Chiral C1-symmetric 2,2′:6′,2′′-terpyridine ligands: Synthesis, characterization, complexation with copper(II), rhodium(III) and ruthenium(II) ions and use of the complexes in catalytic cyclopropanation of styrene

Article abstract of DOI:10.1016/j.poly.2010.01.017

Three new optically pure C₁-terpyridine ligands (L1-3) were prepared and the copper(II) complexes, of formula [Cu(L)Cl₂], the rhodium(III) complexes, of formula [Rh(L)Cl₃], and the ruthenium(II) complexes, of formula cis-

Full text of DOI:10.1016/j.poly.2010.01.017

Polyhedron 29 (2010) 1497–1507
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
0
0
00
Chiral C -symmetric 2,2 :6 ,2 -terpyridine ligands: Synthesis, characterization,
1
complexation with copper(II), rhodium(III) and ruthenium(II) ions and use of
the complexes in catalytic cyclopropanation of styrene
a
a
a
a
b
Chi-Tung Yeung , Wing-Sze Lee , Chui-Shan Tsang , Shek-Man Yiu , Wing-Tak Wong ,
c
a,
*
Wai-Yeung Wong , Hoi-Lun Kwong
a
Department of Biology and Chemistry and Open Laboratory of Chirotechnology of the Institute of Molecular Technology for Drugs Discovery and Synthesis,
City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
b
c
Department of Chemistry, Hong Kong Baptist University, Waterloo Road, Hong Kong, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Three new optically pure C -terpyridine ligands (L1–3) were prepared and the copper(II) complexes, of
1
Received 3 September 2009
Accepted 13 January 2010
Available online 20 January 2010
formula [Cu(L)Cl
of formula cis- or trans-[Ru(L)(X)Cl
2
], the rhodium(III) complexes, of formula [Rh(L)Cl
3
], and the ruthenium(II) complexes,
-ligand,
2
] (X = DMSO or CO), were synthesized. Structures of a chiral C
1
a copper complex, a rhodium complex and a ruthenium DMSO complex were analysed using X-ray crystal
structure analysis. The copper, rhodium and ruthenium complexes were shown to be precursors of cat-
Keywords:
Chiral terpyridine
Copper
Rhodium
Ruthenium
alysts for cyclopropanation. Reaction of [Cu(L)Cl
converted the complex to catalyst, which in the case of trans-[Ru(L)(CO)Cl
of up to 67% ee for the cis-isomers of styrene cyclopropanes with t-butyl diazoacetate. Comparisons with
-analog of copper, rhodium and ruthenium catalysts were made.
Ó 2010 Elsevier Ltd. All rights reserved.
2
], [Rh(L)Cl
3
] or cis- or trans-[Ru(L)(X)Cl
2
] with AgOTf
2
] gave enantioselectivities
C
2
Metal-catalyzed cyclopropanation
Asymmetric catalysis
1
. Introduction
0
0
00
N
2
,2 :6 ,2 -Terpyridine (tpy) ligands are of great interest in many
N
research fields [1–4]. One such area is supramolecular chemistry,
as tpy can form supermolecular self-assembly through coordina-
tion with metal ions [5–8]. Recently, we have been reported the
N
N
R
N
N
2
use of chiral C -symmetric tpy for supramolecular assembly which
L1: R = H
L2: R = methyl
L3
can be used in catalysis [9]. The development of new chiral version
of tpy should lead to more interesting supermolecular architec-
tural structure and interesting new catalysts. In this study, we re-
port three new C
ruthenium complexes, which are of formula [Cu(L)Cl
and cis- or trans-[Ru(L)(X)Cl ] (X = DMSO or CO), respectively.
The use of some of these complexes in cyclopropanation are dem-
onstrated. To the best of our knowledge, the use of ruthenium ter-
pyridine complexes have not been reported to be efficient catalysts
in the cyclopropanation of olefins before [10]. Comparisons be-
1
-tpy L1–3 and their copper, rhodium and
2
], [Rh(L)Cl
3
]
N
N
2
N
N
N
R
N
R
L4: R = H
L5: R = methyl
L6
tween C
1 2
- and analog C -symmetric ligands, L4–6, of similar com-
plexes have been made.
*
Corresponding author. Tel.: +852 27777304; fax: +852 27887406.
E-mail address: bhhoik@cityu.edu.hk (H.-L. Kwong).
0
277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.01.017

1
498
C.-T. Yeung et al. / Polyhedron 29 (2010) 1497–1507
2
. Experimental
L3. With ketone (1R,5R)-6,6-dimethyl-3-methylenebicy-
clo[3.1.1]heptan-2-one, after workup and purification by recrystal-
2
.1. General information
lization with acetonitrile, the procedure gave 0.35 g (57%) L3: mp
2
5
1
1
26–128 °C; [
a]
D
2 2
= ꢀ58.5° (c = 0.33, CH Cl ); H NMR (300
All reactions were carried out under a dinitrogen atmosphere
MHz, CDCl
3
): d 0.72 (s, 3H), 1.37 (d, J = 9.6 Hz, 1H), 1.46 (s, 3H),
using standard Schlenk techniques. Dichloromethane was distilled
over calcium hydride. THF was distilled under N over sodium/ben-
zophenone. Ethyl diazoacetate, t-butyl diazoacetate and [RuCl (p-
cymene)] of reagent-grade quality were obtained commercially.
Ligands L4–6 were prepared as previously described [11–13].
Chiral ,b-unsaturated ketones (1R,5R)-6,6-dimethyl-2-methyle-
2.35–2.39 (m, 1H), 2.76 (dt, J = 9.7, 3.8 Hz, 1H), 3.02 (d, J = 5.3 Hz,
2H), 3.15 (t, J = 5.3 Hz, 1H), 7.31–7.36 (m, 1H), 7.59 (d, J = 7.9 Hz,
1H), 7.86 (td, J = 7.6, 1.8 Hz, 1H), 7.93 (t, J = 7.9 Hz, 1H), 8.39 (d,
J = 7.6 Hz, 1H), 8.40 (dd, J = 7.9, 0.9 Hz, 1H), 8.45 (dd, J = 7.9, 0.9
2
2
2
1
3
3
Hz, 1H), 8.62–8.65 (m, 1H), 8.69–8.71 (m, 1H); C NMR (CDCl ):
a
d 21.31, 26.05, 30.91, 31.31, 39.20, 40.15, 50.45, 118.88, 120.40,
120.95, 121.19, 123.65, 130.71, 135.99, 136.84, 137.78, 149.04,
152.03, 155.15, 155.83, 156.39, 165.80; ESI-MS (MeOH) m/z: 328
nebicyclo[3.1.1]heptan-3-one, (1R,4S,5R)-4,6,6-trimethyl-2-meth-
ylenebicyclo[3.1.1]heptan-3-one and (1R,5R)-6,6-dimethyl-3-
methylenebicyclo[3.1.1]heptan-2-one were prepared in good
overall yields from (–)-b-pinene and (1R,2R,3R,5S)-(–)-isopinocam-
phenol according to literature procedures [13,14]. 2-Acetyl-6-
+
[M+H] . Single crystals of L3 suitable for X-ray diffraction analysis
were obtained by slow evaporation of a CH
2
Cl
2
solution.
2
] (L = L13)
0
bromopyridine [15], 6-acetyl-2,2 -bipyridine [15] and 6-(1-pyridi-
2.3. General procedure for preparation of [Cu(L)Cl
0
nioacetyl)-2,2 -bipyridine iodide [16] were prepared as previously
ꢀ1
described. Infrared spectra in the range 500–4000 cm
as KBr
2 2
A solution of L (0.2 mmol) in CH Cl (2.5 mL) was added drop-
plates were recorded on a Perkin Elmer Model FT-IR-1600 spec-
wise to a solution of CuCl O (34 mg, 0.2 mmol) in ethanol
2
ꢂ2H
2
1
13
trometer. H and C NMR spectra were recorded on a Varian
00 MHz Mercury instrument. Positive ion mass spectra were
(2.5 mL). The reaction mixture was stirred at reflux for 3 h. The
solution was then cooled to room temperature and diethyl ether
was added until a precipitate was formed. The product was filtered
and washed with diethyl ether. The complex was characterized by
ESI-MS and elemental analyses.
3
taken by PE SCIEX API 365 electro-spray mass spectrometer.
Elemental analyses were performed on a Vario EL elemental ana-
lyzer. Optical rotations were measured by JASCO DIP-370 digital
polarimeter. Melting points were measured by electrothermal dig-
ital melting point apparatus.
[Cu(L1)Cl
82 mg product (89%). Anal. Calc. for C22
6.10; H, 4.67; N, 8.93. Found: C, 56.25; H, 4.67; N, 9.01%; ESI-
2
]. The above procedure was followed using L1 to give
21
H N
3
CuCl O)0.5: C,
2
ꢂ(H
2
5
+
MS (MeOH): m/z 425.3 [MꢀCl] .
[Cu(L2)Cl ]. The above procedure was followed using L2 to give
9 mg product (95%). Anal. Calc. for C23 CuCl O): C, 55.92;
2.2. General procedure for synthesis of terpyridines L1–3
2
8
H
23
N
3
2
ꢂ(H
2
The ligands were synthesized by Kröhnke condensation [17].
H, 5.06; N, 8.51. Found: C, 56.09; H, 5.03; N, 8.50%; ESI-MS
(MeOH): m/z 439.6 [MꢀCl] .
0
+
6
-(1-Pyridinoacetyl)-2,2 -bipyridine iodide (1.5 mmol, 0.58 g),
a
(
,b-unsaturated ketone (2 mmol) and ammonium acetate
25.9 mmol, 2 g) were dissolved in glacial acetic acid (2 mL). The
mixture was refluxed (120 °C) for 12 h. Reaction was quenched
by the addition of saturated NaHCO and then extracted with
Et
O (50 mL ꢁ 3). Solvent was removed under reduced pressure
and brown residue was purified by recrystallization. Products were
2
[Cu(L3)Cl ]. The above procedure was followed using L3 to give
87 mg product (94%). Anal. Calc. for C22
H
21
N
3
CuCl
2
ꢂ(H
2
O)2.5: C,
52.11; H, 5.13; N, 8.30. Found: C, 51.57; H, 5.08; N, 8.48%; ESI-
+
3
MS (MeOH): m/z 425.3 [MꢀCl] .
2
2.4. General procedure for preparation of [Rh(L)Cl
3
] (L = L13)
1
13
characterized by IR, H NMR, C NMR and MS.
L1. With ketone (1R,5R)-6,6-dimethyl-2-methylenebicy-
clo[3.1.1]heptan-3-one, after workup and purification by recrystal-
lization with acetonitrile, the procedure gave 0.31 g (63%) L1: mp
A mixture of L (0.2 mmol) and RhCl O (53 mg, 0.2 mmol) in
ethanol (10 mL) was stirred at reflux for 5 h. After cooling to room
temperature, the solvent was removed under reduced pressure.
3
ꢂ3H
2
2
5
1
1
53–155 °C;
MHz, CDCl ): d 0.70 (s, 3H), 1.34 (d, J = 9.9 Hz, 1H), 1.44 (s, 3H),
.42–2.46 (m, 1H), 2.71–2.78 (m, 1H), 2.84–2.89 (m, 1H), 3.27–
.30 (m, 2H), 7.32–7.38 (m, 1H), 7.41–7.46 (m, 1H), 7.85–7.99
[
a
]
D
= ꢀ80.7° (c = 0.31, CH
2
Cl
2
);
H
NMR (300
2 2 2
The product was recrystallized from CH Cl /Et O to give yellow so-
3
lid, which was filtered and washed with diethyl ether. The complex
1
2
3
was characterized by H NMR, ESI-MS and elemental analyses.
[Rh(L1)Cl
3
]. The above procedure was followed using L1 to give
1
(
m, 2H), 8.31–8.35 (m, 1H), 8.42–8.53 (m, 2H), 8.63–8.66 (m,
98 mg product (91%). H NMR (CDCl ): d 0.71 (s, 3H), 1.38 (d, J = 9.7
3
1
3
1
1
H), 8.71–8.73 (m, 1H); 13C NMR (CDCl
3
): d 21.59, 25.70, 31.27,
Hz, 1H), 1.43 (s, 3H), 2.55–2.62 (m, 1H), 2.69–2.76 (m, 1H), 2.91 (t,
J = 5.86 Hz, 1H), 4.08–4.24 (m, 2H), 7.55 (d, J = 7.6 Hz, 1H), 7.67 (t,
J = 6.7 Hz, 1H), 7.90 (t, J = 7.9 Hz, 1H), 8.02 (t, J = 7.6 Hz, 1H), 8.12–
5.68, 39.31, 39.64, 46.70, 118.32, 120.61, 120.72, 121.08, 126.56,
35.25, 139.17, 142.04, 144.18, 146.39, 146.95, 148.69, 149.15,
+
50.18, 159.72; ESI-MS (MeOH) m/z: 328 [M+H] .
8.18 (m, 4H), 9.91 (d, J = 5.6 Hz, 1H); C22
H
21
N
3
RhCl
3
ꢂ(H
2 2
O) : C,
L2. With ketone (1R,4S,5R)-4,6,6-trimethyl-2-methylenebicy-
clo[3.1.1]heptan-3-one, after workup and purification by recrys-
tallization with acetonitrile, the procedure gave 0.23 g (44%) L2:
46.10; H, 4.37; N, 7.34. Found: C, 45.85; H, 4.35; N, 7.32%; ESI-
+
MS (MeOH): m/z 500.4 [MꢀCl] .
3
[Rh(L2)Cl ]. The above procedure was followed using L2 to give
2
5
1
1
mp 149–151 °C;
300 MHz, CDCl ): d 0.69 (s, 3H), 1.35 (d, J = 9.6 Hz, 1H), 1.44 (s,
H), 1.49 (d, J = 7.2 Hz, 3H), 2.18–2.21 (m, 1H), 2.56–2.63 (m,
[
a
]
D
= ꢀ58.5° (c = 0.33, CH
2
Cl
2
);
H
NMR
3
90 mg product (82%). H NMR (CDCl ): d 0.77 (s, 3H), 1.45 (s, 3H),
(
3
1.57 (d, J = 9.7 Hz, 1H), 1.73 (d, J = 6.7 Hz, 3H), 2.31–2.35 (m, 1H),
2.56–2.63 (m, 1H), 2.89 (t, J = 5.86 Hz, 1H), 4.89–4.93 (m, 1H),
7.52 (d, J = 7.6 Hz, 1H), 7.59 (t, J = 13.2 Hz, 1H), 7.90–7.98 (m,
3
1
7
8
H), 2.81–2.85 (m, 1H), 3.27–3.29 (m, 1H), 7.30–7.37 (m, 2H),
.83–7.88 (m, 1H), 7.91–7.96 (m, 1H), 8.29 (d, J = 7.8 Hz, 1H),
.40 (d, J = 7.5 Hz, 1H), 8.50 (d, J = 7.8 Hz, 1H), 8.63 (d, J = 7.5
2H),
8.14–8.20
RhCl ?(CH
C, 50.52; H, 4.54; N, 7.37%; ESI-MS (MeOH): m/z 414.3 [MꢀCl] .
[Rh(L3)Cl ]. The above procedure was followed using L3 to give
92 mg product (86%). H NMR (CDCl
(m,
4H),
9.90
(d,
J = 5.5 Hz,
1H);
C
23
H
23
N
3
3
3
CH
2
OH)0.5: C, 50.22; H, 4.53; N, 7.32. Found:
13
+
Hz, 1H), 8.70 (d, J = 4.2 Hz, 1H); C NMR (CDCl
3
): d 18.26,
2
1
1
3
0.94, 26.37, 28.66, 38.95, 41.50, 46.92, 47.29, 117.86, 120.29,
20.76, 121.17, 123.56, 133.42, 136.75, 137.66, 142.16, 149.07,
3
1
3
): d 0.87 (s, 3H), 1.29 (d,
53.46, 155.17, 156.19, 156.57, 160.21; ESI-MS (MeOH) m/z:
J = 10.4 Hz, 1H), 1.61 (s, 3H), 2.37–2.42 (m, 1H), 2.86–2.95 (m,
1H), 3.12–3.15 (m, 2H), 5.60 (t, J = 5.5 Hz, 1H), 7.68–7.76 (m, 2H),
+
42 [M+H] .

C.-T. Yeung et al. / Polyhedron 29 (2010) 1497–1507
1499
7
C
.92 (d, J = 8.0 Hz, 1H), 8.03–8.21 (m, 5H), 9.93 (d, J = 5.5 Hz, 1H);
RhCl O) : C, 46.10; H, 4.37; N, 7.34. Found: C, 46.10;
ꢂ(H
(s, 6H), 1.80 (d, J = 7.0 Hz, 6H), 2.38–2.39 (m, 2H), 2.54–2.57 (m,
22
H
21
N
3
3
2
2
2H), 2.78–2.79 (m, 2H), 4.26–4.29 (m, 2H), 7.28 (s, 2H), 7.88–
+
13
H, 4.44; N, 7.46%; ESI-MS (MeOH): m/z 500.3 [MꢀCl] .
3
8.14 (m, 5H); C NMR (CDCl ): d 20.53, 20.89, 25.62, 27.69,
4
1.26, 41.83, 47.74, 48.42, 120.77, 121.03, 134.68, 138.64, 146.49,
156.15, 156.35, 170.61, 209.60 (CO); Anal. Calc. for C32 OR-
uCl ?(CH Cl ): C, 53.95; H, 5.04; N, 5.72. Found: C, 53.67; H,
.94; N, 5.65%; ESI-MS (MeOH) m/z: 616.7 [MꢀCl] .
2.5. General procedure for preparation of [Ru(L)Cl ] (L = L1, L2 and
2
35 3
H N
L5)
2
2
2
+
4
Ligand
L
(0.20 mmol) and [RuCl
2
(p-cymene)]
2
(61 mg,
0
.1 mmol) were refluxed in degassed ethanol (10 mL) for 2 days.
2.8. X-ray structure analysis
The resulting deep purple or brown solution was cooled to room
temperature and filtered under nitrogen to remove any of undis-
solved black solid. The solvent was then removed under reduced
2 3
Crystallographic data for L3, [Cu(L3)Cl ], [Rh(L1)Cl ] and cis-
[Ru(L1)(DMSO)Cl
tions, intensity data for L3 was collected on a Bruker SMART CCD
area detector using graphite monochromator with Mo K radiation
(k = 0.7107 Å), while the data for [Rh(L1)Cl ] was collected on a
Bruker SMART 1000 CCD area detector. The intensity data for
[Cu(L3)Cl ] and cis-[Ru(L1)(DMSO)Cl ] were collected on a Oxford
Diffraction Gemini S Ultra X-ray single crystal diffractometer with
Mo K radiation (k = 0.7107 Å) and processed using CrysAlis. For
the structure solutions, all the structures were solved with SHELXS
2
] are tabulated in Table 1. For the data collec-
pressure. The residue was washed with dried Et
tered and dried under vacuum to afford deep purple or deep red-
dish brown solids. For [Ru(L1)Cl ], the yield was 98%. For
Ru(L2)Cl ], the yield was 96%. For [Ru(L5)Cl ], degassed n-butanol
was used and the reaction was refluxed for 4 days. The yield was
2%.
2
O (10 mL ꢁ 3), fil-
a
2
3
[
2
2
2
2
3
a
2
.6. Procedure for preparation of cis-[Ru(L1)(DMSO)Cl
2
]
-
9
7. For the structures refinements, L3, [Cu(L3)Cl
2
] and [Ru(L1)(DM-
2
[
Ru(L1)Cl
temperature. Then DMSO (0.2 mmol, 7.1
solution was stirred for 2 h. Solvent was reduced to ca. 1 mL under
vacuum and then Et O (20 mL) was added. The deep brown solid
was filtered and washed with Et
O (10 mL ꢁ 3). Recrystallization
from acetonitrile yielded crystal of the desired product of 102 mg
2
] was dissolved in degassed CH
2
Cl
2
(5 mL) at room
SO)Cl
2
] were refined on F with SHELXL-97 (Sheldrick 1997). The
2
lL) was added and the
3
structure of [Rh(L1)Cl ] was refined on F with SHELXL (Sheldrick
2008). Crystallographic data for the structures have been deposited
with the Cambridge Crystallographic Data Center as Supplemen-
tary Publication Numbers CCDC 703308, 736281–736283.
2
2
ꢀ1
1
(
88%). IR (KBr)
m
= 1086.2 cm s (SO); H NMR (CDCl
3
, two isomers
2.9. Procedure for copper-catalyzed cyclopropanation reactions
were observed in a ratio of 1:1): d 0.71 (s, 3H), 0.76 (s, 3H), 1.21 (d,
J = 10.6 Hz, 1H), 1.38 (d, J = 10.0 Hz, 1H), 1.42 (s, 3H), 1.45 (s, 3H),
To a mixture of [Cu(L)Cl
in a two-necked pear-shaped flask was added CH
nitrogen. The reaction mixture was stirred in the dark at room
temperature for 30 min. After filtration, styrene (4 mmol) and
ethyl diazoacetate (0.2 mmol) were added and the mixture was
stirred at room temperature for 30 min. A solution of ethyl diazo-
2
] (0.02 mmol) and AgOTf (0.04 mmol)
Cl (2 mL) under
2
2
7
4
2
.55–2.59 (m, 2H), 2.68 (s, 3H), 2.71 (s, 3H), 2.75–2.80 (m, 2H),
.87–2.91 (m, 2H), 2.93 (s, 3H), 2.99 (s, 3H), 3.62–4.03 (m, 4H),
.46 (dd, J = 7.9, 1.5 Hz, 2H), 7.58–7.62 (m, 2H), 7.78–7.83 (m,
H), 7.89–7.97 (m, 6H), 8.06 (d, J = 7.6 Hz, 2H), 9.62 (d, 5.9 Hz,
2
2
H); Anal. Calc. for C24
H
27
N SORuCl
3
2
2
ꢂ(MeCN)0.25(H O): C, 48.57;
H, 4.92; N, 7.52. Found: C, 48.35; H, 4.81; N, 7.53%; ESI-MS
2 2
acetate (1 mmol) in CH Cl (0.5 mL) was slowly added over 4 h.
+
(
MeOH): m/z 542.4 [MꢀCl] .
After the addition of ethyl diazoacetate, the mixture was allowed
to stir for 16 h at room temperature. The crude product was puri-
fied by column chromatography (petroleum ether/EtOAc). All of
the cyclopropanes obtained are known compounds and were char-
2
.7. General procedure for preparation of trans-[Ru(L)(CO)Cl
2
] (L = L2
and L5)
1
13
acterized by H, C NMR, IR and GC–MS. Enantiomeric excesses of
the cyclopropanes were determined by HPLC with a Daicel Chiral-
cel OJ column. Absolute configurations were determined by com-
[
Ru(L)Cl
2
] (0.1 mmol) was dissolved in degassed CH
2
Cl
2
(5 mL)
at room temperature. Then carbon monoxide was bubbled into
the reaction mixture for 15 min and the color of the mixture chan-
ged from purple to deep brown. Solvent was then reduced to ca.
paring the order of elution of samples with
configuration. Diastereoselectivities were measured by GC-FID
with Ultra
crosslinked 5% PhMesilcone (25 m ꢁ 0.2 mm ꢁ
0.33 m film thickness).
a
known
1
mL under vacuum and Et
2
O (20 mL) was added. The deep brown
2
solid was filtered and washed with Et
sired product. The products were characterized by IR, H NMR,
NMR, elemental analyses and ESI-MS.
2
O (10 mL ꢁ 3) to give the de-
l
1
13
C
2.10. Procedure for rhodium-catalyzed cyclopropanation reactions
[
Ru(L2)(CO)Cl
give 48 mg product (89%). IR (KBr)
NMR (CDCl ): d 0.70 (s, 3H), 1.46 (s, 3H), 1.49 (d, J = 10.3 Hz, 1H),
.86 (d, J = 6.7 Hz, 3H), 2.35–2.40 (m, 1H), 2.57–2.64 (m, 1H),
2
]. The above procedure was followed using L2 to
ꢀ1
1
m
= 1946.5 cm versus (CO); H
To a mixture of [Rh(L)Cl ] (0.02 mmol) and AgOTf (0.08 mmol)
3
3
in a two-necked pear-shaped flask was added THF (1.5 mL) under
nitrogen. The reaction mixture was stirred in the dark at room
temperature for 30 min. After filtration, styrene (5 mmol) was
added to the mixture. A solution of ethyl diazoacetate (1 mmol)
in THF (0.5 mL) was slowly added over 4 h. After the addition of
ethyl diazoacetate, the mixture was allowed to stir for 16 h at room
temperature. The mixture was worked-up as described above.
1
2
7
1
.82 (t, J = 5.6 Hz, 1H), 3.94–4.02 (m, 1H), 7.33 (d, J = 7.9 Hz, 1H),
.35 (t, J = 6.6 Hz, 1H), 7.75 (t, J = 7.9 Hz, 1H), 7.83 (d, J = 7.6 Hz,
H), 8.00–8.13 (m, 4H), 9.09 (d, J = 4.7 Hz, 1H); 13C NMR (CDCl
):
3
d 20.05, 21.02, 25.78, 27.86, 41.73, 42.58, 47.78, 48.22, 120.74,
1
1
21.12, 121.24, 123.42, 126.83, 134.55, 136.73, 138.55, 146.97,
54.62, 155.33, 156.99, 157.12, 158.17, 168.76, 206.00 (CO); Anal.
Calc. for C24
H
23
N
3
ORuCl
2
ꢂ(MeOH)ꢂ(H
2
O): C, 50.80; H, 4.91; N,
2.11. Procedure for ruthenium-catalyzed cyclopropanation reactions
and competition experiments
7
5
.11. Found: C, 51.20; H, 5.05; N, 7.30%; ESI-MS (MeOH): m/z
+
2+
08.1 [MꢀCl] , 392.1 [Mꢀ2Cl]
Ru(L5)(CO)Cl
and 1-butanol (10 mL) as solvent. The reaction was refluxed for 4
.
[
2
]. The above procedure was followed using L5
To
a
mixture of [Ru(L)(CO)Cl
2
]
(0.02 mmol) and AgOTf
Cl
(0.04 mmol) in a two-necked pear-shaped flask was added CH
2
2
ꢀ1
days to give 53 mg product (82%). IR (KBr)
m
= 1947.6 cm versus
(1.25 mL) under nitrogen. The reaction mixture was stirred in the
dark at room temperature for 30 min. After filtration, styrene
1
(
CO); H NMR (CDCl ): d 0.76 (s, 6H), 1.41 (d, J = 11.1 Hz, 2H), 1.45
3

1
500
C.-T. Yeung et al. / Polyhedron 29 (2010) 1497–1507
Table 1
General crystallographic data for L3, [Cu(L3)Cl
2
], [Rh(L1)Cl
3 2
] and cis-[Ru(L1)(DMSO)Cl ].
L3
[Cu(L3)Cl
23Cl
700.59
2
]
[Rh(L1)Cl
79Cl
1742.19
3
]
cis-[Ru(L1)(DMSO)Cl
27Cl ORuSN
577.52
2
]
Formula
M
C
22
H
21
N
3
C
24
H
8
CuN
3
C
69
H
9
N
9
Rh
3
O
5
C
24
H
2
3
327.42
Crystal size/mm3
Temperature
Crystal system
Space group
a (Å)
0.32 ꢁ 0.26 ꢁ 0.24
0.4 ꢁ 0.3 ꢁ 0.2
0.42 ꢁ 0.10 ꢁ 0.06
301(2)
trigonal
R3
24.930(2)
24.930(2)
10.389(1)
90.00
0.4 ꢁ 0.3 ꢁ 0.1
293(2)
193(2)
173(2)
orthorhombic
triclinic
P1ꢀ
orthorhombic
P2 2 2
1 1 1
P2
1
1
2 2
1
6.6714(4)
13.8836(8)
19.335(1)
90.00
90.00
90.00
1790.9(2)
4
0.73
9.6360(4)
10.6966(4)
14.7297(6)
73.475(4)
88.096(3)
79.433(3)
1430.5(1)
2
12.2925(2)
16.3747(3)
23.2165(5)
90.00
90.00
90.00
4673.2(2)
8
10.12
b (Å)
c (Å)
a
(°)
b (°)
(°)
90.00
c
120.00
5592(1)
3
3
V (Å )
Z
l
ꢀ
(Mo K
a
) (cm 1
)
15.31
10.33
Reflection collected
Unique reflections
8894
1826
10033
8216
2822
2248
8205
6792
R
int
0.016
0.035
0.101
n.a.
0.029
0.040
0.100
0.0325
0.0339
0.0798
ꢀ0.03(5)
0.969
0.0314
0.0267
0.0539
ꢀ0.01(3)
0.956
Residuals: R (I > 2
Residuals: Rw (I > 2
Flack parameter
Goodness-of-fit indicator
r
(I))
(I))
r
ꢀ0.007(11)
1.077
0.966
were characterized by H NMR, 13C NMR, IR and ESI-MS. From the
1
(
8 mmol) was added to the mixture. A solution of alkyl diazoace-
1
tate (1 mmol) in CH Cl (0.5 mL) was slowly added over 4 h. After
2
2
H NMR spectra of L1, L2 and L3, nine sets of aromatic proton sig-
the addition of ethyl diazoacetate, the mixture was allowed to stir
for 16 h at room temperature. The mixture was worked-up as de-
scribed above. For the cyclopropanation with t-butyl diazoacetate,
enantiomeric excesses were determined by GC with a chiraldex b-
PH column. For the competition reactions, styrene (2 mmol) and
substituted styrene (2 mmol) were added to the catalytic solution
nals of the same integral ratio appeared as multiplets between 7.2
and 8.8 ppm. In addition, all ligands exhibited 15 sets of aromatic
carbon signals from 117 to 161 ppm in their C NMR spectra.
For L3, crystals of X-ray quality were obtained by slow evaporation
of a dichloromethane solution of L3 and the structure is shown in
1
3
2
Fig. 1. Similar to its C -counterpart [18], the pyridine rings adopt
generated from [Ru(L)(CO)Cl
2
] (0.01 mmol) and AgOTf (0.02 mmol)
transoid configurations about the interannular C–C bonds. The
three pyridine rings are not coplanar. Dihedral angle of the pyri-
dine ring with the chiral moiety (12.2(2)°) is larger than the one
without any substituent (6.1(3)°).
in 0.63 mL CH Cl . Ethyl diazoacetate (0.5 mmol) was added in one
2
2
portion to the reaction mixture. After 30 min, the reaction mix-
tures were checked with GC.
3.2. Complexes synthesis and characterization
3
. Results and discussion
The C
L1–3) and rhodium(III) complexes [Rh(L)Cl
pared by methods that were similar to the synthesis for C
metric copper and rhodium complexes [10,12]. The copper
complexes were isolated as green solids by reaction of a dichloro-
methane solution of the appropriate ligand with an ethanolic solu-
1
-symmetric terpyridine copper(II) complexes [Cu(L)Cl
] (L1–3) were pre-
-sym-
2
]
3
.1. Preparation of C -terpyridines L1–3
1
(
3
2
The synthesis of ligands L1–3 is outlined in Scheme 1. Kröhnke
0
condensations of 6-(1-pyridinioacetyl)-2,2 -bipyridine iodide with
suitable a,b-unsaturated ketones in acetic acid at 120 °C for 12 h
gave ligands L1–3. After washing with acetonitrile to dissolve col-
ored impurities, the products were obtained as pale-yellow solid in
tion of CuCl
treating the corresponding L with RhCl
For all these C -symmetric copper and rhodium complexes, iso-
lated yields were good and generally higher than their C -analog.
2
ꢂ2H
2
O. The rhodium complexes were formed by
3
ꢂ3H O in refluxing ethanol.
2
6
3%, 44% and 57% yields for L1, L2 and L3, respectively. The ligands
1
2
Characterizations with elemental analysis showed that all the
complexes exhibited a 1:1 metal to ligand ratio. For the ESI-MS
analysis, fragmentation peaks corresponding to the loss of one
O
ꢀ
L1
Cl from the parent molecules were observed.
6
3%
Crystals of [Cu(L3)Cl
were grown by slow evaporation of a chloroform solution of
[Cu(L3)Cl ]. The molecular structure is shown in Fig. 2 while se-
2
] suitable for X-ray structural analysis
O
O
2
lected bond lengths and angles are listed in Table 2. The copper
atom is surrounded by two chloride ions and three nitrogen atoms
from a terpyridine. Coordination geometry around the copper atom
can best be described as square pyramidal distorted trigonal bipyr-
HOAc, NH OAc
4
N
N
+N
L2
L3
I-
44%
120°C, 12h
O
amid as the geometric parameters (
for ideal square pyramidal and = 1 for ideal trigonal bipyramidal)
19]. This geometry is very different from that of the other achiral
copper–terpyridine complexes, which are generally square pyra-
mid as are in the range of 0.09–0.183 [20,21]. In the [Cu(L3)Cl ],
deviation from the ideal orthogonal arrangement between the
s) is observed to be 0.57 (s = 0
s
[
57%
s
2
Scheme 1.

C.-T. Yeung et al. / Polyhedron 29 (2010) 1497–1507
1501
Fig. 1. Molecular structure of L3 including the atom numbering scheme. All hydrogen atoms have been omitted for clarity.
2
Fig. 2. ORTEP view for [Cu(L3)Cl ] including the atom numbering scheme. All hydrogen atoms and solvent molecules have been omitted for clarity.
plane containing N(2)–Cl(1)–Cl(2) and the plane of the central pyr-
1
Nevertheless, the sterically less bulkiness of the C -symmetric
idyl ring is less as the deviation angle is 3.87°. Indeed, the coordi-
complex can be reflected by the co-planarity of the terpyridine li-
gand. The average dihedral angle between the adjacent pyridyl
nation geometry and the deviation angle in [Cu(L3)Cl
to the corresponding C -symmetric complex, [Cu(L6)Cl
and the deviation angle are 0.58 and 3.91°, respectively.
2
] are similar
2
2
] [18] in
rings in [Cu(L3)Cl
[Cu(L6)Cl ]. Consequently, the bond distances between the copper
and nitrogen atoms in [Cu(L3)Cl ] (1.969(5), 2.035(7) and 2.050(6)
Å) are shorter than those in [Cu(L6)Cl ] (1.974(9), 2.075(4) and
2
] is 2.44° and this is smaller than the 9.38° in
which
s
2
2
2
2
.080(3) Å).
Table 2
3
Crystals of [Rh(L1)Cl ] suitable for X-ray structural analysis
2
Selected bond lengths (Å) and angles (deg) for [Cu(L3)Cl ].
were grown by slow evaporation of an ethanolic solution of
Rh(L1)Cl ]. The crystal structure is shown in Fig. 3 and the se-
Bond lengths
Cu(1)–Cl(1)
Cu(1)–Cl(2)
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–N(3)
[
3
2.340(4)
2.311(3)
2.040(6)
1.972(5)
2.048(6)
lected bond distance and bond angles are given in Table 3. In the
molecular structure, the six-coordinated rhodium atom is bound
by three nitrogen atoms from L1 and three chlorides to exhibit a
distorted octahedral geometry. Similar to other Rh–terpyridine
complex [12,22], the distortion is principally originated from the
small bite angles of N(1)–Rh(1)–N(2) and N(2)–Rh(1)–N(3)
Bond angles
N(1)–Cu(1)–N(2)
N(2)–Cu(1)–N(3)
N(1)–Cu(1)–N(3)
Cl(1)–Cu(1)–N(2)
Cl(2)–Cu(1)–N(2)
Cl(1)–Cu(1)–Cl(2)
Cl(1)–Cu(1)–N(1)
Cl(1)–Cu(1)–N(3)
Cl(2)–Cu(1)–N(1)
Cl(2)–Cu(1)–N(3)
78.3(2)
79.7(2)
158.0(2)
123.6(1)
123.0(2)
113.14(5)
94.9(1)
96.7(1)
93.0(1)
99.6(1)
(
80.8(3) and 80.1(3)°, respectively), causing the N(1)–Rh(1)–N(3)
angle of 160.6(3)° to deviate from the linearity. Moreover, the three
pyridyl nitrogen–rhodium bond distances are not identical and the
distances of Rh to the two distal nitrogens N(1) and N(3) (2.051(6)
and 2.096(5) Å, respectively) are longer than the Rh–N(2)
(
1.940(9) Å).
In addition, bulky chiral moiety also exerts significantly to the
geometric distortion. Steric interaction between an equatorial

1
502
C.-T. Yeung et al. / Polyhedron 29 (2010) 1497–1507
Fig. 3. ORTEP view for [Rh(L1)Cl
3
] including the atom numbering scheme. All hydrogen atoms and solvent molecules have been omitted for clarity.
sult in a long bond distances between Rh and the N atoms from
Table 3
the two distal pyridyl units (2.111(5) and 2.110(5) Å). For the C
1
-
3
Selected bond lengths (Å) and angles (deg) for [Rh(L1)Cl ].
symmetric [Rh(L1)Cl ], the mean dihedral angle is smaller 2.9°
and the bond distances are shorter, Rh(1)–N(1) and Rh(1)–N(3)
are 2.051(6) Å and 2.096(5) Å, respectively.
3
Bond lengths
Rh(1)–Cl(1)
Rh(1)–Cl(2)
Rh(1)–Cl(3)
Rh(1)–N(1)
Rh(1)–N(2)
Rh(1)–N(3)
2.330(2)
2.375(3)
2.354(2)
2.051(6)
1.940(9)
2.096(5)
For the ruthenium complexes, [Ru(L)Cl
2
] were firstly prepared
to 1 equiv of L in
by reacting 0.5 equiv of [RuCl (p-cymene)]
2
2
refluxing ethanol/n-butanol. However, the products obtained gave
1
complicated H NMR spectra which may be attributed to the ex-
Bond angles
change of coordinated solvent molecules. This observation has
been reported previously with a tridentate pyridyl-diimine ligand
C1(1)–Rh(1)–Cl(2)
Cl(2)–Rh(1)–Cl(3)
N(1)–Rh(1)–N(2)
N(2)–Rh(1)–N(3)
N(1)–Rh(1)–N(3)
N(1)–Rh(1)–Cl(2)
N(2)–Rh(1)–Cl(2)
N(3)–Rh(1)–Cl(2)
N(1)–Rh(1)–Cl(1)
N(2)–Rh(1)–Cl(1)
N(3)–Rh(1)–Cl(1)
N(1)–Rh(1)–Cl(3)
N(2)–Rh(1)–Cl(3)
N(3)–Rh(1)–Cl(3)
93.07(8)
89.72(8)
80.8(3)
80.1(3)
160.6(3)
92.3(2)
171.0(2)
107.1(2)
89.7(2)
90.9(2)
87.3(2)
90.3(2)
86.4(2)
91.8(2)
[23]. Therefore, no full characterizations of [Ru(L)Cl
2
] have been
made. Nevertheless, the stoichiometry of the complexes,
[
(
Ru(L)Cl
2
], was revealed by coordinating with a DMSO molecule
], the col-
Scheme 2). After addition of 1 equiv DMSO to [Ru(L1)Cl
2
or of the reaction mixture changed immediately from violet to
brown. After isolation and recrystallization of the product, 1
H
NMR analysis showed that two compounds, in a ratio of 1:1, were
presented. Unambiguous identification of the product was pro-
ceeded via X-ray structural analysis (vide infra). For the more bulky
2
C -symmetric ligand L4, however, isolation of the DMSO complex
resulted in failure. For ligands L2 and L3, DMSO complexes were
not prepared because existence of isomers as in the case of cis-
chloride atom Cl(2) and a carbon atom C(18) is partially relieved by
displacing the Cl(2) away from the chiral moiety, as evidences by a
larger angle of N(3)–Rh(1)–Cl(2) (107.1(2)°) than N(1)–Rh(1)–Cl(2)
[Ru(L1)(DMSO)Cl
catalyst.
Crystals of cis-[Ru(L1)(DMSO)Cl
analysis were grown by slow diffusion of distilled diethyl ether
to an acetonitrile solution of cis-[Ru(L1)(DMSO)Cl ]. As shown in
2
]
precludes the development of selective
2
] suitable for X-ray structural
(
92.3(2)°). However, for a corresponding C
2
-symmetric complex,
[
Rh(L4)Cl ] [11], the steric interaction is not simply relieved by
3
2
the chloride displacement as the corresponding angles that are
mentioned as above are similar to each other (99.9(2)° and
Fig. 4, the structure revealed that two independent diastereomers
A and B, differ in the position of the DMSO molecules relative to
the dimethyl substituents (C(21) and C(22)) and (C(45) and
C(46)) of chiral moieties on L4, are comprised in a unit cell. In these
1
00.0(2)°). The steric interaction is relieved by twisting of the adja-
cent pyridyl rings (mean dihedral angle = 16.9°) and hence to re-

C.-T. Yeung et al. / Polyhedron 29 (2010) 1497–1507
1503
DMSO
[
Ru(L)(DMSO)Cl2]
CH Cl , 25 °C, 2 h
2
2
(L = L1)
0.5 eq [RuCl2(p-cymene)]2
L
[Ru(L)Cl2]
EtOH, reflux, 2 days
or
-BuOH, reflux, 4 days
CO
CH Cl , 25 °C, 15 min
[
(
Ru(L)(CO)Cl2]
L = L2 and L5)
n
2
2
Scheme 2.
2
Fig. 4. ORTEP views for cis-[Ru(L1)(DMSO)Cl ] including the atom numbering scheme. All hydrogen atoms and solvent molecules have been omitted for clarity (upper:
diastereomer A, lower: diastereomer B).

1
504
C.-T. Yeung et al. / Polyhedron 29 (2010) 1497–1507
Table 4
Selected bond lengths (Å) and angles (deg) for cis-[Ru(L1)(DMSO)Cl
their corresponding bond lengths and bond angles, no notable dif-
ference is observed as the deviations of them are not larger than
0.016 Å and 2.64°, respectively (Table 4). The bulky chiral moiety
on L4 exerts significant effect to the geometric distortion. As
observed by the three asymmetric bond distances of the ruthe-
nium-nitrogen bonds, the longest distances, Ru(1)–N(3) =
2
].
Diastereomer A
Diastereomer B
Bond lengths
Ru(1)–N(1)
Ru(1)–N(2)
Ru(1)–N(3)
Ru(1)–Cl(1)
Ru(1)–Cl(2)
Ru(1)–S(1)
S(1)–O(1)
Bond lengths
Ru(2)–N(4)
Ru(2)–N(5)
Ru(2)–N(6)
Ru(2)–Cl(3)
Ru(2)–Cl(4)
Ru(2)–S(2)
S(2)–O(2)
2.073(3)
1.953(3)
2.142(3)
2.429(1)
2.461(1)
2.232(1)
1.491(3)
2.072(3)
1.961(3)
2.140(3)
2.418(1)
2.455(1)
2.222(1)
1.475(3)
2
.142(3) Å and Ru(2)–N(6) = 2.140(3) Å, are originated from the
pyridyl rings with chiral moieties and these are significant longer
than that from the side without chiral substituent (Ru(1)–
N(1) = 2.073(3) Å and Ru(2)–N(4) = 2.072(3) Å). The shortest dis-
tance is from the middle pyridyl rings Ru(1)–N(2) = 1.953(3) Å
and Ru(2)–N(5) = 1.961(3) Å. Moreover, steric interaction between
the chiral moiety and equatorial chloride atoms Cl(2)/Cl(4) is ob-
served to be more significant than that between the chiral moiety
to the vertical molecules of bulky DMSO molecules. With diaste-
reomer A as an example, the difference in angles of N(3)–Ru(1)–
Cl(2) and N(1)–Ru(1)–Cl(2) is 14.48° which is larger than the differ-
ence in angles of 3.39° of N(3)–Ru(1)–S(1) and N(1)–Ru(1)–S(1).
Similar observation has been found for diastereomer B as the two
different angles are 13.71° and 0.23°, respectively.
Bond angles
Bond angles
C1(1)–Ru(1)–Cl(2)
Cl(1)–Ru(1)–S(1)
S(1)–Ru(1)–Cl(2)
N(1)–Ru(1)–N(2)
N(2)–Ru(1)–N(3)
N(1)–Ru(1)–N(3)
N(2)–Ru(1)–Cl(1)
N(1)–Ru(1)–Cl(1)
N(3)–Ru(1)–Cl(1)
N(1)–Ru(1)–S(1)
N(2)–Ru(1)–S(1)
N(3)–Ru(1)–S(1)
N(1)–Ru(1)–Cl(2)
N(2)–Ru(1)–Cl(2)
N(3)–Ru(1)–Cl(2)
C(23)–S(1)–Ru(1)
C(24)–S(1)–Ru(1)
O(1)–S(1)–Ru(1)
C(23)–S(1)–O(1)
C(24)–S(1)–O(1)
C(23)–S(1)–C(24)
91.99(4)
179.73(4)
88.25(4)
79.6(1)
79.2(1)
158.2(1)
89.9(1)
89.18(9)
85.96(9)
90.68(9)
89.8(1)
94.07(9)
93.47(9)
172.2(1)
107.95(9)
113.2(2)
113.7(1)
117.1(1)
105.1(2)
107.3(2)
98.6(2)
C1(3)–Ru(2)–Cl(4)
Cl(3)–Ru(2)–S(2)
S(2)–Ru(2)–Cl(4)
N(4)–Ru(2)–N(5)
N(5)–Ru(2)–N(6)
N(4)–Ru(2)–N(6)
N(5)–Ru(2)–Cl(3)
N(4)–Ru(2)–Cl(3)
N(6)–Ru(2)–Cl(3)
N(4)–Ru(2)–S(2)
N(5)–Ru(2)–S(2)
N(6)–Ru(2)–S(2)
N(4)–Ru(2)–Cl(4)
N(5)–Ru(2)–Cl(4)
N(6)–Ru(2)–Cl(4)
C(47)–S(2)–Ru(2)
C(48)–S(2)–Ru(2)
O(2)–S(2)–Ru(2)
C(47)–S(2)–O(2)
C(48)–S(2)–O(2)
C(47)–S(2)–C(48)
91.54(4)
178.33(4)
89.85(4)
79.5(1)
79.3(1)
158.5(1)
87.3(1)
87.74(9)
87.51(9)
91.24(9)
91.2 (1)
92.97(9)
93.71(9)
173.1(1)
107.42(9)
112.6(2)
115.3(1)
116.4(1)
106.6(2)
105.7(2)
98.6(2)
Other than coordinating with the DMSO molecule, the stoichi-
ometry of [Ru(L)Cl
carbon monoxide molecule (Scheme 2). By bubbling CO into
dichloromethane solutions of the [Ru(L)Cl ] for 15 min, the com-
plexes, trans-[Ru(L)(CO)Cl ], could be isolated in good yields. The
2
] can also be revealed by coordinating with a
2
2
presence of CO in the complex was confirmed by the appearance
ꢀ1
of a strong absorption band at 1940–1950 cm in the IR analyses
13
[
24] and a downfield chemical shift at 206.0–209.2 ppm in the
C
1
13
NMR spectra [25]. For L = L5, the H and C NMR spectra sug-
gested an overall C -symmetrical environment, implicating a trans
arrangement of the two chloride ligands. For the C -symmetric L2,
2
1
two structures, the coordination is similar. Coordination geome-
tries for the Ru are octahedral, with a S-bonded DMSO molecule,
two cis spanned Cl ions and three nitrogen atoms from L4. For
a trans arrangement is also proposed as only one isomer was ob-
1
served with H NMR. Carbonyl complexes with other C - and C -
1
2
ꢀ
symmetric terpyridines are not reported because the catalytic re-
Table 5
a
Catalytic asymmetric cyclopropanation of styrene with diazoacetate with chiral copper(II), rhodium(III) and ruthenium(II) terpyridines.
O
Ph
Ph
COOR
COOR
Ph
Ph
COOR
COOR
H
2 mol% catalyst
solvent, N2
+
Ph
OR
+
N2
R = Et or
t
Bu
trans
cis
Entry
1
Complex
Yield (%)b
Trans/cisc
% eed
trans
cis
[Cu(L2)Cl
[Cu(L5)Cl
[Rh(L2)Cl
[Rh(L5)Cl
2
]
2
]
3
]
3
]
87
84
29
54
67:33
67:33
42:58
30:70
66:34
84:16
48:52
52:48
42(1R,2R)
72(1R,2R)
7(1R,2R)
65(1S,2S)
45(1S,2S)
60(1S,2S)
19(1S,2S)
55(1S,2S)
60(1R,2S)
82(1R,2S)
7(1S,2R)
71(1S,2R)
26(1S,2R)
67(1S,2R)
29(1S,2R)
74(1S,2R)
e
2
3
4
e
5
[Ru(L2)(CO)Cl
2
2
]
]
95
f
9
8
6
[Ru(L5)(CO)Cl
93
f
8
9
a
Copper, rhodium and ruthenium catalysts were generated by reactions of the complex with AgOTf and then with ethyl diazoacetate (EDA) (0.2 equiv). Reaction condition
for [Cu(L)Cl ]: AgOTf (2 equiv), catalyst/EDA/styrene = 1:50:200, CH Cl , 25 °C, 4 h addition of EDA and then stirring for 16 h. For [Rh(L)Cl ]: AgOTf (4 equiv), catalyst/EDA/
]: AgOTf (2 equiv), catalyst/EDA/styrene = 1:50:400, CH Cl , 25 °C, 4 h addition
2
2
2
3
styrene = 1:50:250, THF, 25 °C, 4 h addition of EDA and then stirring for 16 h. For [Ru(L)(CO)Cl
2
2
2
of EDA and then stirring for 16 h.
b
Isolated yields of cyclopropanes are based on expected product.
Determined by GC-FID.
c
d
Enantiomeric excesses were determined with chiral columns on a HPLC or GC-FID. Absolute configurations were determined by comparing the order of elution of samples
with known configuration.
e
Data were obtained from reference [13].
t-Butyl diazoacetate was employed instead of EDA.
f

C.-T. Yeung et al. / Polyhedron 29 (2010) 1497–1507
1505
sults are not as good as L2 and L5 in the preliminary screening for
cyclopropanation.
and 60%) than the C
slightly lower% ee for the cis-isomers (26% and 67%) than the C
catalyst (29% and 74%). For the copper and rhodium systems, C
2
-catalyst (19% and 55%). C
1
-catalyst give
2
-
-
1
catalysts resulted in lower% ee of both the trans and cis cyclopro-
panes when compared with the corresponding C -systems (entries
versus 2 and 3 versus 4). Apart from the enantioselectivity, abso-
lute configurations of the cyclopropanes are varied with the ligand
symmetry in some cases. For the rhodium, the trans cyclopropane
from the C -system is in opposite absolute configuration to the C -
1 2
catalyst. But the reverse in configuration is not observed for the cis-
cyclopropane (entries 3 versus 4). For the copper and ruthenium,
3
.3. Catalytic cyclopropanation reactions
2
1
For the copper and rhodium catalyzed cyclopropanation, the
reaction conditions that were employed are the same as the previ-
ously study for C -symmetric copper and rhodium complexes [13].
For the ruthenium catalyzed cyclopropanation, active catalysts
were generated by reacting the [Ru(L)(CO)Cl ] with 2 equiv of
2
2
AgOTf. After some optimization of conditions, a ratio of catalyst/al-
kyl diazoacetate/styrene of 1:50:400 which give fair to good yields
of cyclopropanes as major products were employed. All of the cop-
per, rhodium and ruthenium catalysts are active catalysts for
cyclopropanation of styrene with ethyl diazoacetate (EDA) or t-bu-
tyl diazoacetate (TDA). Because the L2 and L5 gave the highest% ee
and hence can be lead to a more meaningful discussion in reactive
intermediate, only the results with these two ligands are discussed
further. The catalytic activities of these complexes are shown in
Table 5.
the absolute configurations of cyclopropanes from the C
1
- and
C
2
-catalysts remained the same in each case.
To get more information about the effects of C - and C -symme-
1 2
try on the nature of the intermediates involved, the rates of cyclo-
propanation of substituted styrenes relative to styrene with EDA
were measured through competition experiments using trans-
[
Ru(L)(CO)Cl
2
] (L2 and L5), [Cu(L2)Cl
2
] and [Rh(L2)Cl
3
]. The Ham-
+
mett plots of log(k
X
/k ) versus r for these catalysts are shown
H
in Figs. 5–8. The results of the previously reported competitions
1 2
The effects of C - and C -symmetry on the catalytic cycloprop-
anation depend very much on the metal systems. In general, for
the copper (entries 1 versus 2) and ruthenium (entries 5 versus
4-MeO
6
) systems, the yields of cyclopropane from cyclopropanation of
styrene with EDA or TDA from the C -symmetric catalysts are high-
er than that from the C -catalysts. But this is not the case for the
rhodium system. C -Symmetric [Rh(L2)Cl ] gave a significantly
lower yield of cyclopropane than the C -catalyst (entries 3 versus
). Moreover, ratios of trans/cis of the cyclopropanes of styrene
ρ = −1.01
1
0.5
2
4
-Me
1
3
2
4
H
0
.0
with EDA from the rhodium and ruthenium systems are affected
notably with the symmetry of the ligands. Both systems from the
4
-Cl
C
1
-symmetric ligand L2 result in higher trans-cyclopropanes selec-
tions than the corresponding C -catalysts as the trans/cis ratios of
versus C are 42:58 versus 30:70 for the rhodium and 66:34 ver-
2
-
-
0.5
1.0
C
1
2
sus 48:52 for the ruthenium. In particular to the ruthenium cata-
lysts, when a more bulky TDA were employed, the trans/cis ratio
3-NO2
0.8
from the C
creased only slightly to 52:48 for the C
alysts, the trans/cis ratios (67:33) for the C
1
-catalyst increased significantly to 84:16 but it in-
-system. For the copper cat-
- and C -systems are
2
-
1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
+
0.6
1.0
1
2
equal. Furthermore, enantioselectivities were also varied in differ-
ent extent with ligand symmetry from the different metal systems.
For the ruthenium catalysts, no matter whether with EDA or TDA,
Hammett constant σ
Fig. 6. Hammett plot for the cyclopropanation of styrene with EDA using trans-
Ru(L5)(CO)Cl
[
2
] as catalyst precursor.
1
C -catalyst always results in higher% ee for the trans-isomers (45%
1
0
0
.0
.5
.0
0.5
4-MeO
4
-MeO
ρ = −0.64
ρ = −1.22
4-Me
4-Me
H
H
0
.0
4-Cl
4-Cl
-
-
-
0.5
1.0
1.5
3
-NO2
-
0.5
3-NO2
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
+
+
Hammett constant σ
Hammett constant σ
Fig. 5. Hammett plot for the cyclopropanation of styrene with EDA using trans-
Ru(L2)(CO)Cl ] as catalyst precursor.
Fig. 7. Hammett plot for the cyclopropanation of styrene with EDA using
[Cu(L2)Cl ] as catalyst precursor.
[
2
2

1
506
C.-T. Yeung et al. / Polyhedron 29 (2010) 1497–1507
(
1 2
1R,2R) or cis-cyclopropanes (1R,2S) from the C - and C -catalysts
4
-MeO
0
0
0
.4
.2
.0
are the same. This observation suggests that a similar model, with
a horizontal carbene, which was proposed previously [33] can be
1 1
applied in the case of C -catalyst. For the C -rhodium system, the
asymmetric induction for the trans- and cis-cyclopropanes are re-
versed. This observation suggests that different intermediate might
3-NO2
involve with C
systems, both C
urations of (1S,2S) and (1S,2R) for the trans- and cis-cyclopropanes,
respectively, which are the same as the C -rhodium catalyst. A
model that is similar to C -rhodium catalyst [13] is proposed here.
1
- and C
2
-rhodium catalyst [13]. For the ruthenium
4-Me
1
- and C
2
-catalysts gave the same absolute config-
2
4-Cl
2
However, the exact nature of the intermediate is under
investigation.
H
4
. Conclusion
-
1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
+
Hammett constant σ
In summary, chiral terpyridine ligands of copper(II) complexes,
of formula [Cu(L)Cl
2
], rhodium(III) complexes, of formula
] and ruthenium(II) complexes, of formula cis- or trans-
Ru(L)(X)Cl ] (X = DMSO or CO), are effective catalysts that afford
Fig. 8. Hammett plot for the cyclopropanation of styrene with EDA using
Rh(L2)Cl ] as catalyst precursor.
[
Rh(L)Cl
3
[
3
[
2
cyclopropyl esters in good yield. Moderate enantioselectivities of
up to 74% ee have been obtained with complexes having chiral
C and C -terpyridines. We are continuing our effort to metal-ter-
1 2
with C
2
-symmetric [Cu(L5)Cl
2
] and [Rh(L5)Cl
3
] are used for com-
parison [13]. For both of the C
electron-donating substituted styrenes increased the reaction rates
while their electron-withdrawing counterparts produced a de-
1
- and C -ruthenium systems, the
2
pyridine catalysts for other reactions.
+
2
5. Supplementary data
crease. Both of them followed linear
.99) with a slightly larger (more negative) value of
lyst (ꢀ1.22) than that for C -catalyst (ꢀ1.01). Nevertheless, these
values are smaller than the ruthenium–PNNP catalyst (
= ꢀ2.40
correlating to para) [26] but significantly larger than the ruthe-
nium–porphyrin system ( r ) [27]. Correla-
r
correlation (R = 0.97–
0
q
for C -cata-
1
CCDC 703308, 736281, 736282, and 736283 contain the supple-
2
2 3
mentary crystallographic data for L3, [Cu(L3)Cl ], [Rh(L1)Cl ] and
q
[
Ru(L1)(DMSO)Cl ] respectively. These data can be obtained free
2
r
+
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Center, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
q
= 0.44 correlating to
+
tion to the
r in these ruthenium–terpyridine systems imply that
the intermediates are much more closely resembles the porphyrin
system (which has been proposed to have a built-up positive
charge in the intermediate) than the PNNP system. The larger
q
values indicate that the intermediate for the ruthenium–terpyri-
dine catalyst are more electrophilic than that for the ruthenium–
Acknowledgements
porphyrin catalyst. For the copper systems, similar to ruthenium
Financial support for this research from the Hong Kong Re-
search Grants Council the Area of Excellence Scheme established
under the University Grants Committee of the Hong Kong SAR, Chi-
na (Project No. AoE/P-10/01) and GRF grant (CityU 101108). are
gratefully acknowledged.
+
systems, both of the C
(
(
1
- and C
R = 0.98–0.99). However, the
less negative) than that for the C
- and C -catalysts lied within the range of
copper catalysts with ligands such as tris(pyrazolyl) borate
= ꢀ0.85 correlating to ) [28] and bisoxazoline ( = ꢀ0.51 corre-
) [29]. The best fit correlations of the data points to
2
-catalysts gave linear
from C
-copper (ꢀ0.76) [13]. And the
for other
r
correlation
2
q
1
-copper (ꢀ0.64) is smaller
2
q
for both C
1
2
q
(
q
r
q
References
+
+
lating to
r
r
reveal that the copper–terpyridine systems resemble to the cop-
per–bisoxazoline system and the intermediate are more electro-
[1] K.M.-C. Wong, V.W.-W. Yam, Coord. Chem. Rev. 251 (2007) 24772488.
[
[
2] S. Bonnet, J.-P. Collin, J.-P. Sauvage, Inorg. Chem. 46 (2007) 1052010533.
3] F. Liu, T. Cardolaccia, B.J. Hornstein, J.R. Schoonover, T.J. Meyer, J. Am. Chem.
Soc. 129 (2007) 24462447.
philic than the copper–bisoxazoline system as a larger
observed in the copper–terpyridine systems. For the rhodium sys-
tems, the Hammett plot of C -symmetric catalyst showed a non-
linear U-shaped relationship with
different from the negative linear correlation with
catalyst [13]. Hence this may reveal the drastic difference in cata-
lytic reactivity for the C - and C -catalysts (Table 5, entries 3 and
). The non-linearity might suggest the presence of active interme-
q is
[4] C. Duboc, M.-N. Collomb, J. Pécaut, A. Deronzier, F. Neese, Chem. Eur. J. 14
2008) 64986509.
[5] B. Hasenknopf, J.-M. Lehn, G. Baum, D. Fenske, Proc. Natl. Acad. Sci. USA 93
1996) 13971400.
(
1
+
r
. And this observation is very
(
+
r
for the C
2
-
[6] U.S. Schubert, H. Hofmeier, G.R. Newkome, Modern Terpyridine Chemistry,
Wiley-VCH, Weinheim, 2006.
[
[
7] E.C. Constable, Chem. Soc. Rev. 36 (2007) 246253.
8] R. Ziessel, Synthesis 1999 (1999) 18391865.
1
2
4
[9] C.-T. Yeung, H.-L. Yeung, C.-S. Tsang, W.-Y. Wong, H.-L. Kwong, Chem.
Commun. (2007) 52035205.
10] G. Chelucci, A. Saba, D. Vignola, C. Solinas, Tetrahedron 57 (2001) 10991104.
11] M. Ziegler, V. Monney, H. Stoeckli-Evans, A. Von Zelewsky, I. Sasaki, G. Dupic,
J.-C. Daran, G.G.A. Balavoine, J. Chem. Soc., Dalton Trans. (1999) 667. 676.
[12] H.-L. Kwong, W.-S. Lee, Tetrahedron: Asymmetry 11 (2000) 22992308.
13] H.-L. Kwong, W.-L. Wong, W.-S. Lee, L.-S. Cheng, W.-T. Wong, Tetrahedron:
Asymmetry 12 (2001) 26832694.
14] M.P. Hartshorn, A.F.A. Wallis, J. Chem. Soc. (1964) 52545260.
[15] C. Bolm, M. Ewald, M. Felder, G. Schlingloff, Chem. Ber. 125 (1992) 11691190.
16] E.C. Constable, G. Baum, E. Bill, R. Dyson, R. Van Eldik, D. Fenske, S. Kaderli, D.
Morris, A. Neubrand, M. Neuburger, D.R. Smith, K. Wieghardt, M. Zehnder, A.D.
Zuberbühler, Chem. Eur. J. 5 (1999) 498508.
diates that have significant radical character [30] or two pathways
of similar activation energies [31] in the reaction. A study of non-
linear correlations in catalytic cyclopropanation with iron- and co-
balt-terpyridine systems has been reported by our group recently
[
[
[
[
32].
Based on the absolute configurations of the products obtained
from the catalytic cyclopropanation with C - and C -symmetric
[
1
2
[
copper, ruthenium and rhodium catalysts (Table 5), some informa-
tion that related to the mechanism can be obtained. For the copper
systems, the absolute configurations of the trans-cyclopropanes
[17] F. Kröhnke, Synthesis (1976) 124.

C.-T. Yeung et al. / Polyhedron 29 (2010) 1497–1507
1507
[
[
18] F. Pezet, I. Sasaki, J.-C. Daran, J. Hydrio, H. A-Haddou, G. Balavoine, Eur. J. Inorg.
Chem. (2001) 26692674.
19] A.W. Addison, T.N. Rao, J. Reedijk, J. van Rijn, G.C. Verschoor, J. Chem. Soc.,
Dalton Trans. (1984) 1349. 1356.
[27] C.-M. Che, J.-S. Huang, F.-W. Lee, Y. Li, T.-S. Lai, H.-L. Kwong, P.-F. Teng, W.-S.
Lee, W.-C. Lo, S.-M. Peng, Z.-Y. Zhou, J. Am. Chem. Soc. 123 (2001) 41194129.
[28] M.M. Diaz-Requejo, P.J. Pérez, M. Brookhart, J.L. Templeton, Organometallics
16 (1997) 43994402.
[
[
[
20] W. Henke, S. Kremer, D. Reinen, Inorg. Chem. 22 (1983) 28582863.
21] T. Rojo, M. Vlasse, D. Beltran-Porter, Acta Crystallogr., Sect. C39 (1983) 194199.
22] F.P. Pruchnik, P. Jakimowicz, Z. Ciunik, J. Zakrzewska-Czerwi n´ ska, A. Opolski, J.
Wietrzyk, E. Wojdat, Inorg. Chim. Acta 334 (2005) 5966.
[29] T. Rasmussen, J.F. Jensen, N. Østergaard, D. Tanner, T. Ziegler, P.-O. Norrby,
Chem. Eur. J. 8 (2002) 177184.
[30] D.W. Nelson, A. Gypser, P.T. Ho, H.C. Kolb, T. Kondo, H.-L. Kwong, D.V. McGrath,
A.E. Rubin, P.-O. Norrby, K.P. Gable, K.B. Sharpless, J. Am. Chem. Soc. 119
(1997) 18401858.
[31] N.S. Isaacs, Physical Organic Chemistry, Longman Scientific and Technical,
Harlow, 1987.
[32] C.-T. Yeung, K.-C. Sham, W.-S. Lee, W.-T. Wong, W.-Y. Wong, H.-L. Kwong,
Inorg. Chim. Acta 362 (2009) 32673273.
[
[
[
[
23] B. Cetinkaya, E. Cetinkaya, M. Brookhart, P.S. White, J. Mol. Catal. A 142 (1999)
1
01. 112.
24] G.B. Deacon, J.M. Patrick, B.W. Skelton, N.C. Thomas, A.H. White, Aust. J. Chem.
7 (1984) 929945.
25] H. Nishiyama, Y. Itoh, Y. Sugawara, H. Matsumoto, K. Aoki, K. Itoh, Bull. Soc.
Jpn. 68 (1995) 12471262.
3
[33] W.-L. Wong, W.-S. Lee, H.-L. Kwong, Tetrahedron: Asymmetry 13 (2002)
14851492.
26] S. Bachmann, A. Mezzetti, Helv. Chim. Acta 84 (2001) 30633074.