Table 1 Catalytic epoxidation by manganese complexesa
Acknowledgements
[Mn (L) (H O) ](CIO
) , PAA,30 min,0°C
4
Financial support for this research project from the City Univer-
sity of Hong Kong and the Hong Kong Research Grant council
GRF grant (CityU 101108) and CAV grant (CityU 2/06C) is
gratefully acknowledged.
4
4
alkene ⎯⎯2⎯2⎯2⎯⎯⎯⎯⎯⎯⎯⎯→ epoxide
CH CN
3
Entry Ligand (L)
Substrate
Conversionb (%)
99
Yieldb,c (%)
81
1
2
L1
Notes and references
100
92
‡ [Mn2(L1)2(H2O)4](ClO4)4: ESI-MS: m/z 728 [Mn(C40H38N4)](ClO4)+,
+
1558 [Mn2(C40H38N4)2](ClO4)3
; CHN elemental analysis: calc. for
3d
4
90
97
85
>99
83
Mn2(C40H38N4)2(H2O)4(ClO4)4·2CH3CN·7H2O·CH2Cl2: C, 50.48; H, 5.28;
N, 6.92; Found: C, 50.46, H, 5.31, N, 6.98%. [Mn2(L2)2(H2O)4](ClO4)4:
+
ESI-MS: 805 [Mn2(C46H42N4)2](ClO4)22+, 1709 [Mn2(C46H42N4)2](ClO4)3
;
CHN elemental analysis: calc. for Mn2(C46H42N4)2(H2O)4(ClO4)4: C,
58.73; H, 4.93; N, 5.96. Found: C, 58.30, H, 4.93, N, 5.94%.
2+
[Mn2(L3)2(H2O)4](ClO4)4: ESI-MS: 881 [Mn2(C52H46N4)2](ClO4)2
,
5
>99
+
1859 [Mn2(C52H46N4)2](ClO4)3
; CHN elemental analysis: calc. for
Mn2(C52H46N4)2(H2O)4(ClO4)4·5H2O: C, 58.81; H, 5.22; N, 5.28. Found:
C, 58.96, H, 5.20, N, 5.47%.
6
7
100
82
>99
§ Crystal data for [Mn2(L2)2(H2O)(CH3OH)(CH3CN)(ClO4)] (CH3CN)0.5
-
(C4H10O)0.5(ClO4)3: C98H99.5Cl4Mn2N9.5O18.5, M = 1958.05, monoclinic,
90
˚
space group P21, a = 16.5520(6), b = 12.3483(4), c = 25.6368(11) A, V =
3
-3
˚
˚
5072.2(3) A , Z = 2, Dc = 1.282 Mg m , l(Cu-Ka) = 1.54184 A, F000
=
2040, T = 143(2) K, 69145 reflections measured, 17982 unique, Rint = 0.038,
R = 0.0789 (I > 2s(I)) and 0.0865 (for all data), wR2 = 0.2249 (I > 2s(I))
and 0.2375 (for all data), Flack parameter: 0.020(5). CCDC 775970. Crys-
8
89
88
tal data for [Mn2(L3)2(H2O)4](ClO4)4(H2O)1.75: C104H103.5Cl4Mn2N8O21.75
orthorhombic, space group P212121, V = 10173.65(15) A , Z = 4, Dc =
,
3
˚
-3
˚
9e
L2
L3
L4
100
90
78
90
1.348 Mg m , l(Cu-Ka) = 1.54184 A, F000 = 4302, T = 293(2) K, 31704
reflections measured, 16631 unique, Rint = 0.0335, R = 0.0612 (I > 2s(I))
and 0.0796 (for all data), wR2 = 0.1669 (I > 2s(I)) and 0.1799 (for all
data), Flack parameter: 0.009(5). CCDC 775971.
10
1 For review, see: (a) J.-E. Ba¨ckvall, in Modern Oxidation Method, VCH,
Weinheim2004, Chapter 2.5; (b) E. N. Jacobsen, in Comprehensive
Organometallic Chemistry II, ed. E. W. Abel, F. G. A. Stone, G.
Wilkinson, L. S. Hegedus, Pergamon, Oxford, 1995, Vol 12, Chapter
11.1.
2 A. Murphy, G. Dubois and T. D. P. Stack, J. Am. Chem. Soc., 2003,
125, 5250.
3 A. Murphy and T. D. P. Stack, J. Mol. Catal. A: Chem., 2006, 251, 78.
4 I. Garcia-Bosch, A. Company, X. Fontrodona, X. Ribas and M.
Costas, Org. Lett., 2008, 10, 2095.
11e
12
100
100
77
95
13f
3
66
5 I. Garcia-Bosch, X. Ribas and M. Costas, Adv. Synth. Catal., 2009,
351, 348.
6 K. Nehru, S. J. Kim, I. Y. Kim, M. S. Seo, Y. Kim, S.-J. Kim, J. Kim
and W. Nam, Chem. Commun., 2007, 4623.
7 J. Rich, M. Rodr´ıquez, I. Romero, L. Vaquer, X. Sala, A. Llobet, M.
Corbella, M.-N. Collomb and X. Fontrodona, Dalton Trans., 2009,
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a Reaction condition: alkene (0.05 mmol), [Mn2(L)2(H2O)4](ClO4)4 (5 ¥
10-4 mmol), PAA (0.1 mmol), CH3CN (0.15 ml) was used as solvent.
b Determined by GC-FID. c GC yield based on conversion. d Reactions
were carried out at room temperature. e Reaction finished in 60 min.
f Mono-nuclear complex [Mn(L4)2(H2O)2](ClO4)2 was used.
8 For review of polynuclear self-assemble metal complexes, see: (a) M.
Albrecht, Chem. Rev., 2001, 101, 3457; (b) C. Piguet, G. Bernardinelli
and G. Hopfgartner, Chem. Rev., 1997, 97, 2005; (c) J.-M. Lehn,
Supramolecular Chemistry: Concept and perspectives, VCH, Weinheim,
1995, Chapter 9.
9 (a) For earlier report on use of helicate for catalysis, see: H.-L. Kwong,
H.-L. Yeung, W.-S. Lee and W.-T. Wong, Chem. Commun., 2006, 4841;
(b) C.-T. Yeung, H.-L. Yeung, C.-S. Tsang and W.-Y. Wong, Chem.
Commun., 2007, 5203; (c) H.-L. Yeung, K.-C. Sham, C.-S. Tsang, T.-C.
Lau and H.-L. Kwong, Chem. Commun., 2008, 3801.
10 (a) L.-E. Perrett-Aebi, A. von Zelewsky and A. Neels, New J. Chem.,
2009, 33, 462; (b) L.-E. Perret-Aebi, A. von Zelewsky, C. Dietrich-
Buchecker and J.-P. Sauvage, Angew. Chem., Int. Ed., 2004, 43, 4482.
11 (a) E. C. Constable, M. J. Hannon, A. J. Edwards and P. R. Raithby,
J. Chem. Soc., Dalton Trans., 1994, 2669; (b) E. C. Constable, M. J.
Hannon and D. A. Tocher, Angew. Chem., Int. Ed. Engl., 1992, 31, 230.
12 M. Du¨ggeli, C. Goujon-Ginglinger, S. R. Ducotterd, D. Mauron, C.
Bonte, A. von Zelewsky, H. Steockli-Evans and A. Neels, Org. Biomol.
Chem., 2003, 1, 1894.
1-hexene to epoxides with excellent selectively (up to 99%, Entries
2–6). In terms of enantioselectivity, although the catalysts are
chiral, unfortunately no asymmetric induction has been observed
(<5% ee in all cases). To study how the supramolecular structure
affects the catalytic activity of the epoxidation, mononuclear
analogy of L1, [Mn(L4)2(H2O)2](ClO4)2, was also prepared and
its catalytic epoxidation investigated. Under the same conditions,
this mononuclear complex gives almost no reaction (Entry 13).
In summary, we have presented the first synthesis of chiral
supramolecular binuclear manganese double-stranded helicates.
The helical structures have been determined by X-ray crystallog-
raphy. These structures are retained in solution as shown by CD
experiments. These supramolecular manganese systems are excel-
lent epoxidation catalysts. Unfortunately no enantioselectivity has
been observed so far. Further experiments are underway to modify
the systems to achieve more reactive and enantioselective catalysts.
13 L. J. Charbonnie`re, A. F. Williams, U. Frey, A. E. Merbach, P.
Kamalaprija and O. Schaad, J. Am. Chem. Soc., 1997, 119, 2488.
14 M. D. Ward, Chem. Commun., 2009, 4487.
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The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 9469–9471 | 9471
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