electron reduction of the quinonediimine moiety. The EPR
spectrum of 2· in DMSO showed the signals centered at g =
palladium center affords a tetrametallic macrocyclic skeleton as
depicted in Fig. 2, which is consistent with the spectroscopically
nonequivalent protons of the phenylethyl moieties of 3 in the H
2
1
2.004 accompanied by hyperfine coupling (A
N
= 6.7 G; A
H
=
7
.2 G; A = 1.6 G; APd = 4.0 G). The unpaired electron appears
H
NMR spectrum. A remarkable feature in the structure is that the
coordination plane of palladium is composed of the pyridine
and two amide moieties which are orientated in up and down
fashion to create an open cavity with a cone conformation. The
coordination planes of the palladium centers are inclined in a
range of 51.4°–60.5° from the plane defined by the four
coordinated amide oxygen atoms.
to locate mostly on the quinonediimine moiety although some
delocalization onto the metal is indicated by the weak satellite
05
lines due to 1 Pd coupling.
1
It should be noted that the macrocyclic tetramer [(L )Pd]
4
(3)
was obtained quantitatively by treatment of 1 in dichloro-
methane or chloroform at reflux temperature (Scheme 2). No
other products were formed. This stable self-assembled com-
plex is considered to be formed through removal of a labile
acetonitrile ligand in the absence of an additional ligand. The
structure of 3 was elucidated by spectral data. In the H NMR
spectra, the signals attributable to the methylene protons of the
phenylethyl moieties exhibited nonequivalent resonances in
In conclusion, a conjugated homobimetallic palladium(II
)
complex was formed by one-pot oxidative complexation of
1,4-phenylenediamine with a palladium(II) complex bearing the
tridentate ligand, which, in the absence of a ligand undergoes
controlled formation of a macrocyclic tetramer via removal of a
labile solvent ligand.
1
CD
dium center. By contrast, those of 1 are magnetically equivalent
with the expected triplet in CD CN. The ESI-MS spectrum also
2
Cl
2
, indicating unsymmetrical coordination to the palla-
This work was financially supported in part by a Grant-in-
Aid for Scientific Research on Priority Areas from the Ministry
of Education, Culture, Sports, Science and Technology, Japan.
We thank Professor R. Arakawa at Kansai University for the
ESI-MS measurement. Thanks are also due to the Analytical
Center, Faculty of Engineering, Osaka University for the use of
their facilities.
3
+
supported the formation of 3 (m/z 1912.4 [M + H] ).
Interestingly, treatment of 3 with acetonitrile led to the
dissociative formation of 1. The transformation between 1 and
3
was found to be reversible, which can be controlled by the
solvent exchange. Reversible formation of the metal-assembled
complex by solvent exchange provides a strategy to construct
switchable nanostructures.
Further structural information of 3 was obtained by X-ray
crystallography.‡ The coordination of the amide oxygen to the
48 8 4 2 3
H N O Pd ·2CH CN, M = 1143.91,
3
21
3
21
w
= 0.374. Chloroform solvent molecule
was treated isotropically. Despite modelling the disorder, a good result was
not obtained probably due to the data quality. In this context, C214, C219,
C316 and C317 carbon atoms were refined isotropically.
CCDC reference numbers 178475 and 178476. See http://www.rsc.org/
suppdata/cc/b2/b203726m/ for crystallographic data in CIF or other
electronic format.
1
(a) A. G. MacDiarmid, L. S. Yang, W. S. Huang and B. D. Humphrey,
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Treacy, F. Klavetter, N. Colaneri and A. J. Heeger, Nature, 1992, 357,
Scheme 2
4
77; (e) I. Jestin, P. Frère, P. Blanchard and J. Roncali, Angew. Chem.,
Int. Ed., 1998, 37, 942 and references therein. See also the Nobel lectures
of H. Shirakawa, A. G. MacDiarmid and A. J. Heeger, in Angew. Chem./
Angew. Chem., Int. Ed., 2001, 40, issue 14.
2
For reviews on this subject, see: (a) V. Balzani, A. Juris, M. Venturi, S.
Campagna and S. Serroni, Chem. Rev., 1996, 96, 759; (b) A. Harriman
and J.-P. Sauvage, Chem. Soc. Rev., 1996, 41; (c) F. Paul and C. Lapinte,
Coord. Chem. Rev., 1998, 178/180, 431; (d) R. Ziessel, M. Hissler, A. El-
ghayoury and A. Harriman, Coord. Chem. Rev., 1998, 178/180, 1251; (e)
J. A. McCleverty and M. D. Ward, Acc. Chem. Res., 1998, 31, 842; (f) P.
F. H. Schwab, M. D. Levin and J. Michl, Chem. Rev., 1999, 99, 1863.
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Chem., 2001, 651; (b) T. Moriuchi, M. Miyaishi and T. Hirao, Angew.
Chem., Int. Ed., 2001, 40, 3042.
3
4
For reviews on this subject, see: (a) R. V. Slone, K. D. Benkstein, S.
Bélanger, J. T. Hupp, I. A. Guzei and A. L. Rheingold, Coord. Chem.
Rev., 1998, 171, 221; (b) S. Leininger, B. Olenyuk and P. J. Stang, Chem.
Rev., 2000, 100, 853; (c) G. F. Swiegers and T. J. Malefetse, Chem. Rev.,
2
000, 100, 3483; (d) M. Fujita, K. Umemoto, M. Yoshizawa, N. Fujita,
T. Kusukawa and K. Biradha, Chem. Commun., 2001, 509.
5
(a) S. Campagna, G. Denti, S. Serroni, M. Ciano and V. Balzani, Inorg.
Chem., 1991, 30, 3728; (b) W. T. S. Huck, F. C. J. M. van Veggel, B. L.
Kropman, D. H. A. Blank, E. G. Keim, M. M. A. Smithers and D. N.
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and J.-P. Tuchagues, Inorg. Chem., 1999, 38, 1165.
Fig. 2 Molecular structure of 3 (phenylethyl moieties and hydrogen atoms
are omitted for clarity). Selected bond lengths (Å) and angles (°): Pd(1)–
N(1) 1.913(9), Pd(1)–N(2) 2.00(1), Pd(1)–N(3) 2.06(1), Pd(1)–O(8)
2
8
.064(8), O(1)–C(11) 1.27(2), O(2)–C(21) 1.27(2); N(1)–Pd(1)–N(2)
1.2(5), N(2)–Pd(1)–N(3) 161.3(4), N(1)–Pd(1)–O(8) 174.2(5), N(2)–
Pd(1)–O(8) 96.3(4), N(3)–Pd(1)–O(8) 102.4(4), Pd(1)–O(8)–C(321)
34.3(8).
6 T. Moriuchi, S. Bandoh, Y. Miyaji and T. Hirao, J. Organomet. Chem.,
2000, 599, 135.
1
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1477