Synthesis of pyridazinyl ligands for multimetallic complexes

Article abstract of DOI:10.1039/b611561f

A family of ligands based upon the linking of two or three bis-(2-pyridyl)pyridazine (dppz) moieties via the 4- or 4,5-positions of the pyridazine rings has been synthesised using an inverse electron demand Diels-Alder pathway. Thus, reaction of 3,6-di(2-

Full text of DOI:10.1039/b611561f

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Synthesis of pyridazinyl ligands for multimetallic complexes
´
Frederic Thebault, Alexander J. Blake, Claire Wilson, Neil R. Champness* and
Martin Schroder*
´
´
¨
Received (in Montpellier, France) 10th August 2006, Accepted 4th September 2006
First published as an Advance Article on the web 15th September 2006
DOI: 10.1039/b611561f
A family of ligands based upon the linking of two or three bis-(2-pyridyl)pyridazine (dppz)
moieties via the 4- or 4,5-positions of the pyridazine rings has been synthesised using an inverse
electron demand Diels–Alder pathway. Thus, reaction of 3,6-di(2-pyridyl)-1,2,4,5-tetrazine (dptz)
with a series of dienes (1,4-divinylbenzene, 1,5-cyclooctadiene, norbornadiene, 1,5-hexadiene or
1,4-cyclohexadiene), diketones (1,4-diacetylbenzene), or trienes (trans,trans,cis-1,5,9-
cyclododecatriene or trans,trans,trans-1,5,9-cyclododecatriene) has been studied and seven ligands
isolated, namely 4,40-(1,4-phenylene)bis(3,6-dipyridin-2-ylpyridazine) (L1), 5,6,11,12-tetrahydro-
1,4,7,10-tetrapyridin-2-ylcycloocta[1,2-d:5,6-d0]dipyridazine (L2), 5,10-methano-1,4,6,9-
tetrapyridin-2-ylpyridazino[4,5-g]phthalazine (L3), 4,40-ethane-1,2-diylbis(3,6-dipyridin-2-
ylpyridazine) (L4), 1,4,6,9-tetrapyridin-2-ylpyridazino[4,5-g]phthalazine (L5), cyclododeca
[1,2-d:5,6-d0]dipyridazine-(11Z)-5,6,11,12,15,16-hexahydro-1,4,7,10-tetrapyridin-2-yl (L6) and
5,6,11,12,17,18-hexahydro-1,4,7,10,13,16-hexapyridin-2-ylcyclododeca[1,2-d:5,6-d0:9,10-d00]
tripyridazine (L7). Compounds L1, L2 and L4 have been characterised by single crystal X-ray
diffraction revealing the formation of molecular stacking in the solid-state via p–p interactions
between dppz moieties. The potential of these ligands to form multimetallic complexes has been
demonstrated by the successful synthesis and structural characterisation of
{[Cu4(L1)(NO3)6(MeO)2(MeOH)2]}, {[Cu4(L1)(NO3)6(MeO)2(EtOH)2]},
{[Cd(NO3)(EtOH)3][Cd(NO3)3(L2)]} and {[Cd(NO3)2]2(L5)3}.
Stille- or Suzuki-coupling reactions between suitably functio-
Introduction
nalised aryl groups and dihalopyridazine derivatives,12 or via
‘‘inverse electron demand’’ Diels–Alder reactions with 1,2,4,5-
tetrazines.8 We adopted the latter approach to the synthesis of
new pyridazines via reaction of 3,6-diaryl-1,2,4,5-tetrazines
with alkenes or carbonyl moieties, and report herein the
synthesis, and in some instances the structural characterisa-
tion, of a set of new ligands that consist of two 3,6-di
(2-pyridyl)-1,2-pyridazine (dppz) units separated by a variety
of spacers (Scheme 1). In addition, attempts to prepare ligands
with more than two dppz groups will be discussed. In all cases,
the ligands were synthesised from 3,6-di(2-pyridyl)-1,2,4,5-
tetrazine (dptz) through an inverse electron demand Diels–
Alder reaction with alkene or carbonyl groups. Finally, some
complexation reactions are reported which illustrate the po-
tential of these ligands to generate multimetallic arrays.
The synthesis of multimetallic arrays is an area of research that
has received considerable attention over recent years due, in
part, to potential applications in information storage,1 magnetic
arrays,2 porous hosts3 and light-harvesting devices.4 The synth-
esis of multimetallic arrays requires careful design of ligands
that encourage divergent co-ordination processes, and several
successful synthetic protocols have been reported with a variety
of ligand types, with perhaps the greatest variety of ligand
systems based upon N-heterocyclic donor ligands, including
polypyridyl systems.5 Ligands that contain aryl rings with
multiple N-donor atoms such as pyridazine, pyrazine, and
tetrazine can lead to increased proximity of metal cations in
multimetallic complexes and may generate enhanced interme-
tallic interactions. Pyridazine has, therefore, been used for the
construction of multimetallic arrays, most notably grids.6
A
variety of synthetic strategies for the preparation of substituted
pyridazines has been reported, but perhaps one of the most
interesting is via reaction of 1,2,4,5-tetrazines with alkenes.7,8
Indeed, we and others have extensively studied pyridyl-9 or
pyrazinyl-10,11 substituted 1,2,4,5-tetrazines as ligands for gen-
erating multimetallic arrays including co-ordination polymers.
The synthesis of substituted pyridazine derivatives can be
performed either via heteroaryl-coupling reactions, typically
Results and discussion
We have prepared a variety of ligands containing two dppz
units via Diels–Alder reactions between dptz and a series of
dialkenes and diketones. A typical reaction involved stirring of
dptz with a dialkene in a 4 : 1 stoichiometry in a non-polar
solvent, typically toluene or CHCl3. Although the excess of
dptz serves primarily to improve the yield of each reaction, it
also has the effect of partially dehydrogenating the initial
product of reaction. However, this dehydrogenation process
was always incomplete, and addition of an oxidising agent
such as [bis(trifluoroacetoxy)iodo]benzene was necessary to
School of Chemistry, University of Nottingham, University Park,
Nottingham, UK NG7 2RD. E-mail:
Neil.Champness@nottingham.ac.uk; M.Schroder@nottingham.ac.uk
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found to be a very clean and efficient reagent in the systems
studied. Final products were purified either by column chro-
matography using acetonitrile or a toluene–acetone mixture
(1 : 1) as eluent, or in some instances by precipitation from
acetone. The reactions and products for the synthesis of di-
dppz reactions are summarised in Scheme 2.
Reaction of dptz with 1,4-divinylbenzene or 1,4-diacetyl-
benzene affords L1 in some 18% yield. Whereas the reaction
using 1,4-divinylbenzene as starting reagent requires oxidation
using [bis(trifluoroacetoxy)iodo]benzene, the corresponding
reaction with 1,4-diacetylbenzene requires only dehydration
using para-toluenesulfonic acid.14 These reactions can be
performed under reflux or by stirring at room temperature,
and the yields are similar in both cases, but the latter route
requires longer reaction times.
Scheme 1 Structure of the ligands used in this study.
complete the reaction. The choice of [bis(trifluoroacetoxy)
iodo]benzene as oxidant follows a previously described proce-
dure for related compounds.13 Although other oxidants can be
used, such as ddq,8 [bis(trifluoroacetoxy)iodo]benzene was
L1 was structurally characterised by single crystal X-ray
diffraction as discussed below. Commercial 1,4-divinylbenzene
can be purchased either in 99%+ purity or, more economically,
Scheme 2 Synthetic approaches to ligands L1–L7. All procedures were carried out using toluene as solvent and [bis(trifluoroacetoxy)iodo]benzene
as oxidant. Where appropriate, yields are indicated in parentheses for each ligand.
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vatives with norbornadiene is an effective synthetic pathway to
unsubstituted pyridazine derivatives.15 The formation of these
by-products cannot be completely avoided even at low tem-
perature, and this complicates the purification procedures for
L3. However, a method that minimises by-product formation
is to oxidise the reaction product with [bis(trifluoroacetoxy)
iodo]benzene immediately after the initial mixing of the dptz
and norbornadiene, thus inhibiting the proton rearrangement
required for the formation of L3a or L3b. However, it is also
important to note that dptz itself can potentially be oxidised to
an oxadiazole16 that similarly has to be separated from the
reaction mixture. This means that L3 only ever forms in very
low yield, typically less than 1%, and, although the presence of
L3 in reaction mixtures can be confirmed by 1H NMR spectro-
scopy and by mass spectrometry, our studies confirmed that
this synthetic route is, on balance, not viable.
In contrast, the formation of L4 from dptz and 1,5-hexa-
diene was found to be successful only under refluxing condi-
tions. The product L4 was readily extracted and purified by
precipitation from acetone. However, when the reaction was
carried out by stirring at room temperature and followed by
mass spectrometry, a stepwise pathway via the formation of
mono and the di-substituted products (291 m/z and 499 m/z,
respectively) prior to the final oxidation step can be discerned
(Scheme 5). We were unable to fully characterise these inter-
mediates which decompose to yield yellow precipitates.
The synthesis of L5 via reaction of dptz with 1,4-cyclohexa-
diene can be performed under reflux or at room temperature,
both reactions leading to the same product in similar yield. In
this case, oxidation with [bis(trifluoroacetoxy)iodo]benzene
forms the planar tetraazaanthracene species L5.
Scheme 3 By-product L1a resulting from the reaction between dptz
and 4-ethylvinylbenzene.
in 80% purity, with the remaining 20% being mostly 4-ethyl-
vinylbenzene. This mixture also affords the desired product L1,
but in combination with a secondary by-product L1a (Scheme
3). However, since L1a can be readily removed from the reaction
product by recrystallisation from acetone, this offers the possi-
bility of a more economical route to L1.
The preparations of L2–L5 proceed similarly via reaction of
dptz with 1,5-cyclooctadiene (for L2), norbornadiene (for L3),
1,5-hexadiene (for L4) or 1,4-cyclohexadiene (for L5) (Scheme
2). In each case [bis(trifluoroacetoxy)iodo]benzene was used as
oxidant to afford the desired di-dppz product. However,
certain details of the synthetic procedure merit some elabora-
tion. In the case of L3, the reaction can only be carried out
successfully at ambient or lower temperature (0 1C is favoured)
because competing pathways lead to the formation of different
products (Scheme 4). The reactions that produce the two by-
products L3a and L3b are favoured at higher temperature and
involve proton rearrangement followed by cyclopentene elim-
ination. Indeed, refluxing dptz or other 1,2,4,5-tetrazine deri-
Scheme 4 Synthesis of L3. At room temperature the formation of L3 is favoured over the formation of the elimination products L3a and L3b
.
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Scheme 5 Stepwise formation of L4.
Attempts to prepare ligands containing three or four dppz
moieties
idine and pyridazine rings were found to be 3.7897(5) A (L1),
3.779(1) A (L1 ꢁ 4CHCl3) and 3.8449(3) A (L4), with dihedral
angles of 12.091 (L1), 3.981 (L1 ꢁ 4CHCl3) and 12.841 (L4)
confirming the presence of p–p interactions within the col-
umns. In the cases of L1 and L1 ꢁ 4CHCl3, the central rings of
each ligand are not involved in p–p interactions, with cen-
troid–centroid distances of 6.239(2) A and 7.656(1) A, respec-
tively. For L2, centroid–centroid distances between pyridine
rings were measured to be 3.747(7) A with dihedral angles of
01. In this case, p–p interactions are not located within
columns but between adjacent ones. It is worth noting that
both molecules L2 and L4 adopt a ‘‘stair-like’’ conformation
with respect of the central ring with each pyridazine ring on
each side of the octyl ring parallel to one another (Fig. 1c).
Reaction of dptz with two isomers of 1,5,9-cyclododecatriene,
trans,trans,cis-1,5,9-cyclododecatriene and trans,trans,trans-
1,5,9-cyclododecatriene afforded disubstituted L6 and (in ex-
tremely low yield) trisubstituted L7, respectively (Scheme 2).
The difference in reactivity is linked to 1,5,9-cyclododecatriene
having either trans or cis arrangements of the alkene group.
Thus, the di-dppz product L6 is formed when there are two
trans-alkenes present in the starting substrate; the third Diels–
Alder reaction at the cis-alkene of trans,trans,cis-1,5,9-cyclo-
dodecatriene is then sterically disfavoured resulting in the final
isolation of L6. Reaction between dptz and cyclooctatetraene
afforded an intractable mixture of products which was ana-
lysed by mass spectrometry. These experiments indicated that
products with up to three dppz moieties had been formed but
all attempts to separate the products were unsuccessful in our
hands.
Multi-metallic complexes
Reaction of the above ligands with a range of metal salts was
{[Cu4(L1)(NO3)6(MeO)2
investigated.
Crystals
of
(MeOH)2] ꢁ 1.25(CHCl3) ꢁ 0.5(MeOH)}, 1, were grown by slow
diffusion of a solution of L1 in CHCl3 with a solution of
Cu(NO3)2 ꢁ 2.5H2O in MeOH. Crystals of {[Cu4(L1)(NO3)6
(MeO)2(EtOH)2] ꢁ 1.2(CHCl3)}, 2, were grown by slow
diffusion of solutions of L1 dissolved in CHCl3 with
Cu(NO3)2 ꢁ 2.5H2O in MeOH in the presence of sodium
trimesate dissolved in EtOH. The crystal structures of 1
and 2 are very similar except that the terminal co-ordinated
MeOH ligands in 1 are replaced by EtOH ligands in 2
Single crystal X-ray structures of L1, L2 and L4
L1 could be crystallised in unsolvated and solvated,
L1 ꢁ 4CHCl3, forms. The structure of L2 contains one ligand
molecule along with one molecule of chloroform disordered
over two positions in each asymmetric unit. L4 crystallises as a
DMSO disolvate (Fig. 1a). All these structures exhibit parallel
columns of the dppz-based molecule (Fig. 1b). For L1,
L1 ꢁ 4CHCl3 and L4, centroid–centroid distances between pyr-
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solutions of the metal salt and L2 in a reaction stoichiometry
for Cd : L2 of 4 : 1. In contrast to the structure of un-
co-ordinated L2, in 3 the ligand does not adopt a ‘‘stair’’
conformation for the central eight-membered ring but rather a
‘‘boat’’ conformation with each of the dppz moieties ap-
proaching one another (Fig. 3). The centroid–centroid dis-
tance between the two pyridazine rings is 3.930(4) A with a
dihedral angle of 52.661. Two of the four dimethylene carbon
atoms inside the eight-membered ring are slightly strained with
larger C–C–C angles of 115.31 and 115.61, when compared to
the angles observed in the crystal structure of L2 which are
112.51 and 113.91. The complex consists of a single molecule of
L2 bound to two Cd(II) cations that occupy co-ordination sites
that are diametrically opposite one another on the ligand,
which is folded in a syn arrangement. Two different Cd(II)
environments are observed [Fig. 3(b); Table 2] with Cd(1)
adopting a hepta-co-ordinate environment bound by two
N-pyridyl/N-pyridazine donors, three ethanol molecules and
one bidentate nitrate anion (Fig. 3b). The other Cd(II) cation,
Cd(2) is octa-co-ordinate with two N-pyridyl/N-pyridazine
donors and three bidentate nitrate anions. The asymmetric
nature of 3 means that Cd(1) and the nitrate anion co-
ordinated to it have a formal monopositive charge whereas
Cd(2) and the three nitrate anions co-ordinated to it are
formally mono-negatively charged. Thus, 3 is zwitterionic
which in part explains the somewhat surprising boat confor-
mation observed for the central eight-membered ring of L2.
A second Cd(NO3)2-based complex has been obtained by
the growth of single crystals of {[Cd(NO3)2]2(L5)3}, 4, from the
slow diffusion of a solution of L5 in CHCl3 into a solution of
Cd(NO3)2 ꢁ 4H2O in MeOH in a reaction stoichiometry for
Cd : L5 of 4 : 1. The structure of 4 contains discrete complexes
that consist of three molecules of L5 bridged by two Cd(II)
centres (Fig. 4). The two Cd(II) cations are related by symme-
try and sit in a distorted cubic co-ordination sphere with four
N-pyridyl/N-pyridazine donors and two bidentate nitrate an-
ions (Table 2). Within each complex, centroid–centroid dis-
tances between pyridazine rings are 3.412(1) A with a dihedral
angle between aromatic rings of 12.181, thus indicating strong
p–p interactions. Between adjacent complexes, the cen-
troid–centroid distances of 3.653(1) A between pyridazine
rings and a dihedral angle between aromatic rings of 1.121,
reveal weaker p–p interactions.
Fig. 1 (a) View of the single crystal X-ray structure of L4 which
crystallises as a DMSO disolvate; (b) formation of stacks of ligands via
p–p interactions between dppz moieties; (c) view of L2 illustrating the
chair-type conformation adopted by the central eight-membered ring
in the solid state. Displacement ellipsoids are drawn at the 50%
probability level.
(Fig. 2). Selected bond lengths and angles for 1 and 2 are give
in Table 1.
The structure of 1 comprises a single molecule of L1
surrounded by four Cu(II) centres, two at each end of L1
(Fig. 2a). Two of the Cu(II) cations have square-based pyr-
amidal geometries and are bound to two N-pyridyl/N-pyrida-
zine donors, one nitrate anion and one bridging methoxide at
the square-base with a nitrate anion at the axial position (Fig.
2c,d). In contrast, the two other Cu(II) centres have a similar
square-based pyramidal co-ordination sphere but with a
MeOH bound at the axial site instead of a nitrate anion.
Moreover, for these two Cu(II) centres there are long-range
interactions to nitrate anion, Cuꢁ ꢁ ꢁO = 2.551(5), 2.658(5) A
with the methoxide group on each side of L1 bridging between
two Cu(II) cations. The contents of each crystallographic
asymmetric unit are completed by solvent chloroform mole-
cules distributed over two partially-occupied sites, and by
solvent methanol molecules over one partially occupied site,
neither of which interact with the metal centres. As only a
single molecule of L1 is bound to each Cu(II) cation the
structure is discrete and not polymeric. A related structure
of a Cu(II) complex of the ligand 3,6-bis(2-pyridyl)-pyridazine
similarly exhibits a bridging oxygen ligand between two Cu(II)
cations, which are in turn co-ordinated to the two bidentate
co-ordination sites of the bis-pyridylpyridazine ligand.17
The complex {[Cd(NO3)(EtOH)3][Cd(NO3)3(L2)]}, 3, was
obtained by reaction of L2 with Cd(NO3)2 ꢁ 4H2O and single
crystals of 3 were grown by slow diffusion of ethanolic
Conclusions
We have demonstrated the successful synthesis of ligands
containing two dppz units joined by a variety of organic
linkers. The ligands have been prepared by the reaction of
the 1,2,4,5-tetrazine group of dptz with a range of dienes, or in
one instance a diketone. In addition, we have explored the
possibility of preparing ligands containing three or four dppz
moieties, but we encountered either very low yields or no
reaction when incorporating more than two dppz groups into
our targets. Thus trans,trans,trans-1,5,9-cyclododecatriene re-
acts with dptz to form the desired tri-dppz product in less than
1% yield, and cis,trans,trans-1,5,9-cyclododecatriene did not
form any tri-dppz product but only the di-dppz species. Solid-
state structural characterisation was carried out for some of
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Fig. 2 Views of the single crystal X-ray structure of (a) 1; (b) 2 showing only one of the disorder components for the atoms on O1; (c), (d) square-
based pyramidal co-ordination spheres of the four Cu(II) cations in 1; (e) square-based pyramidal coordination of Cu(II) centres in 2. Solvent
molecules have been removed for clarity. In the case of (c)–(e) atoms of L1 except for coordinated N-atoms have been removed for clarity.
Displacement ellipsoids are drawn at the 50% probability level.
the free ligands revealing the anticipated molecular conforma-
tions and a strong inclination to form stacks of molecules in
the solid state via p–p interactions between dppz units.
Reactions with Cu(NO3)2 or Cd(NO3)2 gave rise to discrete
metal complexes containing either four Cu(II) or two Cd(II)
cations. The Cu(II) centres incorporate a bridging methoxide
or ethoxide group between metal cations in adjacent bidentate
sites of the dppz groups. In contrast, for Cd(II) complexes,
only one of the bidentate sites on each dppz moiety is
occupied. No examples of co-ordination polymers have been
observed using these ligands, despite the choice of metal
centres known to commonly adopt polymeric structures.18
The facile synthesis of ligands containing two dppz moieties
from readily available tetrazine starting materials makes them
an attractive and potentially highly versatile family of ligands
that may be developed for supramolecular chemistry of multi-
metallic arrays. We are currently seeking to expand the
chemistry reported here.
lyses were carried out by the University of Nottingham School
of Chemistry Microanalysis Service. Infrared spectra were
recorded as KBr pressed disks using a Perkin-Elmer 1600
series FTIR spectrometer. Accurate ES-Mass spectra were
recorded at the National Mass Spectrometry Service Centre
in Swansea.
Syntheses
4,40-(1,4-Phenylene)bis(3,6-dipyridin-2-ylpyridazine) L1. Dptz
(0.5 g, 2.12 mmol) was dissolved in toluene (10 cm3) to give a
deep red solution and 1,4-divinylbenzene (0.1 cm3, 0.7 mmol)
was added to the red solution which was heated under reflux
and turned yellow overnight. After 16 h [bis(trifluoroacetox-
y)iodo]benzene (0.7 g, 1.65 mmol) was added and the solution
was heated under reflux for a further 20 min during which time
the reaction mixture turned black. After cooling to room
temperature aqueous 1 M NaOH (15 cm3) was added and a
viscous black oil formed. The solution was removed and the
black oil was redissolved by stirring with acetone (20 cm3)
at room temperature. The black solution was then left to stand
overnight, and the yellow precipitate which formed was
collected, washed with acetone and dried. The product
was recrystallised from acetone to give a yellow powder (yield
70 mg, 18%). Alternatively, the product can be purified by
Experimental
Starting materials were purchased from Aldrich Chemical
Company or from Lancaster Synthesis and were used without
further purification. 3,6-Di(2-pyridyl)-1,2,4,5-tetrazine was
prepared following the literature procedure.10 Elemental ana-
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Table 1 Selected bond length (A) and angles (1) with s.u.’s for 1 and 2
For 1
Cu(1)–O(1)
Cu(1)–N(2)
Cu(1)–O(4)
Cu(1)–N(1)
Cu(1)–O(2)
Cu(2)–O(1)
Cu(2)–O(8)
Cu(2)–N(4)
Cu(2)–N(3)
Cu(2)–O(10)
Cu(3)–O(12)
Cu(3)–N(5)
Cu(3)–N(6)
Cu(3)–O(18)
Cu(3)–O(16)
Cu(4)–O(12)
Cu(4)–N(7)
Cu(4)–O(21)
Cu(4)–N(8)
Cu(4)–O(13)
1.921(4)
1.992(5)
1.995(4)
2.001(5)
2.309(5)
1.912(4)
1.955(4)
1.992(5)
1.996(5)
2.387(5)
1.898(4)
1.987(5)
2.006(5)
2.012(5)
2.200(6)
1.902(4)
1.984(5)
2.006(4)
2.007(5)
2.215(5)
O(1)–Cu(1)–N(2)
O(1)–Cu(1)–O(4)
N(2)–Cu(1)–N(1)
O(1)–Cu(1)–O(2)
N(1)–Cu(1)–O(2)
O(1)–Cu(2)–O(8)
O(1)–Cu(2)–N(3)
N(4)–Cu(2)–N(3)
O(1)–Cu(2)–O(10)
N(3)–Cu(2)–O(10)
O(12)–Cu(3)–N(6)
N(5)–Cu(3)–N(6)
O(12)–Cu(3)–O(18)
N(6)–Cu(3)–O(18)
O(12)–Cu(3)–O(16)
O(12)–Cu(4)–N(7)
O(12)–Cu(4)–O(21)
N(7)–Cu(4)–N(8)
O(12)–Cu(4)–O(13)
N(7)–Cu(4)–O(13)
87.67(18)
98.47(18)
79.7(2)
91.16(18)
91.6(2)
96.58(18)
89.05(18)
78.99(19)
93.24(19)
84.71(19)
88.61(18)
78.4(2)
97.5(2)
144.2(2)
99.9(2)
88.16(19)
97.82(19)
78.9(2)
95.1(2)
116.0(2)
For 2
Cu1–N1
Cu1–N2
Cu1–O2
Cu1–O4
Cu1–O10
1.975(5)
2.004(5)
1.973(4)
2.332(5)
1.904(4)
Cu2–N3
Cu2–N4
Cu2–O9
Cu2–O10
Cu2–O11
2.008(5)
2.005(6)
1.972(4)
1.912(4)
2.279(5)
O10–Cu1–O2
O10–Cu1–N1
O2–Cu1–N1
O10–Cu1–N2
O2–Cu1–N2
N1–Cu1–N2
O10–Cu1–O4
O2–Cu1–O4
N1–Cu1–O4
N2–Cu1–O4
96.66(18)
162.7(2)
97.9(2)
89.01(18)
166.98(19)
78.8(2)
92.07(19)
81.43(18)
99.28(19)
86.67(19)
O10–Cu2–O9
O10–Cu2–N4
O9–Cu2–N4
O10–Cu2–N3
O9–Cu2–N3
N4–Cu2–N3
O10–Cu2–O11
O9–Cu2–O11
N4–Cu2–O11
N3–Cu2–O11
98.46(19)
167.68(18)
93.3(2)
88.49(18)
168.3(2)
79.3(2)
88.71(19)
96.7(2)
93.6(2)
Fig. 3 (a) View of the structure of 3 illustrating the unusual boat
conformation and showing only one of the disorder components for
the atoms on O1; (b) view of the two Cd(II) coordination spheres in 3.
Atoms of L2 except for coordinated N-atoms have been removed for
clarity. Displacement ellipsoids are drawn at the 50% probability
level.
92.8(2)
as described above to afford L1 as a yellow powder (yield
70 mg, 12%).
column chromatography (silica gel 60, 5 cm column, diameter 2
cm, acetone). Found (calc. for C34H22N8 ꢁ H2O) (%): C 72.64
(72.84), H 4.15 (4.31), N 19.89 (19.99). 1H-NMR (CDCl3,
d/ppm, J/Hz): 8.83 (m, 2H, J = 7.9), 8.78 (m, 2H, J = 3.9, J
= 1.5), 8.70 (s, 2H), 8.52 (m, 2H, J = 5), 8.00–7.94 (m, 4H),
7.86 (m, 2H, J = 7.8, J = 1.8), 7.47 (m, 2H, J = 7.4, J = 4.2, J
= 1.3), 7.34 (m, 2H, J = 7.1, J = 4.3, J = 1.2), 7.26 (s, 4H).
13C-NMR (CDCl3, d/ppm): 158.19, 157.77, 155.57, 153.30,
149.48, 149.01, 145.16, 139.91, 137.46, 137.14, 136.90, 129.12,
125.66, 125.02, 124.98, 123.63, 122.10. IR n/cmꢂ1: 3286m,
1636s, 1582s, 1510m, 1475s, 1442m, 1428m, 1408s, 1385s,
1302m, 1285w, 1276w, 1253s, 1152w, 1098s, 1053m, 1040w,
1019w, 990s, 968w, 932s, 903m, 853w, 839s, 815w, 797s, 765m,
748m, 730m, 651m, 620m, 539m, 529w. Mass spec found (calc.
For C34H22N8) (ES, MH+): 543.2044 (543.2040).
Alternative preparation of L1 using 1,4-diacetylbenzene. Dptz
(0.2 g, 0.85 mmol) was dissolved in of CH2Cl2 (10 cm3) to give
a deep red solution. 1,4-Diacetylbenzene (60 mg, 0.37 mmol)
and para-toluenesulfonic acid (880 mg, 5.12 mmol) were added
to the red solution, which was heated under reflux for 2 d.
After removing the solvent a black solid was recovered. This
solid was dissolved in a mixture of CHCl3 (10 cm3) and
aqueous 1 M NaOH (10 cm3). The CHCl3 phase was collected
and the solvent removed by evaporation. Acetone (15 cm3)
was added to the residue and the resultant precipitate was
collected, washed with acetone and dried to give L1 as a
yellow/brown powder (yield 50 mg, 11%).
Colourless crystals of L1 were grown from a hydrothermal
reaction at 130 1C for 5 d in a sealed steel autoclave in the
presence of Cd(NO3)2 ꢁ 4H2O. Crystals of L1 ꢁ 4CHCl3 were
grown from a solution in deuterated chloroform in a sealed
NMR tube, which had been left undisturbed for three weeks.
After complete evaporation of the solvent, colourless needles
suitable for X-ray diffraction were formed.
Alternative preparation of L1 at room temperature. Dptz (0.5
g, 2.12 mmol) was dissolved in toluene (10 cm3) to give a deep
red solution. 1,4-Divinylbenzene (0.1 cm3, 0.7 mmol) was
added to the red solution and stirred at room temperature
for two weeks over which period the solution became orange.
[Bis(trifluoroacetoxy)iodo]benzene (0.7 g, 1.65 mmol) was
added and the solution stirred for 1 h. Aqueous 1 M NaOH
(15 cm3) was added to the black solution to form a viscous
black oil. The black oil was extracted using the same method
5,6,11,12-Tetrahydro-1,4,7,10-tetrapyridin-2-ylcycloocta[1,2-d:
5,6-d0]dipyridazine. L2. Dptz (1 g, 4.14 mmol) was dissolved in
toluene (10 cm3) to give a deep red solution. 1,5-Cycloocta-
diene (0.2 cm3, 1.63 mmol) was added to the red solution,
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Table 2 Selected bond length (A) and angles (1) with s.u.’s for 3 and 4
For 3
Cd(1)–O(2)
Cd(1)–N(3)
Cd(1)–O(1)
Cd(1)–O(3)
Cd(1)–O(5)
Cd(1)–O(4)
Cd(1)–N(4)
Cd(2)–N(7)
Cd(2)–N(8)
Cd(2)–O(12)
Cd(2)–O(14)
Cd(2)–O(11)
Cd(2)–O(8)
Cd(2)–O(7)
Cd(2)–O(13
2.3131(19)
2.315(2)
2.319(2)
2.3316(19)
2.332(2)
2.437(2)
2.464(2)
2.3453(19)
2.349(2)
2.350(2)
2.367(2)
2.452(2)
2.464(2)
2.481(2)
2.556(3)
O(2)–Cd(1)–N(3)
N(3)–Cd(1)–O(1)
N(3)–Cd(1)–O(3)
O(5)–Cd(1)–O(4)
N(3)–Cd(1)–N(4)
O(1)–Cd(1)–N(4)
O(4)–Cd(1)–N(4)
N(7)–Cd(2)–N(8)
N(7)–Cd(2)–O(12)
O(12)–Cd(2)–O(11)
N(8)–Cd(2)–O(7)
O(8)–Cd(2)–O(7)
N(7)–Cd(2)–O(13)
N(8)–Cd(2)–O(13)
O(14)–Cd(2)–O(13)
85.44(7)
88.20(8)
81.62(7)
52.81(8)
68.66(7)
96.62(8)
130.10(7)
69.14(7)
143.28(7)
53.11(7)
80.34(7)
51.58(6)
74.62(8)
102.50(8)
52.06(8)
For 4
Cd–N(4)
Cd–O(6)
Cd–N(9)
Cd–O(3)
Cd–O(2)
Cd–N(3)
Cd–N(10)
Cd–O(4)
2.307(5)
2.325(4)
2.327(5)
2.390(5)
2.434(5)
2.526(5)
2.545(5)
2.691(5)
N(9)–Cd–O(2)
O(3)–Cd–O(2)
N(4)–Cd–N(3)
O(6)–Cd–N(3)
N(9)–Cd–N(3)
N(4)–Cd–N(10)
N(9)–Cd–N(10)
O(4)–Cd–O(6)
76.09(17)
53.24(16)
67.75(18)
82.17(16)
83.59(17)
88.82(17)
66.84(17)
50.45(16)
which time the toluene was removed and acetone (5 cm3) was
added to the resultant reaction mixture. A precipitate was
obtained by further addition of diethyl ether, and this was
collected and dried to give a crude 27% yield of L3. This
reaction was attempted several times but was successful only
once, all other times leading to the formation of dppz as a
major product, with L3 present as only a very minor compo-
nent, if formed at all. Although the presence of L3 was
Fig. 4 (a) View of the structure of 4 showing Cd(NO3)2 moieties
linking parallel molecules of L5; (b) view of the distorted cubic Cd(II)
coordination sphere observed in 4. Atoms of L5, except for coordi-
nated N-atoms, have been removed for clarity. Displacement ellipsoids
are drawn at the 50% probability level.
which was heated under reflux for 3 h over which period the
solution turned yellow. [Bis(trifluoroacetoxy)iodo]benzene (1
g, 2.36 mmol) was added to the solution, which was heated
under reflux for a further 10 min until the solution turned
black. The solution was allowed to cool to room temperature
and aqueous 1 M NaOH (20 cm3) was added. The reaction
solvent was removed and the viscous black oil was redissolved
in acetone (20 cm3). The black solution was left to stand
overnight and the yellow precipitate which formed was col-
lected, washed with acetone and dried to give a pale yellow
powder (yield 100 mg, 9.4%). The crystal structure of L2 was
determined from crystals grown by slow evaporation from a
CHCl3 solution of L2. Found (calc. for C32H24N8) (%): C
73.28 (73.83), H 4.60 (4.65), N 21.41 (21.52). 1H-NMR
(in CDCl3, d/ppm, J/Hz): 8.30 (m, 4H, J = 4.5), 7.83 (m, 4H,
J = 7.8), 7.76 (m, 4H, J = 7.8, J = 1.8), 7.30 (m, 4H, J = 4.8,
J = 1.4), 3.63 (s, 8H). 13C-NMR (in CDCl3, d/ppm): 158.84,
156.59, 147.93, 140.07, 136.70, 125.32, 123.15, 28.95. IR
n/cmꢂ1: 3458m, 1634w, 1586w, 1384s, 1107w, 992w, 836m,
792m, 745m, 729w, 694w, 677w, 667w, 616w. Mass spec found
(calc. For C32H24N8) (ES, MH+): 521.2201 (521.2197).
1
indicated by H-NMR and mass spectrometry, the very low
yield (typically 5% or less) indicated that this synthetic route
1
was not viable. H-NMR (in CDCl3, d/ppm, J/Hz): 8.75 (m,
4H), 8.32 (m, 4H), 7.83 (m, 4H), 7.31 (m, 4H), 6.61 (s, 2H),
2.99 (s, 2H). Mass spec found (calc. For C31H20N8) (ES,
MH+): 504.1799 (504.1805).
4,40-Ethane-1,2-diylbis(3,6-dipyridin-2-ylpyridazine). L4. Dptz
(0.5 g, 2.12 mmol) was dissolved in CHCl3 (10 cm3) to give a
deep red solution. 1,5-Hexadiene (0.06 cm3, 0.51 mmol) was
added and the reaction mixture heated under reflux for 2 d with
the solution gradually turning yellow. The solution was left to
cool to room temperature and [bis(trifluoroacetoxy)
iodo]benzene (0.5 g, 1.18 mmol) was added and the solution
stirred for 1 h, during which time it turned black. The solvent
was removed and acetone (10 cm3) added to afford a precipi-
tate, which was collected, washed with acetone and dried to give
a pale yellow powder (yield 108 mg, 43%). Crystals of
L4 ꢁ 2DMSO were grown from deuterated DMSO over a period
of a month. Found (calc. for C30H22N8) (%): C 72.37 (72.86), H
4.49 (4.48),
N
22.59 (22.66). 1H-NMR (in CDCl3,
5,10-Methano-1,4,6,9-tetrapyridin-2-ylpyridazino[4,5-g]phtha-
lazine. L3. Dptz (1 g, 4.14 mmol) was dissolved in dry toluene
(7 cm3) to give a deep red solution. Norbornadiene (0.15 cm3,
1.9 mmol) and [bis(trifluoroacetoxy)iodo]benzene (2 g,
4.72 mmol) were added to the solution which turned black.
The solution was left to stir at room temperature for 3 d, after
d/ppm, J/Hz): 8.78–8.72 (m, 6H), 8.56 (s, 2H), 8.12 (dt, 2H,
J = 7.9, J = 1.0), 7.92 (td, 2H, J = 7.8, J = 2.0), 7.84 (td, 2H,
J = 7.7, J = 1.8), 7.43 (m, 2H, J = 7.6, J = 4.8, J = 1.3), 7.31
(m, 2H, J = 7.6, J = 4.8, J = 1.2), 3.60 (s, 4H). 13C-NMR (in
CDCl3, d/ppm): 158.56, 157.30, 155.98, 153.41, 149.42, 148.62,
141.34, 137.30, 137.00, 126.47, 124.78, 124.77, 123.71, 121.80,
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33.26. IR n/cmꢂ1: 3458m, 3064w, 1789w, 1763w, 1580s, 1475s,
1384s, 1259w, 1150w, 1092m, 1080w, 1051w, 992m, 931w,
896w, 836m, 825w, 817w, 791s, 775w, 762m, 747m, 726m,
650s, 620m, 542w, 527w, 406m. Mass spec found (calc. For
C30H22N8) (ES, MH+): 495.2042 (495.2040).
994m, 901w, 836m, 826m, 793m, 746m, 726m, 711m, 677m,
623w, 615m, 517w. Mass spec found (calc. For C36H30N8)
(ES, MH+): 575.2669 (575.2666)
5,6,11,12,17,18-Hexahydro-1,4,7,10,13,16-hexapyridin-2-yl-
cyclododeca[1,2-d:5,6-d0:9,10-d00]tripyridazine. L7. To a solu-
tion of dptz (0.5 g, 2.12 mmol) in CHCl3 (10 cm3) was
added trans,trans,trans-1,5,9-cyclododecatriene (50 mg, 0.31
mmol) and the red solution heated under reflux for 5 d. The
solution maintained its red colour. The solution was cooled to
room temperature, [bis(trifluoroacetoxy)iodo]benzene (0.5 g,
1.18 mmol) was added and the solution refluxed for a further
15 min during which time the solution turned black. The
reaction solvent was evaporated and the product was purified
by column chromatography (silica-gel 60, 15 cm column, 3 cm
diameter). Initially, toluene–acetone 2 : 1 was used as eluent
but when no further material emerged from the column the
eluent was changed to MeOH. The product eluted as the final
fraction out of the column to give colourless crystals (yield
0.4%). Found (calc. for C48H36N12) (%):1H-NMR (DMSO-
d6, d/ppm, J/Hz): 8.25 (m, 6H), 7.87 (td, 6H, J = 7.8, J = 1.5),
7.64 (d, 6H, J = 7.8), 7.40 (td, 6H, J = 6.2, J = 1.8), 3.47
(s, 12H). Mass spec found (calc. For C48H36N12) (ES, MH+):
781.3265 (781.3259).
1,4,6,9-Tetrapyridin-2-ylpyridazino[4,5-g]phthalazine. L5. To
a solution of dptz (0.5 g, 2.12 mmol) in CHCl3 (10 cm3) was
added 1,4-cyclohexadiene (0.05 cm3, 0.53 mmol). The solution
was heated under reflux for 3 days with a small amount of grey
precipitate being formed. The solution was left to cool to room
temperature and [bis(trifluoroacetoxy)iodo]benzene (0.5 g,
1.18 mmol) was added. The solution was stirred for a further
1 h, during which time the solution turned black. Aqueous 1 M
NaOH (10 cm3) was added and the CHCl3 phase separated.
The CHCl3 was removed by evaporation and acetone (5 cm3)
added to afford a yellow precipitate which was collected,
washed with acetone and dried. The product was purified by
re-precipitation from CHCl3 by addition of acetone to give a
yellow powder (yield
5 mg, 1.9%). Found (calc. for
C30H18N8 ꢁ 0.5CHCl3) (%): C 66.25 (66.58), H 3.24 (3.39), N
1
20.03 (20.37). H-NMR (CDCl3, d/ppm, J/Hz): 11.01 (s, 2H),
8.86 (m, 4H, J = 4.8, J = 0.9), 8.48 (m, 4H, J = 7.9), 8.04 (m,
4H, J = 7.8, J = 1.8), 7.55 (m, 4H, J = 7.6, J = 4.8, J = 1.1).
13C-NMR (CDCl3, d/ppm): 157.03, 155.41, 148.63, 137.50,
130.15, 126.16, 126.01, 124.60. IR n/cmꢂ1: 1656m, 1632m,
1384s, 993w, 902w, 836w, 792w, 678w, 652w. Mass spec found
(calc. For C30H18N8) (ES, MH+): 491.1728 (491.1727).
Complexation reactions
[Cu4(L1)(NO3)6(MeO)2(MeOH)2] 1. L1 (10 mg, 0.02 mmol)
dissolved in CHCl3 (4 cm3) was carefully layered over a
solution of Cu(NO3)2 ꢁ 2.5H2O in MeOH (4 cm3) and the
solutions allowed to mix slowly. After one week, green platy
crystals suitable for X-ray diffraction were formed. Found
(calc. for C38H36Cu4N14O22) (%): C 35.35 (35.24), H 2.72
(2.78), N 15.07 (15.15). IR n/cmꢂ1: 3485s (br), 1656w, 1633w,
1602w, 1383s (br), 1258w, 1163w, 1132w, 1045w, 1021m,
934w, 862w, 835m, 825w, 791m, 751w, 720w, 666ew, 648w,
624w.
(11Z)-5,6,11,12,15,16-Hexahydro-1,4,7,10-tetrapyridin-2-yl-
cyclododeca[1,2-d:5,6-d0]dipyridazine. L6. To a solution of dptz
(0.5 g, 2.12 mmol) in CHCl3 (10 cm3) was added trans,tran-
s,cis-1,5,9-cyclododecatriene (0.05 cm3, 0.27 mmol). The solu-
tion was heated under reflux for 3 d over which period the
solution turned orange. After the solution had been left to cool
to room temperature, [bis(trifluoroacetoxy)iodo]benzene (0.5
g, 1.18 mmol) was added and the solution was refluxed for a
further 20 min to yield a black reaction mixture. The solvent
was removed by evaporation and the crude product was
purified by column chromatography (silica-gel 60, 15 cm
column, 3 cm diameter) first using MeCN as eluent and
collecting 12 ꢃ 15 cm3 aliquots. The eluent was then changed
to acetone, and 20 further aliquots were collected and finally
the eluent was changed to methanol. The product crystallised
out as white needles from the aliquots collected when acetone
was used as eluent. The product was collected, washed with a
small quantity of acetone and dried to give colourless crystal-
line needles, (yield 38 mg, 24.5%). Found (calc. for
[Cu4(L1)(NO3)6(MeO)2(EtOH)2] 2. This was prepared in a
similar manner to 1 but in the presence of sodium trimesate (11
mg, 0.04 mmol) dissolved in EtOH (4 cm3). After one week, a
small number of green blocky crystals suitable for X-ray
diffraction had formed. Powder X-ray diffraction patterns
for bulk 1 and 2 were not consistent with the single crystal
structure obtained: we attribute this to the visually apparent
loss of crystallinity, and hence structural integrity, which
occurs as a result of rapid loss of solvent from the crystals.
[Cd2(L2)(NO3)4(EtOH)3] 3. L2 (5 mg, 0.01 mmol) and 4,40-
bipyridine (5 mg, 0.03 mmol) were dissolved in EtOH (10 cm3),
and Cd(NO3)2 ꢁ 4H2O (12 mg, 0.04 mmol) was dissolved in
EtOH (10 cm3). The two solutions were allowed to slowly
diffuse together to afford colourless acicular crystals suitable
for X-ray diffraction. Found (calc. for C38H42Cd2N12O15)
C
36.8H33.2N8O0.8 {L1 ꢁ 0.8(MeOH)}) (%): C 73.65 (73.63), H
5.06 (5.57), N 19.04 (18.67). 1H-NMR (CDCl3, d/ppm, J/Hz):
8.74 (dq, 2H, J = 4.8, J = 0.8), 8.27 (dq, 2H, J = 4.8, J =
0.8), 8.00–7.85 (m, 6H), 7.76 (td, 2H, J = 7.6, J = 1.8), 7.42
(ddd, 2H, J = 7.4, J = 4.8, J = 1.4), 7.23 (ddd, 2H, J = 7.5, J
= 4.8, J = 1.3), 5.70 (t, 2H, J = 5.3), 3.58 (t, 4H), 3.41 (broad
s, 4H), 2.36 (broad s, 4H). 13C-NMR (in CDCl3, d/ppm):
159.10, 158.97, 156.61, 156.53, 148.65, 148.31, 145.14, 139.98,
138.94, 137.01, 136.91, 131.04, 125.07, 124.97, 123.65, 123.50,
28.09, 27.83. IR n/cmꢂ1: 3458w, 3061w, 3009w, 1763w, 1637w,
1586m, 1568m, 1537w, 1475m, 1383s, 1154w, 1107m, 1053w,
(%): C 40.26 (40.33), H 3.69 (3.71), N 14.74 (14.86). IR n/cmꢂ1
:
3401s (br), 1639w, 1593w, 1570w, 1384s (br), 1155w, 1117 w,
1032 w, 1007w, 836w, 817w, 785w, 745m, 628w, 623w.
[Cd2(L5)3(NO3)4] 4. Cd(NO3)2 ꢁ 4H2O (12 mg, 0.04 mmol)
was dissolved in MeOH (4 cm3) and carefully layered over a
solution of L5 (5 mg, 0.01 mmol) in CHCl3 (4 cm3). The
ꢀc
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solutions were allowed to mix slowly over a period of a week,
producing a small number of acicular orange crystals suitable
for X-ray diffraction. The amount of material recovered was
insufficient for elemental analysis or further characterisation.
X-Ray crystallographic studies
Single crystal X-ray data collections were performed in Not-
tingham on Bruker SMART1000 (L1, L2) or Bruker SMART
APEX (L4.2DMSO) CCD area detector diffractometers.
Those for (L1.4CHCl3), 1, 2, and 3 were carried out on a
Bruker APEXII instrument at Station 9.8 or 16.2smx at
CCLRC Daresbury Laboratory, using wavelengths of
0.6768, 0.6768, 0.6906 and 0.6749 A, respectively. All instru-
ments were equipped with Oxford Cryosystems open flow
cryostats.19 The data for 4 were collected on a Nonius
KappaCCD area detector diffractometer also equipped with
an Oxford Cryosystems open flow cryostat,19 controlled by the
COLLECT20 software package and collected images were
processed using DENZO.21 Structures were solved by direct
methods using SHELXS9722 and full-matrix least squares
refinement employed SHELXL97.23 All hydrogen atoms were
placed in geometrically calculated positions and thereafter
refined using a riding model with Uiso(H) = 1.2Ueq (C). All
non-hydrogen atoms were refined with anisotropic displace-
ment parameters. Disorder was encountered in solvent mole-
cules in 1 and 2. In the case of 1, CHCl3 molecules were refined
with partial occupancies of 0.75 and 0.5. The refinement model
for 2 included one nitrate anion disordered over three posi-
tions, with atom O5 modelled over three positions. Atoms
O5A, O5B and O5C were refined isotropically with occupan-
cies of 0.40, 0.40 and 0.20, respectively. Similarity restraints
were applied to the relevant Nꢁ ꢁ ꢁO distances. After refinement,
the occupancy of the chloroform solvent molecule was fixed at
0.60. In the case of 3 one EtOH molecule was found to be
disordered over two positions, O1–C38–C37 and
O1–C380–C370. Similarity restraints were applied to the
Cꢁ ꢁ ꢁO distances, and the occupancies refined to be 0.724(9)
and 0.276(9), respectively. In the case of the crystal structure
of L2, the carbon atom (C17) in the solvate CHCl3 molecule
was found to be disordered over two sites of equal occupancy
with shared Cl atoms. Similarity restraints were applied to the
Cꢁ ꢁ ꢁCl distances. Other details of crystal data and structure
determination are given in Table 3.w
Acknowledgements
We thank EPSRC and the University of Nottingham for
support. We are grateful to CCLRC for access to Station
9.8/16.2smx on the Daresbury SRS and to Dr J. E. Warren
and Dr T. J. Prior for experimental advice. We acknowledge
the use of the EPSRC National Service for Crystallography at
the University of Southampton. MS gratefully acknowledges
receipt of a Royal Society Wolfson Merit Award and of a
Royal Society Leverhulme Trust Senior Research Fellowship.
w CCDC reference numbers 619843–619850. For crystallographic data
in CIF or other electronic format see DOI: 10.1039/b611561f
ꢀc
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Bacsa and K. R. Dunbar, Chem. Commun., 2005, 46; (d) A. J.
Blake, N. R. Brooks, N. R. Champness, M. Crew, A. Deveson, D.
Fenske, D. H. Gregory, L. R. Hanton, P. Hubberstey and M.
Schroder, Chem. Commun., 2001, 1432; (e) M. A. Withersby, A. J.
¨
Blake, N. R. Champness, P. A. Cooke, P. Hubberstey and M.
Schroder, J. Am. Chem. Soc., 2000, 122, 4044; (f) M. A. Withersby,
¨
A. J. Blake, N. R. Champness, P. A. Cooke, P. Hubberstey, A. L.
Realf and M. Schroder, J. Chem. Soc., Dalton Trans., 2000, 3261;
¨
(g) A. J. Blake, G. Baum, N. R. Champness, S. S. M. Chung, P. A.
References
1 M. Ruben, E. Breuning, J. P. Gisselbrecht and J. M. Lehn, Angew.
Chem., Int. Ed., 2000, 39, 4139.
2 (a) N. E. Chakov, S. C. Lee, A. G. Harter, P. L. Kuhns, A. P.
Reyes, S. O. Hill, N. S. Dalal, W. Wernsdorfer, K. A. Abboud and
G. Christou, J. Am. Chem. Soc., 2006, 128, 6975; (b) R. T. W.
Scott, C. J. Milios, A. Vinslava, D. Lifford, S. Parsons, W.
Wernsdorfer, G. Christou and E. K. Brechin, Dalton Trans.,
2006, 3161.
Cooke, D. Fenske, A. N. Khlobystov, D. A. Lemenovskii, W.-S. Li
and M. Schroder, J. Chem. Soc., Dalton Trans., 2000, 4285; (h) M.
¨
A. Withersby, A. J. Blake, N. R. Champness, P. A. Cooke, P.
3 M. Fujita, M. Tominaga, A. Hori and B. Therrien, Acc. Chem.
Res., 2005, 38, 369.
Hubberstey, W.-S. Li and M. Schroder, Inorg. Chem., 1999, 38,
¨
2259; (i) A. J. Blake, N. R. Brooks, N. R. Champness, M. Crew, L.
4 (a) V. Balzani, S. Campagna, G. Denti, A. Juris, S. Serroni and M.
Venturi, Acc. Chem. Res., 1998, 31, 26; (b) D. Kim and A. Osuka,
Acc. Chem. Res., 2004, 37, 735.
R. Hanton, P. Hubberstey, S. Parsons and M. Schroder, J. Chem.
¨
Soc., Dalton Trans., 1999, 2813; (j) A. J. Blake, N. R. Champness,
M. Crew, L. R. Hanton, S. Parsons and M. Schroder, J. Chem.
¨
Soc., Dalton Trans., 1998, 1533; (k) M. A. Withersby, A. J. Blake,
N. R. Champness, P. Hubberstey, W.-S. Li and M. Schroder,
¨
Angew. Chem., Int. Ed. Engl., 1997, 36, 2327.
5 (a) M. W. Hosseini, Chem. Commun., 2005, 5825; (b) P. J. Steel,
Acc. Chem. Res., 2005, 38, 243; (c) M. T. Youinou, N. Rahmounin,
J. Fischer and J. A. Osborn, Angew. Chem., Int. Ed. Engl., 1992, 31,
733; (d) A. Marquis, J. P. Kintzinger, R. Graff, P. N. W. Baxter
and J. M. Lehn, Angew. Chem., Int. Ed., 2002, 41, 2760; (e) E.
Breuning, G. S. Hanan, F. J. Romero-Salguero, A. M. Garcia, P.
N. W. Baxter, J. M. Lehn, E. Wegelius, K. Rissanen, H. Nier-
engarten and A. van Dorsselaer, Chem.–Eur. J., 2002, 8, 3458.
6 (a) N. Tsukada, T. Sato, H. Mori, S. Sugawara, C. Kabuto, S.
Miyano and Y. Inoue, J. Organomet. Chem., 2001, 627, 121; (b) N.-
D. Sung, K.-S. Yun, J.-G. Kim and I.-H. Suh, Acta Crystallogr.,
Sect. C, 2000, C56, e370; (c) E. C. Constable, C. E. Housecroft, B.
M. Kariuki, M. Neuburger and C. B. Smith, Aust. J. Chem., 2003,
56, 653; (d) M. J. Plater, M. R. St. J. Foreman and J. M. S. Skakle,
J. Chem. Crystallogr., 2000, 30, 535; (e) K.-Y. Choi, N.-D. Sung,
K.-S. Yun, Y.-S. Park, J.-G. Kim and I.-H. Suh, Acta Crystallogr.,
10 N. S. Oxtoby, A. J. Blake, N. R. Champness and C. Wilson, Proc.
Natl. Acad. Sci. USA, 2002, 99, 4905.
11 N. S. Oxtoby, N. R. Champness and C. Wilson, CrystEngComm,
2005, 284.
12 (a) L. A. Cuccia, J.-M. Lehn, J.-C. Homo and M. Schmutz, Angew.
Chem., Int. Ed., 2000, 39, 233; (b) L. A. Cuccia, E. Ruiz, J.-M.
Lehn, J.-C. Homo and M. Schmutz, Chem.–Eur. J., 2002, 8, 3448;
(c) R. Dorta, L. Konstantinovski, L. J. W. Shimon, Y. Ben-David
and D. Milstein, Eur. J. Inorg. Chem., 2003, 70.
¨
13 G. Ozer, N. Sarac
7009.
¸ oglu and M. Balci, J. Org. Chem., 2003, 68,
¨
14 (a) D. L. Boger, J. S. Panek and M. Patel, Org. Synth., 1991, 70, 79;
(b) R. Hoogenboom, B. C. Moore and U. S. Schubert, J. Org.
Chem., 2006, 71, 4903.
15 N. S. Oxtoby, A. J. Blake, N. R. Champness and C. Wilson, Dalton
Trans., 2003, 3838.
16 X.-H. Bu, H. Liu, M. Du, L. Zhang, Y.-M. Guo, M. Shionoya and
J. Ribas, Inorg. Chem., 2002, 41, 1855.
17 M. Ghedini, G. De Munno, G. Denti, A. M. Lanfredi and
A. Tiripicchio, Inorg. Chim. Acta, 1982, 57, 87.
Sect. C, 2001, C57, 47; (f) V. J. Catalano, R. A. Heck, A. Ohman
and M. G. Hill, Polyhedron, 2000, 19, 1049; (g) S. Ghumaan, B.
Sarkar, S. Patra, K. Parimal, J. van Slageren, J. Fiedler, W. Kaim
and G. K. Lahiri, Dalton Trans., 2005, 4, 706; (h) B. Sarkar, S.
Frantz, W. Kaim and C. Duboc, Dalton Trans., 2004, 21, 3727; (i)
R. Hoogenboom, G. Kickelbick and U. S. Schubert, Eur. J. Org.
Chem., 2003, 1, 4887; (j) R. Hoogenboom, D. Wouters and U. S.
Schubert, Macromolecules, 2003, 36, 4743; (k) I. Weissbuch, P. N.
W. Baxter, I. Kuzmenko, H. Cohen, S. Cohen, K. Kjaer, P. B.
Howes, J. Als-Nielsen, J.-M. Lehn, L. Leiserowitz and M. Lahav,
Chem.–Eur. J., 2000, 6, 725; (l) E. C. Constable, C. E. Housecroft,
M. Neuburger, S. Reymann and S. Schaffner, Chem. Commun.,
2004, 9, 1056.
18 (a) S. A. Barnett and N. R. Champness, Coord. Chem. Rev., 2003,
246, 145; (b) A. J. Blake, N. R. Champness, P. Hubberstey, W.-S.
¨
Li, M. A. Withersby and M. Schroder, Coord. Chem. Rev., 1999,
183, 117.
19 J. Cosier and A. M. Glazer, J. Appl. Crystallogr., 1986, 19, 105.
20 R. W.W. Hooft. COLLECT. Nonius BV, Delft, The Netherlands,
1998.
21 Z. Otwinowski and W. Minor, Methods in Enzymology, Volume
276: Macromolecular Crystallography, part A, 307, ed. C. W.
Carter, Jr and R. M. Sweet, Academic Press, New York, 1997.
7 W. A. Butte and F. H. Case, J. Org. Chem., 1961, 26, 4690.
8 (a) R. N. Warrener, D. N. Butler and D. Margetic, Aust. J. Chem.,
2003, 56, 811; (b) D. Margetic, D. N. Butler and R. N. Warrener,
Aust. J. Chem., 2000, 53, 959; (c) J. W. Wijnen, S. Zavarise, J. B. F.
N. Engberts and M. Charton, J. Org. Chem., 1996, 61, 2001.
9 (a) B. L. Schottel, H. T. Chifotides, M. Shatruk, A. Chouai, L. M.
22 G. M. Sheldrick, SHELXS97, University of Gottingen, Germany,
¨
1997.
23 G. M. Sheldrick, SHELXL97, University of Gottingen, Germany,
¨
1997.
Perez, J. Bacsa and K. R. Dunbar, J. Am. Chem. Soc., 2006, 128,
´
5895; (b) C. S. Campos-Fernandez, B. L. Schottel, H. T. Chifo-
tides, J. Bacsa, J. K. Bera, J. M. Koomen, D. H. Russell and K. R.
Dunbar, J. Am. Chem. Soc., 2005, 127, 12909; (c) B. L. Schottel, J.
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1508 | New J. Chem., 2006, 30, 1498–1508