Communication
Organic & Biomolecular Chemistry
ported by Grants from the GIF, the German–Israeli Foundation
for Scientific Research and Development, and by the Israel
Science Foundation. VR thanks the PBC foundation for a post-
doctoral fellowship.
Scheme 5 Epoxidation of cyclohexene.
Notes and references
1
For general reviews see: (a) C. Floriani and R. Floriani-
Moro, Adv. Organomet. Chem., 2001, 47, 167; (b) C. Wieser,
C. B. Dieleman and D. Matt, Coord. Chem. Rev., 1997, 165,
93.
a
Table 2 Alkene polymerization catalyzed by 7
Time, Activity 1
(g mol− h−1
)
Stereochemistry
b
Entry Alkene
h
2
(a) S. R. Dubberley, A. Friedrich, D. A. Willman,
P. Mountford and U. Radius, Chem. – Eur. J., 2003, 9, 3634;
1
2
3
1-Hexene (neat)
Styrene (neat)
10
3
15.3
52.3
11.2
Atactic
Syndiotactic
Syndiotactic
(
b) T. Hascall, K. Pang and G. Parkin, Tetrahedron, 2007, 63,
Styrene (toluene) 12
10826; (c) T. Hascall, A. L. Rheingold, I. Guzei and
G. Parkin, Chem. Commun., 1998, 101; (d) L. Liu,
L. N. Zakharov, J. A. Golen, A. L. Rheingold, W. H. Watson
and T. A. Hanna, Inorg. Chem., 2006, 45, 4247.
(a) L. Giannini, A. Caselli, E. Solari, C. Floriani, A. Chiesi-
Villa, C. Rizzoli, N. Re and A. Sgamellotti, J. Am. Chem. Soc.,
a
Reaction conditions 7 mg (10 µmol) of 7, 500 equiv. of MAO
activator), room temperature, 3.39 g (5 mL) of 1-hexene, 1.18 g (2 ml)
of styrene, 2 ml of styrene in 10 ml of toluene. Determined by
NMR.
(
b 13
C
3
1997, 119, 9198; (b) J. Hesschenbrouck, E. Solari,
C. Floriani, N. Re, C. Rizzoli and A. Chiesi-Villa, J. Chem.
Soc., Dalton Trans., 2000, 191; (c) M. G. Gardiner,
S. M. Lawrence, C. L. Raston, B. W. Skelton and
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A. H. White, Chem. Commun., 1996, 2487.
Group 4 metal complexes of multidentate N,O-ligands have
received a great deal of recent attention as catalysts for α-olefin
1
7
polymerization. In this regard, it was important to explore
1
8
7
as a catalyst in α-olefin polymerization reactions. While poor
activity in 1-hexene polymerization was observed when 7 was
activated with B(C F ) , using methylaluminoxane (MAO) as an
6
5 3
4
5
(a) D. M. Homden and C. Redshaw, Chem. Rev., 2008, 108,
activator led to a highly active catalytic system (Table 2, entry
). At room temperature, a polymer with high molecular
weight M of 186 kDa and low polydispersity (1.44) was
obtained. Similarly, a combination of 7 and MAO, was reac-
tive in the polymerization of styrene both in neat styrene and
toluene solution. Syndiotactic polystyrene was obtained in
both cases (Table 2, entries 2 and 3).
In conclusion, we developed a one-step synthetic protocol
toward new N,O-type calixarene molecules that rely on copper-
catalyzed amination at the lower rim. The new compounds
serve as dianionic tetradentate ligands in their main-group
and transition metal complexes. A Ti(IV) complex of one such
ligand showed superior catalytic activity in TMS-CN addition
to benzaldehyde and cyclohexene epoxidation reactions com-
pared with complexes of other calixarene-based ligands. It also
behaves as an efficient catalyst for α-olefin polymerization.
More studies on the catalytic properties of the new ligands are
presently underway.
5086.
1
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1
2
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(
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Author contributions
The manuscript was written through contributions of all authors.
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Acknowledgements
We thank Prof. Moshe Kol, Tel Aviv University for help with
the alkene polymerization experiments. This work was sup-
Org. Biomol. Chem.
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