
5
H
30Br
2
4
N
8
S
4
8 8 4
H28Cu12I N S
−
1
−
1
ν/cm ): 3047 (w), 1614 (m), 1529 (w), 1489 (w), 1445 (w), 1393 (w), 1601 (m), 1551 (w), 1525 (w), 1489 (w), 1367 (s), 1348 (m)
(s), 1369 (s), 1172 (m), 771 (m), 680 (w).
1164 (s), 1151 (m), 762 (m), 693 (m).
Complex 1 was also prepared as yellow crystals by solvo-
thermal reaction of CuBr (10.8 mg, 0.075 mmol), 5-phpymtH
15.1 mg, 0.08 mmol) and one drop of Et N in MeCN (2 mL) Single crystals of 1·2MeCN and 2–5 suitable for X-ray analysis
3
X-Ray data collection and structure determination
(
and DMF (0.2 mL) at 120 °C. Yield: 17.2 mg (86% based on Cu). were obtained directly from the above preparations. Their
Synthesis of [Cu (μ -5-phpymt) (μ-Br) ] (3). Compound 3 crystal data were collected on a Rigaku Mercury CCD X-ray
4
5
2
2 n
was prepared as orange crystals in a similar manner to that diffractometer (for 4) (3 kV, sealed tube) by using graphite
described for 1, using CuBr (21.6 mg, 0.150 mmol), monochromated Mo Kα (λ = 0.71073 Å), an Agilent Xcalibur
5
-phpymtH (14.1 mg, 0.075 mmol) as starting materials in diffractometer (for 2 and 5) or a Bruker APEX-II CCD (for 1
MeCN (4 mL) and DMF (0.2 mL). Yield: 19.8 mg (67%). Anal. and 3) using an X-ray source Mo Kα (λ = 0.71073 Å). Single crys-
Calcd (%) for C20 Cu : C 30.47, H 1.79, N 7.11. tals of 1·2MeCN and 2–5 were mounted on glass fibers with
Found: C 30.67, H 2.08, N 7.33. IR (KBr pellet, ν/cm ): 3053 grease at room temperature (4) or cooled under a liquid nitro-
w), 1631 (m), 1581 (w), 1542 (w), 1492 (w), 1445 (w), 1398 (s), gen stream at 153 K (1, 3) and 223 K (2, 5). The collected data
172 (m), 760 (m), 694 (m).
were reduced by using the program CrystalClear (Rigaku and
Synthesis of [{Cu (μ-5-phpymtH)(μ-5-phpymt)}(μ -I)] (4). MSC, Ver. 1.3, 2001), Bruker APEX2 or CrysAlisPro, Agilent
H
14Br
2
4 4 2
N S
−
1
(
1
2
3
2
Compound 4 was obtained as orange red crystals in an analo- Technologies (CrysAlis171.NET, Version 1.171.36.28) and an
gous manner to that used for 1, using CuI (14.3 mg, absorption correction (multi-scan) was applied. The reflection
0
.075 mmol), 5-phpymtH (14.1 mg, 0.075 mmol) as starting data were also corrected for Lorentz and polarization effects.
Table 3 Crystal data and structure refinement parameters for 1·2MeCN and 2–5
1
·2MeCN
2
3
4
5
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
C
64
H
48Cu
6
14
N S
6
C
40
H
30Br
2
Cu N
4 8
S
4
C
20
H
14Br
2
Cu N
4 4
S
2
C
40
H
30Cu
4
I
2 8
N S
4
C
40 8 8 4
H28Cu12I N S
1586.76
Triclinic
Pˉ1
1164.94
Triclinic
Pˉ1
7.9432(4)
9.9838(7)
12.8707(9)
79.980(6)
82.732(5)
81.898(5)
989.63(11)
1.955
788.45
Triclinic
Pˉ1
8.3588(6)
9.3642(7)
14.7668(11)
88.688(4)
76.130(4)
85.922(4)
1119.29(14)
2.339
1258.92
Monoclinic
P2 /c
9.0698(12)
13.4850(16)
17.156(2)
2526.62
Monoclinic
C2/m
12.5100(9)
9.4515(6)
12.0472(9)
1
8.9345(7)
14.2016(10)
14.3237(11)
105.957(2)
104.457(2)
107.305(2)
1555.8(2)
1.694
α (°)
β (°)
103.926(3)
107.004(8)
γ (°)
3
V (Å )
2036.6(4)
2.053
2
3.824
1224
1362.16(17)
3.080
1
9.306
1160
3
ρ
calc (g cm−
)
Z
1
1
2
−
1
μ (mm
)
2.270
800
4.394
576
7.523
760
F(000)
Total reflns
89 970
7175
6147
6543
3683
2984
260
0.0402
0.0765
1.009
18 795
5133
3441
19 395
3729
3033
3305
1357
1073
94
0.0371
0.0703
0.996
Unique reflns
Observed reflns
Variables
407
283
268
a
R
0.0258
0.0529
1.034
0.0714
0.1883
1.021
0.0498
0.0957
1.099
b
wR
c
GOF
a
b
2
o
2 2
2 2 1/2
c
2
o
2 2
c
1/2
R = ∑||F
o
| − |F
c
||/∑|F
o
|. wR = {∑w(F
− F
c
) /∑w(F
o
) }
.
GOF = {∑w((F
− F
) )/(n − p)} , where n = number of reflections and p = total
number of parameters refined.
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Dalton Trans.

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The crystal structures of 1·2MeCN and 2–5 were solved by
5 D. B. Zhao, N. J. Wu, S. A. Zhang, P. H. Xi, X. Y. Su,
J. B. Lan and J. S. You, Angew. Chem., Int. Ed., 2009, 48,
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Int. Ed., 2009, 48, 8725–8728.
2
direct methods and refined on F by full-matrix least-squares
6
6
methods with the SHELXL-97 program. All non-H atoms
were refined anisotropically. The H atoms of N2 from the
5
-phpymt molecules in 2 and 4 were located using the Fourier
maps with the N–H distance being fixed at 0.82 Å. All other
hydrogen atoms were placed in the geometrically idealized
positions and constrained to ride on their parent atoms.
Pertinent crystal data and collection and refinement para-
meters for 1·2MeCN and 2–5 are summarized in Table 1, while
their selected bond lengths and angles are listed in Table 3.
7 J. M. Xu, X. Y. Wang, C. W. Shao, D. Y. Su, G. L. Cheng and
Y. F. Hu, Org. Lett., 2010, 12, 1964–1967.
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Tetrahedron Lett., 2015, 56, 1780–1783.
10 S. Chatterjee and T. K. Paine, Inorg. Chem., 2015, 54, 9727–
9
732.
General procedure for the preparation of phenols from
arylboronic acids
1
1 Y. Q. Zou, J. R. Chen, X. P. Liu, L. Q. Lu, R. L. Davis,
K. A. Jϕgensen and W. J. Xiao, Angew. Chem., Int. Ed., 2012,
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In a typical procedure, a test tube equipped with a magnetic
stirring bar was charged with phenylboronic acid (0.061 g, 12 S. P. Pitre, C. D. McTiernan, H. Ismaili and J. C. Scaiano,
.5 mmol), 5 (0.0021 g), Et N (0.051 g, 0.5 mmol), MeCN
J. Am. Chem. Soc., 2013, 135, 13286–13289.
1.5 mL) and H O (1.5 mL). The reaction mixture was kept 13 I. G. T. M. Penders, Z. Amara, R. Horvath, K. Rossen,
0
3
(
2
stirring for 48 h under a 45 W fluorescence lamp light,
quenched with water after completion and the catalyst was fil- 14 A. Paul, D. Chatterjee, Rajkamal, T. Halder, S. Banerjee and
tered off. The filtrate was extracted three times with ethylace-
S. Yadav, Tetrahedron Lett., 2015, 56, 2496–2499.
tate (3 × 5 mL). The combined organic layer was washed with 15 S. D. Sawant, A. D. Hudwekar, K. A. A. Kumar,
M. Poliakoff and M. W. George, RSC Adv., 2015, 5, 6501–6504.
brine (20 mL) and dried over anhydrous Na SO and concen-
V. Venkateswarlu, P. P. Singh and R. A. Vishwakarma,
2
4
trated under reduced pressure. The crude product was purified
Tetrahedron Lett., 2014, 55, 811–814.
by flash column chromatography using petroleum ether and 16 J. Luo, X. Zhang and J. Zhang, ACS Catal., 2015, 5, 2250–
ethyl acetate as the eluent and the filtrate was concentrated in
2254.
vacuo.
17 T. Toyao, N. Ueno, K. Miyahara, Y. Matsui, T. H. Kim,
Y. Horiuchi, H. Ikeda and M. Matsuoka, Chem. Commun.,
2015, 51, 16103–16106.
1
1
8 X. Yu and S. M. Cohen, Chem. Commun., 2015, 51, 9880–9883.
9 C. K. Prier, D. A. Rankic and D. W. C. MacMillan, Chem.
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Acknowledgements
This work was financially supported by the National Natural
Science Foundation of China (Grant No. 21373142 and
2
2
2
0 J. R. Chen, X. Q. Hu, L. Q. Lu and W. J. Xiao, Chem. Soc.
Rev., 2016, 45, 2044–2056.
2
1471108 and 21531006), the Natural Science Foundation of
1 X. Z. Shu, M. Zhang, Y. He, H. Frei and F. D. Toste, J. Am.
Chem. Soc., 2014, 136, 5844–5847.
Jiangsu Province (BK20161276), the State Key Laboratory of
Organometallic Chemistry of Shanghai Institute of Organic
Chemistry (2015kf-07), the “333” Project of Jiangsu Province,
the Priority Academic Program Development of Jiangsu Higher
Education Institutions, and the “SooChow Scholar” Program
of Soochow University.
2 Q. Y. Meng, T. Lei, L. M. Zhao, C. J. Wu, J. J. Zhong,
X. W. Gao, C. H. Tung and L. Z. Wu, Org. Lett., 2014, 16,
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