Syntheses and structures of copper complexes of 3-(6-(1H-pyrazol-1-yl) pyridin-2-yl)pyrazol-1-ide and their excellent performance in the syntheses of nitriles and aldehydes

Article abstract of DOI:10.1039/c4dt01765j

Reactions of a pincer ligand 2-(1H-pyrazol-1-yl)-6-(1H-pyrazol-3-yl) pyridine (pzpypzH) with Cu(NO₃)₂, Cu(ClO₄) ₂, CuSO₄, CuCl₂ or CuI produced three dinuclear Cu(ii) complexes [{Cu(NO₃)}(μ-pzpypz)]₂ (1), [{Cu(ClO₄)}(μ-pzpypz)]₂ (2), [Cu₂(μ- SO₄)(μ-pzpypz)₂]·2MeOH (3·2MeOH), one mononuclear Cu(ii) complex [CuCl₂(pzpypzH)] (4) and one trinuclear Cu(i)/Cu(ii) complex [(ICu)(μ-I)₂Cu₂(μ-pzpypz) ₂] (5), respectively. Treatment of 4 with two equiv. of AgNO ₃ in DMF also gave rise to 1. Complexes 1-5 were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Complex 1 or 2 has a dimeric structure in which two {Cu(X)} (X = NO₃, ClO₄) fragments are interconnected by two μ-pzpypz^- ligands. 3 also adopts a dimeric structure in which two Cu(ii) centers are interconnected by a pair of μ-pzpypz^- ligands and one μ-SO ₄^2- ion. The Cu(ii) center in 4 is five-coordinated by three N atoms of the pzpypzH ligand and two Cl atoms. In 5, two Cu(ii) centers are bridged by two μ-pzpypz^- ligands and one CuI₃ ^2- unit, forming a unique trinuclear structure. Complexes 1-5 displayed high catalytic activity toward the ammoxidation of alcohols to nitriles and the aerobic oxidation of alcohols to aldehydes in H₂O. The nitrile or aldehyde products could be readily separated from the catalytic system by extraction and the residual aqueous solution containing 1 retained good activity for several cycles.

Full text of DOI:10.1039/c4dt01765j

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PAPER
Syntheses and structures of copper complexes of
3-(6-(1H-pyrazol-1-yl)pyridin-2-yl)pyrazol-1-ide
and their excellent performance in the syntheses
of nitriles and aldehydes†
Cite this: Dalton Trans., 2014, 43,
14061
Da-Wei Tan,a Jing-Bo Xie,a Qi Li,a Hong-Xi Li,*a Jun-Chi Li,a Hai-Yan Lia and
Jian-Ping Lang*a,b
Reactions of a pincer ligand 2-(1H-pyrazol-1-yl)-6-(1H-pyrazol-3-yl)pyridine (pzpypzH) with Cu(NO3)2,
Cu(ClO4)2, CuSO4, CuCl2 or CuI produced three dinuclear Cu(II) complexes [{Cu(NO3)}(μ-pzpypz)]2 (1),
[{Cu(ClO4)}(μ-pzpypz)]2 (2), [Cu2(μ-SO4)(μ-pzpypz)2]·2MeOH (3·2MeOH), one mononuclear Cu(II)
complex [CuCl2(pzpypzH)] (4) and one trinuclear Cu(I)/Cu(II) complex [(ICu)(μ-I)2Cu2(μ-pzpypz)2] (5),
respectively. Treatment of 4 with two equiv. of AgNO3 in DMF also gave rise to 1. Complexes 1–5 were
characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Complex 1 or 2
has a dimeric structure in which two {Cu(X)} (X = NO3, ClO4) fragments are interconnected by two
μ-pzpypz− ligands. 3 also adopts a dimeric structure in which two Cu(II) centers are interconnected by a
pair of μ-pzpypz− ligands and one μ-SO4 ion. The Cu(II) center in 4 is five-coordinated by three
2−
N atoms of the pzpypzH ligand and two Cl atoms. In 5, two Cu(II) centers are bridged by two μ-pzpypz−
ligands and one CuI32− unit, forming a unique trinuclear structure. Complexes 1–5 displayed high catalytic
activity toward the ammoxidation of alcohols to nitriles and the aerobic oxidation of alcohols to aldehydes
in H2O. The nitrile or aldehyde products could be readily separated from the catalytic system by extraction
and the residual aqueous solution containing 1 retained good activity for several cycles.
Received 14th June 2014,
Accepted 30th July 2014
DOI: 10.1039/c4dt01765j
www.rsc.org/dalton
methods require the use of toxic inorganic cyanide salts, high
temperature, pressure, stoichiometric, and excess amounts of
Introduction
Nitriles are important synthetic precursors1 for the transform- highly reactive oxidants or expensive transition metal catalysts.
ation into esters, amides, carboxylic acids, amines,2 nitrogen- Thus screening inexpensive and environmentally benign metal
containing heterocycles, etc.3 To date, many synthetic routes catalysts for the synthesis of nitriles remains a great challenge.
have been developed for nitriles. General synthetic routes Very recently, inexpensive copper catalysts have provided a
include Sandmeyer’s reaction,4 transition metal-catalyzed cya- highly economical and efficient method for the ammoxidation
nation of aryl halides with metal cyanides via a nucleophilic of alcohols to nitriles by employing O2 as an oxidant.12 Cook
pathway,5 oxidation of amines,6 dehydration of amides and and Muldoon et al. reported that the Cu(OTf)2/2,2′-bipy/
aldoximes,7 transformation of an organic molecule to CN− via TEMPO catalytic system could be used to prepare nitriles from
the C–H functionalization of arenes,8 and oxidative dehydro- reactions of aldehydes with aqueous ammonia in MeCN and
genation of benzylic alcohols and ammonia,9 azides10 or H2O.12a Huang and co-workers prepared nitriles through the
methyl arenes11 to the corresponding nitriles. However, these dehydrogenation cascade mediated by CuI/2,2′-bipy/TEMPO in
EtOH or MeCN using O2 as an oxidant.12b Tao et al. reported
the synthesis of aryl nitriles from the reactions of aryl alcohols
aCollege of Chemistry, Chemical Engineering and Materials Science, Soochow
or aryl aldehydes with aqueous ammonia catalyzed by the
University, Suzhou 215123, People’s Republic of China. E-mail: jplang@suda.edu.cn,
Cu(NO3)2/TEMPO system in DMSO.12c Although the afore-
lihx@suda.edu.cn; Fax: +86 512 65880328; Tel: +86 512 65882865
bState Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic
mentioned copper catalytic systems exhibited good perform-
ances, such methods had some limitations because these
reactions were carried out in organic solvents or aqueous
organic solvent mixtures. However, there is no report on using
well-defined dinuclear copper coordination complexes for the
aerobic double dehydrogenative reaction of alcohols with
Chemistry, Chinese Academy of Sciences, Shanghai 200032, People’s Republic of
China
†Electronic supplementary information (ESI) available: The 1H and 13C NMR
spectra of nitrile and aldehyde products. CCDC 1006054–1006058 for 1, 2,
3·2MeOH, 4 and 5. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c4dt01765j
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Scheme 1 Coordination modes of pyrazolate, the N^N^N ligand, and
their combination.
Scheme 2 Synthesis of pzpypzH.
the presence of K2CO3 at 110 °C for 24 h, generated 1-(6-(1H-
pyrazol-1-yl)pyridin-2-yl)ethanone in 89% yield. The mixture of
1-(6-(1H-pyrazol-1-yl)pyridin-2-yl)ethanone and N,N-dimethyl-
formamide-dimethyl acetal (DMF-DMA) was refluxed for 24 h
to give rise to 1-(6-(1H-pyrazol-1-yl)pyridin-2-yl)-3-(dimethyl-
amino)prop-2-en-1-one in 93% yield. Reaction of the latter
compound with hydrazine hydrate (NH2NH2·H2O) in refluxing
EtOH resulted in the formation of pzpypzH in 83% yield. Reac-
tion of pzpypzH with equimolar Cu(NO3)2·3H2O in MeOH pro-
duced blue crystals of [{Cu(NO3)}(μ-pzpypz)]2 (1) in 89% yield
(Scheme 3). Similar reactions of pzpypzH with Cu(ClO4)2·6H2O
or CuSO4·5H2O yielded two dinuclear Cu(II) complexes [{Cu-
(ClO4)}(μ-pzpypz)]2 (2) and [Cu2(μ-SO4)(μ-pzpypz)2] (3), respect-
ively. Treatment of pzpypzH with CuCl2 gave one mononuclear
Cu(II) adduct [CuCl2(pzpypzH)] (4). Reaction of 4 with AgNO3
in DMF also led to the formation of 1 in a quantitative yield.
However, reaction of CuI with pzpypzH produced one uncom-
mon trimeric Cu(I)/Cu(II) complex [(ICu)(μ-I)2Cu2(μ-pzpypz)2]
(5), in which Cu(I) was partially oxidated to Cu(II) by O2 in air.
The positive-ion ESI mass spectra of 1–5 were measured to
obtain some information about their behavior in solution
(Fig. S2–S5, ESI†). The assignments were made by inspection
of peak positions and isotopic distributions. Compounds 1–5
aqueous ammonia in an aqueous system. The use of dimetal-
lic complexes as catalysts in organic syntheses has aroused
great interest, mainly due to the fact that the synergistic effect
of the two metal centers on the catalytic reactions might
improve their catalytic reactivity and selectivity.13 The well-
defined bimetal catalyst may be an effective tool to promote
such an aerobic double dehydrogenative reaction. As we know,
copper pyrazolate complexes possess high catalytic activity
towards various organic transformations.14,15 The anions of
pyrazole and its derivatives adopt the μ–κ1:κ1 (Scheme 1a)
coordination mode to bind to two Cu atoms to form bi-, poly-
nuclear, polymeric copper(II) complexes.16 In addition, the tri-
dentate N^N^N organic ligands chelate one metal ion through
the κ3 mode (Scheme 1b).17 The copper coordination com-
plexes stabilized by the N^N^N nitrogen donor ligands usually
exhibited enhanced catalytic activity and selectivity.17f,g Thus it
would be a good alternative to synthesize dicopper complexes
if the two ligands could be combined into a new one shown in
Scheme 1c. Such a ligand can adopt a μ–κ3:κ1 mode to bind at
two metal centers.18a–e In this work, we selected 2-(1H-pyrazol-
1-yl)-6-(1H-pyrazol-3-yl)pyridine (pzpypzH)18f,g to react with
Cu(NO3)2, Cu(ClO4)2, CuSO4, CuCl2 or CuI. Three dinuclear
Cu(II) complexes [{Cu(NO3)}(μ-pzpypz)]2 (1), [{Cu(ClO4)}-
(μ-pzpypz)]2 (2), [Cu2(μ-SO4)(μ-pzpypz)2]·2MeOH (3·2MeOH),
one mononuclear Cu(II) complex [CuCl2(pzpypzH)] (4), and
one rare trinuclear Cu(I)/Cu(II) complex [(ICu)(μ-I)2Cu2(μ-
pzpypz)2] (5) were isolated therefrom. The nitrate, perchlorate,
sulfate and chloride anions were chosen to improve the solubi-
lity of the resulting complexes in water media, in view of the
excellent hydrating capability of these anions in the Hofmeister
anion series.19 Complexes 1–5 displayed excellent catalytic per-
formances in the ammoxidation of alcohols to nitriles and the
aerobic oxidation of alcohols to aldehydes in water. The cataly-
tic system modelled by complex 1 could also be recycled
several times. Their syntheses, crystal structures and catalytic
properties are described below.
Results and discussion
Syntheses of pzpypzH and complexes 1–5
The ligand pzpypzH could be prepared by the modified litera-
ture procedures.18f,g As shown in Scheme 2, the Ullmann con-
densation reaction of pyrazole with 1-(6-bromopyridin-2-yl)-
ethanone, which was catalyzed by CuI/1,10-phenanthroline in Scheme 3 Syntheses of complexes 1–5.
14062 | Dalton Trans., 2014, 43, 14061–14071
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in which two “{Cu(X)}” (X = ClO4, NO3) moieties are bridged by
a couple of μ-pzpypz− ligands. A crystallographic center of sym-
metry is located in the midpoint of the two Cu atoms. Each
pzpypz− ligand in 1 and 2 takes a μ–κ3:κ1 mode to coordinate
to two Cu(II) centers. Each Cu atom in 1 and 2 can be
described as having a square pyramidal coordination geometry
in which N(1), N(2A), N(3A) and N(5A) atoms occupy the basal
−
−
plane while the O(1) atom from NO3 or ClO4 anion occupies
the apical position. In 1 and 2, the two pzpypz− ligands are
almost in the plane. The mean Cu–N length (1.999(3) Å) in 1 is
similar to those found in
2 (1.992(5) Å) and [Cu2-
Fig. 1 The calculated isotope patterns (top) and the observed patterns
(below) of the [Cu2(μ-pzpypz)2(OEt)]+ cation in the positive-ion ESI mass
spectra of 1–5.
(bppyH)2(NO3)2] (1.997(5) Å),14c but is slightly shorter than that
in [Cu(bppyH)Cl2] (2.007(10) Å).20 The average Cu–O bond dis-
tance (2.298(2) Å) in 1 is longer than those observed in com-
plexes [Cu2(bppyH)2(NO3)2] (2.273(4) Å)14c and {[Cu-
(Mebta)4(H2O)](ClO4)2·0.4EtOH} (2.216(4) Å),21 but shorter
than the corresponding one in 2 (2.373(12) Å). The Cu–O bond
distance in 1 or 2 is relatively long, indicating that the O atom of
either the nitrate or perchlorate anion binds weakly at the Cu(II)
center. The Cu⋯Cu distance (3.885 Å (1) and 3.896 Å (2)) is
much longer than those observed in [{Cu(μ-dcmpz)}2-
(μ-OMe)2]3 (2.9907(7)–3.1818(8) Å), which excludes any metal–
metal interactions.14a
all showed one strong signal at m/z = 591.09, which may be
associated with the cationic [Cu2(μ-pzpypz)2(OEt)]+ species
(Fig. 1). In addition, one weak signal at m/z = 690.06 (1)
(Fig. S2†), 773.07 (2) (Fig. S3†), 756.04 (3) (Fig. S4†) or 893.06
(5) (Fig. S5†) might be assigned to the [{Cu2(μ-pzpypz)2(NO3)} +
NO3 + 2CH3CN]+ cation (1), the [CuClO4(pzpypzH)Cu(OCH3)
(pzpypz) + 3MeOH]+ cation (2), the [{Cu2(μ-SO4)(μ-pzpypz)2} +
HSO4 + 2MeOH + 4H2O + CH3CN]+ cation (3), and the [{(CuI)
(μ-pzpypz)}2 + I + 3H2O + 4CH3CN]+ cation (5), respectively.
These cations implied that 1–5 might keep their dinuclear
structures in solution. Complexes 1–5 were stable toward
oxygen and moisture, and readily soluble in H2O, DMF, DMSO,
MeCN and MeOH, but insoluble in Et2O and n-hexane. At
room temperature, the solubility of 1–5 in water amounted to
ca. 15 mg mL−1 (1), 8 mg mL−1 (2), 20 mg mL−1 (3), 10 mg
mL−1 (4) and 16 mg mL−1 (5), respectively.
Crystal structures of 3·2MeOH and 5
Compound 3·2MeOH crystallizes in the monoclinic space
group P21/n, and its asymmetric unit contains one discrete
[Cu2(μ-SO4)(μ-pzpypz)2] molecule and two MeOH solvent mole-
cules. However, compound 5 crystallizes in the monoclinic
space group C2/c, and its asymmetric unit has half of a dis-
crete [(ICu)(μ-I)2Cu2(μ-pzpypz)2] molecule. In 3·2MeOH and 5,
two Cu atoms are connected by two μ-pzpypz− ligands, and the
two Cu(II) centers are further bridged by one SO42− ion through
Crystal structures of 1 and 2
Compound 1 crystallizes in the monoclinic space group P21/c
and its asymmetric unit contains half of a discrete molecule
[{Cu(NO3)}(μ-pzpypz)]2. However, 2 crystallizes in the triclinic
2−
two Cu–O bonds in 3·2MeOH (Fig. 3), or by one CuI3 unit
through two Cu–μ-I bonds in 5 (Fig. 4). In 3·2MeOH, Cu(1) and
Cu(2) atoms are square-pyramidally coordinated by four
N atoms from two μ-pzpypz− ligands and one O atom from a
ˉ
space group P1, and the asymmetric unit consists of half of an
independent molecule [{Cu(ClO4)}(μ-pzpypz)]2. As the mole-
cular structures of 1 and 2 are very similar, only that of 1 was
shown in Fig. 2. Complexes 1 and 2 adopt a dimeric structure
2−
SO4 ion. The Cu–N bond distances (1.952(2) Å–2.065(2) Å)
(Table 1) in 3·2MeOH are consistent with those in 1 and 2. The
Fig. 3 View of the molecular structure of 3·2MeOH with a labeling
scheme and 50% thermal ellipsoids. All H atoms and the uncoordinated
MeOH molecules were omitted for clarity.
Fig. 2 View of the molecular structure of 1 with a labeling scheme and
50% thermal ellipsoids. All hydrogen atoms were omitted for clarity.
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Table 1 Selected bond lengths (Å) and angles (°) for 1, 2, 3·2MeOH,
4 and 5a
Compound 1
Cu(1)–N(1)
Cu(1)–N(2A)
1.930(3)
2.011(3)
Cu(1)–N(3A)
Cu(1)–N(5A)
1.970(3)
2.083(3)
Cu(1)–O(1)
2.298(2)
N(1)–Cu(1)–N(3A)
N(3A)–Cu(1)–N(2A)
N(3A)–Cu(1)–N(5A)
N(1)–Cu(1)–O(1)
N(2A)–Cu(1)–O(1)
168.97(11)
79.50(11)
78.05(11)
102.63(10)
94.76(10)
N(1)–Cu(1)–N(2A)
N(1)–Cu(1)–N(5A)
N(2A)–Cu(1)–N(5A)
N(3A)–Cu(1)–O(1)
N(5A)–Cu(1)–O(1)
99.40(11)
101.72(11)
157.04(11)
88.40(10)
89.34(10)
Compound 2
Cu(1)–N(1A)
Cu(1)–N(2)
Cu(1)–O(1)
N(1A)–Cu(1)–N(3)
N(3)–Cu(1)–N(2)
N(3)–Cu(1)–N(5)
N(1A)–Cu(1)–O(1)
N(2)–Cu(1)–O(1)
1.918(5)
2.014(5)
2.373(12)
172.1(2)
79.7(2)
78.3(2)
92.7(3)
Cu(1)–N(3)
Cu(1)–N(5)
1.959(5)
2.078(5)
Fig. 4 View of the molecular structure of 5 with a labeling scheme and
50% thermal ellipsoids. All H atoms were omitted for clarity.
N(1A)–Cu(1)–N(2)
N(1A)–Cu(1)–N(5)
N(2)–Cu(1)–N(5)
N(3)–Cu(1)–O(1)
N(5)–Cu(1)–O(1)
99.0(2)
102.3(2)
157.8(3)
95.2(3)
91.8(3)
mean Cu–O bond distance in 3·2MeOH (2.176(2) Å) is shorter
than those in 1 and 2. In 5, Cu(1) (or Cu(1A)) takes a distorted
square pyramidal coordination geometry, coordinated by four
N atoms from two μ-pzpypz− ligands and one I atom. Cu(2), co-
ordinated by three I atoms, has a trigonal-planar coordination
sphere. The Cu(1)–I(1) (or Cu(1)–I(1A)) bond distance is rela-
tively long (3.0250(11) Å) (Table 1), indicating that I(1) or I(1A)
interacts weakly with Cu(1) or Cu(1A). The mean Cu(2)–I dis-
tance (2.5258(7) Å) is shorter than that observed in [CuI-
(dpypy)]n (2.5415(8); dpypy = 3,5-bis(4-pyridyl)pyridine).22 The
Cu(1)–N bond lengths vary from 1.938(3) Å to 2.062(4) Å,
which are close to those in 3·2MeOH. In 3·2MeOH and 5, the
two pzpypz− ligands also take a trans configuration, and their
phenyl groups are twisted by 28.49° (3·2MeOH) and 37.24° (5),
respectively.
93.4(3)
Compound 3·2MeOH
Cu(1)–N(6)
Cu(1)–N(2)
Cu(1)–O(1)
Cu(2)–N(8)
1.954(2)
1.998(2)
2.158(2)
1.982(2)
2.065(2)
156.18(10)
79.07(9)
77.94(9)
97.66(10)
89.94(10)
156.62(10)
78.51(9)
77.91(9)
96.97(10)
95.46(9)
Cu(1)–N(3)
Cu(1)–N(5)
Cu(2)–N(1)
Cu(2)–N(7)
1.974(2)
2.058(2)
1.952(2)
2.000(2)
2.182(2)
98.58(9)
101.25(9)
156.83(9)
106.00(10)
99.13(9)
99.02(9)
100.72(9)
155.95(9)
106.40(10)
95.66(9)
Cu(2)–N(10)
Cu(2)–O(2)
N(6)–Cu(1)–N(3)
N(3)–Cu(1)–N(2)
N(3)–Cu(1)–N(5)
N(6)–Cu(1)–O(1)
N(2)–Cu(1)–O(1)
N(1)–Cu(2)–N(8)
N(8)–Cu(2)–N(7)
N(8)–Cu(2)–N(10)
N(1)–Cu(2)–O(2)
N(7)–Cu(2)–O(2)
N(6)–Cu(1)–N(2)
N(6)–Cu(1)–N(5)
N(2)–Cu(1)–N(5)
N(3)–Cu(1)–O(1)
N(5)–Cu(1)–O(1)
N(1)–Cu(2)–N(7)
N(1)–Cu(2)–N(10)
N(7)–Cu(2)–N(10)
N(8)–Cu(2)–O(2)
N(10)–Cu(2)–O(2)
Compound 4
Cu(1)–N(3)
Cu(1)–N(5)
Crystal structure of 4
1.990(7)
2.061(7)
2.488(2)
77.7(3)
154.3(3)
96.2(2)
Cu(1)–N(1)
Cu(1)–Cl(2)
2.038(8)
2.284(2)
Complex 4 crystallizes in the monoclinic space group P21/c,
and its asymmetric unit contains one discrete [Cu(pzpypzH)-
Cl2] molecule. Each Cu(II) center in 4 adopts a pseudotrigonal
bipyramidal geometry, coordinated by three N atoms from one
pzpypzH ligand and two Cl− ions (Fig. 5). In 4, the Cu–N(py)
bond distance of 1.990(7) Å is shorter than the Cu–N(pz) bond
lengths (2.038(8) Å and 2.061(7) Å) and that of the corres-
ponding bond length of [CuCl2(bppyH2)] (2.020(11) Å).20 The
Cu–N(pz) bond lengths are slightly longer than those of the
corresponding bond lengths in [CuCl2(bppyH2)] (1.997(10) Å
and 2.004(10) Å).20 The Cu(1)–Cl(1) (2.488(2) Å) bond distance
is longer than the Cu(1)–Cl(2) bond length (2.284(2) Å) and
that observed in [CuCl2(bppyH2)] (2.391(10) Å). The H atom on
N(2) of pzpypzH interacts with Cl(1) (N(2)–H(2A)⋯Cl(1), −x + 2,
y − 1/2, −z + 1/2, 2.68(7) Å), forming a one-dimensional chain
(extended along the b axis) (Fig. S1†).
Cu(1)–Cl(1)
N(3)–Cu(1)–N(1)
N(1)–Cu(1)–N(5)
N(1)–Cu(1)–Cl(2)
N(3)–Cu(1)–Cl(1)
N(5)–Cu(1)–Cl(1)
N(3)–Cu(1)–N(5)
N(3)–Cu(1)–Cl(2)
N(5)–Cu(1)–Cl(2)
N(1)–Cu(1)–Cl(1)
Cl(2)–Cu(1)–Cl(1)
77.7(3)
151.2(2)
102.0(2)
100.3(2)
107.34(8)
101.48(19)
91.55(19)
Compound 5
I(1)–Cu(2)
I(2)–Cu(2)
Cu(1)–N(3)
Cu(1)–N(5)
Cu(2)–I(1)–Cu(1)
N(1A)–Cu(1)–N(2)
N(1A)–Cu(1)–N(5)
N(2)–Cu(1)–N(5)
N(3)–Cu(1)–I(1)
N(5)–Cu(1)–I(1)
I(2A)–Cu(2)–I(1A)
2.5318(7)
2.5197(12)
1.963(3)
I(1)–Cu(1)
Cu(1)–N(1A)
Cu(1)–N(2)
Cu(2)–I(1A)
N(1A)–Cu(1)–N(3)
N(3)–Cu(1)–N(2)
N(3)–Cu(1)–N(5)
N(1A)–Cu(1)–I(1)
N(2)–Cu(1)–I(1)
I(2)–Cu(2)–I(1A)
I(1A)–Cu(2)–I(1)
3.0250(11)
1.938(3)
1.989(4)
2.062(4)
2.5318(7)
156.00(14)
79.77(13)
77.87(13)
104.92(10)
102.30(10)
120.11(2)
119.78(4)
114.58(2)
98.82(13)
100.58(14)
157.50(13)
98.74(10)
83.59(11)
120.11(2)
a Symmetry code: (A) −x, y, −z + 1/2 for 1. (A) −x, −1 − y, 1 − z for 2.
(A) 2 − x, 2 − y, 1 − z for 5.
The ammoxidation of alcohols to nitriles catalyzed by 1–5
The use of copper coordination complexes as catalysts for the
ammoxidation of alcohols to nitriles has remained a topical
research area in recent years.12 Thus, with the as-prepared
copper complexes 1–5 in hand, we investigated their catalytic
activity toward the double dehydrogenation reactions of alco-
hols with aqueous ammonia leading to the formation of
nitriles. We chose 1 and TEMPO as the catalyst system and
p-tolylmethanol (6a) as the model substrate to optimize reac-
tion conditions (Table 2). Initially, we carried out the reaction
14064 | Dalton Trans., 2014, 43, 14061–14071
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24 h at 50 °C in H2O. The product yield was decreased from
99% to 92% when the catalyst loading was changed from 3%
mol [Cu] to 2% mol [Cu] at 50 °C (entries 3 and 7). The reac-
tion temperature also exerted an impact on this reaction.
When the reaction temperature was lowered from 50 °C to
40 °C, the yield of 7a was decreased from 99% to 82% (entries
3 and 8). Inorganic bases such as carbonates, hydroxides, and
phosphate could work and the reaction rate was in the order of
Na2CO3 < KOH < NaOH < K3PO4 < K2CO3 (entries 3, 9–12). In
the absence of the base, 1 exhibited very low activity at 50 °C
(entry 13). To this end, the optimal results were obtained when
benzaldehyde was allowed to react with 3 mol% [Cu] catalyst,
10 mol% base and 5 mol% TEMPO in H2O at 50 °C for 24 h.
With these optimized conditions, the catalytic performances
of 2–5 were also investigated. These complexes also exhibited
excellent catalytic activity for the ammoxidation of p-tolyl-
Fig. 5 View of the molecular structure of 4 with a labeling scheme and
50% thermal ellipsoids. All H atoms were omitted for clarity.
of 6a (2 mmol) with catalyst 1 (1.5 mol%), K2CO3 (10 mol%),
TEMPO (5 mol%) and 300 μL aqueous ammonia in 4 mL
MeCN at 50 °C. After 24 hours, the desired product 4-methyl- methanol to 4-methylbenzonitrile (Table 2, entries 15–18).
benzonitrile (7a) could be isolated in 13% yield coupled with
4-methylbenzaldehyde (8a) (38% yield) (Table 2, entry 1). This
Comparative runs with Cu(NO3)2/1,10-phenanthroline (67%)
and Cu(NO3)2/2,2′-bipyridine (71%) catalytic systems under the
preliminary result implied that 1 might initialize the aerobic same conditions revealed 67% and 71% yields for 4-methyl-
oxidation of alcohol to aldehyde by O2, and further catalyze
benzonitrile (entries 19 and 20), which did not have better
the transformation of the in situ-formed aldehyde into a nitrile
catalytic performance and higher selectivity than 1–5. In the
in the presence of aqueous ammonia. Using 1 as a catalyst, absence of any additional ligands, Cu(NO3)2 did not catalyze
some other solvents were examined (Table 2, entries 2–6). As
the ammoxidation of alcohols to nitriles (entry 21), which
shown in Table 2, the strong solvent dependence of the
might be due to the formation of Werner’s ammonia complex
aerobic double dehydrogenative reaction was observed. 1 did [Cu(NH3)4]2+.12b
not work in toluene, but it showed low activity in MeCN,
EtOH, DMF and DMSO. Almost complete conversion of the
The scope of the present system containing 1 with regard to
various kinds of alcohols was examined. Moderate to excellent
p-tolylmethanol into 4-methylbenzonitrile was achieved within yields could be achieved for a broad range of benzyl alcohols
Table 2 Optimizing the reaction conditions for the synthesis of nitriles from alcohols
Entrya
Cat.
[Cu] loading
Base
Solvent
T (°C)
Time (h)
Yieldb 7a
Yieldb 8a
1
2
3
4
5
6
7
8
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
3
3
3
3
3
3
3
2
3
3
3
3
3
3
3
3
3
3
3
3
3
3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K3PO4
NaOH
KOH
MeCN
EtOH
H2O
DMF
DMSO
Toluene
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
50
50
50
50
50
50
50
40
50
50
50
50
50
50
50
50
50
50
50
50
50
24
24
24
24
24
24
24
24
24
24
24
24
24
12
24
24
24
24
24
24
24
13
31
99
30
28
Trace
92
82
63
53
51
7
38
13
—
15
12
Trace
Trace
8
7
6
9
10
11
12
13
14
15
16
17
18
19c
20d
21
4
Na2CO3
—
Trace
Trace
6
—
—
—
Trace
20
16
Trace
8
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
79
97
98
95
93
67
71
Trace
4
5
1″
1′′′
H2O
H2O
Cu(NO3)2
a 2.0 mmol benzyl alcohol, 10 mol% base, 5 mol% TEMPO, 300 μL aqueous ammonia, in 4 mL H2O, oxygen balloon. b GC yield. c 1″ = Cu(NO3)2/
10-phenanthroline. d 1′′′ = Cu(NO3)2/2,2′-bipyridine.
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Table 3 Scope of alcohols for aerobic double dehydrogenation cata-
lyzed by 1 in water
Table 4 The oxidation of alcohols catalyzed by 1 in water
Entrya
1
Alcohol
Product
Yieldb (%)
95
Entrya
1
Alcohol
Product
Yieldb (%)
95
2
3
91
93
2
3
97
93
4
5
95
90
4
88
5
6
98
96
6
94
7
98
7
76
8
91c
93c
85
8
62c
57c
93
9
9
10
10
11
76
11
98
a Reaction conditions: alcohol (2 mmol), 5 mol% TEMPO, and catalyst
loading = 3 mol% [Cu], 1 atm O2, in 4 mL H2O at 30 °C for 24 hours.
b Isolated yield. c 70 °C.
12
13
83
75
aryl nitrile products 2-methylbenzonitrile (88% yield; entry 4)
and (2-methoxyphenyl)methanol (76% yield; entry 7) in good
5 mol% TEMPO, 10 mol% K2CO3, 1 atm O2, and catalyst loading = yields. It is notable that heteroatom-containing alcohols also
a Reaction conditions: alcohol (2 mmol), 300 μL aqueous ammonia,
3 mol% [Cu] at 50 °C for 24 hours. b Isolated yield. c 80 °C.
reacted smoothly to afford the corresponding nitriles in high
yields (83% for entry 12 and 75% for entry 13).
(Table 3). A variety of functional groups including methyl,
methoxyl, nitryl and chloride groups could be tolerated. The
The aerobic oxidation of alcohols catalyzed by 1
electronic nature of substituents on the benzyl alcohols had
some effect on the double dehydrogenation reactions. Reac-
tions of benzyl alcohols with electron-rich and electron-neutral
groups proceeded efficiently (Table 3). Over 90% isolated
yields were obtained uniformly. However, the moderate yields
were observed for benzyl alcohols with electron-withdrawing
groups such as nitryl (62%) and chloride (57%) at higher reac-
tion temperature (80 °C) (entries 8 and 9). It appeared that the
steric hindrance of benzyl alcohols had an influence on the
catalytic activities of the transformation from benzylic alcohols
to aryl nitriles. The p- and m-benzylic alcohols did not hamper
the N-arylation reaction (entries 2, 3, 5 and 6). We screened the
reaction of o-benzylic alcohol and obtained the corresponding
During the ammoxidation reaction of alcohols, aldehydes were
supposed to form initially. Thus, we evaluated the 1/O2/
TEMPO catalytic system in the direct transformation of alco-
hols into aldehydes (Table 4). The oxidation reaction took
place easily even when the reaction temperature was decreased
to 30 °C in water. The aerobic oxidation of the electron-rich
and -neutral benzyl alcohols proceeded smoothly to the corres-
ponding aryl aldehydes in more than 90% isolated yields.
While the benzyl alcohols with electron-withdrawing ones
(chloro or nitryl) required higher temperature (70 °C) for the
aerobic oxidation reaction to complete the conversion (entries
8 and 9), the heteroaromatic benzylic alcohols such as pyridin-
3-ylmethanol and thiophen-2-ylmethanol went on to give lower
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yields (85% (entry 10) or 76% (entry 11)), which may be due to
the fact that the N atom of the pyridyl ring or the S atom of the
Conclusions
thiophenyl ring might coordinate at the Cu catalytic center, In the work reported here, we have demonstrated that reac-
depressing the oxidation process.
tions of a pincer-bridging ligand pzpypzH with Cu(NO3)2,
Cu(ClO4)2, CuSO4, CuCl2 or CuI afforded three dinuclear Cu(II)
complexes 1–3, one mononuclear Cu(II) complex 4, and one tri-
nuclear Cu(I)/Cu(II) complex 5, respectively. In 1, 2, 3 and 5,
each pzpypz− ligand takes a μ–η3(N,N,N):η1(N) mode to coordi-
nate to two Cu atoms via four Cu–N bonds, while pzpypzH in 4
chelates one Cu2+ ion. Complexes 1–5 displayed high catalytic
activity toward the ammoxidation of alcohols to nitriles and
the aerobic oxidation of alcohols to aldehydes in H2O. Further-
more, the model catalyst 1 was easily recoverable and could be
reused several times, which is anticipated to have potential use
in industrial applications. The design of other copper com-
plexes of bridging/chelating multidentate pyrazolate ligands
with catalytic potential is currently being pursued.
Reusability of the catalyst
The nitrile and aldehyde products are soluble in Et2O, and can
be readily separated by extraction from the aqueous catalytic
systems. The positive-ion ESI mass spectra of the aqueous cata-
lytic solutions revealed the presence of the cationic
[Cu2(μ-pzpypz)2(OEt)]+ signal at m/z = 591.09, which indicated
that the catalyst 1 retained its dinuclear structure after the cat-
alytic reaction. Therefore the remaining aqueous solution con-
taining 1 may be reused for the fresh ammoxidation reaction
and aerobic oxidation of alcohols, which is of importance
from the viewpoints of practical and industrial utilization.
p-Tolylmethanol was selected as a representative example to
check the reusability for the synthesis of 4-methylbenzonitrile
and 4-methylbenzaldehyde. As shown in Table 5, the ammoxi-
dation of p-tolylmethanol and 300 μL aqueous ammonia with
1.5 mol% catalyst 1 led to the formation of 4-methylbenzo-
nitrile in 94% yield. After the completion of the first cycle, the
product was isolated by extraction and the remaining aqueous
Experimental section
General
All reagents were used as purchased from commercial sources
1
without further purification. The H and 13C NMR spectra in
CDCl3 were recorded at ambient temperature on a Varian UNI-
TYplus-400 spectrometer and the chemical shifts δ were
reported as parts per million (ppm) relative to, respectively,
residual CHCl3 (7.26 ppm) and CDCl3 (77.2 ppm) as internal
standards. Resonance patterns were reported with the nota-
tions of s (singlet), d (doublet) and m (multiplet). In addition,
coupling constants J were reported in hertz (Hz). The uncor-
rected melting points were re-determined on Mel-Temo II
apparatus. The IR spectra (KBr disc) were recorded on a
Nicolet MagNa-IR550 FT-IR spectrometer (4000–400 cm−1).
Synthesis of 2-(1H-pyrazol-1-yl)-6-(1H-pyrazol-3-yl)pyridine
(pzpypzH). The pzpypzH ligand was prepared in three steps
from 1-(6-(1H-pyrazol-1-yl)pyridin-2-yl)ethanone according to
the literature method.18f,g Pyrazole (2.55 g, 37.5 mmol), 1,10-
phenanthroline monohydrate (0.99 g, 5 mmol), CuI (0.48 g,
2.5 mmol) and K2CO3 (3.80 g, 25 mmol) were added to a
toluene solution (30 mL) of 1-(6-bromopyridin-2-yl)ethanone
(5 g, 25 mmol) under a N2 atmosphere. The mixture was
stirred at 110 °C for 24 h. After cooling to ambient tempera-
ture, the mixture was partitioned between water and ethyl
acetate. The organic layer was separated, and the aqueous
layer was extracted with ethyl acetate. The combined organic
layers were washed with brine, dried over Na2SO4, and concen-
trated in vacuo. The residue was purified by silica gel column
chromatography (petroleum ether–ethylacetate, v/v = 50 : 1) to
afford the white solid of 1-(6-(1H-pyrazol-1-yl)pyridin-2-yl)etha-
none (4.16 g, 89%). m.p.: 46.2–47.8 °C. 1H NMR (400 MHz,
CDCl3, ppm): δ 2.76 (s, 3H), 6.52 (s, 1H), 7.78 (s, 1H), 7.92 (d,
J = 8.0 Hz, 2H), 7.97 (t, J = 8.0 Hz, 1H), 8.19 (d, J = 8.0 Hz, 1H),
8.64 (s, 1H). 13C NMR (100 MHz, CDCl3, ppm) δ 25.6, 108.1,
115.9, 119.0, 126.9, 139.6, 142.3, 150.5, 151.6, 199.0. IR (KBr
disk, cm−1): 1700 (s), 1591 (m), 1576 (w), 1522 (w), 1470 (s),
solution was recharged with
a base, TEMPO, aqueous
ammonia and p-tolylmethanol for the second cycle. It was
found that the residual aqueous solution containing 1 still
worked and could be reused several times, while the catalyst
deactivation was witnessed during each run. At the sixth reuse
run 27% yield was obtained. However, under the optimized
reaction conditions, the residual aqueous solution generated
from the aerobic oxidation of alcohols could be also recycled
and worked well even after the sixth reuse run. In the presence
of aqueous ammonia, 1 in each catalytic cycle might be par-
tially transformed into pzpypzH and Werner’s ammonia
complex [Cu(NH3)4]2+, which did not catalyze the ammoxida-
tion of alcohols to nitriles. The free pzpypzH along with the
product nitrile could also be separated from the catalytic
system by extraction. Therefore the catalytic activity dropped
down gradually with the increase of catalytic cycle.
Table 5 Reuse of 1 catalyzed the aerobic double dehydrogenation and
the oxidation of p-tolylmethanol
Cycle
4-Methylbenzonitrilea
4-Methylbenzaldehydeb
1
2
3
4
5
6
94
90
81
70
51
27
95
93
91
92
89
90
a 2.0 mmol p-tolylmethanol, 10 mol% base, 5 mol% TEMPO, 300 μL
aqueous ammonia, 1.5 mol% 1 in 4 mL H2O, oxygen balloon.
b 2.0 mmol p-tolylmethanol, 10 mol% base, 5 mol% TEMPO, 1.5 mol%
1 in 4 mL H2O, oxygen balloon.
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1392 (s), 1360 (s), 1338 (m), 1249 (w), 1113 (w), 1073 (w), 1040 0.05 mmol) and CuSO4·5H2O (13 mg, 0.05 mmol) as starting
(m), 946 (m), 817 (w), 765 (s), 599 (m). materials. Yield: 13 mg (80% based on Cu). Anal. Calcd for
mixture of 1-(6-(1H-pyrazol-1-yl)pyridin-2-yl)ethanone C22H16Cu2N10O4S: C, 41.06; H, 2.51; N, 21.76%; found C,
A
(3.0 g, 16 mmol) and N,N-dimethylformamide-dimethyl acetal 40.79; H, 2.06; N, 21.34%. IR (KBr disk, cm−1): 1639 (m),
(4.25 mL) was refluxed at 110 °C for 24 h. After concentration 1577 (w), 1489 (w), 1445 (w), 1400 (w), 1384 (w), 1336 (w),
in vacuo, recrystallisation of the orange residue from ethyl- 1204 (s), 1161 (s), 1064 (s), 974 (m), 654 (w), 615 (w), 599 (w),
acetate afforded the pale yellow powder of 1-(6-(1H-pyrazol-1- 505 (w), 489 (w), 454 (w).
yl)-pyridin-2-yl)-3-(dimethylamino)prop-2-en-1-one (3.87 g,
Synthesis of [CuCl2(pzpypzH)] (4). Blue crystals of 4 were
1
93%). m.p.: 141.6–142.8 °C. H NMR (400 MHz, CDCl3, ppm): isolated in a manner similar to that used for the isolation of 1,
δ 3.00 (s, 3H), 3.18 (s, 3H), 6.45 (s, 2H), 7.72 (s, 1H), 7.91 (q, J = using pzpypzH (11 mg, 0.05 mmol) and CuCl2 (9 mg,
12 Hz, 2H), 8.02 (t, J = 8.0 Hz, 2H), 8.62 (s, 1H). 13C NMR 0.05 mmol) as starting materials. Yield: 16 mg (92% based on
(100 MHz, CDCl3, ppm) δ 37.3, 45.2, 90.8, 107.6, 114.2, 119.5, Cu). Anal. Calcd for C11H9Cl2CuN5: C, 38.22; H, 2.62; N,
126.8, 139.4, 142.0, 150.1, 154.4, 154.8, 185.7. IR (KBr disk, 20.26%; found C, 38.68; H, 2.31; N, 19.88%. IR (KBr disk,
cm−1): 1640 (m), 1577 (s), 1553 (s), 1520 (m), 1489 (m), cm−1): 1620 (m), 1578 (m), 1538 (w), 1480 (s), 1399 (s),
1461 (m), 1439 (m), 1413 (m), 1393 (w), 1360 (m), 1337 (m), 1326 (m), 1126 (w), 1058 (m), 987 (m), 811 (m), 789 (m),
1296 (w), 1272 (w), 1262 (w), 1235 (w), 1202 (w), 1124 (w), 773 (m), 628 (w).
1077 (m), 1038 (w), 908 (w), 759 (m), 753 (w), 729 (w), 647 (w).
Synthesis of [(ICu)(μ-I)2Cu2(μ-pzpypz)2] (5). Dark blue crys-
A mixture of 1-(6-(1H-pyrazol-1-yl)pyridin-2-yl)-3-(dimethyl- tals of 5 were isolated in a manner similar to that used for the
amino)prop-2-en-1-one (3.87 g, 16 mmol), ethanol (25 mL) and isolation of 1, using CuI (10 mg, 0.05 mmol) and pzpypzH
hydrazine hydrate (2.5 mL) was then refluxed for 4 h. After con- (11 mg, 0.05 mmol) as starting materials in MeCN (20 mL).
centration in vacuo, recrystallization of the orange residue Yield: 12 mg (72% based on Cu). Anal. Calcd for
from EtOH (5 mL) and ethylacetate (15 mL) afforded the white C22H16Cu3I3N10: C, 26.64; H, 1.63; N, 14.12%; found C, 26.23;
1
solid of pzpypzH (2.73 g, 83%). m.p.: 140.2–142.6 °C. H NMR H, 1.83; N, 13.77%. IR (KBr disk, cm−1): 1615 (m), 1572 (m),
(400 MHz, CDCl3, ppm): δ 6.52 (t, J = 4.0 Hz, 1H), 6.90 (d, J = 1539 (m), 1458 (s), 1446 (w), 1393 (s), 1213 (w), 1177 (m),
4.0 Hz, 1H), 7.67 (d, J = 8.0 Hz, 1H), 7.71 (d, J = 4.0 Hz, 1H), 1161 (w), 1147 (w), 1127 (w), 1051 (w), 968 (w), 795 (w), 767 (m).
7.79 (s, 1H), 7.89 (t, J = 8.0 Hz, 1H), 7.95 (d, J = 8.0 Hz, 1H),
8.69 (d, J = 4.0 Hz, 1H). 13C NMR (100 MHz, CDCl3, ppm)
Typical procedure for the formation of nitriles
δ 104.0, 108.0, 111.9, 117.7, 127.5, 135.9, 139.7, 142.3, 145.3,
A test tube equipped with a magnetic stirring bar was charged
147.2, 151.2. IR (KBr disk, cm−1): 1656 (s), 1638 (s), 1575 (m),
with complex 1 (20 mg, 0.03 mmol, 1.5 mol%), TEMPO
1530 (s), 1476 (m), 1391 (m), 1261 (m), 1104 (m), 1047 (m),
(16 mg, 0.10 mmol, 5 mol%) and K2CO3 (28 mg, 0.20 mmol,
952 (w), 941 (w), 810 (m), 585 (w).
10 mol%). The reaction vessel was vacuumed and backfilled
Synthesis of [{Cu(NO3)}(μ-pzpypz)]2 (1). To a solution of
with oxygen three times. Benzyl alcohol (0.22 g, 2.0 mmol),
Cu(NO3)2·3H2O (23 mg, 0.05 mmol) in MeOH (10 mL) was
H2O (4 mL), and NH3 (aq., 25–28% w/w, 300 μL, 4 mmol) were
added the solution of pzpypzH (11 mg, 0.05 mmol) in MeOH
added subsequently. The resulting deep blue solution was
(10 mL). The resulting mixture was stirred for 30 min and then
stirred under an oxygen balloon at 50 °C (80 °C for (4-nitro-
filtered. Diethyl ether (50 mL) was allowed to diffuse into the
phenyl)methanol and (4-chlorophenyl)methanol) for 24 h.
filtrate at ambient temperature for several days to form blue
Then it was cooled to ambient temperature, and extracted
crystals of 1, which were collected by filtration and washed
three times with Et2O (3 × 5 mL). The combined organic layer
with Et2O, finally dried in vacuo. Yield: 15 mg (90% based on
was washed with brine (20 mL) and dried over anhydrous
Cu). Anal. Calcd for C11H8CuN6O3: C, 39.35; H, 2.40; N,
Na2SO4 and concentrated under reduced pressure. The crude
25.03%; found C, 38.94; H, 2.31; N, 25.47%. IR (KBr disk,
product was purified by flash column chromatography using
cm−1): 1616 (m), 1577 (m), 1523 (w), 1490 (m), 1444 (w),
petroleum ether and ethyl acetate as the eluent.
1427 (s), 1398 (m), 1384 (s), 1337 (w), 1312 (w), 1119 (w),
1059 (w), 785 (w), 765 (w), 625 (w).
Synthesis of [{Cu(ClO4)}(μ-pzpypz)]2 (2). Blue crystals of 2
Typical procedure for the formation of aldehydes
were isolated in a manner similar to that used for the isolation A test tube equipped with a magnetic stirring bar was charged
of 1, using Cu(ClO4)2·6H2O (19 mg, 0.05 mmol) and pzpypzH with complex 1 (20 mg, 0.03 mmol, 1.5 mol%), TEMPO
(11 mg, 0.05 mmol) as starting materials. Yield: 16 mg (85% (16 mg, 0.10 mmol, 5 mol%), and K2CO3 (28 mg, 0.20 mmol,
based on Cu). Anal. Calcd for C11H8ClCuN5O4: C, 35.40; H, 10 mol%). The reaction vessel was vacuumed and backfilled
2.16; N, 18.77%; found C, 34.98; H, 1.81; N, 18.42%. IR (KBr with oxygen three times. Benzyl alcohol (0.22 g, 2.0 mmol) and
disk, cm−1): 1620 (m), 1577 (m), 1523 (w), 1490 (m), 1444 (w), H2O (4 mL) were added. The resulting deep blue solution was
1427 (s), 1398 (m), 1384 (s), 1337 (w), 1312 (w), 1119 (w), stirred under an oxygen balloon at room temperature for 24 h.
1059 (w), 785 (w), 765 (w), 625 (w).
Then it was extracted three times with Et2O (3 × 5 mL). The
Synthesis of [Cu2(μ-SO4)(μ-pzpypz)2]·2MeOH (3·2MeOH). combined organic layer was washed with brine (20 mL) and
Blue crystals of 3·2MeOH were isolated in a manner similar to dried over anhydrous Na2SO4 and concentrated under reduced
that used for the isolation of 1, using pzpypzH (11 mg, pressure. The crude product was purified by flash column
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Table 6 Crystal data and structure refinement parameters for 1, 2, 3·2MeOH, 4 and 5
1
2
3·2MeOH
4
5
Empirical formula
Formula mass
C
11H8CuN6O3
C22H16Cl2Cu2N10O8
746.43
C24H24Cu2N10O6S
707.67
C11H9Cl2CuN5
345.67
C22H16Cu3I3N10
991.77
335.77
Crystal system
Monoclinic
P21/c
0.04 × 0.04 × 0.10
7.6607(3)
7.4928(3)
20.2477(7)
Triclinic
P1
Monoclinic
P21/n
0.04 × 0.16 × 0.17
10.6914(3)
16.1312(3)
15.9990(3)
Monoclinic
P21/c
0.10 × 0.16 × 0.30
10.4435(9)
8.0268(7)
Monoclinic
C2/c
0.04 × 0.06 × 0.16
16.170(5)
10.516(3)
16.232(5)
ˉ
Space group
Crystal dimension (mm3)
0.08 × 0.08 × 0.40
7.9591(6)
8.4441(5)
9.9410(5)
97.366(4)
91.381(5)
102.354(6)
646.34(7)
1
a (Å)
b (Å)
c (Å)
α (°)
β (°)
γ (°)
V (Å3)
Z
15.2314(13)
92.5160(11)
103.456(2)
95.370(8)
108.588(8)
1161.10(8)
4
1.921
676
2683.50(10)
4
1.752
1440
3.225
1271.21(19)
4
1.806
692
2616.3(13)
4
2.518
1856
Dcalc (g cm−3
F(000)
)
1.918
374
1.924
μ (mm−1
)
1.904
2.129
5.991
Total no. of reflns
No. of unique reflns
No. of obsd reflns
No. of variables
21 901
4866
11 791
5872
20917
2376 (Rint = 0.0335)
2117 (I > 2.00σ(I))
190
0.8324–0.9277
0.0411
0.1048
1.033
2412 (Rint = 0.0297)
1982 (I > 2.00σ(I))
141
0.5133–0.8613
0.0693
0.1807
1.092
5239 (Rint = 0.0332)
4410 (I > 2.00σ(I))
412
0.6101–0.8818
0.0374
0.0986
1.023
2361 (Rint = 0.0485)
1895 (I > 2.00σ(I))
176
0.5676–0.8153
0.0768
0.1907
1.078
2423 (Rint = 0.0647)
2051 (I > 2.00σ(I))
172
0.4474–0.7956
0.0313
0.0820
1.053
Transmission factor
a
R1
b
wR2
GOFc
a R1 = ∑||Fo| − |Fc||/∑|Fo|. b wR2 = {∑w(Fo2 − Fc2)2/Σw(Fo2)2}1/2 c GOF = {∑w((Fo2 − Fc2)2)/(n − p)}1/2, where n = number of reflections and p = total
.
numbers of parameters refined.
2−
chromatography using petroleum ether and ethyl acetate as of SO4 were refined to be disordered over two positions with
the eluent.
an occupancy factor of 0.65/0.35 for O3/O3A and 0.70/0.30 for
O4/O4A. Except for four disordered O atoms of ClO4 in 2, all
−
other non-hydrogen atoms were refined anisotropically. The
hydrogen atoms of O(5) and O(6) from the uncoordinated
MeOH molecules in 3·2MeOH and the hydrogen atom of N(2)
from the pzpypzH ligand in 5 were located from Fourier maps
and then the N–H and O–H bond lengths were fixed to be
0.86 Å. All other H atoms were introduced at the calculated
positions and included in the structure-factor calculations. All
the calculations were performed on a Dell workstation using
the CrystalStructure crystallographic software package (Rigaku
and MSC, Ver. 3.60, 2004). Crystal data along with data collec-
tion and refinement parameters for 1, 2, 3·2MeOH, 4 and 5 are
summarized in Table 6.
X-ray crystallography
Single crystals of 1, 2, 3·2MeOH, 4 and 5 suitable for X-ray ana-
lysis were obtained directly from the above preparations.
Single crystals of 1, 2, 3·2MeOH, 4 and 5 were mounted on
glass fibers with grease and cooled in a liquid nitrogen stream
at 153 K (1) or 223 K (3·2MeOH, 4), or 240 K (2) or 273 K (5).
Crystallographic measurements were made on
a Bruker
APEX-II CCD (1 and 5), or an Xcalibur Atlas Gemini (2,
3·2MeOH and 4) diffractometer using graphite-monochro-
mated Mo-Kα (λ = 0.71070 Å) radiation. Diffraction data were
collected in ω mode with a detector distance of 35 mm to the
crystal. The collected data were reduced using the program
Bruker APEX2 or CrysAlisPro, Agilent Technologies (CrysAlis171.
NET, Version 1.171.36.28) and an absorption correction (multi-
scan) was applied. The reflection data were also corrected for
Lorentz and polarization effects.
Acknowledgements
The crystal structures of 1, 2, 3·2MeOH, 4 and 5 were solved The authors thank the National Natural Science Foundation of
by direct methods and refined on F2 by full-matrix least- China (21171124, 21171125 and 21371126), the State Key Lab-
squares techniques with the SHELXTL-97 program.23 For 2, two oratory of Organometallic Chemistry, the Shanghai Institute of
−
O atoms of ClO4 were refined to be disordered over two posi- Organic Chemistry, the Chinese Academy of Sciences
tions with an occupancy factor of 0.50/0.50 for O1/O1A and (201201006) for financial support. J. P. Lang also highly
−
O4/O4A. The other two O atoms of ClO4 were refined to be appreciates the support for the Qin-Lan Project and the “333”
disordered over three positions with an occupancy factor of Project of Jiangsu Province, the Priority Academic Program
0.50/0.25/0.25 for O2/O2A/O2B and O3/O3A/O3B. Two C atoms Development of Jiangsu Higher Education Institutions, and
of phenyl from the pzpypz− ligand were refined to be dis- the “SooChow Scholar” Program of Soochow University. The
ordered over two positions with an occupancy factor of authors also greatly thank the helpful comments from the
0.50/0.50 for C6/C6A and C7/C7A. For 3·2MeOH, two O atoms editor and the reviewers.
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2002, 1804–1806; (c) G. D. McAllister, C. D. Wilfred and
R. J. K. Taylor, Synlett, 2002, 1291–1295; (d) S. Iida and
H. Togo, Tetrahedron, 2007, 63, 8274–8281; (e) B. V. Rokade,
S. K. Malekar and K. Ramaiah Prabhu, Chem. Commun.,
2012, 48, 5506–5508; (f) Y. Sasano, S. Nagasawa,
M. Yamazaki, M. Shibuya, J. Park and Y. Iwabuchi, Angew.
Chem., Int. Ed., 2014, 53, 3236–3240; (g) K. R. Reddy,
C. U. Maheswari, M. Venkateshwar, S. Prashanthi and
M. L. Kantam, Tetrahedron Lett., 2009, 50, 2050–2053.
References
1 (a) T. M. Harris, C. M. Harris, T. A. Oster, L. E. Brown and
J. Y. C. Lee, J. Am. Chem. Soc., 1988, 110, 6180–6186;
(b) V. V. Grushin and H. Alper, Chem. Rev., 1994, 94, 1047–
1062.
2 (a) K. Yamaguchi, M. Matsushita and N. Mizuno, Angew.
Chem., Int. Ed., 2004, 43, 1576–1580; (b) A. V. Gulevich,
A. S. Dudnik, N. Chernyak and V. Gevorgyan, Chem. Rev.,
2013, 113, 3084–3213; (c) R. García-Álvarez, P. Crochet and 10 (a) W. Zhou, J. J. Xu, L. G. Zhang and N. Jiao, Org. Lett.,
V. Cadierno, Green Chem., 2013, 15, 46–66; (d) R. E. Khidre
and B. F. Abdel-Wahab, Curr. Org. Chem., 2013, 17, 430–
445; (e) G. Abbiati, E. M. Beccalli and E. Rossi, Top. Organo-
met. Chem., 2013, 43, 231–290.
2010, 12, 2888–2891; (b) M. Lamani and K. R. Prabhu,
Angew. Chem., Int. Ed., 2010, 49, 6622–6625;
(c) B. V. Rokade, S. K. Malekar and K. R. Prabhu, Chem.
Commun., 2012, 48, 5506–5508.
3 (a) D. C. McCutcheon, M. A. Paley, R. C. Steinhardt and 11 W. Zhou, L. G. Zhang and N. Jiao, Angew. Chem., Int. Ed.,
J. A. Prescher, J. Am. Chem. Soc., 2012, 134, 7604–7607; 2009, 48, 7094–7097.
(b) S. Ueda and H. Nagasawa, J. Am. Chem. Soc., 2009, 131, 12 (a) L. M. Dornan, Q. Cao, J. C. A. Flanagan, J. J. Crawford,
15080–15081; (c) M. Nasr-Esfahani, M. Montazerozohori
and S. Mehrizi, J. Heterocycl. Chem., 2011, 48, 249–254;
(d) X. N. Li, B. Y. Zhou, J. Zhang, M. Y. She, S. J. An,
H. X. Ge, C. Li, B. Yin, J. L. Li and Z. Shi, Eur. J. Org. Chem.,
2012, 1626–1632; (e) F. Himo, Z. P. Demko, L. Noodleman
M. J. Cook and M. J. Muldoon, Chem. Commun., 2013, 49,
6030–6032; (b) W. Y. Yin, C. M. Wang and Y. Huang, Org.
Lett., 2013, 15, 1850–1853; (c) C. Z. Tao, F. Liu, Y. M. Zhu,
W. W. Liu and Z. L. Cao, Org. Biomol. Chem., 2013, 11,
3349–3354.
and K. Barry Sharpless, J. Am. Chem. Soc., 2003, 125, 9983– 13 (a) Y. S. Lan, B. S. Liao, Y. H. Liu, S. M. Peng and S. T. Liu,
9987; (f) W. X. Wang, H. L. Cai and R. G. Xiong, Chin.
Chem. Lett., 2013, 24, 783–785; (g) X. M. Chen and
M. L. Tong, Acc. Chem. Res., 2007, 40, 162–170.
Eur. J. Org. Chem., 2013, 5160–5164; (b) S. Gonell,
M. Poyatos, J. A. Mata and E. Peris, Organometallics, 2012,
31, 5606–5614; (c) I. Bratko and M. Gómez, Dalton Trans.,
2013, 42, 10664–10681.
4 T. Sandmeyer, Ber. Dtsch. Chem. Ges., 1885, 18, 1492–1496.
5 (a) P. Anbarasan, T. Schareina and M. Beller, Chem. Soc. 14 (a) L. Wang, B. Guo, H. X. Li, Q. Li, H. Y. Li and J. P. Lang,
Rev., 2011, 40, 5049–5067; (b) G. B. Yan, J. Yu and L. Zhang,
Chin. J. Org. Chem., 2012, 32, 294–303; (c) G. A. Ellis and
T. M. Romney-Alexander, Chem. Rev., 1987, 87, 779–794;
(d) T. Schareina, A. Zapf and M. Beller, Chem. Commun.,
2004, 1388–1389.
Dalton Trans., 2013, 42, 15570–15580; (b) H. X. Li,
Z. G. Ren, D. Liu, Y. Chen, J. P. Lang, Z. P. Cheng, X. L. Zhu
and B. F. Abrahams, Chem. Commun., 2010, 46, 8430–8432;
(c) L. L. Miao, H. X. Li, M. Yu, W. Zhao, W. J. Gong, J. Gao,
Z. G. Ren, H. F. Wang and J. P. Lang, Dalton Trans., 2012,
41, 3424–3430.
6 (a) M. T. Schümperli, C. Hammond and I. Hermans, ACS
Catal., 2012, 2, 1108–1117; (b) Y. Zhang, K. L. Xu, 15 (a) J. Ackermann, F. Meyer, E. Kaifer and H. Pritzkow,
X. R. Chen, T. J. Hu, Y. P. Yu, J. L. Zhang and J. Huang,
Catal. Commun., 2010, 11, 951–954; (c) K. Yamaguchi and
N. Mizuno, Angew. Chem., Int. Ed., 2003, 42, 1480–1483;
(d) J. Kim and S. S. Stahl, ACS Catal., 2013, 3, 1652–1656.
7 (a) S. Enthaler, Chem. – Eur. J., 2011, 17, 9316–9319;
(b) S. Sueoka, T. Mitsudome, T. Mizugaki, K. Jitsukawa and
K. Kaneda, Chem. Commun., 2010, 46, 8243–8245;
(c) S. L. Zhou, D. Addis, S. Das, K. Junge and M. Beller,
Chem. Commun., 2009, 4883–4885; (d) K. Yamaguchi,
H. Fujiwara, Y. Ogasawara, M. Kotani and N. Mizuno,
Angew. Chem., Int. Ed., 2007, 46, 3922–3925; (e) K. Ishihara,
Y. Furuya and H. Yamamoto, Angew. Chem., Int. Ed., 2002,
41, 2983–2986.
Chem. – Eur. J., 2002, 8, 247–258; (b) C. Di Nicola, F. Garau,
Y. Y. Karabach, L. M. D. R. S. Martins, M. Monari,
L. Pandolfo, C. Pettinari and A. J. L. Pombeiro, Eur. J. Inorg.
Chem., 2009, 666–676; (c) G. A. Ardizzoia, M. A. Angaroni,
G. L. Monica, F. Cariati, S. Cenini, M. Moret and
N. Masciocchi, Inorg. Chem., 1991, 30, 4341–4353;
(d) M. Casarin, C. Corvaja, C. di Nicola, D. Falcomer,
L. Franco, M. Monari, L. Pandolfo, C. Pettinari, F. Piccinelli
and P. Tagliatesta, Inorg. Chem., 2004, 43, 5865–5876;
(e) A. Maspero, S. Brenna, S. Galli and A. Penoni, J. Organo-
met. Chem., 2003, 672, 123–129; (f) G. A. Ardizzoia,
S. Cenini, G. L. Monica, N. Masciocchi and M. Moret,
Inorg. Chem., 1994, 33, 1458–1463.
8 (a) S. T. Ding and N. Jiao, J. Am. Chem. Soc., 2011, 133, 16 (a) J. C. Jeffery, P. L. Jones, K. L. V. Mann, E. Psillakis,
12374–12377; (b) X. Chen, X. S. Hao, C. E. Goodhue and
J. Q. Yu, J. Am. Chem. Soc., 2006, 128, 6790–6791; (c) J. Kim
and S. Chang, J. Am. Chem. Soc., 2010, 132, 10272–10274;
(d) X. Y. Ren, J. B. Chen, F. Chen and J. Cheng, Chem.
Commun., 2011, 47, 6725–6727.
J. A. McCleverty, M. D. Ward and C. M. White, Chem.
Commun., 1997, 175–176; (b) X. M. Liu, A. C. McLaughlin,
M. P. de Miranda, E. J. L. McInnes, C. A. Kilner and
M. A. Halcrow, Chem. Commun., 2002, 2978–2979;
(c) G. Mezei, P. Baran and R. G. Raptis, Angew. Chem., Int.
Ed., 2004, 43, 574–577; (d) A. A. Mohamed, S. Ricci,
A. Burini, R. Galassi, C. Santini, G. M. Chiarella,
9 (a) S. Yamazaki and Y. Yamazaki, Chem. Lett., 1990, 571–
572; (b) F. E. Chen, Y. Y. Li, M. Xu and H. Q. Jia, Synthesis,
14070 | Dalton Trans., 2014, 43, 14061–14071
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
D. Y. Melgarejo and J. P. Fackler Jr., Inorg. Chem., 2011, 50,
1014–1020; (e) A. Cingolani, S. Galli, N. Masciocchi,
L. Pandolfo, C. Pettinari and A. Sironi, J. Am. Chem. Soc.,
2005, 127, 6144–6145; (f) M. Stollenz, C. Große and
F. Meyer, Chem. Commun., 2008, 1744–1746; (g) G. F. Gao,
M. Li, S. Z. Zhan, Z. Lv, G. H. Chen and D. Li, Chem. – Eur.
J., 2011, 17, 4113–4117; (h) J. P. Zhang and S. Kitagawa,
J. Am. Chem. Soc., 2008, 130, 907–917; (i) H. V. Rasika Dias,
H. V. K. Diyabalanage, M. G. Eldabaja, O. Elbjeirami,
M. A. Rawashdeh-Omary and M. A. Omary, J. Am. Chem.
Soc., 2005, 127, 7489–7750.
E. García-España, M. Kumar, V. J. Arán and P. Navarro,
Chem. Commun., 2002, 936–937; (d) C. Miranda, F. Escartí,
L. Lamarque, E. García-España, P. Navarro, J. Latorre,
F. Lloret, H. R. Jiménez and M. J. R. Yunta, Eur. J. Inorg.
Chem., 2005, 189–208; (e) J. Ackermanna, F. Meyera and
H. Pritzkow, Z. Anorg. Allg. Chem., 2004, 630, 2627–2631;
(f) C. M. Che, C. F. Chow, M. Y. Yuen, V. A. L. Roy, W. Lu,
Y. Chen, S. S. Y. Chui and N. Y. Zhu, Chem. Sci., 2011, 2,
216–220; (g) W. W. Jin, L. D. Wang and Z. K. Yu, Organome-
tallics, 2012, 31, 5664–5667.
19 (a) Y. Chen, K. Li, H. O. Lloyd, W. Lu, S. S. Y. Chui and
C. M. Che, Angew. Chem., Int. Ed., 2010, 49, 9968–9971;
(b) W. Lu, Y. Chen, V. A. L. Roy, S. S. Y. Chui and C. M. Che,
Angew. Chem., Int. Ed., 2009, 48, 7621–7625;
(c) H. P. Gregor, J. Belle and R. A. Marcus, J. Am. Chem.
Soc., 1955, 77, 2713–2719; (d) C. W. Burkhardt,
D. P. Parazak, K. J. Mccarthy and G. J. Jackson, J. Appl.
Polym. Sci., 1986, 32, 4701–4708.
17 (a) M. Vogt, A. Nerush, Y. Diskin-Posner, Y. Ben-David and
D. Milstein, Chem. Sci., 2014, 5, 2043–2051; (b) A. Han,
P. W. Du, Z. J. Sun, H. T. Wu, H. X. Jia, R. Zhang,
Z. N. Liang, R. Cao and R. Eisenberg, Inorg. Chem., 2014,
53, 3338–3344; (c) A. B. Biernesser, B. Li and J. A. Byers,
J. Am. Chem. Soc., 2013, 135, 16553–16560; (d) W. M. Du,
Q. F. Wang, L. D. Wang and Z. K. Yu, Organometallics,
2014, 33, 974–982; (e) W. H. Lam, E. S. H. Lam and 20 P. Gamez, R. H. Steensma, W. L. Driessen and J. Reedijk,
V. W. W. Yam, J. Am. Chem. Soc., 2013, 135, 15135–15143; Inorg. Chim. Acta, 2002, 333, 51–56.
(f) I. Cano, E. Álvarez, M. C. Nicasio and P. J. Pérez, J. Am. 21 K. Skorda, S. P. Perlepes, C. P. Raptopoulou, R. Keuleers,
Chem. Soc., 2011, 133, 191–193; (g) Z. Ma, L. J. Wei, E. C. B.
A. Alegria, L. M. D. R. S. Martins, M. F. C. Guedes da Silvab
and A. J. L. Pombeiro, Dalton Trans., 2014, 43, 4048–4058.
18 (a) K. L. V. Mann, E. Psillakis, J. C. JeVery, L. H. Rees,
N. M. Harden, J. A. McCleverty, M. D. Ward, D. Gatteschi,
A. Terzis and J. C. Plakatouras, Transition Met. Chem., 1999,
24, 541–545.
22 F. Thébault, S. A. Barnett, A. J. Blake, C. Wilson,
N. R. Champness and M. Schröder, Inorg. Chem., 2006, 45,
6179–6187.
F. Totti, F. E. Mabbs, E. J. L. McInnes, P. C. Riedi and 23 (a) G. M. Sheldrick, SHELXS-97, Program for Solution of
G. M. Smith, J. Chem. Soc., Dalton Trans., 1999, 339–348;
(b) L. Siegfried, T. A. Kaden, F. Meyer, P. Kircher and
H. Pritzkow, J. Chem. Soc., Dalton Trans., 2001, 2310–2315;
(c) F. Escartí, C. Miranda, L. Lamarque, J. Latorre,
Crystal Structures, University of Göttingen, Germany,
1997; (b) G. M. Sheldrick, SHELXL-97, Program for Refine-
ment of Crystal Structures, University of Göttingen,
Germany, 1997.
This journal is © The Royal Society of Chemistry 2014
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