Copper-organic frameworks assembled from in situ generated 5-(4-pyridyl)tetrazole building blocks: Synthesis, structural features, topological analysis and catalytic oxidation of alcohols

Article abstract of DOI:10.1039/c4dt00531g

Two new metal-organic compounds {[Cu₃(μ₃-4-ptz) ₄(μ₂-N₃)₂(DMF) ₂](DMF)₂}_n (1) and {[Cu(4-ptz) ₂(H₂O)₂]}_n (2) {4-ptz = 5-(4-pyridyl)tetrazolate} with 3D and 2D coordination networks, respectively, have been synthesized while studying the effect of reaction conditions on the coordination modes of 4-pytz by employing the [2 + 3] cycloaddition as a tool for generating in situ the 5-substituted tetrazole ligands from 4-pyridinecarbonitrile and NaN₃ in the presence of a copper(ii) salt. The obtained compounds have been structurally characterized and the topological analysis of 1 discloses a topologically unique trinodal 3,5,6-connected 3D network which, upon further simplification, results in a uninodal 8-connected underlying net with the bcu (body centred cubic) topology driven by the [Cu ₃(μ₂-N₃)₂] cluster nodes and μ₃-4-ptz linkers. In contrast, the 2D metal-organic network in 2 has been classified as a uninodal 4-connected underlying net with the sql [Shubnikov tetragonal plane net] topology assembled from the Cu nodes and μ₂-4-ptz linkers. The catalytic investigations disclosed that 1 and 2 act as active catalyst precursors towards the microwave-assisted homogeneous oxidation of secondary alcohols (1-phenylethanol, cyclohexanol, 2-hexanol, 3-hexanol, 2-octanol and 3-octanol) with tert-butylhydroperoxide, leading to the yields of the corresponding ketones up to 86% (TOF = 430 h ^-1) and 58% (TOF = 290 h^-1) in the oxidation of 1-phenylethanol and cyclohexanol, respectively, after 1 h under low power (10 W) microwave irradiation, and in the absence of any added solvent or additive.

Full text of DOI:10.1039/c4dt00531g

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PAPER
Copper–organic frameworks assembled from
in situ generated 5-(4-pyridyl)tetrazole building
blocks: synthesis, structural features, topological
analysis and catalytic oxidation of alcohols†
Cite this: Dalton Trans., 2014, 43,
9944
Rajendar Nasani,a Manideepa Saha,a Shaikh M. Mobin,a Luísa M. D. R. S. Martins,*b,c
Armando J. L. Pombeiro,*c Alexander M. Kirillovc and Suman Mukhopadhyay*a
Two new metal–organic compounds {[Cu3(µ3-4-ptz)4(µ2-N3)2(DMF)2](DMF)2}n (1) and {[Cu(4-
ptz)2(H2O)2]}n (2) {4-ptz = 5-(4-pyridyl)tetrazolate} with 3D and 2D coordination networks, respectively,
have been synthesized while studying the effect of reaction conditions on the coordination modes of
4-pytz by employing the [2 + 3] cycloaddition as a tool for generating in situ the 5-substituted tetrazole
ligands from 4-pyridinecarbonitrile and NaN3 in the presence of a copper(II) salt. The obtained com-
pounds have been structurally characterized and the topological analysis of 1 discloses a topologically
unique trinodal 3,5,6-connected 3D network which, upon further simplification, results in a uninodal
8-connected underlying net with the bcu (body centred cubic) topology driven by the [Cu3(µ2-N3)2]
cluster nodes and µ3-4-ptz linkers. In contrast, the 2D metal–organic network in 2 has been classified as
a uninodal 4-connected underlying net with the sql [Shubnikov tetragonal plane net] topology assembled
from the Cu nodes and µ2-4-ptz linkers. The catalytic investigations disclosed that 1 and 2 act as active
catalyst precursors towards the microwave-assisted homogeneous oxidation of secondary alcohols
(1-phenylethanol, cyclohexanol, 2-hexanol, 3-hexanol, 2-octanol and 3-octanol) with tert-butylhydro-
peroxide, leading to the yields of the corresponding ketones up to 86% (TOF = 430 h−1) and 58% (TOF =
290 h−1) in the oxidation of 1-phenylethanol and cyclohexanol, respectively, after 1 h under low power
(10 W) microwave irradiation, and in the absence of any added solvent or additive.
Received 20th February 2014,
Accepted 30th April 2014
DOI: 10.1039/c4dt00531g
www.rsc.org/dalton
blocks towards the design of metal–organic networks.2 In par-
ticular, a combination of 4-ptz with a copper ion has produced
Introduction
Tetrazole ligands have been extensively used to generate a handful of MOFs obtained either in the presence or absence
metal–organic and H-bonded frameworks of different topolo- of co-ligands.3 However, in most of the reported cases, 4-ptz
gies in the last few years.1 The versatility of the tetrazole build- has been generated under solvothermal conditions by cyclo-
ing blocks provides the required template to create a hoard of addition of 4-cyanopyridine and an azide ion in the presence
new materials with interesting properties and diverse applica- of different transition metals. In contrast, the synthesis of
tions.1g,h Among the various tetrazole ligands, 5-(4-pyridyl)- MOFs driven by the 4-ptz blocks in a more controlled manner
tetrazole (4-ptz) has been one of the widely employed building (i.e., at lower temperatures and pressures via a similar cyclo-
addition path) has not been reported so far though there are
reports of formation of tetrazoles under milder conditions in
the presence of metal ions or other catalysts.4
aDepartment of Chemistry, School of Basic Sciences, Indian Institute of Technology
Indore, IET-DAVV Campus, Khandwa Road, Indore 452017, India.
From the other side, the synthesis of new MOFs and their
application in oxidative catalysis represent an interesting
research direction.5,6 In the present study, we have selected the
oxidation of secondary alcohols as a model reaction,7 aiming
at probing catalytic potential of the compounds 1 and 2. Clas-
sical methods for the liquid-phase oxidation of alcohols to
ketones are unfeasible on an industrial-scale and undesirable
from the environmental viewpoint due to the common use of
chlorinated solvents, toxic8a–c or moisture-sensitive oxidants,8d
E-mail: suman@iiti.ac.in; Fax: +91 731 2361 482; Tel: +91 731 2438 705
bChemical Engineering Department, ISEL, R. Conselheiro Emídio Navarro, 1959-007
Lisboa, Portugal. E-mail: lmartins@deq.isel.ipl.pt
cCentro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade
de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
E-mail: pombeiro@tecnico.ulisboa.pt
†Electronic supplementary information (ESI) available. CCDC 940211 and
940212 (squeezed refined structures) for 1 and 2, respectively. For ESI and
crystallographic data in CIF or other electronic format see DOI: 10.1039/
c4dt00531g
9944 | Dalton Trans., 2014, 43, 9944–9954
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high catalyst loadings, presence of bases and phase-transfer- for 3 h, and then a green coloured compound started to pre-
ring agents.8e–h Hence, aerobic8h–l and peroxidative8m–p oxi- cipitate. The stirring was continued for another hour. The
dations of secondary alcohols are regarded as the simplest and mixture was then filtered and the resulting filtrate was left to
most useful synthetic methods for the preparation of ketones, slowly evaporate in air. Green coloured rod shaped X-ray dif-
in view of the versatility of the metal catalysts, oxidants and fraction quality crystals started to form after 1 d. They were fil-
alcohol substrates used. The improvement of these synthetic tered and washed with DMF and diethyl ether. Yield = 112 mg
methodologies, according to green chemistry principles,8q,r is (16.2%), anal. calc. for C42H58Cu3N16O6, C, 46.98, H, 5.45, N,
a challenge to be tackled, focusing on the use of alternative 20.87, found: C, 47.01, H, 5.47, N, 20.90. IR (KBr): 2081(s)
green solvent systems for more efficient and clean syntheses.8s
1670(s), 1624(s), 1434(m), 1383(w), 1296(w), 1219(w), 1093(m),
Herein we report the synthesis and structural features of 1015(m). The purity of the bulk sample of 1 was confirmed by
two copper metal–organic frameworks which have been gen- the PXRD patterns of the sample (Fig. S1†).
erated by the cycloaddition reaction between sodium azide and
Synthesis of {[Cu(4-ptz)2(H2O)2]}n (2). A greenish brown
4-cyanopyridine in the presence of a copper(II) salt. Further- mixture of CuCl2·2H2O (51 mg, 0.3 mmol), NaN3 (39 mg,
more, the present work discloses the catalytic properties of 0.6 mmol) and 4-cyanopyridine (125 mg, 1.2 mmol) in a H2O
these two compounds toward the oxidation of secondary alco- and DMF (1 mL : 6 mL) mixture was placed into a reaction tube
hols under rather mild and green conditions.
and that was irradiated with microwave radiation for 30 min at
85 °C. The resulting green coloured precipitate was filtered off
from brown solution and discarded. The filtrate was left to
slowly evaporate in air resulting in the formation of blue cubic
shaped crystals in 3 d. These were isolated and washed with
DMF and diethyl ether. Yield = 55 mg (19.1%), anal. calc. for
Experimental section
Materials and instrumentation
Reagents were purchased from commercial sources and used C12H12CuN10O2: C, 36.78, H, 3.09, N, 35.75, found: C, 37.00,
without further purification. Microwave irradiation exper- H, 3.11, N, 35.78. IR (KBr): 3486(m), 1659(s), 1494(w), 1438(m),
iments for the synthesis of 2 and for the catalytic tests under 1389(m), 1253(m), 1102(m). The purity of the bulk sample of 2
MW irradiation were performed in a focused microwave CEM was confirmed using the PXRD patterns of the sample (Fig. S2†).
discover reactor (300 W for the synthesis or 10 W for the cataly-
X-ray crystallography
sis), using a 10 mL capacity reaction tube with a 13 mm
internal diameter, fitted with a rotational system and an IR Single crystal X-ray structural studies of compounds 1 and 2
temperature detector. Infrared spectra (4000–500 cm−1) were were performed on a CCD Agilent Technologies (Oxford Diffr-
recorded with a Bio-Rad FTS 3000MX instrument in KBr action) SUPER NOVA diffractometer. Data were collected at
pellets. Elemental analyses were carried out with a Thermo- 150(2) K using graphite-monochromated Mo Kα radiation (λα =
Flash 2000 elemental analyser. Powder X-ray diffraction pat- 0.71073 Å). The strategy for the data collection was evaluated
terns for complexes 1 and 2 were recorded on a Rigaku Smart using the CrysAlisPro CCD software. The data were collected by
Lab X-ray diffractometer. The X-rays were produced using a the standard phi–omega scan techniques and were scaled and
sealed tube and the wavelength of the X-ray was 0.154 nm reduced using the CrysAlisPro RED software. The structures
(CuK-alpha). The X-rays were detected using a linear counting were solved by direct methods using SHELXS-97 and refined
detector (Scintillator NaI photomultiplier detector). Spectro- by full matrix least-squares with SHELXL-97, refining on F2.9
photometric measurements were performed on a Varian
The positions of all the atoms were obtained by direct
UV-Vis spectrophotometer (Model: Cary 100) using a quartz methods. All non-hydrogen atoms were refined anisotropically.
cuvette with a path length of 1 cm. Gas chromatographic (GC) The remaining hydrogen atoms were placed in geometrically
measurements were carried out using a FISONS Instruments constrained positions and refined with isotropic temperature
GC 8000 series gas chromatograph with an FID detector and a factors, generally 1.2Ueq of their parent atoms. The crystal and
capillary column (DB-WAX, column length: 30 m; internal dia- refinement data are summarized in Table 1.
meter: 0.32 mm) and the Jasco-Borwin v.1.50 software. The
It is worth notingthat randomly dispersed solvent molecules
temperature of injection was 240 °C. The initial temperature (DMF–H2O used for crystallization) were found in the framework
was maintained at 120 °C for 1 min, then raised at 10 °C of 2 and attempts were made to refine the structure using con-
min−1 to 200 °C and held at this temperature for 1 min. ventional discrete-atom models remained unsuccessful. This
Helium was used as the carrier gas.
issue was solved by deducting the contribution of the solvent
Caution! Azide and tetrazolate compounds are potentially electron density using the SQUEEZE routine in PLATON.10
explosive. Only a small amount of material should be prepared
and handled with care.
Synthesis of {[Cu3(µ3-4-ptz)4(µ2-N3)2(DMF)2](DMF)2}n (1). An
Typical procedures for the catalytic oxidation of alcohols and
product analysis
excess of solid 4-cyanopyridine (249 mg, 2.4 mmol) was added Oxidation reactions were carried out in sealed cylindrical Pyrex
to the brown coloured mixture of CuCl2·2H2O (102 mg, tubes under focused microwave irradiation as follows: the
0.6 mmol) and NaN3 (78 mg, 1.2 mmol) in water (1 mL) and alcohol substrate (5 mmol), the catalyst precursor 1 or 2
DMF (6 mL). The obtained brown solution was stirred at 85 °C (10 μmol, 0.2 mol% vs. substrate) and a 70% aqueous solution
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with an excess of 4-cyanopyridine (4 equivalents) in a 1 : 6
(v : v) mixture of water and DMF at 85 °C for 4 h (Scheme 1). A
green coloured solid 1 was precipitated and its further crop
was obtained upon filtration and subsequent evaporation of
the mother liquor, producing green crystals suitable for single-
crystal X-ray diffraction.
A different procedure involved a microwave irradiation, at
85 °C for 30 min, of a mixture containing copper(II) chloride,
sodium azide and 4-cyanopyridine in a 1 : 2 : 4 molar ratio
using a water–DMF mixture (1 : 6, v : v). The obtained mixture
was filtered and the filtrate was left in air for 3 d, resulting in
blue coloured cubic crystals of 2, suitable for single-crystal
X-ray diffraction analysis.
The obtained compounds were characterized by IR spec-
troscopy, elemental analysis and single-crystal X-ray crystallo-
graphy. The IR spectrum of 1 shows a strong band at
2081 cm−1 typical for µ-azide ions in a 1,1-bridging mode.11
An additional band due to the presence of tetrazole ions is
observed in the 1655–1670 cm−1 range.12 In 2, the stretching
band at 1659 cm−1 indicates the presence of tetrazolate ions,12
while the characteristic broad band of water molecules at
3486 cm−1 arises from the O–H stretching.11 Powder X-ray
diffraction (PXRD) patterns were recorded for samples 1 and 2
showing a very good match with the respective simulated pat-
terns acquired from the single crystal X-ray data, thus demon-
strating the phase purity of the bulk samples.
Table 1 Crystallographic data and refinement details for 1 and 2
(1)
(2)a
Empirical formula
Mr [g mol−1
Crystal system
Space group
a [Å]
b [Å]
c [Å]
C21H29Cu1.50N16O3
648.91
Monoclinic
P21/n
13.0662(3)
14.7659(3)
15.3925(3)
90.00
C12H12CuN10O7
471.86
Orthorhombic
]
Pbcn
11.9883(7)
16.0417(6)
13.0715(7)
90.00
α [°]
β [°]
90.29
90.00
2969.70(11)
4
1.451
1338
1.095
90.00
90.00
2513.8(2)
4
1.247
956
1.107
γ [°]
V [Å3]
Z
Dcalcd [mg m−3
F(000)
GOF
]
Reflections collected/unique
Final R indices
25 450/5226
R1 = 0.0463,
wR2 = 0.1293
R1 = 0.0505,
wR2 = 0.1329
19 402/2218
R1 = 0.0803,
wR2 = 0.2307
R1 = 0.0987,
wR2 = 0.2465
R indices (all data)
a Contribution of the disordered solvent was subtracted and solvent
electron density was removed by the SQUEEZE routine in PLATON,
before refinement from diffraction data of 2.
of TBHP (10 mmol) were introduced into the tube. This was
then placed in the microwave reactor and the system was
stirred and irradiated (10 W) for 0.25–3 h at 80 °C. After the
reaction, the mixture was allowed to cool down to room temp-
erature. 300 μL of benzaldehyde (internal standard) and 5 mL
of NCMe (to extract the substrate and the organic products
from the reaction mixture) were added. The obtained mixture
was stirred for 10 min and then a sample (1 μL) was taken
from the organic phase and analysed by GC using the internal
standard method.
Crystal structure of {[Cu3(µ3-4-ptz)4(µ2-N3)2(DMF)2](DMF)2}n (1)
The 3D polymeric structure of compound 1 bearing a tri-
nuclear Cu(II) core was revealed by single crystal X-ray diffrac-
tion data. There are two types of copper centres observed in
the trinuclear secondary building unit (SBU) (Fig. 1a). The
“central” six-coordinate Cu1 atom possesses a distorted octa-
hedral geometry filled by four bridging 4-ptz ligands in the
equatorial sites, whereas the axial positions are taken by the
azide moieties that bridge in a μ1,1-mode linking the copper
centres into a Cu3 SBU. The copper azide bond distances are
Results and discussion
Compound 1 has been prepared by reacting a solution of relatively large (2.326 Å) because of the Jahn–Teller effect. The
copper(II) chloride with two equivalents of sodium azide along bond length and bond angle data are summarized in Table 2.
Scheme 1 Synthesis and structural formulae of compounds 1 and 2.
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Fig. 1 Structural fragments of 1. (a) Tricopper(II) secondary building unit. (b) 3D metal–organic framework with open-end voids containing DMF
molecules as the solvent of crystallization (enlarged) (hydrogen atoms other than those involving in interactions have been omitted for clarity). Color
codes: Cu brown, C black, H white, N blue and O red.
Apart from azide linkers, the “outer” six-coordinate Cu2 atoms net.14,15 Hence, after omitting the terminal DMF ligands and
are connected with the “central” Cu1 ion by means of two reducing the µ2-N3 and µ3-4-ptz moieties to their centroids, the
tetrazolate moieties which are bridging in a N2/N3 mode. The resulting network (Fig. 2a) can be described as an underlying
other coordination positions of the Cu2 atoms are occupied by net constructed from the 6-connected Cu1 and 5-connected
two pyridyl groups of the bridging 4-ptz ligands and one term- Cu2 nodes, 3-connected µ3-4-ptz nodes and 2-connected µ2-N3
inal DMF molecule. Each of these trinuclear SBUs is inter- linkers. The topological analysis of this net reveals a complex tri-
linked with eight adjacent Cu3 units via the 4-ptz moieties, nodal 3,5,6-connected network with a unique topology depicted
resulting in an intricate 3D metal–organic framework with the by the point symbol of (3·82)4(32·4·83·93·10)2(34·42·96·103),
box type open-end voids having the 1.3 × 1.5 nm dimensions wherein the (3·82), (32·4·83·93·10) and (34·42·96·103) indices corre-
(Fig. 1b). The solvent of crystallization (DMF molecules) spond to the µ3-4-ptz, Cu2 and Cu1 nodes, respectively. The
occupies the voids and further stabilizes the obtained frame- obtained network can be simplified further, namely by treating
work via H-bonding interactions (Table 3).
the tricopper [Cu3(µ2-N3)2] units as the 8-connected cluster
To better understand the intricate structure of the 3D nodes and the µ3-4-ptz blocks as the 2-connected linkers, result-
metal–organic framework 1, we have carried out its topological ing in a uninodal 8-connected net (Fig. 2b) with the bcu (body
analysis13 using the concept of the simplified underlying centred cubic) topology and the point symbol of (424·64).14,16,17
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Table 2 Bond lengths (Å) and bond angles (°) within and around the trinuclear copper core of 1 and the mononuclear copper centre of 2a
Distance
Angle
Angle
Complex 1
Cu(1)–N(8)
Cu(1)–N(1)
Cu(1)–N(5)
Cu(2)–N(2)
Cu(2)–N(5)
Cu(2)–N(13)#2
Cu(2)–N(12)#3
Cu(2)–O(1)
2.022(3)
2.024(3)
2.326(3)
2.024(3)
1.996(3)
2.013(3)
2.018(3)
2.381(3)
N(1)–Cu(1)–N(5)
N(8)–Cu(1)–N(1)
N(8)–Cu(1)–N(5)
N(8)–Cu(1)–N(8)#1
N(1)–Cu(1)–N(1)#1
N(5)–Cu(1)–N(5)#1
N(5)–Cu(2)–N(2)
N(2)–Cu(2)–O(1)
N(2)–Cu(2)–N(13)
82.27(10)
89.57(10)
92.56(10)
180.0
N(12)#3–Cu(2)–N(2)
N(5)–Cu(2)–N(13)#2
N(5)–Cu(2)–N(12)#3
N(5)–Cu(2)–O(1)
N(13)#2–Cu(2)–N(12)#3
N(13)#2–Cu(2)–O(1)
N(12)#3–Cu(2)–O(1)
94.18(11)
87.78(11)
172.90(11)
95.42(10)
90.44(11)
91.10(10)
91.48(10)
180.0
180.00(14)
87.96(10)
86.00(10)
174.58
Complex 2
Cu(1)–N(2)
Cu(1)–N(1)
Cu(1)–O(101)
2.012(5)
2.066(5)
2.387(5)
N(2)–Cu(1)–N(1)
N(2)–Cu(1)–O(101)
N(1)–Cu(1)–O(101)
92.4(2)
87.88(19)
90.6(2)
N(2)#1–Cu(1)–N(2)
N(1)–Cu(1)–N(1)#1
O(101)–Cu(1)–O(101)#1
180.0(2)
180.0(1)
180.0
a Symmetry codes: #1 −x, −y, −z + 1, #2 x − 1/2, −y + 1/2, z − 1/2, #3 x + 1/2, −y + 1/2, z − 1/2.
the terminal H2O moieties and contracting the µ2-4-ptz
ligands to their centroids. The obtained underlying layer is
thus assembled from the 4-connected Cu1 nodes and 2-con-
nected µ2-4-ptz linkers (Fig. 4). From the topological viewpoint,
this 2D network can be classified as a uninodal 4-connected
net with the sql [Shubnikov tetragonal plane net] topology
described by the point symbol of (44·62).14,16 A number of 4-ptz
derivatives with the sql topology have been reported.3g,18
Added solvent-free microwave-assisted oxidation of second-
ary alcohols. Complexes 1 and 2 have been tested as catalyst
precursors for the homogeneous oxidation of secondary alco-
hols (1-phenylethanol, cyclohexanol, 2-hexanol, 3-hexanol,
2-octanol and 3-octanol) to the corresponding ketones using
Table 3 Important hydrogen bonding interactions
d(D–H)/
Å
d(H⋯A)/
Å
d(D⋯A)/
∠D–H⋯
D–H⋯A
Å
A/°
Complex 1
C(13)–H(13B)⋯O(111)
C(111)–H(11C)⋯O(111)
O(333)–H(333)⋯N(7)
0.970
0.981
0.950
2.478
2.515
2.601
3.371
3.404
3.514
151.46
150.64
161.41
Complex 2
C(5)–H(5)⋯O(1)
0.930
2.558
3.370
146.09
Crystal structure of {[Cu(µ2-4-ptz)2(H2O)2]}n (2)
Single crystal X-ray diffraction data revealed that the structure tert-butylhydroperoxide (TBHP) or hydrogen peroxide as an oxi-
of 2 features a 2D coordination framework assembled from the dizing agent, under typical conditions of 80 °C, and low power
Cu(II) centres and µ2-4-ptz linkers. The geometry around the (10 W) microwave irradiation (MW), 1 h reaction time and in
six-coordinate Cu1 atom is also distorted octahedral, being the absence of any added solvent or additive (Scheme 2).
filled by a pair of N atoms from the pyridyl group and another Selected results are summarized in Table 4, whereas the com-
pair of tetrazolato N atoms from the 4-ptz moieties in the plete set of results is presented in Table S1.†
mutually trans-fashion to complete the square base, whereas
Under typical conditions ketone yields up to 86% (TOF =
the remaining axial positions are occupied by oxygen atoms of 430 h−1) are obtained for the oxidation of 1-phenylethanol
two terminal water ligands (Fig. 3a). The coordinated water (entry 18, Table 4) by 2. As expected, the aliphatic alcohols are
molecules are arranged comparatively far from the basal plane less reactive than the benzylic derivative, 1-phenylethanol,
moieties (Table 2). Hence, each 4-ptz acts as a µ2-linker sewing leading under the same reaction conditions to moderate yields
the Cu centres into a grid-like 2D network. The adjacent 2D in the 38–67% range (Table 4), as reported in other cases.7
layers are stacked and zipped through hydrogen bonding inter- Higher yields of cyclohexanone were previously obtained with
actions [C(5)–H(5)⋯O(1)], to generate a 3D supramolecular a related TBHP/MW system in the presence of the tetranuclear
network (Table 3). The inter-layer distance between two adja- Cu(II) complex derived from 2-(2-(dicyanomethylene)hydrazi-
cent layers is 13.072 Å (Fig. 3b). A 3D supramolecular network nyl)benzoic acid,19a although requiring a 4 times longer reac-
features porosity due to the presence of open-ended rhombic tion time. An almost quantitative formation of acetophenone
shaped voids along the c axis, with the dimensions of 1.6 × after 4 or 2 h reaction was achieved by oxidation of 1-phenyl-
1.1 nm (Fig. 3c). In addition, the above voids were loaded with ethanol with TBHP catalysed by [(PhSiO1.5)10(CuO)2-
disordered solvent molecules (probably water and DMF used (NaO0.5)2·4EtOH]19b or [(PhSiO1.5)12(CuO)4(NaO0.5)4],19c respect-
during crystallization), which could not be refined by discrete- ively. However, the oxidation of 1-phenylethanol by the 1 or 2/
atom models and thus were subtracted from the diffraction TBHP/MW systems affords acetophenone in much higher
pattern by the “SQUEEZE” method.
yields (86% (2) or 79% (1), Table 4) than in the presence of
The 2D metal–organic network of 2 has also been simpli- various mononuclear Cu(II) complexes bearing N2S2 macro-
fied for the sake of topological analysis, namely by omitting cycles20 or dinuclear Mn(II) compounds.7h,i
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Fig. 3 Structural fragments of 2 representing (a) a basic unit, (b) stack-
ing of three 2D metal–organic layers (side view of each layer) and hydro-
gen bonding interactions holding the layers together, (c) view of
rhomboid voids along the c axis (hydrogen atoms other than those
involving in interactions have been omitted for clarity). Color codes: Cu
brown, C black, H white, N blue and O red.
Fig. 2 Topological representations (views along the a axis) of the
underlying 3D networks in
1 showing: (a) a topologically unique
trinodal 3,5,6-connected net with the point symbol of
(3·82)4(32·4·83·93·10)2(34·42·96·103), and (b) a further simplified uninodal
8-connected net with the point symbol of (424·64) and bcu (body cen-
tered cubic) topology obtained after considering the [Cu3(µ2-N3)2]
units as cluster nodes. Further details: (a) 5- and 6-connected Cu2 and
Cu1 nodes (brown), centroids of 3-connected µ3-4-ptz nodes (blue),
centroids of 2-connected µ2-N3 linkers (yellow); (b) centroids of
8-connected [Cu3(µ2-N3)2] cluster nodes (brown) and centroids of
2-connected µ3-4-ptz linkers (blue).
Moreover, it appears that the efficiency of oxidation of linear
aliphatic alcohols (C6 or C8) is not affected by the position of
the OH group in the aliphatic chain of the substrate, as attested
by similar yields of 2- and 3-hexanones or 2- and 3-octanones
(compare e.g., entries 27 and 29 or 31 and 33, Table 4).
However, alcohols with a shorter aliphatic chain typically lead
to higher product yields (Table 4, entries 10, 12 vs. 14, 16).
The relevance of the 4-ptz ligands to the catalytic activity of
the obtained compounds is shown by the catalytic perform-
ances of CuCl2 in the oxidation of the used substrates (yields
in the 2–7% range, entries 69 and 72–76, Table S1†) compared
with those of 1 and 2 under the same reaction conditions.
Fig. 4 Topological representation (view along the c axis) of the under-
lying 2D network in 2 showing a uninodal 4-connected net with the
point symbol of (44·62) and sql [Shubnikov tetragonal plane net] topo-
logy. Further details: 4-connected Cu1 nodes (brown) and centroids of
2-connected µ2-4-ptz linkers (blue).
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Scheme 2 Added solvent-free oxidation of 1-phenylethanol and cyclo-
hexanol to acetophenone and cyclohexanone, respectively, by the 1 or
2/TBHP/MW system.
Fig. 5 Influence of the type of oxidant on the yield of ketone in the
MW-assisted oxidation of secondary alcohols catalysed by 1 or 2.
Addition of a TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)
radical, an efficient mediator for the aerobic oxidation of alco-
hols7d,j,21 although scarcely used for the peroxidative oxida-
tion7h,i,m,22 of those substrates, provided the quantitative
formation of acetophenone (entry 22, Table 4) and a signifi-
cant increase in all other ketone yields (see e.g., entries 1, 4,
10, 12, 14 or 16 vs. 2, 8, 11, 13, 15 or 17, Table 4).
It should be noted that in contrast to TBHP, hydrogen per-
oxide (30% aqueous solution) is a less efficient reagent for the
oxidation of the tested alcohols, as attested by the marked
ketone yield lowering (see Fig. 5 and Table S1†), in accord with
the known decomposition of H2O2 under the used reaction
conditions (80 °C). Moreover, the use of a higher amount of
oxidant (see entries 5, 19 or 2, 45 of Tables 4 and S1,† respect-
ively) or longer reaction time (see e.g., entries 3, 9, 23 and 26,
Table 4) does not lead to a better conversion.
Attempts to perform the oxidation of secondary alcohols in
the presence of 1 or 2 at room temperature failed, whereas the
reaction conducted at 50 °C resulted in a marked ketone yield
drop relative to that at 80 °C (e.g., for 1, from 79, 58, 63, or
38% at 80 °C to 22, 15, 23 or 17% at 50 °C, respectively,
Table S1† and Fig. 6). Moreover, the ketone yield does not
increase significantly above 80 °C (see Fig. 6 and entries 1, 10,
Table 4 Selected results for the MW-assisted oxidation of secondary
alcohols by TBHP with 1 and 2 as catalyst precursorsa
Entry Catalyst precursor Substrate
1
TOFb (h−1
)
Yieldc (%)
397
79
92
78
58
53
2
2d
1-Phenylethanol 460
3e
130
290
265
10
20
335
92
315
385
285
370
190
270
235
315
430
405
25
4
5f
6g
Cyclohexanol
7h
1
4
8d
67
55
63
77
57
74
38
54
47
63
86
81
5
9e
10
2-Hexanol
3-Hexanol
2-Octanol
3-Octanol
11d
12
13d
14
15d
16
17d
18
19f
20g
21h
22d
23e
24
1-Phenylethanol
15
3
495
142
210
320
67
99
85
42
64
40
67
81
66
84
58
79
51
67
25d
26e
27
2
Cyclohexanol
2-Hexanol
3-Hexanol
2-Octanol
3-Octanol
335
405
330
420
290
395
255
335
28d
29
30d
31
32d
33
34d
a Reaction conditions unless stated otherwise: 5 mmol of substrate,
10 μmol (0.2 mol% vs. substrate) of catalyst precursor, 10 mmol of
TBHP (70% aq.), 80 °C, 1 h reaction time, microwave irradiation
(10 W). b Turnover frequency = number of moles of product per mol of
catalyst per hour (turnover number per hour). c Moles of ketone
product per mol of alcohol. d In the presence of TEMPO (5 mol% vs.
substrate). e 3 h reaction time. f 20 mmol of TBHP (4 eq.). g In the
presence of Ph2NH (5 mmol). h In the presence of CBrCl3 (5 mmol).
Fig. 6 Influence of temperature on the yield of ketone in the MW-
assisted oxidation of secondary alcohols catalysed by 1 (cyclohexanol,
2-hexanol and 2-octanol) or
3-octanol).
2 (1-phenylethanol, 3-hexanol and
9950 | Dalton Trans., 2014, 43, 9944–9954
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19, 24, 27, 35, 44, 56, or 64 vs. 9, 18, 23, 26, 31, 43, 52, 60 or time, indicating the initial reduction of copper(II) (green) to
68, Table S1†). copper(I) (orange) in the presence of alcohol and TEMPO.
Microwave irradiation (MW) can provide a more efficient These results also confirm the radical mechanism where
synthetic method than conventional heating, thus allowing the reduction of copper(II) leads to the oxidation of alcohol, fol-
attainment of similar yields in shorter times or improved lowed by the subsequent oxidation of copper(I) by O2/TBHP.
yields and/or selectivities.7c,h–m,22 A favourable effect of MW is
The solids obtained after the oxidation reactions with the
also observed in this study, even with the low power of catalyst precursors 1 and 2 have been analyzed by IR spec-
10 W. Hence, for example, 86% yield of acetophenone was troscopy, PXRD and elemental analyses. From the IR spectrum
obtained after 1 h reaction under microwave irradiation, while of a solid derived from 1 after the catalytic reaction, it has
a similar reaction under conventional heating (oil bath) gives been found that the band at 2081 cm−1 has vanished, clearly
only 7% yield. A noteworthy feature of our MW-assisted oxi- indicating the absence of azide in the system, whereas the
dations is the application of a very weak MW irradiation observed hump at 1656 cm−1 might suggest the presence of
(10 W). This contrasts with most of the MW-assisted organic tetrazole in the residue. The elemental analysis result with a
reactions reported,23 which require a much higher power of high percentage of nitrogen also indicates the probable pres-
MW irradiation (typically above 200 or even 500 W).
ence of tetrazole in the residual compound derived from 1.
Furthermore, important features of 1 and 2 concern their The PXRD pattern confirms that 1 lost its crystalline nature
relatively low loading (0.2 mol% vs. substrate) necessary to and has a structure well distinct from that of the parent com-
reach high yields of ketone (e.g., up to 99% of acetophenone pound 1 (Fig. S4†). In the case of 2, although the IR spectrum
when in the presence of TEMPO), also undergoing under of the corresponding residual compound after the catalytic
solvent- and additive-free conditions. This is advantageous in reaction is almost similar to that of 2 and elemental analysis
comparison with the common use of organic solvents or costly data suggest the presence of tetrazole moieties, the PXRD
ionic liquids in various state-of-the-art methods for the oxi- pattern also indicates the deformation of the framework
dation of alcohols.23b,24
(Fig. S5†). These observations indicate that both compounds 1
The peroxidative oxidation of the tested secondary alcohols and 2 are not intact during the course of catalytic tests and
is believed to proceed mainly via a radical mechanism which thus behave as precursors of homogeneous catalytically active
involves both carbon- and oxygen-centred radicals. In fact, the species. We believe that further research aimed at the incor-
addition to the reaction mixture of Ph2NH or CBrCl3, well poration of the present types of tetrazole based copper–organic
known oxygen- and carbon-radical traps, respectively,25 led to frameworks on solid matrices or supports would allow the
a large yield drop of over 90% (Table S1,† entries 4, 38 vs. 5, 39 generation of more stable and potentially recyclable catalytic
for 1-phenylethanol or 13, 47 vs. 14, 48 for cyclohexanol, systems. This research direction as well as the detailed investi-
respectively), compared to the reaction carried out under the gation of the mechanism will be explored in our future
same conditions but in the absence of
a radical trap studies.
(Table S1,† entries 1, 10, 35 or 44, respectively). This result
suggests the generation of oxygen and carbon radicals in the
reaction, which are trapped by those radical scavengers.
A possible mechanism21i,k,26 for this system may involve
Conclusions
coordination of the alcohol e.g., PhCH(OH)Me (with deproto- Two different metal–organic frameworks 1 and 2 have been
nation to form an alkoxide ligand) and a TEMPO radical, fol- synthesized by means of 1,3-dipolar cycloaddition between
lowed by H transfer from the former to the latter with 4-cyanopyridine and azide in the presence of copper(II) chlor-
formation of the O-ligated radical PhC•(O)Me− and TEMPOH. ide by varying the reaction conditions only. A notable feature
Intramolecular electron-transfer from the PhC•(O)Me− co- of an underlying 3,5,6-connected 3D net of 1 concerns its
ordinated to CuII leads to the formation of the ketone PhC(O)- novel topology described by the point symbol of
Me and CuI which is reoxidised to CuII by O2/TBHP. The (3·82)4(32·4·83·93·10)2(34·42·96·103), which can be further simpli-
TEMPO radical is also regenerated upon oxidation of fied to a body centred cubic (bcu) network bearing a trinuclear
TEMPOH.
Cu3-secondary building unit. In contrast, the 2D network of 2
In order to get further insight into the catalytic cycle, the reveals an underlying Shubnikov tetragonal plane net (sql).
model reaction with 5 mmol of cyclohexanol, 10 mmol of Thus, the present work also contributes to the identification of
aqueous solution of TBHP and 5 mol% TEMPO was moni- novel topological types observed within the metal–organic
tored, under a dinitrogen atmosphere in the presence of cata- framework materials. Furthermore, both compounds show a
lyst precursors 1 and 2, by spectrophotometry. Upon addition high activity as catalyst precursors towards the microwave-
of the catalyst precursor into the reaction mixture [cyclohexa- assisted homogeneous oxidation of secondary alcohols leading
nol and TBHP (70 wt% in water)] a strong MLCT band was to ketone yields up to 99% (2) under added solvent-free con-
instantaneously observed at 442 nm (Fig. S3†), being character- ditions. Hence, this study also widens the scope of MW-
istic of a copper(I) species.27 After addition of TEMPO the solu- assisted transformations applied to the oxidative functionali-
tion color changes from colorless to orange and this color zation of organic substrates and extends the range of efficient
upon exposure to dioxygen gradually changed to brown with catalytic systems applicable to such reactions.
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S.-M. Chen, Y.-M. Xie, X.-Y. Wu, S.-C. Chen, R.-M. Yu and
C.-Z. Lu, CrystEngComm, 2009, 11, 1526–1528; (f) F. Wang,
R.-M. Yu, X.-Y. Wu and C.-Z. Lu, Inorg. Chem. Commun.,
2012, 19, 70–72; (g) F. Wang, R. Yu, Q.-S. Zhang, Z.-G. Zhao,
X.-Y. Wu, Y.-M. Xie, L. Qin, S.-C. Chen and C.-Z. Lu, J. Solid
State Chem., 2009, 182, 2555–2559; (h) F. Wang, J. Zhang,
R. Yu, S.-M. Chen, X.-Y. Wu, S.-C. Chen, Y.-M. Xie,
W.-W. Zhou and C.-Z. Lu, CrystEngComm, 2010, 12, 671–
673.
4 (a) L. V. Myznikov, J. Roh, T. V. Artamonova, A. Hrabalek
and G. I. Koldobskii, Russ. J. Org. Chem., 2007, 43, 765–767;
(b) F. Himo, Z. P. Demko, L. Noodleman and
K. B. Sharpless, J. Am. Chem. Soc., 2003, 125, 9983–9987;
(c) Y. Zhou, C. Yao, R. Ni and G. Yang, Synth. Commun.,
2010, 40, 2624–2632; (d) V. Aureggi and G. Sedelme, Angew.
Chem., Int. Ed., 2007, 46, 8440–8444.
Acknowledgements
We are grateful for the financial support received from the
Council of Scientific and Industrial Research, New Delhi and
from the Fundação para a Ciência e a Tecnologia (FCT), Portu-
gal, and its projects PTDC/EQU-EQU/122025/2010, PTDC/
QUI-QUI/121526/2010 and PEst-OE/QUI/UI0100/2013. One of
us (M. S.) thanks CSIR for the award of JRF in a CSIR spon-
sored project. We are also thankful to the Sophisticated Instru-
ment Centre, IIT Indore for the structure elucidation.
References
1 (a) M.-X. Yang, L.-J. Chen, S. Lin, X.-H. Chen and
H. Huang, Dalton Trans., 2011, 40, 1866–1872;
(b) W. Ouellette, K. Darling, A. Prosvirin, K. Whitenack,
K. R. Dunbar and J. Zubieta, Dalton Trans., 2011, 40,
12288–12300; (c) S. Jeong, X. Song, S. Jeong, M. Oh, X. Liu,
D. Kim, D. Moon and M. S. Lah, Inorg. Chem., 2011, 50,
12133–12140; (d) J.-Z. Liao, H. Ke, J.-J. Liu, Z.-Y. Li,
M.-J. Lin, J.-D. Wang and C.-C. Huang, CrystEngComm,
2013, 15, 4830–4837; (e) H. Deng, Y.-C. Qiu, Y.-H. Li,
Z.-H. Liu, R.-H. Zeng, M. Zeller and S. R. Batten, Chem.
Commun., 2008, 2239–2241; (f) B. Liu, Y.-C. Qiu, G. Peng
and H. Deng, CrystEngComm, 2010, 12, 270–276;
(g) W.-T. Liu, J.-Y. Li, Z.-P. Ni, X. Bao, Y.-C. Ou, J.-D. Leng,
J.-L. Liu and M.-L. Tong, Cryst. Growth Des., 2012, 12, 1482–
1488; (h) P. Cui, Z. Chen, D. Gao, B. Zhao, W. Shi and
P. Cheng, Cryst. Growth Des., 2010, 10, 4370–4378;
(i) R. Nasani, M. Saha, S. M. Mobin and S. Mukhopadhyay,
Polyhedron, 2013, 55, 24–36; ( j) M. Saha, R. Nasani,
S. M. Mobin, B. Pathak and S. Mukhopadhyay, Inorg. Chem.
Commun., 2013, 34, 62–67.
2 (a) W. Ouellette and J. Zubieta, Chem. Commun., 2009,
4533–4535; (b) C.-C. Chang, Y.-C. Huang, S.-M. Huang,
J.-Y. Wu, Y.-H. Liu and K.-L. Lu, Cryst. Growth Des., 2012,
12, 3825–3828; (c) X. Wang, J. Peng, M.-G. Liu, D.-D. Wang,
C.-L. Meng, Y. Li and Z.-Y. Shi, CrystEngComm, 2012, 14,
3220–3226; (d) Y.-T. Yang, F.-H. Zhao, Y.-X. Che and
J.-M. Zheng, Inorg. Chem. Commun., 2011, 14, 1855–1859;
(e) K. Darling, W. Ouellette, S. Pellizzeri, T. Smith,
J. Vargas, S. Tomaszfski, C. J. O’Connor and J. Zubieta,
Inorg. Chim. Acta, 2012, 392, 417–427; (f) F. Yang, B. Li,
W. Xu, G. Li, Q. Zhou, J. Hua, Z. Shi and S. Feng, Inorg.
Chem., 2012, 51, 6813–6820; (g) S. Mukhopadhyay,
B. G. Mukhopadhyay, A. F. C. G. da Silva, J. Lasri,
M. A. J. Charmier and A. J. L. Pombeiro, Inorg. Chem., 2008,
47, 11334–11341.
5 (a) Functional Metal-Organic Frameworks: Gas Storage, Separ-
ation and Catalysis, ed. M. Schroder, Springer, 2010;
(b) Metal-Organic Frameworks: Applications from Catalysis to
Gas Storage, ed. D. Farrusseng, Wiley, 2011.
6 (a) A. M. Kirillov, M. V. Kirillova and A. J. L. Pombeiro,
Coord. Chem. Rev., 2012, 256, 2741–2759; (b) M. V. Kirillova,
A. M. Kirillov, A. N. C. Martins, C. Graiff, A. Tiripicchio and
A. J. L. Pombeiro, Inorg. Chem., 2012, 51, 5224–5234;
(c) Y. Y. Karabach, M. F. C. G. da Silva, M. N. Kopylovich,
B. Gil-Hernandez, J. Sanchiz, A. M. Kirillov and
A. J. L. Pombeiro, Inorg. Chem., 2010, 49, 11096–11105;
(d) A. M. Kirillov, J. A. S. Coelho, M. V. Kirillova,
M. F. C. Guedes da Silva, D. S. Nesterov, K. R. Gruenwald,
M. Haukka and A. J. L. Pombeiro, Inorg. Chem., 2010, 49,
6390–6392.
7 (a) M. N. Kopylovich, J. Lasri, M. F. C. Guedes da Silva,
J. J. R. Fraústo da Silva and A. J. L. Pombeiro, Chem.
Commun., 2010, 46, 2766–2768; (b) R. R. Fernandes,
J. Lasri, M. F. C. Guedes da Silva, J. A. L. da Silva,
J. J. R. Fraústo da Silva and A. J. L. Pombeiro, Appl. Catal.,
A, 2011, 402, 110–120; (c) M. N. Kopylovich, Y. Y. Karabach,
M. F. C. Guedes da Silva, P. J. Figiel, J. Lasri and
A. J. L. Pombeiro, Chem. – Eur. J., 2012, 18, 899–914;
(d) P. J. Figiel, A. M. Kirillov, Y. Y. Karabach,
M. N. Kopylovich and A. J. L. Pombeiro, J. Mol. Catal. A:
Chem., 2009, 305, 178–182; (e) P. J. Figiel, A. M. Kirillov,
M. F. C. Guedes da Silva, J. Lasri and A. J. L. Pombeiro,
Dalton Trans., 2010, 39, 9879–9888; (f) A. M. Kirillov,
M. V. Kirillova, L. S. Shul’pina, P. J. Figiel, K. R. Gruenwald,
M. F. C. Guedes da Silva, M. Haukka, A. J. L. Pombeiro and
G. B. Shul’pin, J. Mol. Catal. A: Chem., 2011, 350, 26–34;
(g) M. V. Kirillova, A. M. Kirillov, D. Mandelli,
W. A. Carvalho, A. J. L. Pombeiro and G. B. Shul’pin,
J. Catal., 2010, 272, 9–17; (h) M. Alexandru, M. Cazacu,
A. Arvinte, S. Shova, C. Turta, B. C. Simionescu, A. Dobrov,
E. C. B. A. Alegria, L. M. D. R. S. Martins, A. J. L. Pombeiro
and V. B. Arion, Eur. J. Inorg. Chem., 2014, 120–131;
(i) M. Sutradhar, L. M. D. R. S. Martins, M. F. C. Guedes da
Silva, E. C. B. A. Alegria, C.-M. Liu and A. J. L. Pombeiro,
Dalton Trans., 2014, 43, 3966–3977; ( j) Z. Ma, L. Wei,
3 (a) K. Darling, W. Ouellette and J. Zubieta, Inorg. Chim.
Acta, 2012, 392, 52–60; (b) C. Jiang, Z. Yu, S. Wang, C. Jiao,
J. Li, Z. Wang and Y. Cui, Eur. J. Inorg. Chem., 2004, 3662–
3667; (c) J.-Q. Sha, J.-W. Sun, M.-T. Li, C. Wang, G.-M. Li,
P.-F. Yan and L.-J. Sun, Dalton Trans., 2013, 42, 1667–1677;
(d) S. Jones, H. Liu, C. C. O’Connor and J. Zubieta, Inorg.
Chem. Commun., 2010, 13, 412–416; (e) F. Wang, J. Zhang,
9952 | Dalton Trans., 2014, 43, 9944–9954
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
E. C. B. A. Alegria, L. M. D. R. S. Martins, M. F. C. Guedes 14 (a) V. A. Blatov and D. M. Proserpio, in Modern Methods of
da Silva and A. J. L. Pombeiro, Dalton Trans., 2014, 43,
4048–4058; (k) R. R. Fernandes, J. Lasri, M. F. C. Guedes da
Silva, J. A. L. Silva, J. J. R. Fraústo da Silva and
A. J. L. Pombeiro, J. Mol. Catal. A: Chem., 2011, 351, 100–
111; (l) J. Lasri, M. J. F. Rodriguez, M. F. C. Guedes da Silva,
Crystal Structure Prediction, ed. A. R. Oganov, Wiley, 2010,
1–28; (b) V. A. Blatov, M. O’Keeffe and D. M. Proserpio,
CrystEngComm, 2010, 12, 44–48; (c) E. V. Alexandrov,
V. A. Blatov, A. V. Kochetkova and D. M. Proserpio, Cryst-
EngComm, 2011, 13, 3947–3958.
P. Smolenski, M. N. Kopylovich, J. J. R. Fraústo da Silva and 15 M. O’Keeffe and O. M. Yaghi, Chem. Rev., 2012, 112, 675–
A. L. Pombeiro, J. Organomet. Chem., 2011, 696, 3513–1520; 702.
(m) A. Sabbatini, L. M. D. R. S. Martins, K. T. Mahmudov, 16 The Reticular Chemistry Structure Resource (RCSR) Data-
M. N. Kopylovich, M. G. B. Drew, C. Pettinari and
A. J. L. Pombeiro, Catal. Commun., 2014, 48, 69–72.
base; M. O’Keeffe, M. A. Peskov, S. J. Ramsden and
O. M. Yaghi, Acc. Chem. Res., 2008, 41, 1782–1789.
8 (a) W. G. Dauben, M. Lorber and D. S. Fullerton, J. Org. 17 For examples of Cu networks with the bcu topology, see:
Chem., 1969, 34, 3587–3592; (b) G. Rothenberg, H. Wiener
and Y. Sasson, J. Mol. Catal. A: Chem., 1998, 136, 253–262;
(c) J. Singh, M. Sharma, M. Chhibber, J. Kaur and
G. L. Kad, Synth. Commun., 2000, 30, 3941–3945;
(d) M. Hudlicky, Oxidations in Organic Chemistry, ACS
(a) T.-T. Lian and S.-M. Chen, Inorg. Chem. Commun., 2012,
18, 8–10; (b) H.-Q. Hao, J. Wang, W.-T. Liu and M.-L. Tong,
CrystEngComm, 2008, 10, 1454–1459; (c) Z.-M. Hao,
R.-Q. Fang, H.-S. Wu and X.-M. Zhang, Inorg. Chem., 2008,
47, 8197–8203.
Monograph 186, Washington, DC, 1990; (e) I. E. Markó, 18 (a) J. M. Seco, M. A. Farias, N. M. Bachs, A. B. Caballero,
P. R. Giles, M. Tsukazaki, S. M. Brown and C. J. Urch,
Science, 1996, 274, 2044–2046; (f) G. Rothenberg,
L. Feldberg, H. Wiener and Y. Sasson, J. Chem. Soc., Perkin
Trans. 2, 1998, 2429–2434; (g) R. Chakrabarty, P. Sarmah,
B. Saha, S. Chakravorty and B. K. Das, Inorg. Chem., 2009,
48, 6371–6379; (h) I. E. Markó, A. Gautier, R. Dumeunier,
K. Doda, F. Philippart, S. M. Brown and C. J. Urch, Angew.
A. S. Castillo and A. R. Dieguez, Inorg. Chim. Acta, 2010,
363, 3194–3199; (b) X.-H. Wei, Acta Crystallogr., Sect.
E: Struct. Rep. Online, 2010, 66, m551; (c) W. Ouellette,
H. Liu, C. J. O’Connor and J. Zubieta, Inorg. Chem.,
2009, 48, 4655–4657; (d) X.-M. Zhang, Y.-F. Zhao,
H.-S. Wu, S. R. Batten and S. W. Ng, Dalton Trans., 2006,
3170–3178.
Chem., Int. Ed., 2004, 43, 1588–1591; (i) S. S. Stahl, Angew. 19 (a) M. N. Kopylovich, A. Mizar, M. F. C. Guedes da Silva,
Chem., Int. Ed., 2004, 43, 3400–3420; ( j) G.-J. ten Brink,
I. W. C. E. Arends and R. A. Sheldon, Science, 2000, 287,
1636–1639; (k) Y. Uozumi and R. Nakao, Angew. Chem., Int.
T. C. O. MacLeod, K. T. Mahmudov and A. J. L. Pombeiro,
Chem. – Eur. J., 2013, 19, 588–600; (b) M. S. Dronova,
A. N. Bilyachenko, A. I. Yalymov, Y. N. Kozlov,
L. S. Shul’pina, A. A. Korlyukov, D. E. Arkhipov,
M. M. Levitsky, E. S. Shubina and G. B. Shul’pin, Dalton
Trans., 2014, 43, 872–882; (c) A. N. Bilyachenko,
M. S. Dronova, A. I. Yalymov, A. A. Korlyukov,
L. S. Shul’pina, D. E. Arkhipov, E. S. Shubina,
M. M. Levitsky, A. D. Kirilin and G. B. Shul’pin,
Eur. J. Inorg. Chem., 2013, 5240–5246.
Ed.,
2003,
42,
194–197;
(l)
D.
S.
Bailie,
G. M. A. Clendenning, L. McNamee and M. J. Muldoon,
Chem. Commun., 2010, 46, 7238–7240; (m) D. S. Rozner,
P. L. Alsters and R. Neumann, J. Am. Chem. Soc., 2003, 125,
5280–5281; (n) V. R. Choudary, D. K. Dumbre, B. S. Uphade
and V. S. Narkhede, J. Mol. Catal. A: Chem., 2004, 215, 129–
135; (o) J. Boudreau, M. Doucette and A. N. Ajjou, Tetrahe-
dron Lett., 2006, 47, 1695–1698; (p) W. Zhao, Y. Zhang, 20 R. R. Fernandes, J. Lasri, A. M. Kirillov, M. F. C. Guedes da
B. Ma, Y. Ding and W. Qiu, Catal. Commun., 2010, 11, 527–
531; (q) R. A. Sheldon, I. Arends and U. Hanefeld, Green
Silva, J. A. L. Silva, J. J. R. Fraústo da Silva and
A. J. L. Pombeiro, Eur. J. Inorg. Chem., 2011, 3781–3790.
Chemistry and Catalysis, Wiley-VCH, 2007; (r) P. Anastas 21 (a) M. V. N. de Souza, Mini-Rev. Org. Chem., 2006, 3, 155;
and N. Eghbali, Chem. Soc. Rev., 2010, 39, 301–312;
(s) S. Liu and J. Xiao, J. Mol. Catal. A: Chem., 2007, 270,
1–43.
9 (a) G. M. Sheldrick, Acta Crystallogr., Sect. A: Fundam. Crys-
tallogr., 2008, 64, 112–122; (b) Program for Crystal Structure
Solution and Refinement, University of Goettingen, Goettin-
gen, Germany, 1997.
10 A. L. Spek, J. Appl. Crystallogr., 2003, 36, 7–13.
11 K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, Wiley, New Jersey, 2009.
12 (a) S. Mukhopadhyay, J. Lasri, M. A. J. Charmier, M. F. C.
G. Silva and A. J. L. Pombeiro, Dalton Trans., 2007, 5297–
5304; (b) P. Smolenski, S. Mukhopadhyay, M. F. C. G. Silva,
M. A. J. Charmier and A. J. L. Pombeiro, Dalton Trans.,
2008, 6546–6555.
(b) T. Vogler and A. Studer, Synthesis, 2008, 1979–1993;
(c) R. A. Sheldon and I. W. C. E. Arends, J. Mol. Catal. A:
Chem., 2006, 251, 200–214; (d) A. Dijksman, I. W. C.
E. Arends and R. A. Sheldon, Org. Biomol. Chem., 2003, 1,
3232–3237; (e) R. A. Sheldon and I. W. C. E. Arends, Adv.
Synth. Catal., 2004, 346, 1051–1071; (f) R. A. Sheldon,
Chem. Commun., 2008, 3352–3365; (g) F. Minisci,
F. Recupero, G. F. Pedulli and M. Lucarini, J. Mol. Catal. A:
Chem., 2003, 204–205, 63–90; (h) K. T. Mahmudov,
M. N. Kopylovich, M. F. C. Guedes da Silva, P. J. Figiel,
Y. Y. Karabach and A. J. L. Pombeiro, J. Mol. Catal. A:
Chem., 2010, 318, 44–50; (i) P. J. Figiel, M. Leskelä and
T. Repo, Adv. Synth. Catal., 2007, 349, 1173–1179;
( j) P. J. Figiel, A. Sibaouih, J. U. Ahmad, M. Nieger,
M. T. Räisänen, M. Leskelä and T. Repo, Adv. Synth. Catal.,
2009, 351, 2625–2632; (k) J. U. Ahmad, P. J. Figiel,
13 V. A. Blatov, IUCr Comp. Comm. Newslett., 2006, 7, 4.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 9944–9954 | 9953

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Paper
Dalton Transactions
M. T. Räisänen, M. Leskelä and T. Repo, Appl. Catal., A, 24 (a) G. Tojo and M. Fernández, Oxidation of Alcohols to Alde-
2009, 371, 17–21.
hyde and Ketones: A Guide to Current Common Practice,
Springer, New York, 2006; (b) I. W. C. E. Arends and
R. A. Sheldon, in Modern Oxidation Methods, ed. J.-E. Bäck-
vall, Wiley-VCH, Weinheim, Germany, 2004, pp. 83–118;
(c) D. Betz, P. Altmann, M. Cokoja, W. A. Herrmann and
F. E. Kühn, Coord. Chem. Rev., 2011, 255, 1518–1540;
(d) Ionic Liquids in Synthesis, ed. P. Wasserscheid and
T. Welton, Wiley-VCH, Weinheim, Germany, 2008, vol. 2;
(e) S. F. Liu and J. Xiao, J. Mol. Catal. A: Chem., 2007, 270,
1–43; (f) P. J. Dyson and T. J. Geldbach, Metal Catalysed
Reactions in Ionic Liquids, Springer, 2005.
22 (a) J. A. L. Silva, J. J. R. Fraústo da Silva and
A. J. L. Pombeiro, Coord. Chem. Rev., 2011, 255, 2232–2248;
(b) S.-S. Wang, Z. Popovic, H.-H. Wu and Y. Liu, Chem-
CatChem, 2011, 3, 1208–1213; (c) M. N. M. Milunovic,
L. M. D. R. S. Martins, E. C. B. A. Alegria,
A. J. L. Pombeiro, R. Krachler, G. Trettenhahn, C. Turta,
S. Shova and V. B. Arion, Dalton Trans., 2013, 42, 14388–
14401.
23 (a) O. C. Kappe, D. Dallinger and S. Murphree, Practical
Microwave Synthesis for Organic Chemists, Wiley-VCH, Wein-
heim, Germany, 2008; (b) V. Polshettiwar and R. S. Varma, 25 (a) I. N. Moiseeva, A. E. Gekham, V. V. Minin, G. M. Larin,
Acc. Chem. Res., 2008, 41, 629–639; (c) D. Dallinger and
C. O. Kappe, Chem. Rev., 2007, 107, 2563–2591;
(d) Microwave Assisted Organic Synthesis, ed. J. P. Tierney
and P. Lidström, Blackwell Publishing/CRC Press, Oxford,
M. E. Bashtanov, A. A. Krasnovskii and I. I. Moiseev, Kinet.
Catal., 2000, 41, 170–182; (b) J. M. Mattalia, B. Vacher,
A. Samat and M. Chanon, J. Am. Chem. Soc., 1992, 114,
4111–4119.
2005; (e) Microwaves in Organic Synthesis, ed. A. Loupy, 26 (a) C. Michel, P. Belanzoni, P. Gamez, J. Reedijk and
Wiley-VCH, Weinheim, Germany, 2002; (f) Y. Y. Karabach,
M. N. Kopylovich, K. T. Mahmudov and A. J. L. Pombeiro,
Microwave-assisted Catalytic Oxidation of Alcohols to Car-
E. J. Baerends, Inorg. Chem., 2009, 48, 11909–11920;
(b) P. Gamez, I. W. C. E. Arends, R. A. Sheldon and
J. Reedijk, Adv. Synth. Catal., 2004, 346, 805–811.
bonyl Compound, in Advances in Organometallic Chemistry 27 (a) S. Samanta, S. Das, P. K. Samanta, S. Dutta and
and Catalysis: The Silver/Gold Jubilee ICOMC Celebratory
Book, ed. A. J. L. Pombeiro, Wiley, 2014, ch. 18,
pp. 233–245.
P. Biswas, RSC Adv., 2013, 3, 19455–11946; (b) G. B. Shaw,
C. D. Grant, H. Shirota, E. W. Castner Jr., G. J. Meyer and
L. X. Chen, J. Am. Chem. Soc., 2007, 129, 2147–2160.
9954 | Dalton Trans., 2014, 43, 9944–9954
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