A chiral [2]catenane self-assembled from meso-macrocycles of palladium(II)

Article abstract of DOI:10.1039/b413258k

Reaction of trans-[PdX₂(SMe₂)₂] (X = Cl or Br) with the chiral ligand LL = 1,1-binaphthyl-2,2′-(NHC( = O)-3-C ₅H₄N)₂ gave the [2]catenane complexes trans-[{(PdX₂)₂(μ-LL)₂}₂], which are formed by self-assembly from 4 units each of trans-PdX₂ and LL. The catenation is favored by the formation of multiple hydrogen bonds between the constituent macrocycles (4 × NH...ClPd, 2 × NH...O=C). If the ligand LL is racemic, each macrocycle trans-[(PdX₂) ₂(μ-LL),] is formed in the meso form trans-[(PdX₂) ₂(μ-R LL)(μ-S-LL)] but the resulting [2]catenane is chiral as a direct result of the catenation step. This is the first time that this form of chiral [2]catenane has been observed. The enantiomers of the [2]catenane further self-assemble in the crystalline form, through secondary intermolecular Pd...X bonding, to form a racemic infinite supramolecular polymer of [2]catenanes.

Full text of DOI:10.1039/b413258k

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F U L L P A P E R
A chiral [2]catenane self-assembled from meso-macrocycles of
palladium(II)
Tara J. Burchell,a Dana J. Eislerb and Richard J. Puddephatt*a
a Department of Chemistry, The University of Western Ontario, London, ON N6A 5B7,
Canada. E-mail: pudd@uwo.ca; Fax: + (519) 661 3022
b Department of Chemistry, University of Calgary, Calgary, AB T2N 1N4, Canada
Received 31st August 2004, Accepted 24th November 2004
First published as an Advance Article on the web 10th December 2004
Reaction of trans-[PdX2(SMe2)2] (X = Cl or Br) with the chiral ligand LL = 1,1ꢀ-binaphthyl-2,2ꢀ-(NHC( = O)-3-
C5H4N)2 gave the [2]catenane complexes trans-[{(PdX2)2(l-LL)2}2], which are formed by self-assembly from 4 units
each of trans-PdX2 and LL. The catenation is favored by the formation of multiple hydrogen bonds between the
=
constituent macrocycles (4 × NH · · · ClPd, 2 × NH · · · O C). If the ligand LL is racemic, each macrocycle trans-
[(PdX2)2(l-LL)2] is formed in the meso form trans-[(PdX2)2(l-R–LL)(l-S–LL)] but the resulting [2]catenane is chiral
as a direct result of the catenation step. This is the first time that this form of chiral [2]catenane has been observed.
The enantiomers of the [2]catenane further self-assemble in the crystalline form, through secondary intermolecular
Pd · · · X bonding, to form a racemic infinite supramolecular polymer of [2]catenanes.
Introduction
There is great current interest in the synthesis and properties
of catenanes, as promising components of functional molecular
materials.1,2 Many elegant strategies for synthesizing catenanes
have been developed, ranging from purely statistical, to directed
self-assembly and metal templating strategies.3,4 The simplest
approach to [2]catenane formation is the self-assembly from
molecular rings, aided by favorable secondary bonding interac-
tions between the two rings.5,6 For example, Fujita and coworkers
have used the fragment cis-[Pd(H2NCH2CH2NH2)]2+ along with
bridging bis(pyridine) ligands to form a host of macrocycles,
which may self-assemble to give catenanes through favorable
secondary interactions between aromatic groups.5 The equili-
bration between macrocycles and [2]catenane is made possible
by the lability of palladium(II) towards ligand substitution
reactions.5
Catenanes can exhibit interesting and unusual forms of chi-
rality, as illustrated in Scheme 1.7,8 When individual macrocycles
are achiral, the resulting [2]catenanes may also be achiral3–6 but,
if there is a directionality associated with the rings, they can
be topologically chiral [Scheme 1, A and B].7 For example,
Sauvage and Vo¨gtle reported chiral [2]catenanes of type B
7c–e,h
based on the directional macrocycles I and J (Scheme 2).
Enantiomerically pure macrocycles always yield chiral catenanes
[Scheme 1, C and D], and several examples are now known.8
For example, the Sauvage group reported recently [2]catenanes
containing a chiral binaphthol unit in each macrocycle K
8a
(Scheme 2). The formation of [2]catenanes from macrocycles
derived from a racemic mixture of chiral precursors is illustrated
in Scheme 1(ii). If a macrocycle contains a single chiral centre
and combines with a non-chiral macrocycle, a racemic mixture
of R and S [2]catenanes is formed [Scheme 1, E]. Stoddart and
coworkers have prepared catenanes of type E (Scheme 1) from a
Scheme 1
racemic mixture of axially chiral binaphthyl-substituted crown
8b,c
ethers and non-chiral macrocycles. If two enantiomeric rings,
each containing a single chiral centre, self-assemble, then the
resulting [2]catenane may be either chiral (RR, SS) or achiral
(RS) [Scheme 1, F]. The Stoddart group has reported catenanes
of type F, but by combination of unlike rings such that four
diastereomers were obtained (RRꢀ, SSꢀ, RSꢀ, SRꢀ).8
If each macrocycle is self-assembled from a racemic (R,S)
precursor and contains two chiral units, then it can be either
chiral (RR, SS) or achiral (meso, RS), and a still more complex
mixture of [2]catenanes is possible, as illustrated in Scheme 1, G
and H. Combination of pairs of chiral macrocycles can give
the [2]catenanes described as RR–RR, SS–SS, and RR–SS,
while similar combination of pairs of achiral macrocycles will
give the [2]catenane RS–RS, and combination of chiral and
achiral macrocycles can give the [2]catenanes RR–RS and SS–
RS (Scheme 1, H). There may be the additional complication
of chirality arising from the catenation step itself, as described
below. There appear to be no reported examples of catenation of
8
8d
type H (Scheme 1) from like macrocycles. Stoddart has used
2 6 8
D a l t o n T r a n s . , 2 0 0 5 , 2 6 8 – 2 7 2
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
©

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Fig. 1 The conformation of ligand rac-1 and the zig-zag polymeric
structure formed by intermolecular N–H · · · N interactions.
(Fig. 1) that limits the span of the pyridyl donors [N(1) · · · N(4) =
˚
6.6 A]. All NH groups are involved in hydrogen bonding while
only half of the pyridine and carbonyl groups are.
The reaction of ligands rac-1 and R-1 with trans-[PdX2-
(SMe2)2], X = Cl, Br, occurred by displacement of the weakly
coordinating SMe2 groups by the pyridyl groups of 1 to form
chiral [2]catenanes, 2a–c, as shown in Scheme 3. The [2]catenanes
2 were obtained as yellow solids, which were soluble in DMSO
but sparingly soluble in other common organic solvents.
Scheme 2
the electron poor ring complex L (Scheme 2), as a mixture of
racemic and meso isomers, to form [2]catenanes with electron
rich macrocyclic polyethers as illustrated in Scheme 1, G and
found that catenation was favoured for the racemic (RR, SS)
isomer over the meso (RS) isomer, but it is not possible to form
[2]catenanes from like rings in this system.
This article reports the first compounds to be formed by a
catenation process of type H (Scheme 1), involving catenation
of identical meso macrocycles. The self-assembly relies on
dynamic coordination chemistry at palladium(II), using ligands
with hydrogen bonding functionality incorporated to favour
catenation of the self-assembled macrocycles. The self-assembly
from racemic (R,S) ligand proves to be highly stereoselective
in the system studied, and gives only the RS–RS combination
in the [2]catenane product. Although each macrocycle is meso
(RS) and so achiral, with C2h symmetry, the [2]catenane has C2
symmetry and is chiral. The development of the chemistry of
[2]catenanes based on coordination compounds has relied to a
significant extent on the use of labile palladium(II) compounds,
but all reported examples have had the cis stereochemistry at
palladium(II);5 the compounds reported below are the first with
trans stereochemistry.
Scheme 3
The structure of compound 2a is shown in Fig. 2. It shows the
presence of a [2]catenane formed by interlocking of two 30-
membered macrocycles. Each macrocycle contains two ligands 1
and two trans-PdCl2 units, and so the [2]catenane is formed by
4 + 4 self-assembly. The secondary bonding between the macro-
cycles that favours [2]catenane formation is unusual. Thus, there
are four intermolecular N–H · · · ClPd hydrogen bonds [N(2)/
Results and discussion
The 1,1ꢀ-binaphthyl group is widely used as a chiral unit in
asymmetric catalysis and in molecular recognition processes,
so ligands were designed using this group in the backbone.
The readily available 1,1ꢀ-binaphthyl-2,2ꢀ-diamine C20H12(NH2)2
was easily converted to the corresponding bis(pyridine) lig-
˚
(2A) · · · Cl(3A)/(3) = 3.330(9) A, N(7)/(7A) · · · Cl(4A)/(4) =
˚
=
=
and C20H12(NHC( O)-3-C5H4N)2, 1, by reaction with 3-
ClC( O)C5H4N·HCl and base. The ligand was prepared in both
3.61(2) A] and two intermolecular N–H · · · O C [N(6)/
˚
=
(6A) · · · O(2A)/(2) = 2.89(2) A] hydrogen bonds (Fig. 2). It is
the racemic, rac-1, and enantiomerically pure form, R-1, by
using the corresponding diamine precursor. The structure of rac-
1 was determined, and is shown in Fig. 1. The chiral molecules
associate in an · · · R · · · S · · · R · · · S · · · fashion through in-
termolecular hydrogen bonding of an N–H group of one
enantiomer with a pyridyl nitrogen atom of the other enantiomer
likely that the NH · · · ClPd hydrogen bonds make a major contri-
bution to the intermacrocycle binding, and this is notable since
most catenanes contain only hydrogen bonds between organic
groups, dipolar attractions between polar groups or p-stacking
forces between arene units.3–8 Each [2]catenane 2a contains two
NH groups and six carbonyl groups that are not involved
in hydrogen bonding. The conformation of the bis(pyridine)
ligands is more open in the [2]catenane 2a compared to the
free ligand rac-1 (Fig. 1) and the distance between the pyridyl
˚
[N(3) · · · N(4A) = 2.991(4) A] to form a polymeric structure.
There is also an intramolecular hydrogen bond between an N–
˚
=
H and C O group of each molecule [N(2) · · · O(2) = 2.948(3) A]
D a l t o n T r a n s . , 2 0 0 5 , 2 6 8 – 2 7 2
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in the solid state that causes the very low solubility of compounds
2a and 2b.
Does the catenane structure survive in solution? The ESI-MS
of the catenane 2a in CH2Cl2/MeOH, with formic acid added to
aid ionization, contained envelopes of peaks centred at m/z =
1662 [Pd4Cl7(1)2]+, 1483 [Pd3Cl5(1)2]+ and 1307 [Pd2Cl3(1)2]+, but
no parent ion at m/z = 2680 [Pd4Cl8(1)4]+. The spectra indicate
the presence of a tetrapalladium complex, with subsequent loss
of PdCl2 units, as expected for the [2]catenane. However, they
do not prove that the [2]catenane is the dominant species in
solution. Thus, the peak at m/z = 1307 is also consistent with
the presence of the simple macrocycle. The ESI-MS of complex
2c was very similar to that of 2a.
1
The H NMR spectra of ligand rac-1 and catenane 2a in
DMSO-d6 are shown in Fig. 4(a) and (b). At a concentration of
5.2 × 10−3 M, the NMR spectrum of 3a is indicative of catenane
formation [Fig. 4(b)], as indicated by the presence of four distinct
NH resonances (each catenane contains 8 NH groups, and there
is only a two-fold symmetry axis) and multiple pyridyl proton
resonances. The spectrum is broad, indicative of non-rigidity, but
it is reproducible and is unchanged after several days, indicating
that there is little dissociation to simple macrocycles and little
displacement of the bis(pyridine) ligands by DMSO under these
conditions. However, at lower concentration [2.4 × 10−4 M,
Fig. 4(c)], significant reaction with DMSO occurred to give free
ligand rac-1. In confirmation, addition of extra ligand rac-1
caused the equilibrium to move back to favoring 2a. There was
no evidence for the simple macrocycle in the dmso solution,
and so the self-assembly of the new dissymmetric [2]catenane
appears to be selective. The 1H NMR spectra of complexes
2b and 2c in dmso-d6 were similar, and so we suggest that
the enantiopure catenane 2c has a similar structure and H-
bonding interactions as the catenanes self-assembled from the
racemic ligand. The catenane complexes are sparingly soluble
in most organic solvents, so a complete NMR study was not
possible. However, the 1H NMR of a dilute solution of 2a
in CD2Cl2/CD3OD was obtained and contained four equal
intensity NH resonances at d = 9.41, 9.43, 9.61 and 9.66, as
expected for the [2]catenane structure. At room temperature, the
COSY NMR contained correlations between the pairs of NH
resonances at d = 9.41 and 9.43 and d = 9.61 and 9.66, which
were not present at −20 ◦C, indicating that the correlations
arise as a result of an undefined dynamic exchange process. The
Fig. 2 Structure of one enantiomer of the chiral [2]catenane 2a. Selected
˚
bond lengths and angles: Pd(1)–N(1) = 1.996(9) A, Pd(1)–N(8) =
˚
˚
˚
2.023(9) A, Pd(2)–N(4) = 1.994(10) A, Pd(2)–N(5) = 2.000(9) A, Pd(1)–
˚
˚
˚
Cl(1) = 2.291(4) A, Pd(1)–Cl(2) = 2.296(4) A, Pd(2)–Cl(3) = 2.291(3) A,
◦
˚
Pd(2)–Cl(4) = 2.303(3) A, N(1)–Pd(1)–N(8) = 178.1(4) , N(4)–Pd(2)–
N(5) = 174.4(3)◦, Cl(1)–Pd(1)–Cl(2) = 177.56(12)◦, Cl(3)–Pd(2)–Cl(4) =
179.76(13)◦. (symmetry code: −x + 1, y, −z + 3/2)
nitrogen atoms is correspondingly greater in 2a, [N(1) · · · N(4) =
˚
˚
10.0 A, N(5) · · · N(8) = 10.2 A]. This conformational change is
necessary to create a large enough cavity in each macrocycle
=
to allow the catenation. The intramolecular N–H · · · O C
hydrogen bonds that were present in the free ligand rac-1 (Fig. 1)
are replaced by the intermacrocycle N–H · · · ClPd hydrogen
bonds in 2a. The IR spectrum of rac-1 contains a broad N–H
stretch at 3280 cm−1, assigned to the similar strength N–H · · · O
and N–H · · · N hydrogen bonding groups, while the IR spectrum
of 2a contains N–H stretches at 3279, 3403 and 3503 cm−1 for
the more varied NH groups in 2a. Complexes 2a, 2b and 2c have
similar IR spectra.
Each macrocycle in 2a exists in the meso (R,S) form, contain-
ing one ligand R-1 and one ligand S-1, and has approximate
C2h symmetry, with the mirror plane perpendicular to the
macrocycle. However, when the two achiral rings interlock,
the mirror plane is lost and the catenane 2a is chiral and has
crystallographic C2 symmetry (Fig. 2). The overall chirality of
the catenane can be described as R-(R,S)2 or S-(R,S)2, where the
first descriptor refers to the chirality associated with catenation
step. In the solid state, the enantiomers of the [2]catenane 2a
further self-assemble through weak intermolecular interactions
9
˚
(Pd · · · Cl = 3.52A) to form a racemic infinite polymer of
catenanes · · · R-(R,S)2 · · · S-(R,S)2 · · · (Fig. 3).
Fig. 3 One-dimensional polymer of [2]catenanes 2a formed through
intermolecular Pd · · · Cl interactions.
The self-assembly, as represented in the solid state structure, is
highly selective (several single crystals were examined and they
were all isomorphous with the data crystal). Thus, the racemic
ligand could give rise to either chiral or achiral macrocycles (RR,
SS, RS), and the catenanes might contain any combination of
these (Scheme 1, H), but only one form (RS–RS) is observed. A
partial structure determination of [2]catenane 2b was carried
out, and it was found to be isomorphous and isostructural
with 2a, though problems with crystal twinning prevented full
refinement. It is probable that it is the intercatenane association
Fig. 4 1H NMR spectrum of: (a) ligand rac-1; (b) 5.2 × 10−3 M solution
of 2a (equilibrium favours catenane); (c) 2.4 × 10−4 M solution of 2a
(equilibrium favours rac-1).
2 7 0
D a l t o n T r a n s . , 2 0 0 5 , 2 6 8 – 2 7 2

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equilibrium in this solvent system again appears to favour the
[2]catenane.
IR spectra were recorded using a Bruker Vector 33 spectrometer
as KBr pellets.
Synthesis
Conclusions
rac-1,1ꢀ-C20H12-2,2ꢀ-(NHC(O)-3-C5H4N)2 rac-1
In summary, the chiral [2]catenanes 2a–c were prepared
by 4 + 4 self-assembly of trans-PdX2 groups and chiral
bis(amidopyridyl)binaphthyl ligands. When a racemic mixture
of the chiral ligand, rac-1, was used in the catenane synthesis,
the self-assembly occurred in a highly selective fashion in the
crystalline product and, though the evidence is less definitive,
in the solution phase product also. The macrocycles formed
only in the meso (RS) form. These macrocycles further self-
assembled to give the [2]catenanes 2a and 2b, as the RS-RS
stereoisomers. Thus, of the six possible stereoisomers formed
by random 4 + 4 self-assembly (H, Scheme 1), only one is
formed in the crystalline product. Of the several forms of
chirality exhibited by [2]catenanes (Scheme 1), the type in
which a [2]catenane is formed by combination of two identical
macrocycles, each with meso stereochemistry, appears to be new.
It is particularly noteworthy that each individual macrocycle is
meso and has approximate C2h symmetry, but the [2]catenane is
dissymmetric with C2 symmetry as a result of the catenation step.
The [2]catenane enantiomers are described as R-(RS-RS) and S-
(RS-RS), illustrated in simplified form in Scheme 4. Crystals
of the racemic [2]catenane 2a contain self-assembled chains
of these enantiomers connected through secondary Pd · · · Cl
bonding. It has not been possible to grow crystals of the
chiral [2]catenane 2c for structure determination so its detailed
stereochemistry is undetermined. Scheme 4 illustrates that both
the constituent macrocycles and the [2]catenane 2c have highest
possible symmetry D2. However, the 1H NMR spectrum of
complex 2c contains four NH resonances, as for the complexes
2a and 2b with lower symmetry C2. This lower symmetry is
expected to result from the rigid [2]catenane and particularly
Nicotinic acid (1.23 g, 10.0 mmol) was refluxed in thionyl
chloride (10 mL) for 2 h to form the acid chloride. Excess
thionyl chloride was removed under vacuum leaving a colourless
solid. The solid was suspended in tetrahydrofuran (30 mL), and
triethylamine (1.4 mL) was added, followed by addition of a
solution of rac-2,2ꢀ-diamino-1,1ꢀ-binaphthyl (1.42 g, 5.0 mmol)
in tetrahydrofuran (10 mL). The mixture was heated under reflux
for 6 h, then it was allowed to cool and was poured into ice water.
The resulting precipitate was filtered, washed with cold water
and acetone, and dried. Yield 1.75 g, 75%. IR (KBr): m(NH)
1
3280 cm−1 (broad); H NMR (DMSO-d6): 10.02 (s, 2H, NH);
3
8.77 (d, JHH = 5 Hz, 2H, H6 py); 8.55 (s, 2H, H2 py); 8.12 (d,
3
3JHH = 9 Hz, 2H, HB C10H6); 8.01 (d, JHH = 8 Hz, 2H, HC
C10H6); 7.85 (d, 3JHH = 9 Hz, 2H, HA C10H6; d, 3JHH = 5 Hz H4
py); 7.47 (t, 3JHH = 8 Hz, 2H, HD C10H6); 7.38 (dd, 3JHH = 5 Hz,
3
8 Hz, 2H, H5 py); 7.31 (t, JHH = 8 Hz, 2H, HE C10H6); 7.02
3
(d, JHH = 8 Hz, 2H, HF C10H6);13C NMR: d = 165.4, 152.9,
148.6, 135.6, 135.2, 132.8, 132.3, 130.1, 129.7, 129.2, 128.8,
127.5, 126.6, 125.9, 125.6. MS: m/z Calcd.: 494.1742, Found:
494.1737.
R-1,1ꢀ-C20H12-2,2ꢀ-(NHC(O)-3-C5H4N)2 R-1
This was prepared similarly from nicotinic acid (0.271 g,
2.2 mmol), triethylamine (0.3 mL) and R-2,2ꢀ-diamino-1,1ꢀ-
binaphthyl (0.309 g, 1.1 mmol). Yield 0.282 g, 52%. IR, NMR
as for rac-1. MS: m/z Calcd.: 494.1742, Found: 494.1742.
trans-[{(PdCl2)2(l-rac-1)2}2], 2a
=
[PdCl2(SMe2)2] (0.030 g, 0.10 mmol) was added to a solution
of rac-1 (0.049 g, 0.10 mmol) in CH2Cl2. After several minutes
of stirring the product complex precipitated as a pale yellow
solid, which was collected by filtration and dried under vacuum.
Yield 0.060 g, 90%. IR (KBr): m(NH) 3279, 3403, 3503 cm−1;
1H NMR (DMSO-d6): 10.34–9.84 (m, 8H, NH); 9.16–8.51 (m,
16H, H2,6 py); 8.18–7.76 (m, 32H, H4 py, HA,B,C C10H6); 7.67–7.25
(m, 24H, H5 HD,E C10H6); 7.01 (d, 3JHH = 8 Hz, 8H, HF C10H6);
Anal. Calcd. (%) for C32H22N4O2PdCl2: C: 57.21, H: 3.30, N:
8.34 Found: C: 57.33, H: 2.87, N: 8.02.
from the presence of only two NH · · · O C hydrogen bonds.
trans-[{(PdBr2)2(l-rac-1)2}2], 2b
This was prepared similarly from [PdBr2(SMe2)2] (0.039 g,
0.10 mmol) and rac-1 (0.049 g, 0.10 mmol). Yield 0.066 g, 87%.
IR (KBr): m(NH) 3267, 3410, 3503 cm−1; 1H NMR (DMSO-d6):
10.38–9.64 (m, 8H, NH); 9.15–8.31 (m, 16H, H2,6 py); 8.11–
7.57 (m, 32H, H4 py, HA,B,C C10H6); 7.52–7.08 (m, 24H, H5 HD,E
C10H6); 6.85 (d, 3JHH = 8 Hz, 8H, HF C10H6); Anal. Calcd. (%) for
C32H22N4O2PdBr2: C: 50.52, H: 2.91, N: 7.36 Found: C: 50.16,
H: 2.66, N: 6.91.
Scheme 4
The ability to organize self-assembled functional molecules
into ordered arrays is an important step in the development
of molecular materials. This work shows that self-assembly
of novel [2]catenanes in solution can be combined with solid
state self-assembly to give ordered arrays of the [2]catenanes.
The key is to have enough functional groups in the precursor
molecules to direct first the molecular self-assembly, then the
supramolecular self-assembly of the [2]catenane and, finally, the
solid state self-assembly to give the supramolecular polymer of
chiral [2]catenanes.
trans-[{(PdCl2)2(l-R-1)2}2], 2c
This was prepared similarly from [PdCl2(SMe2)2] (0.030 g,
0.10 mmol) and R-1 (0.049 g, 0.10 mmol). Yield 0.057 g, 86%.
IR (KBr): m(NH) 3346, 3409, 3503 cm−1; 1H NMR (DMSO-d6):
10.34–9.79 (m, 8H, NH); 9.10–8.46 (m, 16H, H2,6 py); 8.16–
7.71 (m, 32H, H4 py, HA,B,C C10H6); 7.63–7.21 (m, 24H, H5 HD,E
C10H6); 6.96 (d, 3JHH = 8 Hz, 8H, HF C10H6); Anal. Calcd. (%) for
C32H22N4O2PdCl2: C: 57.21, H: 3.30, N: 8.34 Found: C: 56.83,
H: 2.95, N: 7.79.
Experimental
X-Ray structure determinations
NMR spectra were recorded using a Varian Inova 400 NMR
spectrometer. 1H and 13C chemical shifts are reported relative to
tetramethylsilane (TMS). The NMR labeling is defined in Fig. 4.
Crystals were mounted on glass fibres. Data were collected
using a Nonius-Kappa CCD diffractometer using COLLECT
D a l t o n T r a n s . , 2 0 0 5 , 2 6 8 – 2 7 2
2 7 1

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(Nonius, B.V. 1998) software. The unit cell parameters were
calculated and refined from the full data set. Crystal cell
refinement and data reduction was carried out using the Nonius
DENZO package. The data were scaled using SCALEPACK
(Nonius, B.V. 1998). The SHELX-TL V5.1 and SHELX-TL
V6.1 (G. M. Sheldrick) program packages were used to solve
and refine the structures. The structures were solved by direct
methods. Except as mentioned, all non-hydrogen atoms were
refined with anisotropic thermal parameters. The hydrogen
atoms were calculated geometrically and were riding on their
respective carbon atoms. Thermal ellipsoid diagrams are shown
at 30% probability.
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rac-1,1ꢀ-C20H12-2,2ꢀ-(NHC(O)-3-C5H4N)2, rac-1
Crystals of C32H22N4O2·THF were grown by diffusion of hexane
into a THF solution of the compound. Formula C36H30N4O3,
fw = 566.64, monoclinic, space group P2(1)/n, a = 9.966(2), b =
◦
3
˚
˚
30.966(6), c = 10.167(2) A, b = 113.65(3) , V = 2874.0(10) A ,
Z = 4, T = 150(2) K, qcalcd. = 1.310 Mg m−3, l = 0.085 mm−1, k =
0.71073 A, hmax = 25.04◦, 20639 reflections, 5046 independent
˚
reflections, GOF=1.060, R1[I >2r(I)]=0.0622, wR2=0.1754,
−3
˚
largest difference peaks 0.412/−0.405 e A . One of the pyridyl
groups was disordered over two positions and was modeled as
a 70 : 30 isotropic mixture. The THF solvent molecule was also
disordered over two positions and was modeled as a 50 : 50
isotropic mixture with geometric restraints.
trans-[{(PdCl2)2(l-rac-1)2}2], 2a
Crystals of C128H88Cl8N16O8Pd4·10.1CH2Cl2 were grown by
diffusion of hexane into a solution of 2a, formed in situ
in dichloromethane (the pure complex does not redissolve
in dichloromethane). Formula C138.1H108.2Cl28.2N16O8Pd4, fw =
3543.08, monoclinic, space group C2/c, a = 33.094(7), b =
◦
3
˚
˚
14.712(3), c = 35.077(7) A, b = 107.77(3) , V = 16264(6) A ,
Z = 4, T = 150(2) K, qcalcd. = 1.447 Mg m−3, l = 0.954 mm−1, k =
0.71073 A, hmax = 21.97◦, 15571 reflections, 9413 independent
˚
reflections, GOF = 1.058, R1 [I > 2r(I)] = 0.0871, wR2 =
−3
˚
0.2563, largest difference peaks 1.275/−0.648 e A . One ligand
was disordered over two positions and was modeled as a 50 :
50 isotropic mixture with geometric restraints. The majority
of the solvent molecules were highly disordered and all were
modeled with geometric restraints. One solvent molecule was
modeled as a 50 : 50 mixture, with one shared chlorine atom at
full occupancy. Another solvent was modeled at full occupancy
with one of the chlorine atoms disordered over two positions
in a 70 : 30 ratio. One solvent molecule was highly disordered
around a symmetry element and was modeled as a four part
25 : 25 : 25 : 25 isotropic mixture without hydrogen atoms.
One partial occupancy solvent molecule was modeled as a 4
part isotropic mixture with occupancies of 25 : 25 : 15 : 15.
A 75% occupancy solvent molecule was modeled with two
positions for one of the chlorine atoms in a 40 : 35 ratio.
The remaining two partial occupancy solvent molecules (50%
and 25%, respectively) were not disordered. For the solvent
molecules, only the chlorine atoms with occupancies of at least
50% were refined anisotropically.
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J. F. Stoddart, A. J. P. White, D. J. Williams and P. G. Wyatt, Chem.
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CCDC reference numbers 249203 and 249204.
See http://www.rsc.org/suppdata/dt/b4/b413258k/ for cry-
stallographic data in CIF or other electronic format.
Acknowledgements
We thank the NSERC (Canada) for financial support and for a
scholarship to TJB. RJP thanks the Government of Canada for
a Canada Research Chair.
9 M. M. Olmstead, A. S. Ginwalla, B. C. Noll, D. S. Tinti and A. L.
Balch, J. Am. Chem. Soc., 1996, 118, 7737.
2 7 2
D a l t o n T r a n s . , 2 0 0 5 , 2 6 8 – 2 7 2