Methyl group influence on the formation of CuI complexes with thio-pyridine ligands

Article abstract of DOI:10.1039/b111400j

In order to investigate the effect of methyl group substitution adjacent to a pyridyl N donor, three ligands were synthesised and complexed with CuI in a 1:2 ratio. The crystal structures of three CuI complexes were determined. The dimethylated ligand bis(6-methyl-2-pyridylmethyl)sulfide (L¹) gave rise to a tetranuclear complex with two Cu₂I₂ bridges in which the Cu centres were four-coordinate. The asymmetric ligand 2-(6-methylpyridyl)methyl(2-pyridyl)methylsulfide (L²) gave a tetranuclear complex which contained two parallel Cu₂I₂ bridges. In each Cu₂I₂ bridge, one Cu centre was three- and the other four-coordinate. In contrast, the ligand bis(2-pyridylmethyl)sulfide (L³), with no Me substitution, gave rise to a one-dimensional coordination polymer with CuI chains. It was found that the differences in the complexes were a result of both the electronic and steric effects arising from the Me substitution of the pyridine donors and that no one effect completely dominated.

Full text of DOI:10.1039/b111400j

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Methyl group influence on the formation of CuI complexes with
thio-pyridine ligands
Paula L. Caradoc-Davies,a Lyall R. Hanton,*a Justin M. Hodgkissa and Mark D. Spicerb
a Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
E-mail: lhanton@alkali.otago.ac.nz
b Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street,
Glasgow, Scotland G1 1XL
Received 14th December 2001, Accepted 15th February 2002
First published as an Advance Article on the web 25th March 2002
In order to investigate the effect of methyl group substitution adjacent to a pyridyl N donor, three ligands were
synthesised and complexed with CuI in a 1 : 2 ratio. The crystal structures of three CuI complexes were determined.
The dimethylated ligand bis(6-methyl-2-pyridylmethyl)sulfide (L1) gave rise to a tetranuclear complex with two
Cu2I2 bridges in which the Cu centres were four-coordinate. The asymmetric ligand 2-(6-methylpyridyl)methyl(2-
pyridyl)methylsulfide (L2) gave a tetranuclear complex which contained two parallel Cu2I2 bridges. In each Cu2I2
bridge, one Cu centre was three- and the other four-coordinate. In contrast, the ligand bis(2-pyridylmethyl)sulfide
(L3), with no Me substitution, gave rise to a one-dimensional coordination polymer with CuI chains. It was found
that the differences in the complexes were a result of both the electronic and steric effects arising from the Me
substitution of the pyridine donors and that no one effect completely dominated.
report the copper() iodide complexes of three ligands with
varying degrees of Me substitution adjacent to the pyridine N
donors (Scheme 2).
Introduction
A number of copper() halide complexes formed from mono- or
bi-dentate ligands have previously been investigated.1 Many of
these complexes are derived from two structural motifs namely,
the halide-bridged dimer and the cubane tetramer1,2 (Scheme 1)
Scheme 2
Results and discussion
Scheme 1
Ligand syntheses
of which the former is by far the more common. Structurally
The symmetric ligands bis(6-methyl-2-pyridylmethyl)sulfide13
the two Cu atoms of the halide-bridged dimer can exist with
(L1) and bis(2-pyridylmethyl)sulfide14 (L3) were prepared
coordination numbers of three and three,3 three and four4 or
by reaction of 2-(chloromethyl)-6-methylpyridine15 and of
four and four.5 The three and four combination is the rarest
2-(chloromethyl)pyridine,15 respectively, with thioacetamide
arrangement for such dimers. The formation of these discrete
under basic conditions. The asymmetric ligand 2-(6-methyl-
complexes and the exact type of structural motif adopted are
pyridyl)methyl(2-pyridyl)methylsulfide (L2) was prepared
influenced by the electronic and steric effects exerted by the
by the 1 : 1 molar reaction of 2-(chloromethyl)pyridine15 and
ligands.6 A simple variation such as adding a substituent
6-methyl-2-(sulfanylmethyl)pyridine16 in a solution of sodium
adjacent to a donor atom can have a noticeable effect on the
methoxide. As isolated, ligand L2 was not analytically pure.
overall structure of the complex.7 Previous work examining the
Attempts to obtain analytically pure material using column
chromatography over silica gel were ineffective. However,
effect of ligand substitution on copper() halide complexes
focused on using simple mono- or rigid bi-dentate ligands.8
high-resolution electrospray mass spectrometry confirmed the
In the course of our work we have used small flexible oligo-
successful synthesis of L2. Subsequently, the ligand was reacted
pyridine ligands to probe the coordination preferences of more
with CuI to give a microanalytically pure complex.
complicated ditopic oligopyridine ligands.9–11 In preparing
these more complicated ditopic ligands we have, as a matter of
expediency, incorporated Me groups adjacent to the pyridine
Synthesis and structure of [Cu4(L1)2I4] 1
nitrogen donor atoms.10,12 This has been done to amend the
properties of the unsubstituted ligand in order to try and
increase yields, improve solubility and enhance the chances of
crystallising complexes of interest. In order to try and under-
stand the effect of this simple substitution of the ditopic ligands
on the complexes formed we have undertaken a systematic
study of the simplified oligopyridine ligand system. Herein we
The 1 : 1 molar reaction of L1 with CuI in MeCN gave a yellow
solution from which a tan powder was isolated. The powder
gave a microanalysis consistent with a 2 : 1 metal-to-ligand
ratio. Subsequently the same tan powder was isolated from the
2 : 1 molar reaction of CuI and L1 in moderate yield (50.4%).
Despite careful workup of the reaction solid and filtrate, the
1 : 1 product could not be isolated.
DOI: 10.1039/b111400j
J. Chem. Soc., Dalton Trans., 2002, 1581–1585
This journal is © The Royal Society of Chemistry 2002
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1
The H NMR spectrum of 1 in CD3CN was consistent with
a symmetrical species, which was fluxional in solution. Electro-
spray mass spectrometry under normal operating conditions
showed five peaks which had the correct isotopic patterns for
[Cu(L1)]ϩ at m/z 308, [Cu(L1)2]ϩ at 553, [Cu2(L1)2I]ϩ at 743,
[Cu3(L1)2I2]ϩ at 934 and [Cu4(L1)2I3]ϩ at 1124. The presence of
the latter two peaks suggested that a tetranuclear complex
might exist in solution. X-Ray quality crystals were grown
by the slow diffusion of diethyl ether into a solution of the
complex in MeCN.
The crystal structure of 1 was found to contain one ligand,
two Cu() ions and two IϪ ions in the asymmetric unit. The
molecular formula [Cu4(L1)2I4] was generated by a centre of
inversion (Fig. 1). This was an example of a rare tetranuclear
Fig. 2 A view of the polymeric chain of 1, illustrating the inter-
molecular π-stacking, hydrogens are omitted for clarity.
yield (75%). As in the case of 1, the 1 : 1 product could not be
obtained.
The 1H NMR spectrum of 2 in CD3CN was consistent with a
single environment for the ligand in the complex. The presence
of only two methylene signals at 4.11 and 3.97 ppm indicated
that fluxional processes were occurring in solution at 298 K.
Electrospray mass spectrometry gave peaks for [Cu(L2)]ϩ at m/z
294, [Cu(L2)2]ϩ at 523 and [Cu2(L2)2I]ϩ at 714. The presence of
the peak at m/z 714 suggested that the complex might exist
as a dimer. However, this result was inconsistent with the
microanalysis and, given the tetranuclear nature of 1, suggested
the peaks might have arisen from fragmentation processes.
The asymmetric unit contained one ligand, two Cu() ions
and two IϪ ions. The X-ray structure showed that a rare tetra-
nuclear Cu() complex closely related to 1 had been isolated.
The complete complex was generated by a centre of symmetry
such that 2 had the molecular formula [Cu4(L2)2I4] (Fig. 3). The
Fig. 1 Perspective view (crystallographic numbering) of 1. Thermal
ellipsoids are drawn at the 50% probability level. Selected bond lengths
(Å) and angles (Њ): Cu(1)–N(2) 2.031(3), Cu(1)–S(1) 2.570(1), Cu(1)–
I(1) 2.582(1), Cu(1)–I(2) 2.652(1), Cu(2)–N(1) 2.046(3), Cu(2)–S(1)
2.464(1), Cu(2)–I(1A) 2.586(1), Cu(2)–I(2A) 2.640(1), Cu(1) ؒ ؒ ؒ
Cu(2A) 2.551(1); N(2)–Cu(1)–S(1) 82.47(9), N(2)–Cu(1)–I(1) 129.45(9),
S(1)–Cu(1)–I(1) 108.14(5), N(2)–Cu(1)–I(2) 106.26(9), S(1)–Cu(1)–I(2)
100.88(4), I(1)–Cu(1)–I(2) 119.03(2), N(1)–Cu(2)–S(1) 84.79(9), N(1)–
Cu(2)–I(1A) 125.11(9), S(1)–Cu(2)–I(1A) 111.83(4), N(1)–Cu(2)–I(2A)
107.85(9), S(1)–Cu(2)–I(2A) 99.29(4), I(1A)–Cu(2)–I(2A) 119.32(3).
(Symmetry code: A Ϫx ϩ 1, Ϫy ϩ 1, Ϫz ϩ 2.)
complex with only one other closely related complex [Cu4-
(ddtp)2Br4] (ddtp = 1,5-bis(3Ј,5Ј-dimethylpyrazolyl)-3-thiapen-
tane) previously having been reported.17 The structure of 1 also
had features in common with the recently reported ClϪ bridged
Cu() tetranuclear molecular rectangle.18 The tetranuclear
complex 1 was constructed from two bridging Cu2I2 cores,
which linked the two ligands generating the centrosymmetric
tetranuclear complex. This form of tetranuclear Cu()-halide
complex is unusual since such Cu4X4 complexes typically exist
as cubane or chair forms.19 The four copper atoms all had
similarly distorted tetrahedral geometries, which were provided
by NSI2 donor atoms. The Cu() ions within the Cu2I2 core were
separated by a short distance of 2.551(1) Å.17,20 The ligand
adopted an endo–anti conformation in which the pyridine rings
were tilted at 12Њ with respect to each other and the S atom
behaved as a bridging donor between two metal centres. The
bridging was slightly asymmetric with Cu–S bond distances
of 2.570(1) and 2.464(1) Å, which were within the normal
range (2.18–3.10 Å).21 Two pyridine rings of each tetranuclear
complex were involved in intermolecular π-stacking (centroid–
centroid distance 3.63 Å)22 to form one-dimensional chains
along the diagonal [011] axis (Fig. 2). No other significant
interactions were observed between the chains.
Fig. 3 Perspective view (crystallographic numbering) of 2. Thermal
ellipsoids are drawn at the 50% probability level. Selected bond lengths
(Å) and angles (Њ): Cu(1)–N(1) 2.050(5), Cu(1)–S(1) 2.418(2), Cu(1)–
I(1A) 2.649(1), Cu(1)–I(2A) 2.589(1), Cu(2)–N(2) 1.995(5), Cu(2)–I(1)
2.594(1), Cu(2)–I(2) 2.569(1), Cu(1) ؒ ؒ ؒ Cu(2A) 2.528(1); N(1)–Cu(1)–
S(1) 85.6(2), N(1)–Cu(1)–I(2A) 111.6(1), S(1)–Cu(1)–I(2A) 124.61(6),
N(1)–Cu(1)–I(1A) 116.0(1), S(1)–Cu(1)–I(1A) 98.40(5), I(1A)–Cu(1)–
I(2A) 116.87(3), N(2)–Cu(2)–I(2) 122.5(1), N(2)–Cu(2)–I(1) 117.4(1),
I(1)–Cu(2)–I(2) 119.63(3). (Symmetry code: A Ϫx, Ϫy, Ϫz ϩ 1.)
two ligands were linked together by two Cu2I2 cores, which led
to the formation of a centrosymmetric-tetranuclear complex.
Each Cu2I2 core consisted of a three-coordinate and a four-
coordinate Cu() ion, which is the least common arrangement
for Cu2I2 bridged species. One three-coordinate and one
four-coordinate metal centre was bound to each ligand. Each
three-coordinate Cu() ion adopted a distorted trigonal-planar
arrangement with a coordination sphere provided by an NI2
donor set. The four-coordinate Cu() ions adopted a distorted
tetrahedral arrangement with a coordination sphere consisting
of two bridging IϪ ions, one N and one S donor. The Cu() ions
within each Cu2I2 core were separated by 2.528(1) Å, which was
similar to the short distance found for 1. The ligands in 2 were
in an endo–anti conformation with the pyridine rings tilted at
14Њ to each other, similar to that found in 1. However, in con-
trast to 1, the thioether S donors each were bound to only one
of the available metal centres. The distance of 3.384(2) Å
between the trigonal Cu centre and the adjacent S donor was
too long for any bonding interaction to exist between them. The
ligands were also oriented in a head-to-tail arrangement such
Synthesis and structure of [Cu4(L2)2I4] 2
The 1 : 1 molar reaction of CuI and L2 in MeCN gave a yellow
solution from which a yellow powder was isolated in low yield.
The complex had a microanalysis consistent with a 2 : 1 metal-
to-ligand ratio. Subsequently the same yellow powder was
obtained from the 2 : 1 molar reaction of CuI and L2 in good
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J. Chem. Soc., Dalton Trans., 2002, 1581–1585

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that the methyl arms on the ligands were diametrically opposite
to each other. There were no significant interactions between
adjacent tetranuclear complexes suggesting that weak non-
descript van der Waals interactions controlled the packing.
centroid distance of 3.78 Å.22 Each folded ligand was coordin-
ated to two different Cu centres on the same CuI chain and
stacked along the outside of that chain. In addition, very weak
intermolecular C–H ؒ ؒ ؒ pyridine ring interactions (2.95 and
3.09 Å) existed between the ligands on the outside of
the chains.24 Although the pyridine rings of parallel one-
dimensional chains interdigitated there were no significant
intermolecular interactions.
Synthesis and structure of [Cu2(L3)I2]∞ 3
The reaction of CuI with L3 in a 2 : 1 molar ratio in MeCN gave
a brown solid. Microanalysis showed the complex was consist-
ent with a 2 : 1 metal-to-ligand ratio. In contrast to 1 and 2, the
1 : 1 CuI complex with L3 has been isolated and crystal-
lographically characterised as a discrete Cu2I2 bridged dimer.23
The 1H NMR spectrum of 3 in CDCl3 was consistent with a
symmetrical complex. In addition, the presence of only one
methylene signal at 4.05 ppm indicated that fluxional processes
were occurring in solution at 298 K. Electrospray mass spec-
trometry under normal operating conditions in MeCN–H2O
(1 : 1 v/v) showed five major peaks which had the correct
isotopic patterns for [Cu(L3)]ϩ at m/z 278, [Cu(L3)2]ϩ at 494,
[Cu2(L3)2I]ϩ at 686, [Cu3(L3)2I2]ϩ at 876 and [Cu4(L3)2I3]ϩ at
1066. These results and comparison with 1 and 2 suggested that
a tetranuclear complex might exist in solution. Surprisingly,
X-ray structure analysis showed that 3 existed as a one-
dimensional polymer rather than the remaining member of a
set of discrete tetranuclear complexes.
Comparison
The sequential removal of Me groups from L1 had a dramatic
effect upon the nature of the complexes formed. The most
surprising result of all was the structure of 3, which was poly-
meric rather than discrete and tetranuclear as in 1 and 2. One
of the major differences between the three structures was the
conformation of the ligands. In 1 and 2 the ligands adopted anti
configurations which appeared to dictate formation of tetra-
nuclear species, while in 3 the ligand adopted a syn config-
uration which allowed intramolecular π-stacking to occur. The
presence of Me groups on the pyridyl rings of the ligands in 1
and 2 may have prevented the π-stacking which resulted in
polymer formation for 3. While the different ligand conform-
ations may have led to either tetranuclear or polymeric struc-
ture formation, the differences in coordination for 1 and 2 were
not explained by such arguments. These differences may have
been due to other more subtle electronic and steric effects. The
electronic effect of the Me group on the pyridine ring could
have increased the electron density in the aromatic ring and
made the pyridyl nitrogen a stronger donor. Hence, this could
have caused a Cu atom coordinated to a Me-substituted pyridyl
nitrogen to be more strongly bound than if it was coordinated
to a non-substituted pyridyl nitrogen. This would mean that
the more electron deficient Cu centre might be expected to
coordinate to another donor atom, S in this case, if it was
coordinated to the less strongly donating non-substituted
pyridyl nitrogen. This was exemplified by structures 2 and 3.
However, a complication appeared to arise for 1 where despite
the presence of the Me groups on the pyridyl rings, the Cu
atoms were coordinated to the S donors. This complication
might be explained by steric considerations.
In the structure of 3 the asymmetric unit contained one
ligand, two Cu() ions and two IϪ ions. Two zigzag CuI chains
were arranged parallel to each other such that alternating
Cu(1)–I(1)–Cu(2) and Cu(1)–I(2)–Cu(2) angles were acute and
obtuse, respectively (Fig. 4). The chains propagated along the
It is our belief that in the case of 1, if electronic effects were
predominant, the S atoms should have remained unbound and
the ligand would have adopted an exodentate arrangement.
However, this would then have meant that the Me substituents
clashed unfavourably with the CuI core. Consequently, steric
effects caused the ligand to adopt an endodentate conformation
through coordination of the S donors and so these unfavour-
able interactions were avoided.
It can be concluded that the Me groups were non-innocent
and were responsible for affecting the gross structure of the
complexes through a mix of electronic and steric effects. There-
fore, the placement of Me-substituents on ligands should be
given some careful consideration in the construction of
coordination complexes and arrays.
Fig. 4 Perspective view (crystallographic numbering) of 3. Thermal
ellipsoids are drawn at the 50% probability level. Selected bond lengths
(Å) and angles (Њ): Cu(1)–N(1) 2.024(4), Cu(1)–S(1) 2.515(2), Cu(1)–
I(1) 2.529(1), Cu(1)–I(2A) 2.588(1), Cu(2)–N(2) 2.055(3), Cu(2)–S(1B)
2.292(2), Cu(2)–I(1) 2.661(1), Cu(2)–I(2) 2.672(2), Cu(1) ؒ ؒ ؒ Cu(2)
3.449(2); N(1)–Cu(1)–S(1) 83.0(1), N(1)–Cu(1)–I(1) 116.6(1), S(1)–
Cu(1)–I(1) 120.49(4), N(1)–Cu(1)–I(2A) 119.3(1), S(1)–Cu(1)–I(2A)
96.97(4), I(1)–Cu(1)–I(2A) 114.96(4), Cu(1)–I(1)–Cu(2) 83.25(5),
Cu(1)–I(2A)–Cu(2A) 127.63(4), N(2)–Cu(2)–S(1B) 122.9(1), N(2)–
Cu(2)–I(1) 101.7(1), S(1B)–Cu(2)–I(1) 111.34(4), N(2)–Cu(2)–I(2)
109.8(1), S(1B)–Cu(2)–I(2) 105.77(4), I(1)–Cu(2)–I(2) 103.89(4).
(Symmetry codes: A x ϩ 1, y, z; B 1 Ϫ x, Ϫy, Ϫz.)
Experimental
General
The precursors 2-(chloromethyl)pyridine,15 2-(chloromethyl)-6-
methylpyridine15 and 6-methyl-2-(sulfanylmethyl)pyridine16
and the ligands L1 13 and L3 14 were prepared by literature
methods. The 1H and 13C NMR spectra were recorded on either
a Varian unityINOVA 300 or 500 MHz spectrometer. Elemental
analyses were performed by the Campbell Microanalytical
laboratory at the University of Otago. Electrospray mass
spectra (ES MS) were collected at the University of Waikato in
postive-ion mode with a VG platform II mass spectrometer,
using MeCN–H2O (1 : 1 v/v) as the mobile phase.
a axis and were held together by S donors which bridged
Cu centres on adjacent chains. This gave a one-dimensional
polymer containing a series of centrosymmetric 12-membered
CuICuICuSCuICuICuS trans-bridged rings. Both Cu() ions
adopted distorted tetrahedral geometries. Cu(1) was chelated
by L3 and had a NSI2 donor set and Cu(2) was bound to two
ligands with a NSЈI2 donor set. The ligand L3 was folded in a
syn fashion with the pyridine rings tilted by 20.3Њ with respect
to each other and with an intramolecular π-stacking centroid–
J. Chem. Soc., Dalton Trans., 2002, 1581–1585
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Table 1 Crystallographic data for complexes 1, 2 and 3
1
2
3
Molecular formula
M
C28H32Cu4I4N4S2
1250.46
C26H28Cu4I4N4S2
1222.40
(C24H24Cu4I4N4S2)∞
1194.36
Crystal system
Space group
Triclinic
P1
Monoclinic
P21/n
Triclinic
P1
¯
¯
a/Å
b/Å
c/Å
α/Њ
9.351(5)
10.314(5)
10.441(5)
105.338(5)
102.112(5)
102.073(5)
1049.9(4)
1
10.354(5)
16.245(5)
10.528(5)
7.854(5)
9.670(5)
11.468(5)
78.079(5)
70.344(5)
69.319(5)
763.6(7)
1
β/Њ
100.080(5)
γ/Њ
U/Å3
1744(1)
2
Z
T /K
163(2)
5.829
168(2)
6.091
123(2)
6.951
µ/mmϪ1
Reflections collected
Unique reflections (Rint
R1 indices [I > 2σ(I )]
wR2 (all data)
11726
3680 (0.0196)
0.0273
21993
6386
3462 (0.0278)
0.0287
)
3508 (0.0251)
0.0370
0.1050
0.0708
0.0634
Ligand preparation
7.5 Hz], 4.11(2H, s), 3.97 (2H, s) and 3.02 (3H, s); ES MS: m/z
294 [Cu(L2)]ϩ, 523 [Cu(L2)2]ϩ and 714 [Cu2(L2)2I]ϩ.
2-(6-Methylpyridyl)methyl(2-pyridyl)methylsulfide (L2). 6-
Methyl-2-(sulfanylmethyl)pyridine (4.0 g, 0.028 mol) was added
to degassed MeOH (250 mL) containing 0.60 g (0.028 mol) of
Na metal and was stirred for 1 h. 2-(Chloromethyl)pyridine
(3.6 g, 0.028 mol) was added to the above solution, refluxed for
4 h and stirred overnight. The resulting solution was reduced in
volume to give a brown residue, which was dissolved in CH2Cl2
(100 mL), washed with H2O (2 × 100 mL), dried (MgSO4) and
reduced again to give a crude oil (yield 5.1 g, 80%). Treatment
of the crude product (2.7 g) on a silica gel column (5% hydrated
[Cu2(L3)I2]∞ 3. CuI (176 mg, 0.924 mmol) dissolved in
degassed MeCN (20 mL) was added via cannula to L3 (100 mg,
0.462 mmol) dissolved in degassed MeCN (20 mL) and allowed
to stir overnight. The tan precipitate which resulted was filtered
and dried in vacuo (yield 154 mg, 55.8%). Dark brown crystals
were grown from the slow diffusion of diethyl ether into a con-
centrated solution of the complex in MeCN. (Found: C, 24.8;
H, 1.9; N, 5.5; S, 5.4. Calc. for C24H24N4S2Cu4I4ؒ1/2CH3CN: C,
24.7; H, 2.1; N, 5.2; S, 5.3%); 1H NMR (CDCl3): δ 8.94 [2H, d,
v/v) eluted with CH2Cl2–CHCl3 (6 : 4 v/v) gave L2 as a golden
3
4
3J(HH) 5.1, py-H], 7.71 [2H, dt, J(HH) 7.5, J(HH) 1.8 Hz,
py-H], 7.32 [4H, m, py-H] and 4.05 (4H, s, CH2); ES MS:
m/z 278 [Cu(L3)]ϩ, 494 [Cu(L3)2]ϩ, 686 [Cu2(L3)2I]ϩ, 876
[Cu3(L3)2I2]ϩ and 1066 [Cu4(L3)2I3]ϩ.
oil (0.94 g, 35%). (Found: Mϩ, 231.0963,
C
1H1514N232S
13
12
requires M, 231.0956); 1H NMR (CDCl3): δ 8.52 [1H, d, 3J(HH)
4.0], 7.61 [1H, t, 3J(HH) 7.5], 7.48 [1H, t, 3J(HH) 7.5], 7.36 [1H,
3
3
3
d, J(HH) 7.5], 7.16 [1H, d, J(HH) 7.5], 7.13 [1H, dd, J(HH)
7.5, 4.0], 6.98 [1H, d, 3J(HH) 7.5 Hz], 3.81 (2H, s), 3.77 (2H, s)
and 2.52 (3H, s); 13C NMR (CDCl3): δ 158.4, 157.9, 157.5,
149.2, 136.8, 136.5, 123.2, 121.8, 121.4, 120.1, 37.6, 37.5 and
24.3.
X-Ray crystallography
Diffraction data for 1 and 2 were collected on a Bruker SMART
CCD diffractometer and data for 3 were collected on a Nonius
Kappa-CCD diffractometer, both had graphite mono-
chromated Mo-Kα (λ = 0.71073 Å) radiation. Intensities were
corrected for Lorentz-polarisation effects25 and for 1 and 2 a
multiscan absorption correction26 was applied. The structures
were solved by direct methods (SHELXS)27 and refined on
F 2 using all data by full-matrix least-squares procedures
(SHELXL 97).28 All calculations were performed using the
WinGX interface.29 For 2 a large peak, possibly a Fourier
ripple, of 3.2 e ÅϪ3 was located at 1.0 Å from an I atom. Crystal-
lographic data for the three structures are listed in Table 1.
CCDC reference numbers 176214–176216.
Complexes
[Cu4(L1)2I4] 1. CuI (156 mg, 0.819 mmol) dissolved in
degassed MeCN (20 mL) was added via cannula to L1 (100 mg,
0.409 mmol) dissolved in degassed MeCN (20 mL) and allowed
to stir for 1 h. The yellow solution was reduced in volume,
diethyl ether was added and a tan powder was isolated (yield
129 mg, 50.4%). Pale yellow–green crystals were grown from the
slow diffusion of diethyl ether into a concentrated solution of
the complex in MeCN. (Found: C, 27.3; H, 2.7; N, 4.4; S, 5.1.
Calc. for C28H32N4S2Cu4I4: C, 26.9; H, 2.6; N, 4.5; S, 5.1%); 1H
NMR (CD3CN): δ 7.67 [2H, t, 3J(HH) 7.5], 7.24 [2H, d, 3J(HH)
7.5], 7.21 [2H, d, 3J(HH) 7.5 Hz], 4.09 (4H, s) and 2.83 (6H, s);
ES MS: m/z 308 [Cu(L1)]ϩ, 553 [Cu(L1)2]ϩ, 743 [Cu2(L1)2I]ϩ, 934
[Cu3(L1)2I2]ϩ and 1124 [Cu4(L1)2I3]ϩ.
See http://www.rsc.org/suppdata/dt/b1/b111400j/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
We thank Professor Ward T. Robinson and Dr Jan Wikaira
(University of Canterbury) for X-ray data collection, Associate
Professor Bill Henderson (University of Waikato) for electro-
spray data and the University of Otago for financial support.
[Cu4(L2)2I4] 2. CuI (83 mg, 0.44 mmol) dissolved in degassed
MeCN (20 mL) was added via cannula to L2 (50 mg, 0.22
mmol) dissolved in degassed MeCN (20 mL) and allowed to stir
for 1 h. The yellow solution was reduced in volume, diethyl
ether was added and a yellow powder was isolated (yield 100
mg, 75%). Pale yellow crystals were grown from the slow diffu-
sion of diethyl ether into a concentrated solution of the com-
plex in MeCN. (Found: C, 25.7; H, 2.1; N, 4.6; S, 5.2. Calc. for
References
1 B. J. Hathaway, in Comprehensive Coordination Chemistry, eds.
G. Wilkinson, R. D. Gillard and J. A. McCleverty, Pergamon,
Oxford, 1987, vol. 5, p. 533.
2 (a) A. J. Blake, N. R. Brooks, N. R. Champness, L. R. Hanton,
P. Hubberstey and M. Schröder, Pure Appl. Chem., 1998, 70, 2351;
(b) M. Munakata, T. Kuroda-Sowa, M. Maekawa, A. Honda and
S. Kitagawa, J. Chem. Soc., Dalton Trans., 1994, 2771.
1
C26H28N4S2Cu4I4: C, 25.5; H, 2.3; N, 4.6; S, 5.3%); H NMR
3
3
(CD3CN): δ 8.95 [1H, d, J(HH) 4.2], 7.70 [1H, t, J(HH) 7.5],
3
3
7.60 [1H, t, J(HH) 7.5], 7.37 [1H, d, J(HH) 7.5], 7.35 [1H, d,
3J(HH) 7.5], 7.18 [1H, dd, 3J(HH) 7.5, 4.2], 7.03 [1H, d, 3J(HH)
1584
J. Chem. Soc., Dalton Trans., 2002, 1581–1585

View Article Online
3 S. Ramaprabhu, N. Amstutz, E. A. C. Lucken and G. Bernardinelli,
J. Chem. Soc., Dalton Trans., 1993, 871; G. L. Soloveichik,
O. Eisenstein, J. T. Poulton, W. E. Strieb, J. C. Huffman and
K. G. Caulton, Inorg. Chem., 1992, 31, 3306; M. R. Churchill and
F. J. Rotella, Inorg. Chem., 1979, 18, 166; J. A. Campbell, C. L.
Raston and A. H. White, Aust. J. Chem., 1977, 30, 1937.
4 P. D. Aknvos, S. K. Hadjikakou, P. Karagiannidis, D. Nemtzafos
and A. Terzis, Inorg. Chim. Acta, 1993, 206, 163; J. T. Gill, J. J.
Mayerle, P. S. Welcker, D. F. Lewis, D. A. Ucko, D. J. Barton,
D. Stowens and S. J. Lippard, Inorg. Chem., 1976, 15, 1155.
5 R. Turpin, N. Bruno, J.-P. Legros and P. Castan, Inorg. Chim. Acta,
1998, 271, 217; S. Kubo, T. Nishioka, K. Ishikawa, I. Kinoshita and
K. Isobe, Chem. Lett., 1998, 1067; N. P. Rath, E. M. Holt and
K. Tanimura, J. Chem. Soc., Dalton Trans., 1986, 2303;
M. R. Churchill, G. Davies, M. A. El-Sayed, J. A. Fournier,
J. P. Hutchinson and J. A. Zubieta, Inorg. Chem., 1984, 23, 783.
6 A. J. Blake, N. R. Brooks, N. R. Champness, P. A. Cooke,
A. M. Deveson, D. Fenske, P. Hubberstey, W.-S. Li and M. Schröder,
J. Chem. Soc., Dalton Trans., 1999, 2103.
12 L. R. Hanton and K. Lee, Inorg. Chem., 1999, 38, 1634.
13 A. Diebold, N. Kyritsakas, J. Fischer and R. Weiss, Acta
Crystallogr., Sect. C, 1996, 52, 632.
14 H. J. J.-B. Martel and M. Rasmussen, Tetrahedron Lett., 1971, 41,
3843.
15 G. E. Jeromin, W. Orth, B. Rapp and W. Weiß, Chem. Ber., 1987,
120, 649.
16 E. C. Constable, A. C. King and P. R. Raithby, Polyhedron, 1998, 17,
4275.
17 A. L. E. Stoffels, W. G. Haanstra, W. L. Driessen and J. Reedijk,
Angew. Chem., Int. Ed. Engl., 1990, 29, 1419.
18 H. Cheng, D. Chun-ying, F. Chen-jie, L. Yong-jiang and
M. Qing-jin, J. Chem. Soc., Dalton Trans., 2000, 1207.
19 C.-Y. Su, B.-S. Kang and J. Sun, Chem. Lett., 1997, 821.
20 F. H. Allen, J. E. Davies, J. J. Galloy, O. Johnson, O. Kennard,
C. F. Macrae, E. M. Mitchell, G. F. Mitchell, J. M. Smith and
D. G. Watson, J. Chem. Inf. Comput. Sci., 1987, 31, 187.
21 L. R. Hanton, C. Richardson, W. T. Robinson and J. M. Turnbull,
Chem. Commun., 2000, 2465.
7 (a) P. C. Healy, J. D. Kildea and A. H. White, Aust. J. Chem., 1989,
42, 137; (b) L. M. Engelhardt, P. C. Healy, J. D. Kildea and
A. H. White, Aust. J. Chem., 1989, 42, 107; (c) J. C. Dyason,
L. M. Engelhardt, P. C. Healy, C. Pakawatchai and A. H. White,
Inorg. Chem., 1985, 24, 1950; (d ) P. C. Healy, C. Pakawatchai,
C. L. Raston, B. W. Skelton and A. H. White, J. Chem. Soc., Dalton
Trans., 1983, 1905.
8 (a) A. J. Pallenberg, K. S. Koenig and D. M. Barnhart, Inorg. Chem.,
1995, 34, 2833; (b) G. A. Bowmaker, P. C. Healy, D. L. Kepert,
J. D. Kildea, B. W. Skelton and A. H. White, J. Chem. Soc., Dalton
Trans., 1989, 1639; (c) L. M. Engelhardt, C. Pakawatchai,
A. H. White and P. C. Healy, J. Chem. Soc., Dalton Trans., 1985, 117;
(d ) P. C. Healy, C. Pakawatchai and A. H. White, J. Chem. Soc.,
Dalton Trans., 1983, 1917.
22 C. Janiak, J. Chem. Soc., Dalton Trans., 2000, 3885.
23 P. L. Caradoc-Davies, D. H. Gregory, L. R. Hanton and
J. M. Turnbull, J. Chem. Soc., Dalton Trans., 2002, DOI: 10.1039/
b111176k.
24 Y. Umezawa, S. Tsuboyama, K. Honda, J. Uzawa and M. Nishio,
Bull. Chem. Soc. Jpn., 1998, 71, 1207; M. Nishio, Y. Umezawa,
M. Hirota and Y. Takeuchi, Tetrahedron, 1995, 51, 8665.
25 SAINT V4, Area Detector Control and Integration Software,
Siemens Analytical X-Ray Systems Inc., Madison, WI, 1996;
DENZO-SCALEPACK Z. Otwinowski and W. Minor, Processing
of X-ray Diffraction Data Collected in Oscillation Mode, Methods in
Enzymology, Macromolecular Crystallography, eds., C. W. Carter, Jr.
and R. M. Sweet, Academic Press, 1997, vol. 276, part A,
pp. 307–326.
9 L. R. Hanton and K. Lee, J. Chem. Soc., Dalton Trans., 2000, 1161.
10 P. L. Caradoc-Davies and L. R. Hanton, Chem. Commun., 2001,
1098.
11 P. L. Caradoc-Davies, L. R. Hanton and W. Henderson, J. Chem.
Soc., Dalton Trans., 2001, 2749.
26 G. M. Sheldrick, SADABS, Program for Absorption Correction,
University of Göttingen, 1996.
27 G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467.
28 G. M. Sheldrick, SHELXL 97, University of Göttingen, 1997.
29 L. J. Farrugia, J. Appl. Crystallogr., 1999, 32, 837.
J. Chem. Soc., Dalton Trans., 2002, 1581–1585
1585