process. To the best of our knowledge, the framework
constitutes the first example of a 3D metal-coordination
driven cage with three compartments.
catenanes,15 grids,16 and Borromean links.17 Extending
the homoleptic [M(iminopyridine)m]nþ motif to constitu-
tionally dynamic heteroleptic [M(L)(iminopyridine)]nþ
complexes (Scheme 1) should even further increase our
options for highly intricate and diverse structures.18
For a start, we envisaged that already a precursor to the
iminopyridine such as 5-bromo-pyridine-2-carbaldehyde (2)
may combine with 2,9-dimesityl[1,10]phenanthroline (1)
and Cuþ to the heteroleptic copper(I) complex C1
(Scheme 2). Indeed, quantitative formation of C1 was
immediately observed upon addition of 2 to a solution of 1
and [Cu(CH3CN)4]PF6 in CD2Cl2 as evidenced from spec-
troscopic data (see Supporting Information). As a result of
the complexation of 2 to Cuþ, the aldehyde functionality
should become even more susceptible toward nucleophilic
reagents, such as amines. Indeed, addition of p-toluidine (3)
to a solution of C1 (Scheme 2) led to quantitative formation
of the iminopyridine ligand 4 at the Cuþ center, thereby
furnishing the heteroletic complex C2, as confirmed by
spectroscopic evidence (see Supporting Information).
Scheme 1. Illustration of the HETPHEN Concept8 and Its
Extention to Heteroleptic Complexes Involving the Iminopyr-
idine Ligand
Over years, heteroleptic copper(I) bisphenanthroline
complexes have been prepared in our group using the
HETPHEN concept (Scheme 1). As a result of a finely
tuned balance of steric and electronic effects, emerging
from the two bulky diaryl substituents of phenanthroline
L, the thermodynamically controlled, exclusive formation
of the heteroleptic complex is warranted despite the fact
that it is kinetically labile. The latter property has been
essential for the use of this complex motif in the construc-
tion of a wide number of dynamic supramolecular
structures.9
Scheme 2. Synthesis of Heteroleptic Complexes C1 and C2
The charm of using imine bond formation at metal ions
lies in the fact that it involves the coupled formation of a
covalent CdN and a new coordinative (nitrogenꢀmetal)
bond, establishing both the new ligand and complex at the
same time.10 As a consequence, the metal ion directed and
templated synthesis of imine bonds has been employed
in the creation of a good number of complex structures,
such as macrocycles,7a,11 helicates,12 cages,13 rotaxanes,14
To gain additional mechanistic insight into the forma-
tion of the iminopyridine ligand at the phenanthroline-
Cuþ center, some model experiments were carried out. In a
first set of experiments, both 2 and 3 were taken in a 1:1
(9) (a) Schmittel, M.; Ganz, A.; Fenske, D. Org. Lett. 2002, 4, 2289.
(b) Schmittel, M.; Kishore, R. S. K. Org. Lett. 2004, 6, 1923.
(c) Schmittel, M.; Mahata, K. Chem. Commun. 2008, 2550.
(10) (a) Nitschke, J. R. Acc. Chem. Res. 2007, 40, 103. (b) Meyer,
C. D.; Joiner, C. S.; Stoddart, J. F. Chem. Soc. Rev. 2007, 36, 1705.
(11) Hubin, T, J.; Busch, D. H. Coord. Chem. Rev. 2000, 200, 5.
(12) (a) Barbiou, M.; Dumitru, F.; Legrand, Y.-M; Petit, E.; Van der
Lee, A. Chem. Commun. 2009, 2192. (b) Campbell, V. E.; de Hatten, X.;
Delsuc, N.; Kauffmann, B.; Huc, I.; Nitschke, J. R. Nat. Chem. 2010, 2,
1
ratio in an NMR tube and dissolved in CD2Cl2. The H
NMR of the resulting solution showed that 4 emerged in a
typical equilibrium with both starting materials, 2 and 3,
1
€
684. (c) Domer, J.; Slootweg, J. C.; Hupka, F.; Lammertsma, K.; Hahn,
(4:2:3 ≈ 1:0.1:0.1; based on integration in the H NMR)
F. E. Angew. Chem., Int. Ed. 2010, 49, 6430.
remaining constant over 3 days after mixing (see
Supporting Information). Upon addition of 1 equiv of
[Cu(CH3CN)4]PF6 and 1 each, a red solution formed
instantaneously. A 1H NMR measurement confirmed the
clean formation of C2 (Scheme 2). Thus, the metal ion,
acting as both catalyst and binding “glue” to the emergent
ligand, drives the formation of 4 to completion.
(13) (a) Fan, J.; Bats, J. W.; Schmittel, M. Inorg. Chem. 2009, 48,
6338. (b) Granzhan, A.; Riis-Johannessen, T.; Scopelliti, R.; Severin, K.
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(14) Hogg, L.; Leigh, D. A.; Lusby, P. J.; Morelli, A.; Parsons, S.;
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(15) Leigh, D. A.; Lusby, P. J.; Teat, S. J.; Wilson, A. J.; Wong,
J. K. Y. Angew. Chem., Int. Ed. 2001, 40, 1538.
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2003, 100, 11970. (b) Barbiou, M.; Petit, E.; van der Lee, A.; Vaughan,
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