Half-rotation in a [2]catenane via interconvertible Pd(II) coordination modes

Article abstract of DOI:10.1039/b510663j

Reaction of a [2]catenane with Pd(OAc)₂ binds both macrocycles to the metal, locking them in position; treatment with PdCl₂, however, results in coordination of only one ring, producing a half-turn in the relative orientation of the [2]catenane components in both solution and the solid state. The Royal Society of Chemistry 2005.

Full text of DOI:10.1039/b510663j

View Article Online / Journal Homepage / Table of Contents for this issue
COMMUNICATION
www.rsc.org/chemcomm | ChemComm
Half-rotation in a [2]catenane via interconvertible Pd(II) coordination
modes{
a
David A. Leigh,* Paul J. Lusby, Alexandra M. Z. Slawin and D. Barney Walker
a
b
a
Received (in Cambridge, UK) 27th July 2005, Accepted 15th August 2005
First published as an Advance Article on the web 13th September 2005
DOI: 10.1039/b510663j
Reaction of a [2]catenane with Pd(OAc)
cycles to the metal, locking them in position; treatment with
PdCl , however, results in coordination of only one ring,
producing a half-turn in the relative orientation of the
2]catenane components in both solution and the solid state.
2
binds both macro-
The square planar coordination preference of Pd(II) can be used
to direct the macrocyclization of suitable tridentate ligands around
5,6
2,6-dimethyleneoxypyridine-based threads to form rotaxanes.
2
We reasoned that a similar strategy could be used to make a
palladium [2]catenate by incorporating the monodentate unit into
a macrocycle. Pleasingly, Pd1 was isolated in 58% yield from 2 via
the three step (ligand coordination, ring-closing olefin metathesis,
[
The development of novel ways to bring about changes in the
relative positions of mechanically interlocked sub-molecular
components is an important area of investigation in the emerging
7
hydrogenation) reaction sequence shown in Scheme 1.
De-metallation of Pd1 (KCN, MeOH–CH Cl , 20 A 40 uC,
2
2
1
field of synthetic molecular machines. In terms of rotational
2
processes, a formal half-turn of a ring in a [2]catenane not only
1.5 h, 97%) afforded the catenane 1H in which pyridine–amide–
2
6
pyridine H-bonding holds the macrocycles in a similar position to
3
corresponds to a simple mechanical switch, but is also a step
that seen for Pd1 in both solution and the solid state. The well
towards the more demanding requirements of a synthetic rotary
4
molecular motor. Here we report on a simple [2]catenane system
defined orientation of the two fragments is clearly apparent from
1
comparison of the H NMR spectra of the two catenanes (Fig. 1b
in which the different binding modes of the interlocked rings to
Pd(II) cause a major change in the position and orientation of the
macrocycles in the resulting complexes.
and c) with those of the non-interlocked component macrocycles
(Fig. 1a and 1e). In the room temperature spectra of both 1H2
(Fig. 1b) and Pd1 (Fig. 1c) the upfield shift of the H , H and H
D
E
F
Scheme 1 Synthesis and interconversion of Pd1, 1H
Pd(1H )Cl MeCN.{
2
and
2
2
a
School of Chemistry, University of Edinburgh, The King’s Buildings,
West Mains Road, Edinburgh, UK EH9 3JJ.
1
2 2 3
Fig. 1 H NMR spectra (400 MHz, 9 : 1 CD Cl : CD CN, 298 K,
E-mail: David.Leigh@ed.ac.uk; Fax: +44-131-667-9085
School of Chemistry, University of St. Andrews, Purdie Building, St.
2
.5 mM) (a) non-interlocked bis-amide macrocycle, (b) 1H
Pd(1H )Cl MeCN and (e) Pd2Cl MeCN (non-interlocked tetra-ether
macrocycle bound to PdCl MeCN). The grey signals correspond to
2
, (c) Pd1, (d)
b
2
2
2
Andrews, Fife, UK KY16 9ST
{
2
Electronic supplementary information (ESI) available: Experimental
procedures and X-ray crystallographic data. See http://dx.doi.org/10.1039/
b510663j
residual solvents. The dark blue circles in the cartoon rings indicate the
position of the pyridine nitrogen atoms.
This journal is ß The Royal Society of Chemistry 2005
Chem. Commun., 2005, 4919–4921 | 4919

View Article Online
1
is dramatic. In the H NMR spectrum of Pd(1H MeCN
Fig. 1d) the resonances corresponding to H , H and H are
alkyl
2
)Cl
2
(
G
g
shifted significantly upfield, indicating that each macrocycle is
9
located preferentially over the aliphatic region of the other. The
X-ray crystal structure (Fig. 2c and d) shows a similar geometry
exists in the solid state. An additional feature of the X-ray crystal
structure of Pd(1H
2
)Cl
Pd–Cl HNCO hydrogen bonds between adjacent molecules
Fig. 2d). The negligible change in the chemical shift of the amide
protons (H ) between 1H (Fig. 1a) and Pd(1H )Cl MeCN
Fig. 1d) suggests this interaction is weak in solution, nevertheless
2
MeCN is the presence of intermolecular
…
(
C
2
2
2
6
(
10
it has been successfully utilised to direct the formation of
pseudorotaxanes.
The three catenanes 1H2, Pd1 and Pd(1H
directly interconvertible (Scheme 1): the palladium complexes
are de-metallated with KCN; Pd(1H )Cl MeCN is converted
into Pd1 by treatment with NaH, and the reverse reaction is
2 2
)Cl MeCN are all
2
2
1
1
promoted by HCl in MeCN. It is interesting to note the
macrocycles adopt similar positions and orientations in Pd1 and
2
1H but in the former they are locked in place by a coordination
bond whereas in the latter they are held in the thermodynamic
minimum only by weak and dynamic H-bonds. The preferred
2 2
co-conformation of Pd(1H )Cl MeCN is very different to the
other two, presumably on steric grounds, and as such its formation
from either of the others corresponds to a large amplitude
rotational switch. It is rare to find such a rich variation in structure
and dynamics made possible through simple manipulation of
coordination modes.
6
7
Fig. 2 X-Ray crystal structures of: (a) 1H
2
,
(b) Pd1, (c)
MeCN (single molecule view; note the change of position
and orientation of the yellow macrocycle compared to Pd1 and 1H ) and
d) adjacent molecules of Pd(1H )Cl MeCN showing intermolecular
8
2 2
Pd(1H )Cl
2
(
2
2
…
Pd–Cl HN hydrogen bonding. Carbon atoms of the bis-amide macro-
cycle are shown in light blue and those of the tetra-ether macrocycle and
coordinated acetonitrile molecule in yellow; oxygen atoms are red,
nitrogen dark blue, hydrogen white, palladium grey, chlorine green. For
clarity only amide hydrogen atoms are shown. Selected bond lengths for
Notes and references
1 V. Balzani, A. Credi, F. M. Raymo and J. F. Stoddart, Angew. Chem.,
Int. Ed., 2000, 39, 3348; J.-P. Sauvage, Chem. Commun., 2005, 1507;
K. Kinbara and T. Aida, Chem. Rev., 2005, 105, 1377.
2
For examples of catenanes which undergo stimuli-induced half-rotations
see: M. Cesario, C. O. Dietrich-Buchecker, J. Guilhem, C. Pascard and
J.-P. Sauvage, J. Chem. Soc., Chem. Commun, 1985, 244; A. Livoreil,
C. O. Dietrich-Buchecker and J.-P. Sauvage, J. Am. Chem. Soc., 1994,
˚
Pd(1H
Selected bond angles for Pd(1H
N5 104.1.
2
)Cl
2
MeCN [A]: N2H–N5 2.21; N11H–N5 2.31; N5–N41 12.93.
2
)Cl MeCN [u]: N2–H–N5 108.8; N11–H–
2
1
16, 9399; D. B. Amabilino, C. O. Dietrich-Buchecker, A. Livoreil,
L. P e´ rez-Garc ´ı a, J.-P. Sauvage and J. F. Stoddart, J. Am. Chem. Soc,
996, 118, 3905; D. A. Leigh, K. Moody, J. P. Smart, K. J. Watson and
1
resonances indicate a p-stacking arrangement between the benzylic
A. M. Z. Slawin, Angew. Chem., Int. Ed. Engl., 1996, 35, 306; A. Livoreil,
J. P. Sauvage, N. Armaroli, V. Balzani, L. Flamigni and B. Ventura,
J. Am. Chem. Soc., 1997, 119, 12114; C. P. Collier, G. Mattersteig,
E. W. Wong, Y. Luo, K. Beverly, J. Sampaio, F. M. Raymo,
J. F. Stoddart and J. R. Heath, Science, 2000, 289, 1172; V. Balzani,
A. Credi, S. J. Langford, F. M. Raymo, J. F. Stoddart and M. Venturi,
J. Am. Chem. Soc., 2000, 122, 3542; D. W. Steuerman, H. R. Tseng,
A. J. Peters, A. H. Flood, J. O. Jeppesen, K. A. Nielsen, J. F. Stoddart
and J. R. Heath, Angew. Chem., Int. Ed., 2004, 43, 6486; B. Korybut-
Daszkiewicz, A. Wie c¸ kowska, R. Bilewicz, S. Domagala and
K. W o´ zniak, Angew. Chem., Int. Ed., 2004, 43, 1668.
amide rings of the ‘blue’ macrocycle and the pyridine group of the
‘orange’ macrocycle. In contrast, the alkyl chain protons are not
shielded by interactions with aromatic rings in either catenane.
1
The solution geometries suggested by H NMR studies correspond
well to the solid state structures of 1H
Fig. 2b) determined by X-ray crystallography. Reaction of
with Pd(OAc) (MeCN, 60 uC, 4 h, 79%) re-forms the
2
(Fig. 2a) and Pd1
(
1
H
2
2
co-conformationally locked catenate, Pd1.
Reaction of 1H with PdCl (MeCN) in MeCN (20 uC, 1 h,
5%) afforded a second catenane Pd(II) complex in which the
3 A ‘switch’ influences a system as a function of state; a ‘motor’ influences
a system as a function of trajectory. For a discussion see: E. R. Kay and
D. A. Leigh, Top. Curr. Chem. (in press).
2
2
2
8
amide protons (H ) of the ‘blue’ macrocycle were clearly still
C
4
D. A. Leigh, J. K. Y. Wong, F. Dehez and F. Zerbetto, Nature, 2003,
24, 174; J. V. Hern a´ ndez, E. R. Kay and D. A. Leigh, Science, 2004,
306, 1532.
present (Fig. 1d). X-Ray crystallography (Fig. 2c and d) on a single
crystal obtained from slow cooling a saturated acetonitrile solution
4
5
A.-M. Fuller, D. A. Leigh, P. J. Lusby, I. D. H. Oswald, S. Parsons and
D. B. Walker, Angew. Chem., Int. Ed, 2004, 43, 3914; Y. Furusho,
T. Matsuyama, T. Takata, T. Moriuchi and T. Hirao, Tetrahedron
Lett., 2004, 45, 9593.
2 2
confirmed this complex to be Pd(1H )Cl MeCN, in which only
one of the macrocyclic rings is coordinated to the palladium
metal ion, presumably as a consequence of both the greater
strength of the Pd–Cl bond compared to Pd–OAc and the poor
6 D. A. Leigh, P. J. Lusby, A. M. Z. Slawin and D. B. Walker, Angew.
Chem., Int. Ed., 2005, 44, 4557.
7
2
basicity of the Cl ion.
For various synthetic routes to Pd1 see: A.-M. L. Fuller, D. A. Leigh,
P. J. Lusby, A. M. Z. Slawin and D. B. Walker, J. Am. Chem. Soc. web
release date 17th August 2005.
The effect of the different coordination mode on the relative
positions and orientations of the two macrocycles in the catenane
4
920 | Chem. Commun., 2005, 4919–4921
This journal is ß The Royal Society of Chemistry 2005

View Article Online
8
Crystallographic data for Pd(1H
diffractometer with graphite-monochromated Mo-Ka radiation (l 5
2
)Cl MeCN: Rigaku MM007/Mercury
2
9 The downfield shift of H
1H is probably caused by coordination of the Pd rather than the
absence of macrocyclic shielding. Similar chemical shifts are observed in
Pd2Cl MeCN (Fig. 1e).
10 B. A. Blight, K. A. Van Noortwyk, J. A. Wisner and M. C. Jennings,
Angew. Chem., Int. Ed, 2005, 44, 1499.
11 For an unusual C-metallated Pd(II) catenate, see: A. J. Blake,
C. O. Dietrich-Buchecker, T. I. Hyde, J.-P. Sauvage and M. Schr o¨ der,
J. Chem. Soc., Chem. Commun., 1989, 1663.
c d 2 2
and H in Pd(1H )Cl MeCN compared to
2
˚
2 5 8 3
.71073 A), 93 K. C64H79Cl N O Pd?CH CN, M 5 1264.68, triclinic,
0
space group P1, a 5 9.8106(8), b 5 25.305(2), c 5 26.820(2) A a 5
¯
˚
2
3
˚
7
D
3.971(4), b 5 82.771(6), c 5 88.050(6)u, V 5 6348.3(9) A , Z 5 4,
23
21
c
5 1.323 Mg m , m 5 0.435 mm . Of 40751 measured data, 21993
were unique (Rint 5 0.0258) and 18202 observed (I . 2s(I)]) to give R
.0524 and wR 5 0.1226. CCDC 279771. See http://dx.doi.org/10.1039/
b510663j for crystallographic data in CIF or other electronic format.
1
5
0
2
This journal is ß The Royal Society of Chemistry 2005
Chem. Commun., 2005, 4919–4921 | 4921