Mono- and tetra-nuclear copper complexes bearing bis(imino)phenoxide derived ligands: Catalytic evaluation for benzene oxidation and ROP of ε-caprolactone

Article abstract of DOI:10.1039/c5ra08696e

Complexes of the type [Cu(L)₂] (1) and [Cu₄L₂(μ₄-O)(OAc)₄] (2) have been obtained from the reaction of the phenoxydiimine 1,3-(2,6-R²₂C₆H₃NCH)₂-5-R¹C₆H₂OH-2 (LH) (where R¹ = Me, tBu, Cl; R² = Me, iPr) with copper(ii) acetate [Cu(OAc)₂]; changing the molar ratio of the reactants affords differing amounts of 1 or 2. Reaction of the parent dialdehyde [1,3-(CHO)₂-5-MeC₆H₂OH-2] with [Cu(OAc)₂] in the presence of Et₃N afforded, following work-up, a polymeric chain (3) comprising {[Cu₂(OAc)₄]OAc}_n, HNEt₃ and MeCN. The crystal structures of 1 (R¹ = Me, R² = iPr 1a; R¹ = Cl, R² = iPr 1b), 2 (R¹ = Me, R² = Me 2a; R¹ = Me, R² = iPr 2b; R¹ = tBu, R² = Me 2c; R¹ = Cl, R² = Me 2d; R¹ = Cl, R² = iPr 2e; R¹ = tBu, R² = iPr 2f) and 3 are reported (synchrotron radiation was necessary for 3). The magnetic properties of the cluster 2b are presented. Complexes of type 2 and 3 were screened for the ring opening polymerization (ROP) of ε-caprolactone, with or without benzyl alcohol present, under a variety of conditions, however only trace polymer was isolated. The electrochemistry of all complexes was also investigated, together with their ability to catalyze benzene oxidation (using hydrogen peroxide); although low conversions were observed, the tetra-nuclear complexes exhibited excellent selectivity.

Full text of DOI:10.1039/c5ra08696e

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DOI: 10.1039/C5RA08696E
Mono-and Tetra-nuclear copper bis(imino)phenoxide complexes
together with a polymer chain derived from the parent
dialdehyde have been evaluation as catalysts for benzene
oxidation and ROP of ε-caprolactone.

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View ArticlPe Oanglinee 2 of 15
►
DOI: 10.1039/C5RA08696E
Journal Name
ARTICLE TYPE
Mono-and Tetra-nuclear copper complexes bearing bis(imino)phenoxide
derived ligands: catalytic evaluation for benzene oxidation and ROP of
-caprolactone
Xue Wang,a Qe-King Zhao,a Mark R.J. Elsegood,b Timothy J. Prior,c Xiaoming Liu,d Li Wu,d Sergio
Sanz,e Euan K. Brechine and Carl Redshaw*a,c
5
Received (in XXX, XXX) XthXXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
Abstract Complexes of the type [Cu(L)2] (1) and [Cu4L2(O)(OAc)4] (2) have been obtained from the
reaction of the phenoxydiimine 1,3-(2,6-R2 C6H3N=CH)2-5-R1C6H2OH-2 (LH) (where R1 = Me, tBu, Cl;
2
10 R2 = Me, iPr) with copper(II) acetate [Cu(OAc)2]; changing the molar ratio of the reactants affords
differing amounts of 1 or 2. Reaction of the parent dialdehyde [1,3-(CHO)2-5-MeC6H2OH-2] with
[Cu(OAc)2] in the presence of Et3N afforded, following work-up, a polymeric chain (3) comprising
{[Cu2(OAc)4]OAc}n, HNEt3 and MeCN. The crystal structures of 1 (R1 = Me, R2 = iPr 1a; R1 = Cl, R2 =
iPr 1b), 2 (R1 = Me, R2 = Me 2a; R1 = Me, R2 = iPr 2b; R1 = tBu, R2 = Me 2c; R1 = Cl, R2 = Me 2d; R1 =
15 Cl, R2 = iPr 2e; R1 = tBu, R2 =iPr 2f) and 3 are reported (synchrotron radiation was necessary for 3). The
magnetic properties of the cluster 2b are presented. Complexes of type 2 and 3 were screened for the ring
opening polymerization (ROP) of-caprolactone, with or without benzyl alcohol present, under a variety
of conditions, however only trace polymer was isolated. The electrochemistry of all complexes was also
investigated, together with their ability to catalyze benzene oxidation (using hydrogen peroxide); although
20 low conversions were observed, the tetra-nuclear complexes exhibited excellent selectivity.
oxide. [5] In terms of a Cu4O core, early structural examples
Introduction
45 utilizing bis(amino)alcohols were reported by Krebbset al, [6]
whilst Chaudhuriet al have extended such studies to related
ONONO-type ligation and have examined the magnetic
susceptibility of the resulting Cu2 and Cu4 complexes. [7] More
recently bis(imino)phenoxy N2O type ligation has been utilized to
50 isolate complexes that can act as catalysts for the oxidation of
cyclohexane and toluene, [8] and in catecholase-like activity. [9]
We also note that Pandey et al have, by employing-ketoaminato
ligands, isolated both mono and tetranuclear copper complexes,
the formation of which was dictated by the use of anhydrous
55 conditions or not. [10] Herein, we explore the chemistry of the
In recent years, ligand frameworks that are capable of binding
two transition metals in close proximity have attracted interest,
due primarily to the possibilities of beneficial cooperative effects.
25 [1] In the field of lactone polymerization, the
coordination/insertion mechanism has drawn analogies with
biological systems and in-particular the mechanism of hydrolysis
of some metalloenzymes, where one of the metal present can
coordinate water thereby lowering its pKa (enhanced
30 nucleophilicity) and generating a hydroxide species. A second
metal can then bind the substrate and make it more susceptible to
nucleophilic attack. With this in mind, Hillmyer and Tolman
probed the potential cooperative influence of the Zn-O-Zn motif
in lactide polymerization. [2] We have been interested in the
35 coordination chemistry of acyclic Schiff base ligands and their
potential to hold metals in close proximity by utilizing the
phenolic group to form an M-O-M linkage. [3] Furthermore, Sun
et al. reported that cobalt and nickel complexes bearing
bis(imino)phenolate type ligands are active for the
40 oligomerization of ethylene. [4] We were also attracted to the
potential catalytic ability of copper; complexes bearing NNO
tridentate Schiff bases have been shown to act as useful catalysts
for the copolymerization of carbon dioxide and cyclohexene
ligand set 1,3-(2,6-R2 C6H3N=CH)2-5-R1C6H2OH-2 (LH) (where
2
R1 = Me, tBu, Cl; R2 = Me, iPr) towards [Cu(OAc)2] and have
structurally characterized both tetranuclear and mononuclear
complexes (see scheme1), the yield of each product can be
60 controlled by the reaction stoichiometry. The polymeric product
resulting from the interaction of [1,3-(CHO)2-5-MeC6H2OH-2]
with [Cu(OAc)2] in the presence of Et3N is also reported. In terms
of catalysis, the tetranuclear complexes and the polymeric
complex were screened for their ability to ring open polymerize
65 (ROP) -caprolactone, but results were disappointing. We have
also investigated the electrochemistry of these complexes and
This journal is © The Royal Society of Chemistry [year]
[journal], [year], [vol], 00–00 |1

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phenolic C-O band, there is a shift to higher frequency upon
coordination (1327-1347 cm-1 in the complexes versus 1254 – 1263
cm-1 in the ‘free ligands’).
their ability to catalyze benzene oxidation.
Results and discussion
The IR spectra of the tetranuclear complexes exhibited a number of
weak to medium vC-H bands in the 2860 - 3020 cm-1 region,
together with a weak band at ca 566 cm-1, which is known to be
associated with the T2 mode of the Cu4O.[11] In their mass
spectra(electrospray), peaks were observed for the fragments
resulting from loss of either one or two OAc groups, namely
[Cu4(OAc)3(L)2(4-O)]+ or [Cu4(OAc)2(L)2(4-O)]2+. ESR spectra,
recorded at ambient temperature and 103 K, exhibited features
similar to that reported by Jian et al for the complex
Synthesis
Bis(imino)phenoxide complexes
5
Interaction of [2,6-(2,6-iPr2C6H3N=CH)24-MeC6H2OH] (LH) and
[Cu(OAc)2] (two equivalents) in refluxing toluene afforded,
following work-up, large green blocks as the major product (ca.
90 %) and thin yellow plates as the minor product (ca. 10 %),
both of which proved to be suitable for single crystal X-ray
[Cu4OCl6(C14H12N2)4] (g
┴
= 2.107, g
║
= 2.210); [12] g values
┴
herein were found at about g
┴
= 2.42 (see ESI, Figs. S1 – S3).
10 diffraction.
Solid state structures
General: There are two basic modes of coordination of the ligand
observed: (1) bidentate coordination by the ligand through
phenoxide and nitrogen; (2) bis-bidentate coordination through μ-
phenoxide and both imine nitrogen atoms to two copper ions.
Bidentate coordination leads to discrete monomeric complexes that
feature centrosymmetric binding of the copper ion in a square planar
geometry. The bis-bidentate arrangement is found in tetrahedral
Cu4O clusters that contain a central oxoanion. A third structure type
has
been
observed
in
the
case
of
[Et3NH]
[Cu2(OAc)4](OAc)]·MeCN and this does not contain the Schiff base
ligand. [Cu2(OAc)4] paddlewheels are linked by bridging bidentate
acetate into a 1-D chain.
Monomeric complexes: The compounds 1a and 1b display very
similar ligands, differing in the replacement of a methyl group by
chloride. As has been noted before, the structural demand of a
methyl group and chloride are roughly similar and these two
compounds are isomorphous, crystallising in the space group P21/c
with similar unit cell parameters. The complex is centrosymmetric
with the 4-coordinate square planar Cu2+ ion residing on the
inversion centre. For 1a (collected at 160 K) the Cu–O and Cu–N
distances are 1.917(2) and 1.971(2) Å and the N–Cu–O bite angle is
o
91.73(9) . For 1b (collected at 293 K), the analogous values are
1.9129(15) Å, 1.9841(17) Å, and 91.36(7) o. These geometrical
parameters are similar to those reported for related [Cu(N–O)2] type
systems; Cu–O 1.889(4) [1.880(5)]* – 1.938(5) Å and Cu–N
1.989(7) [1.901(7)]* – 2.021(5) Å. [13] There are no intermolecular
contacts of note for either structure. Crystal data for these are
contained in Table 2.
Scheme 1. Copper complexes prepared herein.
The minor yellow complex was shown to be the bis-complex [CuL2]
(1a), whilst the major green product was found to be the tetranuclear
complex [Cu4L2(O)(OAc)4] (2b). By varying the reaction
stoichiometry (L:Cu 1:1 for 1a,b; 1:2 for 2a-f, see experimental), it
proved possible to also isolate the monomeric complexes 1b (for R1
= Cl, R2 = iPr) and tetrametallic type complexes for R1 = Me, R2 =
Me 2a; R1 = tBu, R2 = Me 2c; R1 = Cl, R2 = Me 2d, R1 = Cl, R2 =
iPr 2e; R1 = tBu, R2 =iPr 2f.
For the mononuclear complexes, mass spectra exhibited peaks for
[M + H]+, whilst in the IR spectra bands at 1612/1617 and 1542 (for
type 1 complexes) and 1617 and ca. 1550 (for type 2) cm-1 were
consistent with the presence of the imine C=N linkage. In the IR
spectra of the ‘free ligands’, two strong absorptions are observed in
the region 1580 – 1630 cm-1 for the imine stretching mode. There is
thus a shift to lower frequency upon coordination. In the case of the
Figure 1.ORTEP representation of the coordination about Cu2+ in 1a, with
thermal ellipsoids at 50% probability level. Hydrogen atoms are omitted for

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clarity. Selected bond lengths (Å) and angles (o): Cu(1) – O(1) 1.917(2), Cu(1)
– N(1) 1.971(2), N(1) – C(13) 1.293(4), N(2) – C(22) 1.442(4); O(1) – Cu(1) –
N(2) 91.73(9).
within the oxo-cluster lie in the range 1.910(3) to 1.928(3) Å.
Coordination by the ligand through O2 and O3 (i.e.Cu–O2 and Cu–
O3) distances lie in the range 1.968(3) to 1.995(3) Å. Copper-
nitrogen distances (ligand) lie in the range 1.988(4) to 2.008(4) Å.
Each of these copper ions display square-based pyramidal geometry
where the apical Cu–O bond is much longer those bonds in the
square plane. For example, for Cu1, Cu–L distances in the plane are
1.928(3), 1.922(4), 1.968(3), 1.993(4) Å, but the apical Cu–O
distance is 2.308(4) Å. Each of the structures 2a, 2b, 2c, 2c·MeCN,
2d, 2e and 2f display a very similar cluster and orientation of the
pair of ligands. Shown above and below are representations of the
cluster in 2a, 2c and 2e.
Figure 2. ORTEP representation of the coordination about Cu2+ in 1b, with
thermal ellipsoids at 50% probability level. Hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (o): Cu(1) – O(1) 1.9129(15),
Cu(1) – N(1) 1.9841(17), N(1) – C(13) 1.282(3), N(2) – C(22) 1.449(3); O(1) –
Cu(1) N(2) 91.36(7).
Cu4O oxo-clusters: Each of the remaining five ligands (L) forms a
similar cluster with formula Cu4OL2(OAc)4 in which each of the
copper ions is five coordinated in a square pyramidal geometry. The
cluster contains two ligands, each of which binds two copper ions.
The ligands are approximately orthogonal and lie on opposite sides
of the cluster. Coordination about the copper is completed by
bridging bidentate acetate as shown below. Crystal data for these are
contained in Table 3. The central 4-oxo is thought to arise due the
presence of adventitious oxygen.
Figure 4. ORTEP representation of the [Cu4O]6+ cluster in 2c, with thermal
ellipsoids at 50% probability level. Hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (o): Cu(1) – O(1) 1.9142(19), Cu(1) –
O(2) 1.963(2), Cu(1) – O(6) 1.930(3), Cu(1) – N(1) 1.991(3), Cu(1) – Cu(2)
2.9640(6); Cu(1) – O(1) – Cu(2) 101.15(2), Cu(1) – O(2) – C(14) 131.4(2),
Cu(1) – O(2) – Cu(2) 97.22(11).
Figure 5. ORTEP representation of the cluster in 2e, with thermal ellipsoids
at 50% probability level. Hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and angles (o): Cu(1) – O(1) 1.914(3), Cu(1) – O(2) 1.992(3),
Cu(1) – O(4) 2,235(5), Cu(1) – O(8) 1.908(4), Cu(1) – N(1) 2.014(4); Cu(1) –
O(1) – Cu(2) 103.14(14), Cu(1) – O(2) – Cu(2) 98.23(14).
Figure 3. ORTEP representation of the cluster in 2a, with thermal ellipsoids
at 50% probability level. Hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and angles (o): Cu(1) – O(1) 1.9246(17), Cu(1) – O(2)
1.968(3), Cu(1) – O(5) 2.308(4), Cu(1) – O(7) 1.922(4), Cu(1) - N(2) 1.933(4),
Cu(1) – Cu(2) 2.9907(10); Cu(1) – O(1) – Cu(2) 79.21(14), Cu(1) – O(2) –
C(13) 131.8(2), Cu(1) – O(2) – Cu(2) 79.30(14).
The arrangement of these clusters is unremarkable. There are no
hydrogen bonds between the clusters in any case. For some
examples, solvent molecules are included in the crystal structure.
The complex 2c is representative of the others. Cu–O1 distances

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Full details of stoichiometry and crystal data are found in Table 3.
A search of the Cambridge Crystallographic Database (CSD) for the
motif 1,3-(C(R)N)2-C6H3O-2 bound to copper found 16 hits for R =
Me. Of the non-macrocyclic examples, there was a preference for
dinuclear coordination of the bis(imino)phenoxy ligand set as
opposed to the mononuclear coordination observed herein for 1a
and 1b; representative examples are given in reference [14]. We
note that 1:1 complexes have been isolated from reactions involving
CuCl2.H2O and 2,6-bis(imino)phenols. [15] In the case of R = H,
there were far more hits (356), of which approximately half (48 %)
were macrocyclic, whilst of the remainder, there were 26 hits
involving four copper centres bound to a central 4-oxo group, 23 of
which also involved acetate-type bridging. [7, 8, 14c, 16]
Copper acetate coordination polymer:
Figure 7. Cyclic voltammograms of complex 1a (3.2 mmol L−1) in 0.1 mol
L−1 [NBut4]BF4−CH3CN under Ar atmosphere (298 K, scanning rate = 100
30 mV s−1, red dot-line: reduction process; blue dot- and red solid-lines:
oxidation).
Treatment of copper acetate with the dialdehyde 1,3-(CHO)2-5-
MeC6H2OH-2 in acetonitrile yielded well-formed blue blocks that
were
found
to
have
the
composition
5
[Et3NH]+[Cu2(OAc)4(OAc)]−·CH3CN, which contain copper
acetate paddlewheels, [Cu2(OAc)4], which are linked into
undulating 1-D chains by bridging acetate that binds in the
terminal site at each end of the paddlewheel. The asymmetric unit
is shown below. The bridging acetate assembles the paddlewheels
10 into chains that run parallel to the crystallographic c direction
(see below).
Between the chains lie Et3NH+cations and acetonitrile. The
Et3NH+cations form a hydrogen bond to acetate through N1. For
the hydrogen bond N1–H1···O10, N–H distance = 0.91(2) Å,
15 N···O distance = 2.806(3) Å, N–H···O angle = 172(2) Å. Crystal
data for 3 are contained in Table 2.
Figure 8. Cyclic voltammograms of complex 2a (3.2 mmol L−1) in 0.1 mol
L−1[NtBu4]BF4−CH3CN under Ar atmosphere (298 K, scanning rate = 100
35 mV s−1, red solid-, blue dash- and purple dot-lines: reduction process;
turquoise dot-dash-line: oxidation).
Electrochemistry
The electrochemistry of selected complexes is shown in Figs. 7-9.
In the reduction, the first process is attributed to the reduction of
40 Cu(II) to Cu(I) which can be further reduced to Cu(0). The latter
reduction is confirmed by the characteristic anodic stripping
process, a sharp peak in the returning wave (Figs. 8 and 9). In the
cyclic voltammogram of complex 2a, there are three reduction
processes observed between -0.5 and -1.5 V, which is in
45 agreement with its tetra-nuclear core (Fig. 8). For the polymer 3,
further scanning could reveal more reduction processes from Cu(I)
to Cu(0). The reduction potentials of the process, Cu(II)Cu(I),
correlate clearly to the coordinating environment. For the mono-
nuclear complex (1a), it possesses two phenolates, whereas the
50 tetra-nuclear cluster (2a) possesses on average half a phenolate
Figure 6. ORTEP representation of a portion of one infinite chain running
parallel to c in 3, with thermal ellipsoids at 50% probability level.
Selected bond lengths (Å) and angles (o): Cu(1) – O(1) 1.9832(17), Cu(1) –
20 O(3) 1.9648(18), Cu(1) – O(9) 2.1166(15); O(1) – Cu(1) – O(3) 88.72(8).
In the IR spectrum of the polymeric chain {[Cu2(OAc)4]OAc}n
(3), it was not possible to distinguish between the two different
types of bridging acetate groups; only a strong broad carbonyl
stretch at 1603 cm-1 together with a stretch at 1422 cm-1 were
25
observable.

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DOI: 10.1039/C5RA08696E
per metal ion. Due to the strong electron-donating capability of
the phenolate, more negative reduction potential is expected for
complex 1a versus complex 2a.
Figure 10. Plot of the χMT product versus T for complex 2b in the T = 300
– 5 K range in an applied field of 0.1 T. The solid red line is a fit of the
35 experimental data to the isotropic model shown schematically in the
inset, and spin-Hamiltonian (1).
-Caprolactone polymerization
Metal alkoxides are known to initiate the ring opening
polymerization (ROP) of lactones. [17] Given this, we attempted
to initiate the ROP of -caprolactone by addition of benzyl
5 Figure 9. Cyclic voltammograms of complex 3 (3.2 mmol L−1) in 0.1 mol
L−1 [NBut4]BF4−CH3CN under Ar atmosphere (298 K, scanning rate = 100
mV s−1 red dot- and blue solid-lines: reduction process; purple dot-dash-
line: anodic region).
40
alcohol to the tetranuclear cores, generating metal alkoxides via
alkoxy/carboxylate exchange. The complexes were screened in
toluene over the temperature range 20 to 120 C and for various
Magnetic studies
o
ratios of Cu to BnOH over either 12 or 24 h and the results are
presented in Table 1. In all cases however, activities were either
nil or very low and in the best runs, only trace polymer was
isolated. Although the PDI values were low, a plot of Mn versus
[CL]/[Cu] molar ratio was not linear and so living behavior
cannot be inferred. In the MALDI-TOF spectra, only one major
10 Dc magnetic susceptibility studies on a powdered sample of 2b
(R1 = Me, R2 = iPr) were performed in the 300 – 5 K temperature
range in an applied field of 0.1 T, and are plotted as the χMT
product versus T in Figure 7.
45
The room temperature value of 0.8 cm3mol-1K is well below that
15 expected for four non-interacting s = ½ ions with g = 2.0 (1.5 cm3
K mol-1). As the temperature is decreased the value of χMT
decreases rapidly to a value of 0.1 cm3 K mol-1 at T = 100 K,
before decreasing more slowly to a value of zero at the lowest
temperature measured. This behaviour is indicative of the
20 presence of strong antiferromagnetic interactions between the
Cu(II) ions. The experimental susceptibility data can be fitted to
the simple 2J model shown in the inset of Figure 10 and
expressed in isotropic spin-Hamiltonian (1) in which J1
corresponds to the Cu···Cu interaction mediated through one oxo
25 and one carboxylate bridge, and J2 that mediated via one oxo and
one alkoxo bridge. The best fit afforded J1= –192 cm-1, J2 = –61
cm-1 with g = 2.2, values consistent with those previously seen
for similar species. [6b, 7, 10] This results in a spin singlet
ground state (S= 0) with the first excited (S = 1) triplet state some
30 384 cm-1 higher in energy.
population of peaks, which possesses the spacing 114 Da (the
50
molecular weight of the monomer), was detected. The peaks are
assigned to the sodium adducts of the polymer chains with
benzyloxy end groups. A smaller series of peaks is associated
with the use of protonated/sodiated (from the matrix) species. [18]
Representative MALDI-TOF spectra are given in the ESI for runs
55
5 (2a) and 7 (2b) in Table 1, - see figures S4 and S5. A
1
representative H NMR spectrum (for 2b, run 7, Table 1) of the
PCL is shown in the ESI (Fig. S6), and the peaks in a 5:2 ratio at
7.35 and 5.10 ppm suggested that there was a benzyl ester cap
present.
60
Due to these disappointing results, no further investigation of the
potential of these complexes for ring opening polymerization was
conducted.
Ĥex= -2J1(Ŝ1·Ŝ3 + Ŝ1·Ŝ4 + Ŝ2·Ŝ3 + Ŝ2·Ŝ4) -2J2(Ŝ1·Ŝ2 + Ŝ3·Ŝ4) (1)
Benzene oxidation
65 All the complexes catalyzed the direct oxidation of benzene by
hydrogen peroxide. Although the mononuclear complex 1a
showed comparable conversion to that we reported recently, its
selectivity was rather poor due to over-oxidation of the product
phenol. [19] Previously, we observed that in the oxidation of
70 benzene catalysed by copper (II) complexes, the more negative
the reduction potential, the higher the conversion of benzene. As

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Sample
Conversion
(%)
Yield
(%)
Selectivity
(%)
Reduction potential
Ep (V)
shown in Table 2, the copper (II) clusters exhibited more positive
reduction potentials, which may explain their low conversion.
What is surprising is that they showed much improved selectivity
compared to the monocopper (II) complex. For the clusters, 2c
and 2e, the selectivity is almost quantitative. The exact reason for
this drastic improvement in selectivity is not understood at this
stage.
1a
2a
31.5
7.2
12.2
5.5
39
76
1.32
5
0.719, 1.019,
1.535
2b
2c
2d
2e
2f
3
7.6
7.3
6.9
7.7
13.4
8.5
5.7
7.6
3.9
8.7
11.3
7.0
75
Table 1. ROP of ε-caprolactone using compounds of type 2†
> 99
57
CL : Time Conva
b
c
Run Pre- Cat T (°C)
Mn ,GPC Mn,Cal
PDI
BnOH
250 : 1
250 : 1
250 : 1
(h)
24
24
24
24
24
12
12
24
24
12
24
24
24
12
12
12
12
(%)
1
2
2a
2a
2a
2a
2a
2a
2b
2b
2c
2c
2d
2e
2f
2f
2f
2f
2f
2f
3
40
60
80
--
--
--
--
--
--
--
> 99
84
--
3
--
--
--
--
82
0.963, 1.598
4
100 250 : 1
110 250 : 1
120 250: 1
100 800 : 1
120 250 : 1
110 250 : 1
120 250 : 1
3
--
--
--
15 a The substrate (benzene) is 10 mmol; the copper complex (0.02
mmol); conducted in 2.5 ml MeCN.
5
3
374
--
885
--
1.01
--
Conclusion
6
10
2.2
25
22
--
In conclusion, both mononuclear and tetranuclear complexes are
accessible form the reaction of 2,6-(2,6-iPr2C6H3N=CH)2-4-
MeC6H2OH] (LH) and [Cu(OAc)2], the yields of which can be
controlled by variation of the reaction stoichiometry. Changing
the substituents at the ortho position of the aryl (imino) ring leads
to slight variations in the tetrametallic core. The tetrametallic
complexes were found to be virtually inactive for the ring
7
389
2006
1.01
1.08
1.10
--
8
2936 7125
1644 6270
20
9
10
11
12
13
14
15
16
17
18
19
20
--
676
412
--
--
5700
998
--
opening polymerization of -caprolactone in the presence of
20
110 250 : 1
80 250 : 1
250 : 1
20
3.5
--
1.02
1.01
--
25
benzyl alcohol. Magnetic susceptibility studies on the
tetrametallic complex with R1 = Me and R2 = iPr indicated the
presence of strong antiferromagnetic interactions between the
Cu(II) ions. The complexes catalyze the hydroxylation of
benzene into phenol by hydrogen peroxide. The yields were not
superior to others recently reported, however the tetra-nuclear
complexes exhibited excellent (near quantitative) selectivities.
100 250 : 1
120 400 : 1
120 600 : 1
120 800 : 1
--
--
--
--
30
--
--
--
--
--
--
--
--
Experimental
--
--
--
--
General
120 1000 : 1 12
25 250 : 1 24
--
--
--
--
35 All manipulations were carried out under an atmosphere of dry
nitrogen using conventional Schlenk and cannula techniques or in
a conventional nitrogen-filled glove box. Diethyl ether and
tetrahydrofuran were refluxed over sodium and benzophenone.
Toluene was refluxed over sodium. Dichloromethane and
40 acetonitrile were refluxed over calcium hydride. All solvents
were distilled and degassed prior to use. IR spectra (nujol mulls,
KBr or NaCl windows) were recorded on a Nicolet Avatar 360
FT IR spectrometer; Elemental analyses were performed by the
elemental analysis service at Sichuan Normal University. Ligands
45 of type LH were prepared as described in the literature. [7] All
other chemicals were purchased from commercial sources and
were used as received.
--
--
--
--
3
†Runs conducted in toluene using 0.04 mmol of catalyst; CL = -caprolactone.
10 a Determined by1H NMR spectroscopy,b GPC data in THF versus polystyrene
standard using a correction factor of 0.56 c Calculated from ([CL]0/[BnOH]0) x
conv.(%) x Monomer molecular weight.
Table 2. Catalysis of the complexes on direct oxidation of
benzene into phenol.a

RSC Advances
View ArticlPe Oanglinee 8 of 15
DOI: 10.1039/C5RA08696E
Synthesis of[1,3-(2,6-iPr2C6H3N=CH)2-5-MeC6H2O-2)]2Cu(1a)
6.45; N, 3.81. Found: C, 60.53; H, 6.93; N, 4.01 %. IR (nujol
null,KBr): 3064(w), 2962(s), 2925(s), 2867(s), 2357(w), 1923(w),
1784(w), 1612(s), 1587(s), 1550(s), 1456(s), 1450(m), 1397(s),
1327(s), 1258(m), 1232(w), 1174(s), 1104(m), 1070(s), 1014(m),
50
2,6-Diformyl-4-methyl-phenoxy(2,6-diisopropylaniline) (0.49 g,
1.0 mmol) and copper diacetate (0.18g, 1.0 mmol) in toluene (30
ml) were refluxed under an argon atmosphere for 12 h. The
solvent was then removed in-vacuo and the residue was extracted
into either hot acetonitrile (25 ml) or ethanol (25 ml). Prolonged
standing at ambient temperature afforded 1a as green/yellow
crystals. Yield: 0.18 g, 35 %; elemental analysis calculated for
C66H82CuN4O2: C, 77.19; H, 8.05; N, 5.46. Found: C, 76.68;
H,8.15; N, 5.22 %. IR (nujol null, KBr): 3059(w), 3005(w),
2959(s), 2926(s), 2867(s), 2357(w), 1923(w), 1617)s), 1601(w),
1587(w), 1542(s), 1443(s), 1381(s), 1364(s), 1342(m), 1326(m),
1294(m), 1258(s), 1228(s), 1180(s), 1165(m), 1108(w), 1097(w),
1043(w), 978(w), 934(w), 820(m), 798(m), 775(s), 761(w),
702(w), 638(w), 561(w), 520(s), 474(w); MS (ESI): m/z 1026 M+.
932(w), 867(w), 828(w), 800(s), 770(m), 727(m), 665(m),
m
620(m), 564(m), 528(m), 487(s), 425(w). MS (ESI):
/ 1408
z
5
10
15
{Cu4(OAc)3[1,3-(2,6-iPr2C6H3N=CH)2-5-MeC6H2O)-2)]2(4-
55
O)}+.
Synthesis
of
{Cu4(OAc)4[1,3-(2,6-Me2C6H3N=CH)2-5-
tBuC6H2O-2]2(4-O)} (2c)
As for 2a, but using 2,6-diformyl-4-t-butyl-phenoxy(2,6-
dimethylaniline) (0.42 g, 1.0 mmol) and copper diacetate (0.37 g,
2.0 mmol) affording 2c as green crystals. Crystals suitable for
single crystal X-ray diffraction can be grown from either
methanol or acetonitrile. Yield: 0.32 g, 48 %; elemental analysis
calculated for C64H74Cu4N4O11: C, 57.82; H, 5.61; N, 4.21. Found:
C, 57.71; H, 5.69; N, 4.14 %. IR (nujol null, KBr): 3422(s),
3020(w), 2962(s), 2924(s), 2869(w), 2361(w), 1611(s), 1548(m),
1471(m), 1451(m), 1397(s), 1347(m), 1294(w), 1232(m), 1183(s),
1092(w), 1068(s), 1023(w), 923(w), 891(w), 868(w), 841(w),
60
65
70
Synthesis of[1,3-(2,6-iPr2C6H3N=CH)2-5-ClC6H2O)-2)]2Cu(1b)
As for 1a, but using 2,6-diformyl-4-chloro-phenoxy(2,6-
diisopropylaniline) (0.51g, 1.0 mmol) and copper diacetate (0.18
g, 1.0 mmol) affording 1b as green/yellow crystals. Yield: 0.22 g,
41 %. elemental analysis calculated for C64H76Cl2CuN4O2: C,
71.99; H, 7.17; N, 5.25. Found: C, 72.16; H, 7.32; N, 5.13 %.IR
(nujol null, KBr): 3066(s), 2961(s), 2095(s), 2866(m), 2356(w),
1737(w), 1612(s), 1588(w), 1542(s), 1436(s), 1385(m), 1367(s),
1332(s), 1292(w),1256(m), 1215(s), 1172(s), 1097(m), 1059(w),
1044(w), 1023(s), 932(s), 871(w), 862(w), 797(s), 771(m), 756(s),
728(s), 697(w), 660(w), 638(w), 562(w), 533(m), 510(m), 481(w).
797(w), 768(s), 722(w), 667(m), 630(m), 566(m), 510(m),
20
m
438(m).
MS
(ESI):
/
1247
{Cu4(OAc)2[1,3-(2,6-
z
Me2C6H3N=CH)2-5-tBuC6H2O-2]2(4-O)}2+.
Synthesis of {Cu4(OAc)4[1,3-(2,6-Me2C6H3N=CH)2-5-ClC6H2O-
2]2(4-O)} (2d)
25
MS (ESI): m/z 1068 [M + H]+
As for 2a, but using 2,6-diformyl-4-chloride-phenoxy(2,6-
dimethylaniline) (0.39g, 1.0 mmol) and copper diacetate (0.37 g,
2.0 mmol) affording 2d as green crystals. Yield: 0.37 g, 58 %;
elemental analysis calculated for C56H56Cl2Cu4N4O11: C, 52.30;
H, 4.39; N, 4.36. Found: C, 52.64; H, 4.51; N, 4.53 %. IR (nujol
null, KBr): 3437(s), 2973(w), 2918(w), 1612(s), 1546(m),
1471(w), 1440(m), 1395(s), 1342(m), 1316(w), 1258(w),
1226(m), 1179(m), 1092(w), 1059(s), 984(w), 924(w), 883(w),
.
75
Synthesis of {Cu4(OAc)4[1,3-(2,6-Me2C6H3N=CH)2-5-MeC6H2O-
2]2(4-O)} (2a)
80
A toluene solution (30ml) of 2,6-diformyl-4-methyl-phenoxy(2,6-
dimethylaniline) (0.37g, 1.0mmol), copper diacetate (0.37 g, 2.0
mmol) was refluxed under an argon atmosphere for 12 h. The
solvent was then removed in-vacuo and the residue extracted in
hot acetonitrile (30 ml) or ethanol (30 ml). Prolonged standing (2
– 3 days) afforded 2a as green crystals. Yield: 0.36 g, 57 %;
elemental analysis calculated for C58H62Cu4N4O11: C, 55.94; H,
5.02; N, 4.50. Found: C, 55.63; H, 5.25; N, 4.31 %. IR (nujol null,
KBr): 3447(s), 2924(m), 2856(w), 2362(s), 2337(s), 1612(s),
1549(m), 1452(m), 1394(s), 1341(w), 1262(w), 1181(m), 1074(s),
30
35
40
808(m), 766(w), 720(w), 668(m), 627(m), 565(w), 515(w),
m
438(w).
MS
(ESI):
/
1227
{Cu4(OAc)3[1,3-(2,6-
z
Me2C6H3N=CH)2-5-ClC6H2O-2]2(4-O)}2+.
Synthesis of {Cu4(OAc)4[1,3-(2,6-iPr2C6H3N=CH)2-5-ClC6H2O-
2]2(4-O)} (2e)
85
As for 2a, but using 2,6-diformyl-4-chloro-phenoxy(2,6-
diisopropylaniline) (0.51 g, 1.0 mmol) and copper diacetate (0.37
g, 2.0 mmol) affording 2e as green crystals. Yield: 0.35 g, 46 %;
elemental analysis calculated for C72H88Cl2Cu4N4O11: C, 57.25;
H, 5.87; N, 3.71. Found: C, 57.36; H, 6.02; N, 3.88 %. IR (nujol
null, KBr): 3065(w), 2962(s), 2927(s), 2868(s), 2360(w),
1931(w), 1860(w), 1777(w), 1613(s), 1587(s), 1548(s), 1440(s),
1398(s), 1347(s), 1256(w), 1221(w), 1172(s), 1107(m), 1058(s),
990(w), 932(w), 882(w), 863(w), 791(s), 768(w), 724(s), 667(m),
621(s), 563(m). MS (ESI): m/z 991.5 (M+– L – O).
830(w), 769(w), 719(w), 669(w), 566(w), 517(w), 489(w).MS
m
(ESI):
/
1312 {Cu4(OAc)2[1,3-(2,6-Me2C6H3N=CH)2-5-
z
90
MeC6H2O-2]2(4-O)}2+
Synthesis of{Cu4(OAc)4[1,3-(2,6-iPr2C6H3N=CH)2-5-MeC6H2O-
2]2(4-O)} (2b)
95
As for 2a, but using 2,6-diformyl-4-methyl-phenoxy(2,6-
diisopropylaniline) (0.49 g, 1.0 mmol) and copper diacetate (0.37
g, 2.0 mmol) afforded 2b as green crystals. Yield: 0.44 g, 60 %;
elemental analysis calculated for C74H94Cu4N4O11: C, 60.47; H,
45
Synthesis of {Cu4(OAc)4[1,3-(2,6-iPr2C6H3N=CH)2-5-tBuC6H2O-
2]2(4-O)} (2f)

View Article Online
DOI: 10.1039/C5RA08696E
Page 9 of 15
RSC Advances
As for 2a, but using 2,6-diformyl-4-t-butyl-phenoxy(2,6-
50 resultant polymer was then dried on filter paper was was dried in-
diisopropylaniline) (0.52 g, 1.0 mmol) and copper diacetate (0.37
g, 2.0 mmol) affording 2f as green crystals. Yield: 0.52 g, 67 %;
elemental analysis calculated for C80H106Cu4N4O11: C, 61.83; H,
6.88; N, 3.61. Found:C, 61.47; H, 6.96; N, 3.55 %. IR (nujol null,
KBr): 3447(s), 2962(s), 2869(w), 1612(s), 1553(m), 1458(s),
1397(s), 1360(w), 1331(w), 1261(s), 1175(w), 1097(s), 1068(s),
vacuo.
Procedure for oxidation of benzene
5
Benzene (0.9 mL, 10 mmol), acetonitrile (2.5 mL) and catalytic
amount of the copper complex (0.02 mmol) were placed into a
55 reaction vessel equipped with cooling condenser and placed in an
oil-bath. The reaction was heated at appropriate temperature for a
period of time. When the reaction reached the specified
temperature, appropriate amount of aqueous H2O2 (1.5 mL, 30
wt%) was slowly and carefully added in one-go. When the
60 reaction was stopped and cooled, the volume of the reaction
mixture was calibrated to 10 mL with CH3CN in which there was
an appropriate amount of toluene as an internal standard. To the
calibrated reaction solution was added MgSO4 (3 g) to remove
the water in the reaction before being analyzed by gas
65 chromatography. Quantitative analysis of both benzene and
phenol was achieved by establishing their calibration curves with
two linear equations under optimized conditions, Ab = 0.0053 Wb
+ 0.1266 ( R = 0.9986) and Ap = 0.0034 Wp  0.1635 ( R =
0.9943) for benzene and phenol, respectively (Figs. S7 and S8,
70 ESI), where A is the ratio of the peak areas of the analyte
(benzene or phenol) and the internal standard toluene, W (mg) is
the mass of the analytes, and the subscripts b and p denote
benzene and phenol, respectively. The yield of phenol and
benzene conversion was calculated as follows: phenol (mmol) /
75 benzene initially used (mmol) ×100% and benzenereacted
(mmol) / benzene initially used (mmol) ×100%, respectively.
1023(s), 931(w), 865(w), 804(s), 725(w), 666(w),623(w), 566(w),
m
530(w);
MS
(ESI):
/
1485
{Cu4(OAc)3[1,3-(2,6-
z
iPr2C6H3N=CH)2-5-tBuC6H2O)-2)]2(4-O)}+
10
Synthesis of {[Cu2(OAc)4](OAc)(HNEt3)(MeCN)}n(3)
To 2-hydroxy-5-methyl-isophthaldehyde(0.16 g,1.0 mmol) and
copper diacetate (0.37 g, 2.0 mmol) was added toluene (30 ml),
and the system was stirred at room temperature for 30 min.
Triethylamine (0.31 ml, 2.2 mmol) was then added and the
solution brought to reflux for 12 h. The solvent was then removed
in-vacuo and the residue extracted in hot acetonitrile (30 ml).
15
20
25
Prolonged standing at ambient temperature afforded
3 as
green/blue crystals. Yield: 0.56 g, 66 %; elemental analysis
calculated for C18H34Cu2N2O10 – MeCN (sample dried in-vacuo
for 2 h): C, 36.64; H, 5.96; N, 2.69. Found: C, 36.83; H, 5.93; N,
2.63 %. IR (nujol null, KBr): 3478(s), 3375(s), 3272(m), 2942(w),
2898(w), 1603(s), 1446(s), 1422(m), 1355(w), 1052(w), 1033(w),
m
692(s), 629(m), 559(m). MS (ESI):
/
872 {2x
z
[Cu2(OAc)4(OAc)][Et3NH].CH3CN} – 2CH3CN – 3OAc.
Electrochemistry
Crystallography details
Electrochemistry was performed in a gas-tighten three-electrode
system in which a vitreous carbon disk (Ф = 1 mm) was used as a
Data collection
30 working electrode, a carbon strip as counter electrode, and Ag /
AgCl (inner reference solution: 0.45 mol L−1 [NtBu4]BF4 + 0.05
mol L−1 [NtBu4]Cl in dichloromethane) against which the
potential of ferrocenium / ferrocene couple is 0.55 V in 0.5 mol
L−1 [NtBu4]BF4 in CH3CN. Ferrocene was added as an internal
35 standard, and all potentials are quoted against ferrocenium /
ferrocene couple (Fc+ / Fc).
For 1a: Single crystal X-ray diffraction data were collected using
80 a Bruker SMART 1K CCD diffractometer using ω scans with
narrow frames. Crystals were mounted at the end of a glass fibre
under and held at 160 K in an Oxford Cryosystems nitrogen gas
Cryostream.
All other samples (except 3): Single crystal X-ray diffraction data
85 were collected at room temperature (293 K) using an Agilent
Technologies Xcalibur diffractometer operating with Mo
Kαradiation and an Eos CCD detector in a series of ω-scans. [20]
Data were integrated using standard procedure using
CrysAlisProsoftware (Agilent). Data were corrected for
Procedure for ROP of -caprolactone
Typical polymerization procedures in the presence of one
40 equivalent of benzyl alcohol (Table 1) are as follows. A toluene
solution of 2 (0.04 mmol) and benzyl alcohol (0.04 mmol) were
added into a Schlenk tube in the glove box at room temperature.
The solution was stirred for 2 min., and then -caprolactone (10.0
mmol) along with 2 ml toluene was added to the solution. The
45 reaction mixture was then palced into an oil bath pre-heated to
the required temperature, and the solution was stirred for the
prescribed time. The polymerization mixture was then quenched
by the addition of excess glacial acetic acid (0.2 ml) and the
resultant solution then poured into methanol (200 ml). The
90 absorption effects using
a multi-scan method based on
equivalents. In the case of 2f, the crystals appeared to be unstable
in the X-ray beam, presumably due to solvent loss. Given this,
data for 2f were collected at 150 K, in contrast to the other
structures and were coated in a thin film of perfluoropolyether
95 oil. Furthermore, the structure of 2f at room temperature appears
different to that at 150 K. At room temperature, the structure is
triclinic and centrosymmetric with a single copper cluster in the
asymmetric unit. Upon cooling below about 240 K, a larger
monoclinic cell of approximately twice the volume emerges. This

View Article Online
DOI: 10.1039/C5RA08696E
RSC Advances
Page 10 of 15
45
low temperature form is non-centric and has two unique oxo
clusters in the asymmetric unit.
[1]
[2]
I. Bratko and M. Gómez, Dalton Trans. 2013, 42, 10664 and
references therein.
C.K. Williams, N.R. Brooks, M.A. Hillmyer and W.B.
Tolman, Chem. Commun. 2002, 2132.
A. Arbaoui, C. Redshaw, N.M. Sanchez-Ballester, M.R.J.
Elsegood and D.L. Hughes, Inorg. Chimica Acta 2011, 365,
96.
For 3: Data were collected on a Bruker SMART 1K CCD
diffractometer at Daresbury SRS station 9.8 (λ = 0.6710 Å}. [21]
50 [3]
5
Structure solution and refinement
[4]
55 [5]
[6]
L. Wang, W.-H. Sun, L. Han, Z. Li, Y. Hu, C. He and C. Yan,
J. Organomet. Chem. 2002, 650, 59.
C.-Y. Tsai, B.-H. Huang, M.-W. Hsiao, C.-C. Lin and B.-T.
Ko, Inorg. Chem. 2014, 53, 5109.
(a) S. Teipel, K. Griesar, W. Haase and B. Krebs, Inorg.
Chem.1994,33, 456. (b) J. Reim, K. Griesar, W. Haase and B.
Krebs, J. Chem. Soc. Dalton Trans. 1995, 2649.
S. Mukherjee, T. Weyhermüller, E. Bothe, K. Wieghardt and
P. Chaudhuri, Eur. J. Inorg. Chem. 2003, 863.
P. Roy and M. Manassero, Dalton Trans. 2010, 39, 1539.
T. Ghosh, J. Adhikary, P. Chakraborty, P.K. Sukul, M. Sekhar
Jana, T. K. Mondal, E. Zangrando and D. Das, Dalton Trans.
2014, 43, 841.
A. Kumar, R. Pandey, R.K. Gupta, M. Dubey and D.S.
Pandey, Dalton Trans. 2014, 43, 13169.
J. T Guy Jr., J.C. Cooper, R.D. Gilardi and J.L. Flippen-
Anderson, Inorg Chem. 1988, 27, 635. (b) A.R. Paital, P.K.
Nanda, S. Das, G. Aromi and D. Ray, Inorg Chem. 2006, 45,
505.
Structures were solved using automated direct methods within
SHELXS-86 or intrinsic phasing within SHELXT. Structures
were refined by full-matrix least squares refinement within
SHELXL-2014 using all unique data. Hydrogen atoms were
10 placed using a riding model. Where data were sufficiently good,
methyl group orientations were refined. Many of the structures
displayed disorder in the position of methyl groups or in solvent
of crystallization. This disorder was modelled using standard
techniques. In the case of structure 2e it was not possible to locate
15 the solvent molecules precisely and electron density in these
regions was modelled using the Platon SQUEEZE routine. [22]
For 2d there was some evidence that the true lattice symmetry
was primitive rather than C-centred, but it was not possible to
obtain stable refinements with a primitive cell. The refinement in
20 C2/c, which converged with RF = 0.0734 and wR(F2) = 0.1317
(all data), was therefore retained.
60 [7]
[8]
[9]
65
[10]
[11]
70
[12]
F.-F. Jian, P.-S. Zhao, H.-X. Wang and L.D. Wu, Bull. Korean
Chem. Soc. 2004, 25, 673.
[13]
(a) P. Mukherjee, M.G.B. Drew and A. Figuerola, Polyhedron
2008, 27, 3343. (b) H Karabiyuk, O. Erdem and M.Aygun, J.
Inorg. Organomet. Polym. 2010, 20, 142. (c) L. Mouni, M.
Akkurt and S.O. Yildirm, J. Chem. Crystallogr. 2010, 40, 169.
(d) A. Kumar, M. Dubey, R.Pandey, R.K. Gupta, A. Kumar,
A.C. Kalita and D. S. Pandey, Inorg. Chem. 2014, 53, 4944.
*The values in square brackets are for a system exhibiting
significant tautomerism. [13b]
75
80
CCDC 1040530
–
1040539 contain the supplementary
crystallographic data for this paper.
25 Acknowledgements
[14] (a) N.A. Bailey, D.E. Fenton, J. Lay, P.B. Roberts, J.-M.
Latour and D. Limosin, J. Chem., Soc. Dalton Trans. 1986,
2681. (b) N.E. Borisova, M.D. Reshetova, T.V. Magdesieva,
V.N. Khrustalev, G.G. Aleksandrov, M. Kuznetsov, R.S.
Skazov, A.V. Dolganov, V.N. Ikorskiy, V.M. Novotortsev, I.L.
Eremenko, I.I. Moiseev and Y.A. Ustynyuk, Inorg. Chimica
Acta 2008, 361, 2032. (c) M.-F. Zaltariov, M. Alexandru, M.
Cazacu, S. Shova, G. Novitchi, C. Train, A. Dobrov, M.V.
Kirillova, E.C.B.A. Alegria, A.J.L. Pombeiro and V.B. Arion,
Eur. J. Inorg. Chem. 2014, 4946. (d) M. Pait, M. Shatruk, J.
Lengyel, S. Gómez-Coca, A. Bauzá, A. Frontera, V. Bertolasi
and D. Ray, Dalton Trans. 2015, in-press. Doi:
10.1039/C5DT90077H.
Sichuan Normal University and the National Natural Science
Foundation of China (grants 51443004 and 51273133) are
thanked for financial support. The CCLRC is thanked for the
award of beam-time at SRS Daresbury Laboratory (Station 9.8),
30 and Dr. Simon J. Teat is thanked for scientific support.
85
90
Notes and references
a College of Chemistry and Materials Science, Sichuan Normal University,
Chengdu, 610066, China.
b Chemistry Department, Loughborough University, Loughborough,
35 Leicestershire, LE11 3TU, U.K.
95 [15]
[16]
L. Han, Y. Cui, Y. Li, W.-H. Sun, J. Du and J. Li, J. Chem.
Res. 2003, 157.
c Department of Chemistry, The University of Hull, Cottingham Rd,
Hull, HU6 7RX, U.K. Email: C.Redshaw@hull.ac.uk
d College of Biological, Chemical Sciences and Engineering, Jiaxing
University, Jiaxing 314001, China.
(a) V. McKee and S.S. Tandon, J. Chem. Soc., Dalton Trans.
1991, 221. (b) W.-X. Zhang, C.-Q. Ma, X.-N.Wang, Z.-G. Yu,
Q.-J. Lin and D. –H. Jiang, Chin. J. Chem. 1995, 13, 497. (c)
R. Shakya, P.H. Keyes, M.J. Heeg, A. Moussawel, P.A.
Heiney and C.N. Verani, Inorg. Chem. 2006, 45, 7587. (d) R.
Shakya, S.S. Hindo, L. Wu, S. Ni, M. Allard, M.J.
Heeg,S.R.P. da Rocha, G.T. Yee, H.P. Hratchian and C.N.
Verani, Chem. Eur. J. 2007, 13, 9948. (e) S.S. Hindo, R.
Shakya,R. Shanmugam, M.J. Heeg and C.N. Verani, Eur. J.
Inorg. Chem. 2009, 4686. (f) P. Roy, M. Nandi, M.
Manassero, M. Ricco, M. Mazzani, A. Bhaumik and
P.Banerjee, Dalton Trans. 2009, 9543. (g) M.Sarkar, R.
Clerac, C. Mathoniere, N.G.R. Hearns, V. Bertolasi and D.
Ray, Inorg. Chem. 2010, 49, 6575. (h) M. Sarkar, R. Clerac,
C. Mathoniere, N.G.R. Hearns, V. Bertolasi and D. Ray,
Inorg. Chem. 2011, 50, 3922. (i) D. Das, A. Guha, S. Das, P.
Chakraborty, T.K. Mondal, S. Goswami and E. Zangrando,
100
40 e EaStCHEM School of Chemistry, University of Edinburgh,
David Brewster Road, Edinburgh, EH9 3FJ, Scotland.
105
110
† Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/b000000x/

View Article Online
DOI: 10.1039/C5RA08696E
Page 11 of 15
RSC Advances
Inorg. Chem. Commun. 2012, 23, 113. (j) M.S.Jana, S. Dey,
[18]
N. Ikpo, C. Hoffmann, L.N. Dawe and F.M. Kerton, Dalton
Trans. 2012, 41, 6631.
J.L. Priego, R. Jimemez-Aparicio, Polyhedron 2013, 59, 101.
(k) A.K. Ghosh and D. Ray, Polyhedron 2013, 52, 370. (l) S.
Halder, S. Dey, C. Rizzoli and P. Roy, Polyhedron 2014, 78,
85. (m) S. Das, L. Sorace, A. Guha, R. Sanyal, H. Kara, A.
Caneschi, E. Zangrando and D. Das, Eur. J. Inorg. Chem.
2014, 2753. (n) M. Pait, E. Colacio and D. Ray, Polyhedron
2015, 88, 90.
(a) M. Labet and W. Thielemans, Chem. Soc. Rev. 2009, 38,
3484. (b) A. Arbaoui and C. Redshaw, Polym. Chem. 2010, 1,
801. (c) X. Rong and C. Chunxia, Prog. Chem. 2012, 24,
1519.
15 [19]
(a) B. Xu, W. Zhong, Z. Wei, H. Wang, J. Liu, L. Wu, Y. Feng
and X. Liu, Dalton Trans., 2014, 43, 15337. (b) X. You, Z.
Wei, H. Wang, D. Li, J. Liu, B. Xu and X. Liu, RSC Adv.,
2014, 4, 61790. (c) L. Wu, W. Zhong, B. Xu, Z. Wei, X. Liu,
Dalton Trans., 2015, 44, 8013.
CrysAlisPro Softwarefor CCD diffractometers, Agilent
Technologies,2012.
SAINT and SMART software for CCD diffractometers,
Bruker AXS Inc.,Madison, USA, 2000.
5
20 [20]
[21]
[17]
10
[22]
A. L. Spek, Acta Crystallogr. Sect. A. Fundam. Crystallogr.
1990, 46, C34.
25
Table 2: Crystal data for the monomeric complexes 1a, 1b and polymeric 3.
Identification code
Empirical formula
Formula weight
Temperature
1a
1b
3
C66H82CuN4O2
1026.89
C64H76Cl2CuN4O2
1067.72
C18H34Cu2N2O10
565.55
160(2) K
0.71073 Å
Monoclinic
P21/c
293(2) K
293(2) K
Wavelength
0.71073 Å
0.71073 Å
Crystal system
Space group
Monoclinic
Monoclinic
P21/c
P21/n
Unit cell dimensions
a = 9.8597(6) Å
= 90°.
a = 10.0099(2) Å = 90°.
a = 12.2105(4) Å = 90°.
b = 11.5458(4) Å = 101.407(3)°.
c = 17.7582(5) Å  = 90°.
b = 12.1852(8) Å = 97.5566(13)°. b = 12.1157(2) Å = 97.487(2)°.
c = 24.1112(16) Å  = 90°.
c = 24.5154(5) Å  = 90°.
Volume
3
3
3
2871.6(3) Å
2947.80(10) Å
2454.10(14) Å
Z
2
2
4
Density (calculated)
3
3
3
1.188 Mg/m
1.203 Mg/m
1.531 Mg/m
Absorption coefficient
-1
-1
-1
0.427 mm
0.506 mm
1.785 mm
F(000)
1102
1134
1176
Crystal size
3
3
3
0.64 × 0.05 × 0.02 mm
0.25 × 0.25 × 0.20 mm
0.25 × 0.20 × 0.15 mm
Theta range for data collection 1.704 to 25.998°.
2.862 to 28.938°.
2.931 to 28.942°.
Index ranges
-11 ≤ h ≤ 12, -15 ≤ k ≤ 14, -29 ≤ l ≤
-13 ≤ h ≤ 12, -15 ≤ k ≤ 13, -33 ≤ l ≤
-12 ≤ h ≤ 15, -15 ≤ k ≤ 9, -21 ≤ l ≤ 24
28
20
Reflections collected
16148
14090
11719
Independent reflections
Completeness (to 2θ = 25.242
5606 [R(int) = 0.0835]
99.6 %
6775 [R(int) = 0.0246]
99.8 %
5625 [R(int) = 0.0257]
99.8 %

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DOI: 10.1039/C5RA08696E
RSC Advances
Page 12 of 15
°)
Absorption correction
Max. and min. transmission
Refinement method
Empirical
Semi-empirical from equivalents
Semi-empirical from equivalents
1.000 and 0.835
0.992 and 0.772
1.000 and 0.958
2
2
2
Full-matrix least-squares on F
5606 / 0 / 340
Full-matrix least-squares on F
6775 / 7 / 331
Full-matrix least-squares on F
Data / restraints / parameters
5625 / 1 / 301
1.038
2
1.000
1.024
Goodness-of-fit on F
Final R indices [I>2σ(I)]
R indices (all data)
R1 = 0.0528, wR2 = 0.1035
R1 = 0.1074, wR2 = 0.1247
R1 = 0.0502, wR2 = 0.1125
R1 = 0.0801, wR2 = 0.1270
R1 = 0.0359, wR2 = 0.0771
R1 = 0.0517, wR2 = 0.0853
Largest diff. peak and hole
-3
-3
-3
0.465 and –0.581 e.Å
0.348 and –0.306 e.Å
0.374 and –0.499 e.Å
Table 3: Crystal data for Cu4OL2(OAc)4 complexes.
Identification
code
2c·MeCN
2a
2b
2c
Empirical
formula
C66H86Cu4N4O15
C76H94Cu4N5O11
C70.67H88Cu4N4O14.33
C72H86Cu4N8O11
Formula weight
Temperature
Wavelength
1429.54
1507.72
1477.00
1493.64
293(2) K
293(2) K
293(2) K
0.71073 Å
Triclinic
293(2) K
0.71073 Å
0.71073 Å
Monoclinic
P21/n
0.71073 Å
Crystal system
Space group
Monoclinic
C2/c
Monoclinic
P21/c
̅
P̅1
Unit cell
a = 24.5344(10) Å
b = 13.0252(4) Å
c = 22.7527(8) Å
=90°
a = 20.028(11) Å
b = 15.1113(5) Å
c = 25.249(4) Å
= 90°
a = 14.1438(9) Å
b = 14.8853(5) Å
c = 20.3062(5) Å 
= 82.021(2)°
= 88.299(3)°
a = 23.6777(5) Å
b = 12.2318(3) Å
c = 27.2068(6) Å
= 90°
dimensions
= 104.984(4)°
 = 90°.
= 98.68(4)°
 = 90°
= 113.205(2)°
 = 90°
 = 64.613(5)°
Volume
3
3
3
3
7023.7(5) Å
7554(5) Å
3822.8(3) Å
7242.2(3) Å
Z
4
4
2
4
Density
3
3
3
3
1.352 Mg/m
1.326 Mg/m
1.284 Mg/m
1.370 Mg/m
(calculated)
Absorption
coefficient
-1
-1
-1
-1
1.259 mm
1.171 mm
1.158 mm
1.222 mm

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DOI: 10.1039/C5RA08696E
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RSC Advances
F(000)
2984
3156
1541.3
3112
Crystal size
0.25 × 0.20 × 0.20
0.40 × 0.35 × 0.20
0.35 × 0.25 × 0.25
0.35 × 0.25 × 0.20
3
3
3
3
mm
mm
mm
mm
Theta range for
data collection
2.953 to 28.956°.
2.956 to 28.991°.
2.923 to 29.028°.
2.854 to 29.127°.
Index ranges
-19 ≤ h ≤ 33, -10 ≤ -25 ≤ h ≤ 27, -19 ≤ -18 ≤ h ≤ 19, -20 ≤ k ≤
-23 ≤ h ≤ 32, -15
≤ k ≤ 16, -36 ≤ l ≤
29
k ≤ 17, -30 ≤ l ≤
k ≤ 8, -32 ≤ l ≤ 24
20, -27 ≤ l ≤ 26
30
Reflections
collected
16990
43429
33076
41758
Independent
reflections
8067 [R(int) =
17557 [R(int) =
17406 [R(int) = 0.0463] 16766 [R(int) =
0.0270]
0.0311]
0.0283]
Completeness (to
99.9 %
99.8 %
99.8 %
99.6 %
2θ = 25.242 °)
Absorption
correction
Semi-empirical
from equivalents
Semi-empirical
from equivalents
Semi-empirical from
equivalents
Semi-empirical
from equivalents
Max. and min.
transmission
1.000 and 0.787
1.000 and 0.840
1.000 and 0.843
1.000 and 0.881
Refinement
method
Full-matrix least-
Full-matrix least-
Full-matrix least-
Full-matrix least-
2
2
2
2
squares on F
squares on F
squares on F
squares on F
Data / restraints /
parameters
8067 / 6 / 386
1.022
17557 / 4 / 859
1.033
17406 / 12 / 838
1.072
16766 / 10 / 880
1.037
Goodness-of-fit
2
on F
Final R indices
[I>2σ(I)]
R1 = 0.0547, wR2
R1 = 0.0426, wR2
R1 = 0.0736, wR2 =
R1 = 0.0388, wR2
= 0.1321
= 0.0935
0.1908
= 0.0837
R indices (all
R1 = 0.0898, wR2
R1 = 0.0727, wR2
R1 = 0.1248, wR2 =
R1 = 0.0547, wR2
data)
= 0.1537
= 0.1075
0.2288
= 0.0914
Largest diff. peak
and hole
0.849 and –0.658
0.468 and –0.381
-3 0.728 and –0.463
1.099 and –0.605 e.Å
-3
-3
-3
e.Å
e.Å
e.Å
…Table 3 (cont).
Identification code
Empirical formula
Formula weight
Temperature
2d
2e
2f
C178H183Cl6Cu12N17O33
C72H88Cl2Cu4N4O11
1510.52
C350H183Cu16N31O44
6764.65
4063.58
293(2) K
0.71073 Å
293(2) K
150(2) K
0.71073 Å
Wavelength
0.71073 Å

View Article Online
DOI: 10.1039/C5RA08696E
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Page 14 of 15
Crystal system
Space group
Monoclinic
C2/c
Monoclinic
Monoclinic
P21
C2/c
Unit cell dimensions
a = 65.736(3) Å
b = 13.0482(4) Å
c = 22.1089(5) Å
= 90°
a = 28.827(2) Å
b = 28.771(3) Å
c = 22.942(2) Å
= 90°.
a = 14.2390(6) Å
b = 51.092(2) Å
c = 14.3358(5) Å
= 90°
= 98.395(2)°
 = 90°
= 120.445(11)°.
 = 90°.
= 118.806(3)
 = 90°
Volume
3
3
3
18760.4(11) Å
16405(3) Å
9138.7(7) Å
Z
4
8
1
Density (calculated)
3
3
3
1.439 Mg/m
1.223 Mg/m
1.229 Mg/m
Absorption coefficient
-1
-1
-1
1.488 mm
1.141 mm
0.976 mm
F(000)
8336
6288
3536
Crystal size
3
3
3
0.35 × 0.30 × 0.25 mm
2.896 to 29.172°.
0.20 × 0.15 × 0.15 mm
3.009 to 25.601°.
0.42 × 0.38 × 0.32 mm
1.594 to 25.285°.
Theta range for data
collection
Index ranges
-55 ≤ h ≤ 87, -16 ≤ k ≤
16, -27 ≤ l ≤ 25
-35 ≤ h ≤ 34, -34 ≤ k ≤ 31,
-27 ≤ l ≤ 24
-17 ≤ h ≤ 17, -58 ≤ k ≤ 61, -
15 ≤ l ≤ 17
Reflections collected
50651
35204
48175
Independent reflections
20415 [R(int) = 0.0369]
15360 [R(int) = 0.0497]
27844 [R(int) = 0.1154]
98.9 % (25.242 °)
Completeness (to 2θ =
98.7 % (25.242 °)
99.5 %
25.242 °)
Absorption correction
Semi-empirical from
equivalents
Semi-empirical from
equivalents
Empirical
Max. and min. transmission
Refinement method
1.000 and 0.628
1.000 and 0.404
1.000 and 0.721
Full-matrix least-squares
Full-matrix least-squares
Full-matrix least-squares on
2
2
2
on F
on F
F
Data / restraints / parameters
20415 / 27 / 1126
1.050
15360 / 0 / 838
1.038
27844 / 36 / 1980
0.874
2
Goodness-of-fit on F
Final R indices [I>2σ(I)]
R indices (all data)
R1 = 0.0497, wR2 =
R1 = 0.0643, wR2 =
R1 = 0.0777, wR2 = 0.1991
R1 = 0.1362, wR2 = 0.2448
0.1175
0.1577
R1 = 0.0734, wR2 =
R1 = 0.1204, wR2 =
0.1317
0.1951

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DOI: 10.1039/C5RA08696E
Page 15 of 15
RSC Advances
Largest diff. peak and hole
-3
0.918 and -0.632 e.Å
-3
-3
0.611 and -1.187e.Å
0.681 and -0.580 e.Å