Molecular capsules and coordination polymers from a backbone-modified cyclic peptide bearing pyridyl arms

Article abstract of DOI:10.1080/10610278.2012.688128

A tris-pyridyl-substituted Lissoclinum-type cyclic peptide forms a trinuclear molecular capsule on addition of Ag(I) ions and an infinite one-dimensional coordination polymer on addition of Pd(II) ions.

Full text of DOI:10.1080/10610278.2012.688128

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Supramolecular Chemistry
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Molecular capsules and coordination polymers from a
backbone-modified cyclic peptide bearing pyridyl arms
Ying Dong a , David T.J. Loong a , Alex K.L. Yuen a , Richard J. Black a , Shane O'Malley a ,
Jack K. Clegg a , Leonard F. Lindoy a & Katrina A. Jolliffe a
a School of Chemistry, The University of Sydney, 2006 NSW, Australia
Version of record first published: 20 Jun 2012.
To cite this article: Ying Dong, David T.J. Loong, Alex K.L. Yuen, Richard J. Black, Shane O'Malley, Jack K. Clegg, Leonard F.
Lindoy & Katrina A. Jolliffe (2012): Molecular capsules and coordination polymers from a backbone-modified cyclic peptide
bearing pyridyl arms, Supramolecular Chemistry, 24:7, 508-519
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Supramolecular Chemistry
Vol. 24, No. 7, July 2012, 508–519
Molecular capsules and coordination polymers from a backbone-modified cyclic peptide
bearing pyridyl arms
Ying Dong, David T.J. Loong, Alex K.L. Yuen, Richard J. Black, Shane O’Malley, Jack K. Clegg,
Leonard F. Lindoy and Katrina A. Jolliffe*
School of Chemistry, The University of Sydney, 2006 NSW, Australia
(Received 13 March 2012; final version received 18 April 2012)
A tris-pyridyl-substituted Lissoclinum-type cyclic peptide forms a trinuclear molecular capsule on addition of Ag(I) ions and
an infinite one-dimensional coordination polymer on addition of Pd(II) ions.
Keywords: cyclic peptide; metallo-supramolecular chemistry
Introduction
polymers in a manner similar to that observed for
the macrocyclic scaffolds described above. We report
here our initial studies involving the functionalisation of
a Lissoclinum-type cyclic peptide with pyridyl ligands to
provide 1 and the interactions of this moleculewith silver(I)
and palladium(II) ions to form a molecular capsule and
coordination polymer, respectively.
Metal-directed self-assembly has been widely used to
construct both discrete architectures such as helicates,
capsules and cages (1–4) and larger aggregates such as
coordination polymers (5). The metal ion-directed
self-assembly of discrete systems incorporating a central
cavity is of particular interest. One of the major challenges in
this area is the design of scaffolds bearing multiple ligands,
which can be directed, upon addition of an appropriate
metal ion, to form pre-determined architectures. One class
of molecular scaffold, which has been little explored in
this area, is backbone-modified cyclic peptides.
Results and discussion
Both the metal ion properties (charge, radius, spin state,
preferred coordination geometry and kinetic inertness) and
those of the organic components (shape, flexibility and
electronics) play important roles in the self-assembly
process. We designed our cyclic peptide scaffold such that a
variety of ligands could readily be appended to enable
future exploration of the effect of ligand structure on
self-assembly processes. This led to the design of scaffold 2
in which ethylenebromide side chains are appended to the
scaffold. We envisaged that these side chains would be
flexible enough to allow the formation of both molecular
capsules and coordination polymers depending on the
coordination geometry required by the added metal ions,
while being short enough to prevent the formation of simple
complexes in which one metal ion is bound to a single cyclic
peptide through all three ligands. As proof of principle,
we chose to use pyridyl groups to functionalise the scaffold
as these have previously been widely utilised as ligands in
the formation of self-assembled metallo-supramolecular
structures (15, 16).
Analogues of the Lissoclinum class of cyclic peptides
(6) have found application as receptors for anions (7, 8),
cations (9) and neutral molecules (10); as scaffolds for
the display of peptide architectures (11); as stabilisers of
G-quadruplex structure (12); as chiral tripodal ligands for
metal ions (13) and in the preparation of covalent cage
structures (8, 14). However, to date, the ability of these
scaffolds to form well-defined metallo-supramolecular
architectures by self-assembly has not been examined.
The structure of this class of backbone-modified cyclic
peptide, resulting from a network of bifurcated hydrogen
bonds between the amide protons and azole nitrogen atoms
in the macrocycle, lends itself to the display of multiple
ligands for metal binding with well-defined geometry.
If all amino acids are of the same configuration, the side
chains project from one face of the peptide scaffold, in an
arrangement similar to that observed for other macrocyclic
scaffolds such as the resorcinarenes (2, 3) and cyclotriver-
atrylene (4). Functionalisation of these side chains with
ligands should allow, upon addition of metal ions with
the appropriate coordination geometry, the formation of
self-assembled molecular capsules or coordination
There are a number of approaches to the synthesis of
trimeric scaffolds such as 2 (17, 18), the most attractive
of which involves the cyclooligomerisation of an appro-
priately side-chain-protected oxazole (17). Therefore, our
*Corresponding author. Email: kate.jolliffe@sydney.edu.au
ISSN 1061-0278 print/ISSN 1029-0478 online
q 2012 Taylor & Francis
http://dx.doi.org/10.1080/10610278.2012.688128
http://www.tandfonline.com

Supramolecular Chemistry
initial synthetic target was the homoserine-derived oxazole
509
OBn
OBn
building block 3. We first coupled Boc-Hse(Bn)-OH with
threonine methyl ester using diphenylphosphoryl azide
(DPPA) as the coupling reagent to give the dipeptide 4 in
62% yield (Scheme 1). Treatment of 4 with deoxofluor,
followed by immediate oxidation of the intermediate
oxazoline with 1,8-diazabicycloundec-7-ene (DBU) and
BrCCl3 (19), gave the oxazole 3 in 50% yield. Single
crystals of 3 were grown by the slow evaporation of an
acetone solution (see Supplementary Information available
online for details).
O
a
O
H
BocHN
N
BocHN
OMe
N
O
HO
4
MeO
O
3
b
OBn
OBn
It has previously been established that the choice of
peptide-coupling agent for the cyclooligomerisation of
azole heterocycle-derived amino acids can significantly
affect both the cyclisation yield and ratio of cyclotrimer to
cyclotetramer (18). Therefore, we examined the cyclooli-
gomerisation reaction under two sets of conditions.
Hydrolysis of the methyl ester of 3 upon treatment with
aqueous sodium hydroxide gave carboxylic acid 5 which
was either subjected to Boc-deprotection upon treatment
with HCl in dioxane to give amino acid 6 or subjected to
reaction with pentafluorophenol in the presence of
dicyclohexylcarbodiimide (DCC) to give the activated
ester 7 which was subsequently Boc-deprotected upon
treatment with trifluoroacetic acid to give the amino salt 8.
Treatment of 6 with pentafluorophenyldiphenylphosphi-
nate (FDPP) resulted in cyclooligomerisation to provide the
cyclic trimer 9 in 42% yield (Scheme 2). While traces of the
cyclic tetramer 10 were observed by mass spectrometry of
the crude reaction mixture, thiswas not isolated. In contrast,
treatment of the preformed pentafluorophenyl ester 8 with
diisopropylethylamine gave both the cyclic trimer 9 (52%)
and cyclic tetramer 10 (18%) as isolable compounds.
To install the bromide functional groups on the cyclic
peptide scaffold, the side-chain benzyl-protecting groups
were removed upon hydrogenolysis of 9 to give the triol 11
(Scheme 3). A number of attempts were made to directly
convert the triol 11 into tribromide 2; however, these
O
d
O
BocHN
BocHN
N
N
PfpO
e
O
HO
O
7
5
c
OBn
OBn
O
O
CF3CO2- H3N
Cl-H3N
N
N
PfpO
O
HO
O
6
8
Scheme 1. Synthesis of oxazole building blocks. Conditions:
(a) i) deoxofluor, CH2Cl2, 2208C – rt; ii) DBU, BrCCl3,
CH2Cl2, 50% over two steps; (b) NaOH, MeOH, H2O, quant.;
(c) 4 M HCl in dioxane, 96%; (d) pentafluorophenol, DCC, THF,
81%; (e) CF3CO2H, CH2Cl2, quant.
were all low yielding or gave mixtures that were difficult
to purify. Therefore, 11 was firstly treated with p-
toluenesulfonylchloride to give the tritosylate 12 in 95%
yield, then subsequent substitution of the tosylate groups
with LiBr gave the tribromide 2 in 85% yield. Treatment of
OBn
OBn
O
O
O
O
N
H
O
N
H
BnO
N
N
N
O
O
N
N
a or b
+
6 or 8
NH
HN
BnO
O
HN
O
NH
N
OBn
H
N
N
O
O
O
O
O
OBn
OBn
9
10
i
Scheme 2. Conditions: (a) 6, FDPP, Pr2NEt, DMF, 0.05 M; (b) 8, Pr2NEt, DMF, 0.05 M.
i

510
Y. Dong et al.
R
O
O
N
H
O
N
N
R
NH
HN
O
R
N
O
O
9: R = OBn
11: R = OH
a
c
b
12: R = OTs
2: R = Br
Figure 1. Structure of one of the two macrocycles in crystal
structure of 2. Disorder and solvent removed for clarity.
d
(8) that we have previously reported, the macrocycle is
largely planar with one of the oxazole rings tilted slightly
out of the plane; an arrangement stabilised by intramo-
lecular hydrogen bonding.
N
S
O
N
N
O
Each of the disordered bromoethyl side chains projects
from the same face of the macrocycle, and adjacent
macrocycles pack closely together in a dimeric arrange-
ment such that the side chain of one peptide is directed
towards the centre of the adjacent peptide taking
advantage of weak hydrogen bonding interactions
O
H
N
S
N
NH
HN
O
O
N
˚
O
(NH···Br ¼ 2.35–2.94 A; Figure 2). These dimers further
interact with adjacent pairs of molecules through weak
offset face-to-face oxazole–oxazole p-stacking indicated
S
˚
by a ring centroid–centroid separation of 3.5 A, resulting
in the formation of infinite undulating 1D polymers
extending along the crystallographic b-axis.
1
N
With the tri(pyridyl) functionalised scaffold 1 in hand,
we chose to examine the formation of complexes with both
silver(I) and palladium(II) as both of these have frequently
been used in the formation of self-assembled metallo-
supramolecular structures using pyridyl ligands and
provide access to different coordination geometries (3, 4,
15, 16).
Scheme 3. Conditions: (a) H2, Pd/C, CH3OH, ethyl acetate,
99%; (b) p-toluenesulphoonylchloride, Et3N, Me3N.HCl,
CH3CN, 95%; (c) LiBr, DMF, 558C, 85%; (d) 4-
mercaptopyridine, Cs2CO3, CH3CN, 84%.
2 with 4-mercaptopyridine in the presence of caesium
carbonate gave the required pyridyl-functionalised scaf-
fold 1 in 84% yield.
Addition of a solution of silver nitrate in methanol/a-
cetonitrile (1:1) to a solution of 1 in methanol resulted in
immediate precipitation of a colourless solid, the
microanalysis of which confirmed a stoichiometry of
L2Ag3(NO3)3 (L ¼ 1). The positive ion mass spectrum
[electrospray ionisation (ESI)] of this complex revealed a
peak corresponding to [L2Ag3(NO3)2]þ (m/z ¼ 2099 for
the parent ion) with an isotopic distribution pattern which
matched that calculated for this ion (Figure 3). Similarly,
Crystals of the intermediate tribromide 2·0.25CH2-
Cl2·0.875MeOH·0.625H2O suitable for diffraction studies
were grown from the slow evaporation of a dichloro-
methane/methanol solution (Figure 1). Tribromide 2
crystallises in the monoclinic space group P21 with two
cyclic peptides in the asymmetric unit. The refined Flack
parameter (20) (0.075(14)) confirms the enantiopurity of
the structure. In a similar manner to the crystal structures
of the oxazole-containing cyclic peptides and cryptands

Supramolecular Chemistry
511
In contrast to the behaviour observed with silver(I)
ions, addition of Pd(dppp)OTf2 to a solution of cyclic
peptide 1 in methanol resulted in immediate precipitation
of a colourless solid. This was redissolved in CDCl3, and
significant broadening of all signals in the 1H NMR
spectrum and a loss of the C3 symmetry of 1 were
observed. No change in the spectrum was observed after
standing at room temperature (rt) for 7 days. Slow
diffusion of diethyl ether into this mixture yielded a small
number of colourless plate-like crystals suitable for X-ray
studies, which revealed a polymeric complex of
composition {[Pd(dppp)1]·OTf·Cl·3MeOH·3Et2O}n had
formed (Figure 5). The Pd(dppp)OTf2 was obtained from
reaction of Pd(dppp)Cl2 with excess silver triflate (21).
Presumably, the chloride ions in {[Pd(dppp)1]·OTf·Cl·
3MeOH·3Et2O}n are present as a result of a small amount
of chloride remaining in the Pd(dppp)OTf2 sample due to
incomplete ligand exchange. The complex crystallises in
the enantiomorphic chiral space group P3121, and the
refined Flack (20) parameter (0.02(5)) confirms the
enantiopurity of the peptide. The cis-Pd(II) centres are
square planar, coordinated to the bidentate dppp ligand
and pyridyl ligands from two different cyclic peptides
forming a coordination polymer that extends along the
crystallographic a-axis. One of the pyridyl groups from
the peptide remains uncoordinated, reflecting the loss of
C3 symmetry observed in solution. Each of the
coordinated pyridines undergoes offset face-to-face p–
p interactions with the adjacent phenyl rings of the dppp
˚
ligands (centroid–centroid distances of 3.63 and 3.65 A).
Figure 2. Dimeric arrangement observed in crystal structure
of 2. Dashed lines indicate intermolecular hydrogen bonds.
The macrocyclic units are once again largely planar,
stabilised by intramolecular hydrogen bonding. The
triflate counterions are just above the face of the cyclic
peptide with one of the oxygen atoms hydrogen bonded
by the three amide nitrogens such that each macrocyclic
unit serves as a receptor for triflate anion, in a similar
manner to that proposed for related cyclic peptide anion
receptors (8).
the mass spectrum of a sample of 1 after addition of silver
hexafluorophosphate gave a parent peak at m/z ¼ 2265 and
an isotopic distribution pattern corresponding to the
desired silver(I) cage stoichiometry of L2Ag3(PF6)þ2 . The
1H nuclear magnetic resonance (NMR) spectra of mixtures
of 1 and silver hexafluorophosphate in deuteromethanol,
deuterodimethylsulphoxide or deuteroacetonitrile resulted
in small downfield shifts (,0.2 ppm) of the signals
attributable to the pyridyl protons. The signals remained
sharp, indicating that the C3 symmetry of 1 was
maintained and that the silver sites were equivalent in all
three solvents. Unfortunately, single crystals of this
complex could not be obtained. The structure of
[L2Ag3]3þ was modelled using the semi-empirical AM1
level in Spartan 10 (Figure 4). The modelled structure
shows the expected coordination between the silver ions
and the pyridyl nitrogen rings, in analogy to the simpler
benzene-derived metallo-capsule previously reported by
Bray et al. (16). Notably, in this case, the chiral nature of
the cyclic peptide scaffold is reflected in a slight helical
twist of the self-assembled structure.
While the metal centres are formally four–coordinated
(Figure 6), the chloride anions are located in close
proximity to the divalent palladium such that a contact
˚
(3.136(3) A) exists between them creating a pseudo-
square-based pyramidal arrangement, which is presum-
ably stabilised by electrostatic attraction. This arrange-
ment also allows four further favourable CphenyleneH···Cl
and CpyridylH···Cl interactions to occur with H···Cl
˚
distances of 2.78–2.98 A. Non-classical interactions of
this type have been observed in a number of pyridyl and
chloride-containing metal complexes (22).
The polymeric species formed upon the reaction of 1
and [Pd(dppp)]2þ thus contains two distinct anion-binding
pockets, which serve to bind both chloride and triflate in
the solid state. Given the infinite polymeric arrangement of
the complex this yields to the complementary binding of
an infinite number of anions, such that one chloride anion

512
Y. Dong et al.
Figure 3. Calculated isotopic distribution for [(C39H39N9O6S3)2Ag3(NO3)2]þ (top); observed isotopic distribution for
[(C39H39N9O6S3)2Ag3(NO3)2]þ (bottom).
and one triflate anion can be bound for each [Pd(dppp)]2þ
unit.
Experimental
General
Melting points were measured using a Stanford Research
Systems Optimelt melting apparatus and are uncorrected.
Optical rotations were performed using a PerkinElmer
Model 341 polarimeter using the indicated spectroscopic
Conclusions
In summary, we have shown that the new cyclic peptide-
derived tripodal ligand 1 can form either a molecular
capsule in the presence of Ag(I) or a 1D infinite
coordination polymer upon addition of Pd(II). Functio-
nalisation of scaffold 2 with a range of ligands will
provide new tripodal systems for the formation of further
metallo-supramolecular structures with a variety of metal
ions.
1
grade solvents. H and 13C NMR spectra were recorded
usingeitheraBrukerAvanceDPX400/BrukerAvanceDPX
300 spectrometer at a frequency of 300.13 MHz, or a Bruker
Avance DPX 200 spectrometer and are reported as parts
per million (ppm) downfield shift from tetramethylsilane
using the residual solvent peak as reference. Low-resolution

Supramolecular Chemistry
Boc-Hse(Bn)-Thr-OMe (4)
513
A magnetically stirred solution of H-Thr-OMe·HCl
(14.2 g, 83.7 mmol) in DMF (50 ml) was treated with
NEtiPr2 (14.5 ml, 84 mmol) and maintained at 188C for
0.5 h. The mixture was cooled to 08C, and a solution of
Boc-HSe(Bn)-OH (12.9 g, 41.7 mmol) in DMF (10 ml) and
DPPA (13.5 ml, 62.5 mmol) was added. The resulting red
solution was warmed to 188C, and NEtiPr2 (29 ml,
166 mmol) was added via a dropping funnel. After 16 h,
the reaction was quenched by the addition of water
(30 mL), and all volatiles were removed by rotary
evaporation. The resulting oil was treated with HCl
(50 ml of a 1 M aq. solution) and extracted with EtOAc
(4 £ 200 ml). The combined organic fractions were dried
(MgSO4), and the solvent was removed under reduced
pressure to give a yellow oil. Subjection of this material to
flash chromatography (1:3 to 1:1, ethyl acetate–hexane)
followed by concentration of the appropriate fractions
(Rf ¼ 0.2 in 1:1 ethyl acetate–hexane) gave the dipeptide
4 (11 g, 62%) as an oil that solidified to a white solid,
m.p. 1148C, [a]D þ 3 (c ¼ 1.8 in CHCl3) after prolonged
1
storage (1 month). H NMR (CDCl3, 300 MHz) d 7.39–
7.27 (5H, complex m), 7.17 (1H, d, J ¼ 8.8 Hz), 5.69 (1H,
d, J ¼ 7.3 Hz), 4.55 (1H, J ¼ 8.8 and 2.7 Hz), 4.51 (2H, s),
4.38–4.23 (2H, m), 3.72 (3H, s), 3.63 (2H, m), 2.88 (1H,
br s), 2.06 (2H, m), 1.43 (9H, s), 1.16 (3H, d, J ¼ 6.6 Hz);
13C NMR (CDCl3, 75 MHz) d 172.5 (C), 171.1 (C), 155.8
(C), 137.9 (C), 128.4 (CH), 127.8 (CH), 127.7 (CH), 80.0
(C), 73.3 (CH), 68.0 (C), 67.3 (CH2), 57.4 (CH), 53.1
(CH), 52.4 (CH3), 32.2 (CH2), 28.3 (CH3), 19.8 (CH3); IR
nmax 3342, 2975, 2933, 2875, 1737, 1666, 1531, 914,
864 cm21; ESI-MS m/z 447 [(M þ Na)þ, 100]; HRMS-
ESI (m/z) calcd for C21H32N2O7Na (M þ Na)þ, 447.2210,
found 447.2102.
Figure 4. Molecular structure of the (L2Ag3)3þ capsule
modelled with SPARTAN 10 (AM1).
ESI mass spectra were recorded on a Thermo Finnigan
LCQ Deca Ion Trap mass spectrometer. High resolution
mass spectra (HRMS) were recorded on a Bruker BioApex
Fourier Transform Ion Cyclotron Resonance mass spec-
trometer with an analytical ESI source, operating at 4.7 T.
Preparative reversed-phase HPLC was performed on
a Waters 600E multisolvent delivery system with a Waters
U6Kinjector, Waters490E programmablemultiwavelength
detector, Waters busSAT/IN module and Waters Empower
2 software.
Boc-Hse(Bn)-Thr(Oxz)-OMe (3)
A stirred solution of dipeptide 4 (5.01 g, 11.8 mmol) in
anhydrous dichloromethane (160 mL) was cooled to
2208C under a nitrogen atmosphere. Deoxofluor
(3.25 mL, 17.6 mmol) was added dropwise, and the
mixture was stirred at 2208C for 1 h, then warmed to rt
Figure 5. Part of the infinite 1D coordination polymer in the crystal structure of {[Pd(dppp)1]·OTf·Cl·3MeOH·3Et2O}n. Dashed lines
represent hydrogen bonds, and double-headed arrows represent p–p interactions. Regions of disorder removed for clarity.

514
Y. Dong et al.
Figure 6. Schematic representation of part of the X-ray structure of {[Pd(dppp)1]·OTf·Cl·3MeOH·3Et2O}n. Dashed lines indicate
non-classical hydrogen bonds, and double-headed arrow indicates a short Pd–Cl contact.
and stirred for a further 6 h. The mixture was cooled to
2208C and quenched by the addition of saturated aqueous
NaHCO3 (70 mL) then allowed to warm slowly to rt with
vigorous stirring. The resulting mixture was extracted with
CHCl3 (2 £ 25 mL), and the combined organic phases
were dried (MgSO4) and concentrated under reduced
pressure to give a yellow oil. The oil was dissolved in
anhydrous dichloromethane (200 mL), and the solution
was cooled to 2208C. Bromotrichloromethane (2.34 ml,
24.8 mmol) and DBU (3.69 mL, 24.75 mmol) were then
added, and the mixture was allowed to warm slowly to rt
and stirred for 6 h. The volume was reduced to 10 mL
under reduced pressure, then a solution of saturated
aqueous NH4Cl (20 mL) was added. The resulting mixture
was extracted with ethyl acetate (2 £ 25 mL), then the
combined organic phases were dried (MgSO4) and
concentrated under reduced pressure to give a brown oil.
Subjection of this material to flash chromatography (2:3,
ethyl acetate–hexane) followed by concentration of the
appropriate fractions gave the oxazole 3 (2.39 g, 50%) as a
colourless solid, m.p. 92–93oC; [a]D 231 (c 2.1 in
(43), 349 (14). HRMS-ESI (m/z) calcd for C21H28N2O6Na
(M þ Na)þ, 427.1845, found 427.1830. Elemental anal-
ysis calculated for C21H28N2O6: C, 62.36; H, 6.98; N,
6.93. Found: C, 62.57; H, 6.90; N, 6.99%. Single crystals
suitable for X-ray structure analysis were obtained by slow
evaporation of an acetone solution.
Boc-Hse(Bn)-Thr(Oxz)-OPfp (7)
Methyl ester 3 (760 mg, 1.88 mmol) was dissolved in
MeOH (12 ml), and H2O (4 ml) was added. Solid NaOH
(226 mg, 5.64 mmol) was added at rt, and the reaction
mixture was stirred for 2 h, upon which all starting
material had been consumed. MeOH was evaporated, and
the resulting aqueous mixture was acidified to pH 5 with
aqueous 1 M HCl solution (4 ml). The organic material
was extracted with EtOAc (2 £ 20 ml) and washed with
brine solution (20 ml), dried (MgSO4) and concentrated in
vacuo leaving a sticky green foam. This was immediately
dissolved in THF (19 ml), and DCC (465 mg, 2.26 mmol)
followed by pentafluorophenol (415 mg, 2.26 mmol) was
added at rt. The reaction mixture was stirred for 16 h after
which time a white precipitate had formed. This was
collected by Buchner filtration and washed with a little
cold THF. The filtrate was concentrated in vacuo leaving
an orange oil (1.39 g), which was purified by flash column
chromatography (EtOAc:CHCl3, 3:100) giving pentafluor-
ophenyl ester 7 as a colourless oil (842 mg, 81% over two
steps), ½aꢀ2D0 227.6 (c ¼ 1.0, CHCl3); 1H NMR (400 MHz,
CDCl3) d 7.34–7.26 (5H, m), 5.65 (1H, d, J ¼ 7.3 Hz),
1
CHCl3). H NMR (CDCl3, 300 MHz) d 7.34–7.18 (5H,
complex m), 5.58 (1H, m), 5.04 (1H, m), 4.43 (2H, m),
3.88 (3H, s), 3.54 (2H, t, J ¼ 5.8 Hz), 2.53 (3H, s),
2.35 2 2.03 (2H, complex m), 1.42 (9H, s); 13C NMR
(CDCl3, 75 MHz) d 163.19 (C), 162.7 (C), 156.8 (C),
155.5 (C), 138.4 (C), 128.7 (CH), 128.0 (CH), 127.7 (C),
80.3 (C), 73.6 (CH2), 66.8 (CH2), 52.3 (CH3), 47.6 (CH),
34.2 (CH2), 28.7 (CH3), 12.3 (CH3; one signal obscured or
overlapping); ESI-MS m/z 427 [(M þ Na)þ, 100], 371

Supramolecular Chemistry
515
5.08 (1H, app dd, J ¼ 7.3, 5.7 Hz), 4.48 (1H, d,
J ¼ 11.8 Hz), 4.44 (1H, d, J ¼ 11.8 Hz), 3.60 (2H, t,
J ¼ 5.7 Hz), 2.59 (3H, s), 2.28 (1H, dq, J ¼ 14.3, 5.7 Hz),
2.18 (1H, dq, J ¼ 14.3, 5.7 Hz), 1.44 (9H, s); 13C NMR
(100 MHz, CDCl3) d 163.2, 159.6, 157.9, 137.9, 128.4,
127.8, 127.7, 125.3, 80.3, 73.3, 66.5, 47.6, 33.7, 28.4, 12.4
(one signal obscured or overlapping); ESI-MS m/z 579
[(M þ Na)þ, 100], 1134 [(2M þ Na)þ, 18]; HRMS-ESI
(m/z) found [M þ Na]þ 579.1531, C26H25F5N2NaO6
requires [M þ Na]þ 579.1525.
4.46 (3H, d, J ¼ 11.7 Hz), 4.35 (3H, d, J ¼ 11.7 Hz), 3.70–
3.60 (6H, m), 2.58 (9H, s), 2.44–2.39 (6H, m); 13C NMR
(100 MHz, CDCl3) d 161.2, 161.1, 153.9, 138.2, 128.4,
128.3, 127.6, 127.6, 73.0, 65.9, 46.1, 34.4, 11.6; IR nmax
3381, 2927, 2860, 2359, 1676, 1639, 1585, 1519, 1452,
1436, 1392, 1369, 1265, 1200, 1146, 1111, 1078, 1041, 997,
902, 736, 698, 605; ESI-MS m/z 839 [(M þ Na)þ, 50], 817
[(M þ H)þ, 100], 455 (32), 399 (22), 233 (68). HRMS-ESI
(m/z) calcd for C45H48N6O9Na (M þ Na)þ, 839.3380;
found 839.3375.
20
Cyclic tetramer 10: m.p. 61–638C; ½aꢀD 2131
(c ¼ 2.0, CHCl3); 1H NMR (400 MHz, CDCl3) d 7.52
(4H, d, J ¼ 9.3 Hz), 7.32–7.26 (20H, m), 5.53 (4H, m),
4.43 (8H, s), 3.51–3.42 (8H, m), 2.59 (12H, s), 2.17 (4H,
m), 1.98 (4H, m); 13C NMR (100 MHz, CDCl3) d 161.1,
160.9, 153.9, 138.2, 128.7, 128.4, 127.7, 127.7, 73.2, 66.6,
43.7, 33.4, 11.8. ESI-MS m/z 1090 [(M þ H)þ, 100], 1112
[(M þ Na)þ, 33]; HRMS-ESI (m/z) found [M þ H]þ
1089.4734, C60H65N8O12 requires [M þ H]þ 1089.4717.
H2N-Hse(Bn)-Thr(Oxz)-OPfp·CF3COOH (8)
TFA (12 ml) was added to a solution of Pfp ester 7
(842 mg, 1.51 mmol) in CH2Cl2 (4 ml) at rt. The reaction
mixture was stirred for 2 h, and the solvents were removed
leaving an orange oil. Toluene (2 £ 10 ml) was added to
azeotrope off remaining TFA, and the solvents were once
again removed leaving the TFA salt 8 as an orange oil
1
20
(861 mg, quantitative), ½aꢀD þ 3.0 (c ¼ 1.0, MeOH); H
NMR (400 MHz, MeOD) d 7.30–7.14 (5H, m), 4.79 (1H,
t, J ¼ 6.5 Hz), 4.47 (2H, s), 3.68 (2H, t, J ¼ 5.5 Hz), 2.60
(3H, s), 2.44–2.35 (2H, app dt, J ¼ 6.5, 5.5 Hz); 13C NMR
(100 MHz, MeOD) d 162.5, 159.9, 158.7, 139.1, 129.4,
128.9, 128.8, 126.5, 118.6, 74.1, 66.6, 49.0, 32.8, 12.2;
ESI-MS m/z 913 [(2M þ H)þ, 100], 457 [(M þ H)þ, 48],
935 [(2M þ Na)þ, 39]; HRMS-ESI (m/z) found [M þ H]þ
457.1194, C21H18F5N2O4 requires [M þ H]þ 457.1181.
H2N-Hse(Bn)-Thr(Oxz)-OH·HCl (6)
A magnetically stirred solution of oxazole 4 (4.51 g,
11.16 mmol) in MeOH (40 mL) was cooled to 08C, treated
with NaOH (12.8 mL of a 2 M aq. solution) and allowed to
warm to 188C over 16 h. Subsequently, HCl (20 mL of a 1 M
aq. solution) was added, and the mixture was extracted with
CHCl3-isopropyl alcohol (3 £ 50 mL of a 3:1 v/v mixture).
The combined organic fractions were dried (MgSO4), and
the solvent was removed under reduced pressure to give the
free carboxylic acid as a yellow oil (4.229 g, 10.83 mmol).
This was dissolved in 4 M HCl in dioxane (60 ml) at 08C and
was allowed to warm slowly to rt. Stirring was continued
until TLC showed the consumption of all starting material
(5 h). The mixturewas concentrated under reduced pressure
to yield the HCl salt 6 as a hygroscopic yellow oil (3.49 g,
Cyclo[Hse(Bn)-Thr(Oxz)]3 (9) and Cyclo[Hse(Bn)-
Thr(Oxz)]4 (10) (Method 1)
The TFA salt 8 (861 mg, 1.51 mmol) was dissolved in DMF
(30 ml) at rt, NEtiPr2 (0.77 ml, 4.53 mmol) was added, and
the reaction mixture was stirred for 72 h, turning from pale
orange to dark orange. DMF was removed on a rotary
evaporator, and the resulting orange oil was dissolved in
EtOAc (50 ml) and washed with 1 M HCl solution
(2 £ 50 ml). The aqueous fractions were back extracted
with EtOAc (50 ml), and the combined organics were
washed with half-saturated brine solution (50 ml), dried
(MgSO4) and concentrated in vacuo leaving an orange oil.
This oil was subjected to a plug silica column (1:3 to 3:1,
EtOAc:hexane) leaving an orange oil (330 mg). The cyclic
products were separated from each other by preparative
HPLC [Waters Sunfire C18 column, 19 mm, gradient elution
55–90% of MeCN:TFA (100:0.1)/H2O:MeCN:TFA
(95:5:0.1), flow rate ¼ 7 ml/min: tR (cyclic trimer
9) ¼ 46.9 min, tR (cyclic tetramer 10) ¼ 51.7 min] leaving
9 (214 mg, 52%) and 10 (75 mg, 18%) as hygroscopic white
solids after lyophilisation from t-BuOH.
96%). ½aꢀD ¼ þ13.7 (c ¼ 0.526, MeOH); 1H NMR
20
(200 MHz, MeOD) d 7.31 (s, 5H, aromatic), 4.78 (s, 1 H,
CH), 4.49 (s, 2 H, CH2), 3.67–3.69 (m, 2 H, CH2), 2.57 (s, 3
H, CH3), 2.42 (m, 2 H, CH2); 13C NMR (75 MHz, MeOD) d
165.72, 159.93, 159.64, 139.83, 130.24, 130.05, 129.77,
129.67, 74.93, 68.29, 33.54, 12.95. HRMS-ESI (m/z) calcd
for C15H18N2O4 [M þ H]þ 291.13395, found 291.13435.
Elemental analysis calculated for C15H19ClN2O4.0.5 H2O:
C, 53.7; H, 5.7; N, 8.3. Found: C, 53.4; H, 6.1; N, 8.4%.
Cyclo[Hse(Bn)-Thr(Oxz)]3 (9) (Method 2)
Oxazole 6 (3.30 g, 10.1 mmol) was dissolved in DMF
(200 mL), treated sequentially with FDPP (8.45 g,
22.0 mmol) and NEtiPr2 (5.23 mL, 30.0 mmol), and the
resulting mixture was stirred at 188C for 5 days.
Subsequently, excess DMF was removed under reduced
pressure, and the residue was partitioned between HCl
20
Cyclic trimer 9: m.p. 46–478C; ½aꢀD 24.8 (c ¼ 2.7,
CHCl3); 1H NMR (400 MHz, CDCl3) d 8.50 (3H, d,
J ¼ 6.0 Hz), 7.35–7.24 (15H, m), 5.26 (3H, q, J ¼ 6.0 Hz),

516
Y. Dong et al.
(100 ml of a 1 M aq. solution) and CHCl3-isopropyl
alcohol (100 ml of a 3:1 v/v mixture). The separated
aqueous fraction was extracted with CHCl3-isopropyl
alcohol (3 £ 100 ml of a 3:1 v/v mixture), and the
combined organic fractions were dried (MgSO4) then the
solvent was removed under reduced pressure to give a
yellow residue. Subjection of this material of flash
chromatography (1:3 to 1:1, ethyl acetate–hexane)
followed by concentration of the relevant fractions
(Rf ¼ 0.3 in 1:1, ethyl acetate–hexane) gave the
cyclotrimer 9 (1.15 g, 42%) as a yellow oil, data identical
to that described above.
(6H, d, J ¼ 8.2 Hz), 5.16 (3H, ddd, J ¼ 6.3, 5.5, 5.5 Hz),
4.22 (6H, dd, J ¼ 6.2, 6.2 Hz), 2.57 (9H, s), 2.40 (9H, s),
2.33–2.54 (6H, m); 13C NMR (75 MHz, CDCl3) d 160.9,
159.7, 154.4, 144.8, 132.9, 129.8, 128.2, 127.8, 65.8, 45.3,
33.8, 21.5, 11.5. HRMS-ESI (m/z) calcd for
C45H48N6O15S3 [M þ H]þ 1009.2418, found 1009.2414.
Tribromide (2)
LiBr (0.255 g, 2.94 mmol) was added to a solution of 12
(0.247 g, 0.245 mmol) in anhydrous DMF (0.735 mL) at rt,
and the resulting suspension was stirred at 55oC for 24 h.
The mixture was diluted with water (5 mL) and extracted
with CHCl3-isopropyl alcohol (3 £ 10 mL of a 3:1 v/v
mixture). The combined organic phases were washed with
water (5 mL) and brine (5 mL), dried (MgSO4), and
concentrated under reduced pressure. The residue was
purified by column chromatography (0.5% MeOH in
CH2Cl2) to afford the tribromide 2 as a white powder
(0.152 g, 85%). Single crystals suitable for X-ray structure
analysis were obtained by slow evaporation from a mixture
Cyclo[Hse-Thr(Oxz)]3 (11)
Benzyl-protected trioxazole 9 (3.00 g, 3.68 mmol) was
dissolved in a mixture of ethyl acetate (25 mL) and
methanol (25 mL) in a glass pressure hydrogenation vessel
under a stream of N2. Palladium on charcoal (10%) was
carefully added to the solution, and the mixture was
agitated under H2 for 12 h. The mixture was filtered
through a Celite pad, and the Celite was washed with hot
methanol. The organic filtrates were combined, and the
solvent was removed under reduced pressure. The residue
was purified by column chromatography (2% MeOH in
CH2Cl2) to give the triol 11 as a colourless oil (2.00 g,
20
of dichloromethane and methanol, m.p. 63–658C; ½aꢀD
216.8 (c ¼ 2.66, CHCl3); 1H NMR (200 MHz, CDCl3) d
8.36 (3H, d, J ¼ 6.4 Hz), 5.24 (3H, ddd, J ¼ 6.4, 6.1, 6.1),
3.41–3.61 (6H, m), 2.68 (9H, s, CH3), 2.48–2.78 (6H, m);
13C NMR (50 MHz, CDCl3) d 161.0, 159.9, 154.5, 128.4,
47.2, 38.1, 27.3, 11.7. HRMS-ESI (m/z) calcd for
C24H27Br3N6O6 [M þ Na]þ 756.9421, found 756.9422.
Elemental analysis calculated for C24H27Br3N6O6: C,
39.2; H, 3.7; N, 11.4. Found: C, 39.3; H, 3.7; N, 11.3%.
99%). ½aꢀD ¼ 245 (c ¼ 1.86, MeOH); 1H NMR
20
(200 MHz, MeOD) d 8.55 (3H, d, J ¼ 6.4 Hz), 5.20 (3H,
m), 3.61–3.69 (6H, m, CH2), 2.63 (9H, s), 2.09–2.35 (6H,
m); 13C NMR (50 MHz, MeOD) d 162.7, 162.4, 155.4,
129.3, 58.5, 46.9, 38.0, 11.6. HRMS-ESI (m/z) calcd for
C24H30N6O9 [M þ Na]þ 569.1967, found 569.1965.
Elemental analysis calculated for C24H30N6O9.0.5H2O:
C, 51.9; H, 5.6; N, 15.1. Found: C, 51.7; H, 5.5; N, 15.0%.
Tris-mercaptopyridine (1)
A suspensionof2(70 mgg, 0.09 mmol)andCs2CO3 (0.25 g,
0.77 mmol) in anhydrous acetonitrile (1 mL) was stirred for
1 h under a nitrogen atmosphere. A solution of 4-
mercaptopyridine (0.43 g, 0.39 mmol) anhydrous aceto-
nitrile (1 mL) was then added, and the solution was stirred at
08C for a further 3 h. The solvent was removed under
reduced pressure, and the residue was partitioned between
chloroform (20 ml) and water (10 ml). The organic phase
was washed with water (10 ml), dried (MgSO4) and the
solvent was removed under reduced pressure. The residue
was purified by column chromatography (CHCl3/CH3-
OH/CH3CN; 25:1:1) to give the title compound as a white
Tritosylate (12)
A solution of TsCl (3.14 g, 16.5 mmol) in acetonitrile
(10 mL) was added slowly to a stirred solution of triol 11
(2.00 g, 3.66 mmol), Et3N (2.78 g, 27.5 mmol) and Me3-
N·HCl (0.21 g, 2.20 mmol) in acetonitrile (10 mL) at 0oC,
and the mixture was stirred for 3 h. Methanol (2 mL) was
then added to decompose excess TsCl, and the mixture was
stirred for a further 0.5 h. The solvent was removed under
reduced pressure, and the residue was partitioned between
chloroform (50 mL) and water (25 mL). The aqueous
phase was extracted with chloroform (2 £ 50 mL), then the
combined organic fractions were washed with water and
brine, dried (MgSO4) and concentrated under reduced
pressure. The residue was purified by column chromatog-
raphy (0.5% MeOH in CH2Cl2) to give the desired
20
powder (62 mg, 84%), m.p. 58–598C; ½aꢀD ¼ 28.5
(c ¼ 2.25, CHCl3); 1H NMR (300 MHz, CDCl3) 8.39 (9H,
m), 7.09 (6H, d, J ¼ 9.3), 5.28 (3H, m), 3.28–3.02 (6H, m),
2.67 (9 H, s), 2.58–2.47 (3H, m), 2.37–2.23 (3H, m); 13
C
NMR (75 MHz, CDCl3) d 161.2 (C), 160.1 (C), 154.7 (C),
149.4 (CH), 148.3 (C), 128.8 (C), 120.9 (CH), 47.4 (CH),
34.0 (CH2), 26.4 (CH2), 11.7 (CH3). HRMS-ESI (m/z) calcd
for C39H39N9O6S3 [M þ H]þ 826.2264, found 826.2279.
20
tritosylate 12 as a colourless oil (3.50 g, 95%), ½aꢀD þ 6.2
(c ¼ 1.46, CHCl3); 1H NMR (300 MHz, CDCl3) d
8.40 (3H, d, J ¼ 6.3 Hz), 7.72 (6H, d, J ¼ 8.2 Hz), 7.29

Supramolecular Chemistry
517
Elemental analysis calculated for C39H39N9O6S3.H2O: C,
55.5; H, 4.9; N, 14.9. Found: C, 55.8; H, 4.8; N, 14.5%.
greater than 0.5 were refined anisotropically. Carbon-
bound hydrogen atoms were included in idealised
positions and refined using a riding model. Oxygen- and
nitrogen-bound hydrogen atoms were first located in the
difference Fourier map before refinement with bond length
and angle restraints where required. Disorder was
modelled using standard crystallographic methods includ-
ing constraints and restraints where necessary. Crystal-
lographic data are summarised below along with specific
details regarding the refinement where required. CIFs
(CCDC 870355–870357) have been deposited with the
Cambridge Crystallographic Data Centre and can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or 12 Union Road, Cambridge CB2
1EZ, UK; fax: (þ44) 1223-336-033; or e-mail: deposit@
ccdc.cam.ac.uk.
Preparation of silver complex of 1
A solution of silver nitrate (27 mg, 0.016 mmol) in
acetonitrile/methanol (4 mL, 1:1 v/v) was added to a
solution of trispyridine 1 (9.0 mg, 0.011 mmol) in
methanol/acetone (2 mL 1:1 v/v). The resulting precipitate
was collected by filtration, washed with acetone and dried
over P2O5 to give [(12Ag3(NO3)3] as a colourless solid
(11 mg, 95%). Elemental analysis calculated for C78H78-
N21O21S6Ag3.2(C3H6O): C, 44.3; H, 4.0; N, 12.9; S, 8.5; Ag
14.2%. Found: C, 44.7; H, 3.9; N, 13.2; S, 8.3; Ag, 13.8%.
{[Pd(dppp)1]·OTf·Cl·3MeOH·3Et2O}n
Cyclic peptide 2
A solution of Pd(dppp)OTf2 (21) (7.4 mg, 9.0 mmol) in
CD3OD (0.35 mL) was added to a solution of 1 (5.0 mg,
6 mmol) in CD3OD (0.35 mL) resulting in the immediate
formation of a colourless precipitate. The CD3OD was
removed by blowing a stream of nitrogen across the
sample, then CDCl3 (0.7 mL) was added to dissolve the
residue. Diethyl ether was slowly diffused into the sample
resulting in the formation of a small number of colourless
plate-like crystals. One of these was used directly in
determination of the X-ray crystallographic structure of
{[Pd(dppp)1]·OTf·Cl·3MeOH·3Et2O}n.
Formula C25.125H32.215Br3Cl0.50N6O7.50, M 795.75, mono-
clinic, space group P21(#4), a 12.9142(12), b 20.1964(19),
3
˚
˚
c 12.9732(12) A, b 106.964(2), V 3236.4(5) A , Dc 1.633 g
cm23, Z 4, crystal size 0.3 £ 0.1 £ 0.05 mm, colour
colourless, habit needle, temperature 150(2) K, l(Mo Ka)
0.71073 A, m(MoKa) 3.833 mm21, T(SADABS)min,max
˚
0.595956, 1.000000, 2umax 56.62, hkl range 216 16, 226
25, 216 16, N 31,950, Nind 14,996(Rmerge 0.0524), Nobs
7438(I . 2s(I)), Nvar 861, residuals* R1(F) 0.0832,
wR2(F 2) 0.2606, GoF(all) 0.973, Drmin,max 20.766, 0.915
23
e2
.
˚
A
*R1 ¼ SkFoj–jFck/SjFoj for Fo . 2s(Fo); wR2 ¼
(Sw(Fo2–F2c)2/S(wFc2)2)1/2 all reflections w ¼ 1/[s2(Fo2) þ
(0.1535P)2 þ 0.0000P] where P ¼ (Fo2 þ 2F2c)/3.
X-ray data
Data for 2 and 3 (see Supplementary Information available
online for details of 3) were collected with v scans to
approximately 568 2u using a Bruker SMART 1000
diffractometer employing graphite-monochromated Mo
Specific refinement details
Each of the bromoethyl side chains except the Br(6)
containing arm is disordered over a number of positions and
a number of constraints and restraints (including the use of
some constrained isotropic displacement parameters on
low occupancy bromine atoms) were required to facilitate
realistic modelling. The solvent is also significantly
disordered; the dichloromethane was modelled over two
0.25 occupancy positions (each with identical isotropic
displacement parameters). The methanol was modelled
over four positions with a total occupancy of 2.25, and
the water was modelled over two positions of 0.5 and 0.25.
The oxygen-bound hydrogen atoms could not be located
in the difference Fourier map and were not modelled.
˚
Ka radiation generated from a sealed tube (0.71073 A) at
150(2) K. Data integration and reduction were undertaken
with SAINT and XPREP (SMART, SAINT and XPREP
Bruker Analytical X-ray Instruments Inc., Madison, WI,
USA). Data for {[Pd(dppp)1]·OTf·Cl·3MeOH·3Et2O}n
were collected on a Bruker-Nonius APEX2-X8-FR591
diffractometer employing graphite-monochromated Mo–
˚
Ka radiation generated from a rotating anode (0.71073 A)
with v and c scans to approximately 568 2u at 150(2) K
(APEX v2.1, SAINT v.7 and XPREP v.6.14, Bruker
AXS Inc., Madison, Wisconsin, USA, 2003). Subsequent
computations were carried out using the WinGX-32
graphical user interface (23). Structures were solved by
direct methods using SIR97 (24). Multi-scan empirical
absorption corrections were applied to the data-set using
the program SADABS (25). Data were refined and
extended with SHELXL-97 (SHELX-97: Programs for
{[Pd(dppp)1]·OTf·Cl·3MeOH·3Et2O}n
Formula C82H107ClF3N9O15P2PdS4, M 1847.80, trigonal,
space group P3121(#152), a 19.3608(3), b 19.3608(3),
¨
Crystal Structure Analysis, University of Gottingen, 1997)
(26). In general, non-hydrogen atoms with occupancies
3
c 36.6284(13) A, g 120.008, V 11,890.4(5) A , Dc 1.548 g
˚
˚

518
Y. Dong et al.
cm23, Z 6, crystal size 0.3 £ 0.3 £ 0.01 mm, colour
colourless, habit plate, temperature 150(2) K, l(Mo Ka)
Ed. 2008, 47, 8794–8824. Tranchemontagne, D.J.; Ni, Z.;
O’Keeffe, M.; Yaghi, O.M. Angew. Chem. Int. Ed. 2008, 47,
5136–5147. Tidmarsh, I.S.; Faust, T.B.; Adams, H.;
Harding, L.P.; Russo, L.; Clegg, W.; Ward, M.D. J. Am.
Chem. Soc. 2008, 130, 15167–15175. Dalgarno, S.J.;
Power, N.P.; Atwood, J.L. Coord. Chem. Rev. 2008, 252,
825–841. Fujita, M.; Tominaga, M.; Hori, A.; Therrien, B.
Acc. Chem. Res. 2005, 38, 369–378. Fiedler, D.;
Leung, D.H.; Bergman, R.G.; Raymond, K.N. Acc. Chem.
Res. 2005, 38, 349–358.
0.71073 A, m(Mo Ka) 0.495 mm21, T(SADABS)min,max
˚
0.710509, 1.000000, 2umax 56.50, hkl range 225 25, 224
24, 241 48, N 110,846, Nind 19,480(Rmerge 0.0704), Nobs
12,009(I . 2s(I)), Nvar 736, residuals* R1(F) 0.0821,
wR2(F 2) 0.2431, GoF(all) 0.982, Drmin,max 21.166, 1.606
23
˚
A
e2
.
*R1 ¼ SkFoj–jFck/SjFoj for Fo . 2s(Fo); wR2 ¼
(2) Gardner, J.S.; Harrison, R.G.; Lamb, J.D.; Dearden, D.V.
New J. Chem. 2006, 30, 1276–1282. McKinlay, R.M.;
Cave, G.W.V.; Atwood, J.L. Proc. Nat. Acad. Sci. USA.
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Pinalli, R.; Dalcanale, E.; Macchioni, A. J. Am. Chem. Soc.
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Hansen, L.D. Chem. Eur. J. 2005, 11, 5881–5888.
Pirondini, L.; Bertolini, F.; Cantadori, B.; Ugozzoli, F.;
Massera, C.; Dalcanale, E. Proc. Nat. Acad. Sci. USA. 2002,
99, 4911–4915.
(3) Yamanaka, M.; Toyoda, N.; Kobayashi, K. J. Am. Chem.
Soc. 2009, 131, 9880–9881. Haino, T.; Kobayashi, M.;
Fukazawa, Y. Chem. Eur. J. 2006, 12, 3310–3319.
Yamanaka, M.; Yamada, Y.; Sei, Y.; Yamaguchi, K.;
Kobayashi, K. J. Am. Chem. Soc. 2006, 128, 1531–1539.
Kobayashi, K.; Yamada, Y.; Yamanaka, M.; Sei, Y.;
Yamaguchi, K. J. Am. Chem. Soc., 2004, 126,
13896–13897.
(4) Ronson, T.K.; Fisher, J.; Harding, L.P.; Hardie, M.J.
Angew. Chem. Int. Ed. 2007, 46, 9086–9088. Sumby, C.J.;
Gordon, K.C.; Walsh, T.J.; Hardie, M.J. Chem. Eur. J. 2008,
14, 4415–4425. Ronson, T.K.; Carruthers, C.; Fisher, J.;
Brotin, T.; Harding, L.P.; Rizkallah, P.J.; Hardie, M.J.
Inorg. Chem. 2010, 49, 675–685. Carruthers, C.;
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44, 6395–6399.
(5) Batten, S.R.; Neville, S.M.; Turner, D.R. Coordination
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Angew. Chem. Int. Ed., 2004, 43, 2334–2375.
(Sw(F2o –F2c)2/S(wFc2)2)1/2 all reflections w ¼ 1/[s 2(Fo2) þ
(0.1628P)2 þ 0.0000P] where P ¼ (Fo2 þ 2F2c)/3.
Specific refinement details
The S(3) arm of the ligand is disordered over two positions
with occupancies of 0.7 and 0.3, which were modelled with
equal anisotropic displacement parameters and a number of
bond length and angle restraints. Both the S(1) containing
arm and the triflate anion display a significant amount of
thermal motion and/or unresolved disorder. Accordingly,
both bond length and angle restraints along with thermal
parameter restraints were required. In addition to these
problems, there is a significant amount of unresolved
electron density present in the lattice. Despite numerous
attempts at modelling this disorder including the use of
rigid bodies, no satisfactory model could be found, and
accordingly, the SQUEEZE (27) function of PLATON (28)
was employed to remove the contributions of this
unresolved electron density from the model.
Acknowledgements
We thank the Australian Research Council for funding
(DP0555883) and Dr Nicholas Proschogo (The University of
Sydney) for assistance with mass spectral data.
References
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