Exo-ligands based on two p-aminopyridine interconnection by tuneable alkyl chains: Design, synthesis and structural analysis of silver and palladium metallamacrocycles

Article abstract of DOI:10.1039/a803166e

Exo-ligands based on functionalisation of diazacyclic cores of variable size by two pyridines has been achieved; under self-assembly conditions, their ability to form metallamacrocycles in the presence of Pd^II or Ag^II was demonstrated by X-ray crystallography.

Full text of DOI:10.1039/a803166e

View Article Online / Journal Homepage / Table of Contents for this issue
Exo-ligands based on two p-aminopyridine interconnection by tuneable alkyl
chains: design, synthesis and structural analysis of silver and palladium
metallamacrocycles
Raoul Schneider,a Mir Wais Hosseini,*a† Jean-Marc Planeix,a Andre´ De Cianb and Jean Fischerb
a Laboratoire de Chimie de Coordination Organique, Universite´ Louis Pasteur, F-67000 Strasbourg, France, UMR CNRS 7513
b Laboratoire de Cristallochimie et Chimie Structurale, Universite´ Louis Pasteur, F-67000 Strasbourg, France, UMR CNRS 7513
Exo-ligands based on functionalisation of diazacyclic cores
of variable size by two pyridines has been achieved; under
self-assembly conditions, their ability to form
metallamacrocycles in the presence of PdII or AgII was
demonstrated by X-ray crystallography.
treatment of 1, 2 or 313 with 4-chloropyridine gave compounds
4 (20%) and 7 (22%), 5 (39%) and 8 (28%) or 6 (13%) and 9
(38%) respectively.
The formation of metallamacrocycles using PdII was
achieved by mixing at room temp. an EtOH solution of ligands
4–6 with an aqueous solution of [Pd(NO3)2(en)] (en
=
Since the pioneering investigations by Fujita et al.1 and by
Saalfranck et al.2 on metallamacrocycles considerable efforts
have been focused on the design and synthesis of macrocyclic
and macrobicyclic structures composed of metal centres
connected by organic fragments.3 The majority of metallmac-
rocycles reported so far are based on bis-monodentate ligands
such as 4,4A-bipyridine, pyrimidine, bipyrazine, 4,7-phenan-
throline or bis-pyridines interconnected by rigid or flexible
spacers.4 The same type of ligands has been also used for the
formation of coordination networks.5 p-Dimethylaminopyri-
dine (dmap) shows strong alkaline character. We thought that
one could take advantage of its peculiar electronic distribution
for the design of ligands capable of forming metallamacro-
cycles. In order to interconnect two or more metals into a cyclic
framework, the ligand needs to be of the exo type, i.e. it should
possess at least two coordination sites oriented in divergent
fashion. We have previously reported exo-ligands based on
2,2A-bipyridine derivatives,6 catechol units7 or of mercaptoca-
lixarene type.8 We now report the design, synthesis and
structural analysis of exo-bis-monodentate ligands based on two
dmap derivatives and of their binuclear silver and palladium
metallamacrocycles.
The design of exo-ligands 4–6 (Scheme 1) was based on the
interconnection of two p-aminopyridine substructures at the 4
position by two tuneable alkyl bridges. Ligands 4–6 may also be
regarded as diazacycloalkanes9 1–3 bearing two pyridines. We
have previously used cyclic diamines for the design of
cyclospermidines and cyclospermines10 and as backbones
connecting donor and acceptor groups.11 The design of 4–6 is
rather versatile since, by controlling the size and thus the
conformation of the medium size cyclic core and by choosing
metals with specific coordination demands, one may investigate
structural aspects in the formation of metallamacrocycles under
self-assembly conditions.
ethylenediamine). Upon addition of EtOH and Et2O complexes
were collected after several days as colourless crystalline
materials. In addition to solution NMR spectroscopy, crystals
were analysed by FAB+ spectrometry which revealed the
formation of a trinuclear complex {[43{Pd(en)}3(NO3)6]} for
the ligand 4 and binuclear complexes {[L2{Pd(en)}2(NO3)4], L
= 5 or 6} for ligands 5 and 6. For the [62{Pd(en)}2(NO3)4]
complex the structure could be determined by X-ray crystallog-
raphy which indeed revealed the formation of a PdII binuclear
metallamacrocycle.‡ Although in the crystal H2O and EtOH
2
molecules were present none of them nor NO3 anions were
clathrated in the cavity of the macrocycle. In principle, owing to
the non-symmetric nature of 6, two different isomeric com-
plexes, one with C2v and the other with D2h ideal symmetry may
be envisaged (Fig. 1). The difference between these two isomers
originates from the mutual orientation of the cyclic cores.
However in the solid state, only the complex with C2v symmetry
was observed (Fig. 2). The crystal structure showed the
following features: (i) two ligands 6 bridge two Pd centres by
adopting a bent conformation; (ii) as expected, both nitrogen
atoms of the diaza core show a marked sp2 character with an
average C–N–C angle of ca. 120.3° and N–C distance of 1.37 Å
demonstrating the delocalization of the nitrogen lone pairs on
the pyridine rings; (iii) the coordination geometry around Pd
atoms is almost square planar with the N–Pd–N angle varying
from 83.7 to 93.5°; (iv) the average N–Pd distance is ca. 2.03 Å;
(v) with Pd···Pd distance is 11.35 Å.
4+
N
N
N
N
N
N
N
N
N
N
N
N
–
Pd
Pd
4NO3
The synthesis of 4–6 was achieved by treating under reflux a
mixture of 4-chloropyridine, PhLi and compounds 1–3 in a
1:2.2:2.5 ratio in diethylether.12 The yields reported are based
on 4-chloropyridine. In all cases studied, in addition to 4–6, the
mono-substituted compounds 7–9 were also isolated. Thus,
4+
N
N
N
N
N
N
N
N
1 X = Y = H, n = m = 0
2 X = Y = H, n = 0, m = 1
3 X = Y = H, n = 1, m = 2
N
N
N
N
–
Pd
Pd
4NO3
4 X = Y = Py, n = m = 0
(CH2)n
(CH2)m
5 X = Y = Py, n = 0, m = 1
6 X = Y = Py, n = 1, m = 2
7 X = H, Y = Py, n = m = 0
8 X = H, Y = Py, n = 0, m = 1
9 X = H, Y = Py, n = 1, m = 2
XN
NY
Fig. 1 Two possible isomeric structures D2h (top) and C2v (bottom) for the
[62{Pd(en)}2] metallamacrocycle
Scheme 1
Chem. Commun., 1998
1625

View Article Online
6 which adopt a bent conformation; (ii) as in the previous case,
both nitrogen atoms of the diaza core show a marked sp2
character with an average C–N–C angle of ca. 121.1° and N–C
distance of 1.36 Å; (iii) the coordination geometry around Ag
atoms is almost linear with an average N–Ag–N angle of ca.
175.8°; (iv) the average N–Ag distance is ca. 2.10 Å; (v) the
Ag···Ag distance is 3.36 Å; (vi) quite interestingly, in the crystal
the metallamacrocycles form a one dimensional network
through four strong silver–aromatic (pyridine) interactions per
unit with an average Ag–centroid distance of 3.43 Å (Fig. 4).
In conclusion, it has been demonstrated that a class of exo
ligands based on the interconnection of two p-aminopyridines
forms by self-assembly metallamacrocycles in the presence of
PdII or AgI metals. A systematic investigation on the role of the
conformation of the cyclic core is under current investigation.
N
C
Pd
Fig. 2 Crystal structure of the [62{Pd(en)}2 (NO3)4] metallamacrocycle (see
text for bond angles and distances). Solvent molecules, anions and H atoms
are not presented for sake of calrity.
Notes and References
† E-mail: hosseini@chimie.u-strasbg.fr
‡
Crystallographic data: [62{Pd(en)}2(NO3)4] (colorless, 173 K):
2+
C19H30N6Pd·4NO3·2C2H5OH·5H2O, M = 1328.02, monoclininc, space
group P21/c, a = 13.005(2) b = 16.532(2), c = 13.622(1) Å, U = 2927(1)
Å3, b = 91.603(9)°, Z = 2, Dc = 1.34 g cm23, MACH3 Nonius, Mo-Ka,
m/mm21 = 0.657, 4549 data with I > 3s(I), R = 0.057, Rw = 0.075.
[62Ag2(PF6)2] (colorless, 173 K): C34H44N8Ag2·2PF6, M = 1070.45,
monoclinic, space group P21/c, a = 7.6250(2), b = 23.5140(9), c =
10.9360(4) Å, b = 93.105(7)°, U = 1957.9(2) Å3, Z = 2, Dc = 1.82
g cm23, Nonius Kappa CCD, Mo-Ka, m/mm21 = 1.164, 2958 data with
I > 3s(I), R = 0.053, Rw = 0.073. CCDC 182/885.
N
N
N
N
Ag
Ag
N
N
N
N
–
2PF6
2+
N
N
N
N
Ag
Ag
N
N
N
N
–
2PF6
1 M. Fujita, J. Yakaki and K. Ogura, J. Am. Chem. Soc., 1990, 112, 5645;
M. Fujita, J. Synth. Org. Chem. Jpn., 1996, 54, 953.
2 R. W. Saalfrank, A. Stark, K. Peters and H.-G. von Schnering, Angew.
Chem., Int. Ed. Engl., 1988, 27, 851.
3 J. K. M. Sanders, Comprehensive Supramolecular Chemistry, ed. J. L.
Atwood, J. E. D. Davies, D. D. MacNicol and F. Vo¨gtle, vol. 9 (ed. J. P.
Sauvage and M. W. Hosseini), Elsevier, Amsterdam, 1996, pp.
131–164; P. J. Stang and B. Olenyuk, Acc. Chem. Res., 1997, 30, 502;
C. M. Drain and J.-M. Lehn, J. Chem. Soc., Chem. Commun., 1994,
2313; T. Beissel, R. E. Powers and K. N. Raymond, Angew. Chem., Int.
Ed. Engl., 1996, 35, 1084.
Fig. 3 Two possible isomeric structures D2h (top) and C2v (bottom) for the
[62Ag2] metallamacrocycle
C
N
Ag
4 C. V. Krishnamohan Sharma, S. T. Griffin and R. D. Rogers, Chem.
Commun., 1998, 215; R.-D. Schnebeck, L. Randaccio, E. Zangrando
and B. Lippert, Angew. Chem., Int. Ed. Engl., 1998, 37, 119; J. R. Hall,
S. J. Loeb, G. K. H. Shimizu and G. P. A. Yap, Angew. Chem., Int. Ed.
Engl., 1998, 37, 121.
5 R. Robson, in Comprehensive Supramolecular Chemistry, ed. D. D.
Macnicol, F. Toda and R. Bishop, Pergamon, New York, 1996, vol. 6,
p. 733; L. Carluci, G. Ciani, D. M. Proserpio and A. Sironi, J. Am. Chem.
Soc., 1995, 117, 4562; T. L. Hennigar, D. C. MacQuarrie, P. Losier,
R. D. Rogers and M. J. Zaworotko, Angew. Chem., Int. Ed. Engl., 1997,
36, 972; M. A. Withersby, A. J. Blake, N. R. Champness, P. Hubberstey,
W.-S. Li and M. Schro¨der, Angew. Chem., Int. Ed. Engl., 1997, 36,
2327; D. Whang and K. Kim, J. Am. Chem. Soc., 1997, 119, 451; O. M.
Yaghi, H. Li and T. L. Groy, Inorg. Chem., 1997, 36, 4292.
6 C. Kaes, M. W. Hosseini, R. Ruppert, A. De Cian and J. Fischer,
Tetrahedron Lett., 1994, 35, 7233; J. Chem. Soc., Chem. Commun.,
1995, 1445; C. Kaes, M. W. Hosseini, A. De Cian and J. Fischer,
Tetrahedron Lett., 1997, 38, 3901; 4389; Chem. Commun., 1997, 229.
7 E. Graf, M. W. Hosseini and R. Ruppert, Tetrahedron Lett., 1994, 35,
7779; C. Drexler, M. W. Hosseini, A. De Cian and J. Fischer,
Tetrahedron Lett., 1997, 38, 2993; C. M. Drexler, M. W. Hosseini, G.
Stupka, J.-M. Planeix, A. De Cian and J. Fischer, Chem. Commun.,
1998, 689; G. Mislin, E. Graf and M. W. Hosseini, Tetrahedron Lett.,
1996, 37, 4503.
8 X. Delaigue, J. McB. Harrowfield, M. W. Hosseini, A. De Cian, J.
Fischer and N. Kyritsakas, J. Chem. Soc., Chem. Commun., 1994, 1579;
X. Delaigue, M. W. Hosseini, A. De Cian, N. Kyritsakas and J. Fischer,
J. Chem. Soc., Chem. Commun., 1995, 609.
9 R. W. Alder, Acc. Chem. Res., 1983, 16, 321.
10 G. Brand, M. W. Hosseini and R. Ruppert, Tetrahedron Lett., 1994, 35,
8609.
11 R. Schneider, M. W. Hosseini and J.-M. Planeix, Tetrahedron Lett.,
1996, 35, 4721.
12 T. Kauffmann and F.-P. Boettcher, Chem. Ber., 1962, 88, 1528.
13 H. Yamamoto and K. Maruoka, J. Am. Chem. Soc., 1981, 103, 4186.
Fig. 4 A portion of the crystal structure of the [62Ag2(PF6)2] metal-
lamacrocycle (see text for bond angles and distances) showing the
formation of an infinite network formed by double Ag–aromatic inter-
actions between consecutive units. Anions and H atoms are not presented
for sake of clarity.
The formation of metallamacrocycles using AgI was investi-
gated by diffusion at room temp. of a EtOH solution of ligand
6 with an aqueous solution of AgPF6. After several days
colourless crystals of the complex were filtered and further
washed with Et2O. The complex was characterised by NMR and
by FAB spectrometry. Furthermore, in the solid state the
structure of [62Ag2(PF6)2] complex was elucidated by X-ray
crystallography.‡ Again, as in the above mentioned Pd case,
two different isomeric complexes may be envisagted (Fig. 3).
Once again the complex with C2v symmetry was observed (Fig.
4). The crystal analysis showed the following features: (i) the
binuclear metallamacrocycle is formed through the bridging of
two AgI atoms by two pyridine units belonging to two ligands
Received in Basel, Switzerland, 27th April 1998, 8/03166E
1626
Chem. Commun., 1998