N-Propylphthalimide-Substituted Silver(I) N-Heterocyclic Carbene Complexes and Ruthenium(II) N-Heterocyclic Carbene Complexes: Synthesis and Transfer Hydrogenation of Ketones

Article abstract of DOI:10.1007/s10562-014-1453-8

This study deals with the synthesis of N-propylphthalimide substituted Ag(I)-N-heterocyclic carbene (NHC) complexes and N-propylphthalimide substituted Ru(II)-NHC complexes in the transfer hydrogenation of ketones. The Ag(I)-NHC complexes were synthesized

Full text of DOI:10.1007/s10562-014-1453-8

Catal Lett (2015) 145:631–639
DOI 10.1007/s10562-014-1453-8
N-Propylphthalimide-Substituted Silver(I) N-Heterocyclic
Carbene Complexes and Ruthenium(II) N-Heterocyclic Carbene
Complexes: Synthesis and Transfer Hydrogenation of Ketones
Aydın Aktas¸
Yetkin G o¨ k
•
Received: 8 August 2014 / Accepted: 24 November 2014 / Published online: 6 December 2014
Ó Springer Science+Business Media New York 2014
Abstract This study deals with the synthesis of N-pro-
pylphthalimide substituted Ag(I)–N-heterocyclic carbene
Wanzlick at the beginning of 1960s [3]. The first execution
of NHCs as a ligand for metal complexes were separately
¨
synthesized by Wanzlick [4] and Ofele [5] in 1968. How-
(
NHC) complexes and N-propylphthalimide substituted
Ru(II)–NHC complexes in the transfer hydrogenation of
ketones. The Ag(I)–NHC complexes were synthesized
ever, the field of NHCs as ligands in transition metal
chemistry haven’t changed much until a report on the
extraordinary stability, isolation and storability of crystal-
line NHC IAd by Arduengo et al. in 1991 [6, 7].
from the imidazolium salts and Ag O in dichloromethane
2
at room temperature. The Ru(II)–NHC complexes have
been prepared from Ag(I)–NHC complexes using trans-
metallation method. The six N-propylphthalimide substi-
tuted Ag(I)–NHC complexes and six N-propylphthalimide
substituted Ru(II)–NHC complexes have been character-
ized by spectroscopic techniques and elemental analyses.
N-propylphthalimide substituted Ru(II)–NHC complexes
have been analyzed as catalysts for the transfer hydroge-
nation of ketones and exhibit activity in this reaction.
NHC form intriguingly stable bonds with the majority of
metals [8–10]. Phosphines contain usually much weaker
bonds but for saturated and unsaturated NHCs of compa-
rable steric demand very similar bond dissociation energies
have been observed [11]. Consequently, the balance
between the free carbene and the carbene metal complex
lies more suitable than the case for phosphines. This
minimizes the amount of free NHC in solution and thus
increases the life-time of the complex as well as its strength
against heat, air and moisture.
Keywords N-heterocyclic carbenes Á Silver and
ruthenium complexes Á Catalysis Á Transfer hydrogenation
Ag(I)–NHC complexes have taken considerable attention
due to simpler synthetic strategies, fascinating structural
diversity, stability and most importantly they have been
admitted as effective carbene group transfer agents in the
synthesis of many structurally and catalytically important
transitionmetalNHCcomplexes[12].InthebeginningAg(I)–
NHC complexes demonstrate good precursor for the synthesis
of other transition metal–carbene complexes. For example,
Au(I), Rh(I), Pd(II), Cu(I), Ru(II), Ru(III), Ir(I), and Pt(II)
complexes are synthesized by transmetallation [13].
1
Introduction
Carbenes, divalent and six valence electrons containing in
shells are neutral carbon species. For many years, carbenes
have been known as very reactive and can not be isolated
[
1]. The majority of carbenes is known as short-lived
reagents intermediates [2]. For this reason many chemists
have hesitated to use of carbene compounds, especially as
precursors ligands in the transition metal chemistry. N-
heterocyclic carbenes (NHCs) were first studied by
For the past 20 years Ru complexes have increased
application in the field catalysis and organometallic
chemistry [14–18]. Recently, the newly synthesized Ru
complexes have provided with particularly ligands to
maintain a compatible equilibrium between the electronic
and steric environment around the metal and to control on
their stability, activity and chemoselectivity profiles [19–
30]. Typically, most of NHC ligands emerge quite
A. Akta s¸ (&) Á Y. G o¨ k
Department of Chemistry, Faculty of Arts and Sciences,
´
In o¨ n u¨ University, 44280 Malatya, Turkey
e-mail: aydinaktash@hotmail.com
123

6
32
A. Akta s¸ et al.
suitability with heteroatom including air, moisture and
functional groups, thus expanding areas of application [31]
in the many organic transformations. The structural motifs
of Ru(II)–NHC complexes have found wide application in
catalytic processes [32–34].
silver(I)oxide (0.139 g, 0.6 mmol) and activated 4 molec-
ular sieves was added. The reaction mixture was stirred for
24 h at room temperature in dark condition. The reaction
mixture was filtered through Celite and the solvent were
evaporated under vacuum to afford the product as a white
solid. The crude product was recrystallized from dichlo-
romethane/diethyl ether (1:3) at room temperature. Yield:
490 mg, (77 %).
Transition metal-catalysed transfer hydrogenation of
2
-propanol used as the hydrogen source is an effective
method in organic synthesis [35]. In recent years a large
number of applications dealing with this issue have been
reported [36, 37]. In this process, the reaction conditions,
partially contain mild conditions, economic and environ-
mentally friendly is very important. In this reaction com-
monly used the catalysts of ruthenium(II) complexes.
However sometimes rhodium and iridium derivatives have
also been used [38].
2.1.1 Analytical Data for Bromo[1-(N-
Propylphthalimide)-3-Benzylimidazol-2-
Ylidene]Silver(I), 2a
1
H NMR (300 MHz, DMSO-d ), d 1.91–1.95 (m, 2H,
6
–CH CH CH NC O ); 2.51 (t, 2H, J: 3.3 Hz –NCH CH
2
2
2
2
8
2
2
In our study, illustrates the synthesis of six N-propyl-
phthalimide substituted Ag(I)–NHC complexes, six N-
propylphthalimide substituted Ru(II)–NHC complexes and
their application in the transfer hydrogenation of aromatic
ketones using 2-propanol.
CH NC O ); 3.47–3.50 (m, 4H, –NCH CH N–); 3.54–3.58
2 8 2 2 2
(m, 2H, –CH CH NC O ); 4.66 (s, 2H, –NCH C H );
2
2
2
8
2 6 5
1
3
7.25–7.89 (m, 9H, Ar–H). C NMR (300 MHz, DMSO-d6),
d22.5 (–CH CH CH NC O ); 27.0 (–NCH CH NC O );
35.4 (–CH CH NC O ); 48.6 and 48.9 (–NCH CH N–);
2
2
2
8
2
2
2
8 2
2
2
8
2
2
2
55.4 (–NCH C H ); 123.5, 128.1, 128.3, 128.9, 128.9,
2 6 5
1
29.0, 129.4, 132.1, 132.2, 134.8 and 136.7. (Ar–C); 168.4
-
1
2
Experimental
(C=O); 204.3 (2-C). m.p.: 308–310 °C; m(CN): 1,662.5 cm
Anal. Calc. for C H AgBrN O : C: 47.04; H: 4.14; N:
.
2
1
22
3 2
All synthesis involving Ag(I)–NHC complexes 2a–f and
Ru(II)–NHC complexes 3a–f were carried out under an
inert atmosphere in flame-dried glassware using standard
schlenk techniques. The solvents used were purified by
distillation over the drying agents indicated and were
transferred under Ar: Et O (Na/K alloy), CH Cl (P O ),
7.84. Found: C: 47.02; H: 4.12; N: 7.83.
2.2 Synthesis of Bromo[1-(N-Propylphthalimide)-3-(2-
Methylbenzyl)Imidazol-2-Ylidene]Silandr(I), 2b
2
2
2
4 10
The synthesis of 2b was carried out in the same way as that
described for 2a, but 1-(N-propylphthalimide)-3-(2-meth-
ylbenzyl)imidazol bromide (0.531 g, 1.2 mmol) was used
instead of 1-(N-propylphthalimide)-3-benzylimidazol bro-
mide. Yield: 480 mg, (74 %).
hexane, toluene (Na).
All other reagents were commercially available by
Aldrich Chemical Co. and used without further purifica-
tion. Melting points were identified in glass capillaries
under air with an Electrothermal-9200 melting point
apparatus. FT-IR spectra were saved as KBr pellets in the
-
1
range 400–4,000 cm on a AT, UNICAM 1000 spec-
13
2.2.1 Analytical Data for Bromo[1-(N-
Propylphthalimide)-3-(2-Methylbenzyl)Imidazol-2-
ylidene]Silandr(I), 2b
1
trometer. Proton ( H) and Carbon ( C) NMR spectra were
recorded using either a Varian AS 400 Merkur spectrom-
1 13
eter operating at 400 MHz ( H), 100 MHz ( C) in CDCl
3
1
and DMSO-D6-d with tetramethylsilane as an internal
6
H NMR (300 MHz, DMSO-d ); d 1.91–1.93 (m, 2H,
6
reference. All reactions were observed on a Agilent 6890 N
GC system by GC-FID with a HP-5 column of 30 m
length, 0.32 mm diameter and 0.25 lm film thickness.
Column chromatography was performed using silica gel 60
–CH CH CH NC O ); 2.24 (s, 3H, –C H CH ); 2.51 (t,
3
2
2
2
8
2
6
4
2H, J: 3.6 Hz –NCH CH CH NC O ); 3.46–3.48 (m, 4H,
2
2
2
8 2
–NCH CH N–); 3.50–3.65 (m, 2H, –CH CH NC O );
8 2
2
2
2
2
1
3
4.59 (s, 2H, –NCH C H ); 7.20–7.86 (m, 8H, Ar–H).
6 4
C
2
(
70–230 mesh). Elemental analyses were performed by
NMR (300 MHz, DMSO-d ); d19.6 (–CH CH CH NC
6
2
2
2
8
Turkish Research Council (Ankara, TURKEY) Microlab.
O ); 26.7 (–CH C H CH ); 27.0 (–NCH CH CH NC O );
2
2
2
6
4
3
2
2
8 2
35.4 (–CH CH NC O ); 48.6 and 48.8 (–NCH CH N–);
2 2 8 2 2 2
2
.1 Synthesis of Bromo[1-(N-Propylphthalimide)-3-
Benzylimidazol-2-Ylidene]Silver(I), 2a
52.3 (–NCH C H ); 123.5, 126.6, 128.3, 131.0, 132.1,
2 6 4
134.5, 134.8 and 136.7 (Ar–C); 168.4 (C=O); 204.6
-
1
(
2-CH). m.p.: 295–297 °C; m(CN): 1,665.8 cm . Anal.
To a solution of 1-(N-propylphthalimide)-3-benzylimidazol
Calc. for C H AgBrN O : C: 48.02; H: 4.40; N: 7.64.
2
2
24
3 2
bromide (0.514 g, 1.2 mmol) in dichloromethane (30 mL),
Found: C: 47.99; H: 4.38; N: 7.62.
1
23

Synthesis and Transfer Hydrogenation of Ketones
633
2
.3 Synthesis of Bromo[1-(N-Propylphthalimide)-3-(3-
Methylbenzyl)Imidazol-2-Ylidene]Silandr(I), 2c
2.5 Synthesis of Bromo[1-(N-Propylphthalimide)-3-
(2,4,6-Trimethylbenzyl)Imidazol-2-
Ylidene]Silandr(I), 2e
The synthesis of 2c was carried out in the same way as that
described for 2a, but 1-(N-propylphthalimide)-3-(3-meth-
ylbenzyl)imidazol bromide (0.531 g, 1.2 mmol) was used
instead of 1-(N-propylphthalimide)-3-benzylimidazol bro-
mide. Yield: 490 mg, (75 %).
The synthesis of 2e was carried out in the same way as that
described for 2a, but 1-(N-propylphthalimide)-3-(2,4,6-
trimethylbenzyl)imidazol bromide (0.565 g, 1.2 mmol) was
used instead of 1-(N-propylphthalimide)-3-benzylimidazol
bromide. Yield: 560 mg, (81 %).
2
.3.1 Analytical Data for Bromo[1-(N-
Propylphthalimide)-3-(3-Methylbenzyl)Imidazol-2-
Ylidene]Silandr(I), 2c
2.5.1 Analytical Data for Bromo[1-(N-
Propylphthalimide)-3-(2,4,6-
Trimethylbenzyl)Imidazol-2-Ylidene]Silandr(I), 2e
1
H NMR (300 MHz, DMSO-d ); d 1.92–1.94 (m, 2H,
6
1
–
CH CH CH NC O ); 2.29 (s, 3H, –C H CH ); 2.51 (t, 2H,
4
H NMR (300 MHz, DMSO-d ), d 1.87–1.91 (m, 2H,
2
2
2
8
2
6
3
6
J: 3.6 Hz –NCH CH CH NC O ); 3.50–3.53 (m, 4H,
2
–CH CH CH NC O ); 2.21 and 2.26 (s, 9H, –CH C H
2 6 2
2
2
8
2
2
2
2
8
2
–
NCH CH N–); 3.63–3.65 (m, 2H, –CH CH NC O ); 4.60
8
(CH ) ); 2.51 (t, 2H, J: 3.3 Hz –NCH CH CH NC O );
3 3 2 2 2 8 2
2
2
2
2
2
1
s, 2H, –NCH C H ); 7.08–7.87 (m, 8H, Ar–H). C NMR
3
(
(
(
3.48–3.52 (m, 4H, –NCH CH N–); 3.58–3.62 (m, 2H,
2 2
2
6
4
300 MHz, DMSO-d ), d21.4 (–CH CH CH NC O ); 26.9
–CH C H CH ); 28.9 (–NCH CH NC O ); 35.3 (–CH
2
–CH CH NC O ); 4.52 (s, 2H, –NCH C H ); 6.87–7.82
2 2 8 2 2 6 2
6
2
2
2
8
2
1
3
(m, 6H, Ar–H). C NMR (300 MHz, DMSO-d ), d16.5
2
6
4
3
2
8
2
2
6
CH NC O ); 48.5 and 48.8 (–NCH CH N–); 54.3
2
(–CH CH CH NC O ); 20.5 (–CH C H (CH ) ); 21.0
6
2
8
2
2
2
2
2
8
2
2
2
3 2
(
–NCH C H ); 123.5, 125.2, 128.7, 128.9, 129.1, 132.1,
2
(–C H CH ); 27.1 (–NCH CH NC O ); 35.4 (–CH CH
6 2 3 2 2 8 2 2
6
4
2
6
1
32.2, 134.8, 136.5 and 138.4. (Ar–C); 168.4 (C=O); 204.3
-
NC O ); 48.5 and 49.0 (–NCH CH N–); 55.4 (–NCH C
8 2 2 2 2
1
(
2-CH). m.p.: 288–290 °C; m(CN): 1,665.8 cm . Anal. Calc.
H ); 123.5, 128.9, 129.7, 132.1, 134.8, 137.6 and 137.8.
2
for C H AgBrN O : C: 48.02; H: 4.40; N: 7.64. Found: C:
(Ar–C); 168.3 (C=O); not obserand (2-CH). m.p.:
1
2
2
24
3 2
-
4
2
8.00; H: 4.39; N: 7.62.
193–195 °C; m(CN): 1,666.7 cm . Anal. Calc. for C H
24
28
AgBrN O : C: 49.85; H: 4.88; N: 7.27. Found: C: 49.83; H:
3
2
.4 Synthesis of Bromo[1-(N-Propylphthalimide)-3-(4-
Methylbenzyl)Imidazol-2-Ylidene]Silandr(I), 2d
4.86; N: 7.25.
2
.6 Synthesis of Bromo[1-(N-Propylphthalimide)-3-
(2,3,5,6-Tetramethylbenzyl)Imidazol-2-
Ylidene]Silandr(I), 2f
The synthesis of 2d was carried out in the same way as that
described for 2a, but 1-(N-propylphthalimide)-3-(4-meth-
ylbenzyl)imidazol bromide (0.531 g, 1.2 mmol) was used
instead of 1-(N-propylphthalimide)-3-benzylimidazol bro-
mide. Yield: 510 mg, (78 %).
The synthesis of 2f was carried out in the same way as that
described for 2a, but 1-(N-propylphthalimide)-3-(2,3,5,6-
tetramethylbenzyl)imidazol bromide (0.582 g, 1.2 mmol)
was used instead of 1-(N-propylphthalimide)-3-ben-
zylimidazol bromide. Yield: 580 mg, (82 %).
2
.4.1 Analytical Data for Bromo[1-(N-
Propylphthalimide)-3-(4-Methylbenzyl)Imidazol-2-
Ylidene]Silandr(I), 2d
2
.6.1 Analytical Data for Bromo[1-(N-
1
H NMR (300 MHz, DMSO-d ), d 1.90–1.93 (m, 2H,
Propylphthalimide)-3-(2,3,5,6-
6
–
CH CH CH NC O ); 2.28 (s, 3H, –C H CH ); 2.51 (s,
4
Tetramethylbenzyl)Imidazol-2-Ylidene]Silandr(I), 2f
2
2
2
8
2
6
3
2
H, –NCH CH CH NC O ); 3.49–3.54 (m, 4H, –NCH
2 2 2 8 2 2-
1
CH N–); 3.59–3.65 (m, 2H, –CH CH NC O ); 4.60 (s,
2
H NMR (300 MHz, DMSO-d ), d 1.86–1.93 (m, 2H,
2
2
8
2
6
1
3
H, –NCH C H ); 7.12–7.86 (m, 8H, Ar–H). C NMR
2
–CH CH CH NC O ); 2.16 and 2.17 (s, 12H, –CH C
2 6-
2
6
4
2
2
2
8
2
(
300 MHz, DMSO-d ), d 16.8 (–CH CH CH NC O );
H(CH ) ); 2.51 (t, 2H, J: 3.0 Hz –NCH CH CH NC O );
3 4 2 2 2 8 2
6
2
2
2
8
2
2
1.2 (–CH C H CH ); 27.0 (–NCH CH NC O ); 35.4
2
3.45–3.49 (m, 4H, –NCH CH N–); 3.56–3.58 (m, 2H,
2 2
6
4
3
2
2
8
2
(
–CH CH NC O ); 48.5 and 48.9 (–NCH CH N–); 54.0
2
–CH CH NC O ); 4.53 (s, 2H, –NCH C H); 6.96–7.81
2 2 8 2 2 6
2
8
2
2
2
1
3
(
–NCH C H ); 123.5, 128.1, 128.2, 128.4, 129.5, 129.6,
6
(m, 5H, Ar–H). C NMR (300 MHz, DMSO-d ), d15.7
2
4
6
1
29.7, 132.1, 133.6, 134.8 and 137.5; (2-CH); 168.4
(–CH CH CH NC O ); 16.3 and 20.7 (–CH C H(CH ) );
6
2
2
2
8
2
2
3 4
(
C=O); (Ar–C); 204.2. m.p.: 310–312 °C; m(CN)
:
27.1 (–NCH CH NC O ); 35.4 (–CH CH NC O ); 48.8
2 2 8 2 2 2 8 2
-
,667.8 cm . Anal. Calc. for C H AgBrN O : C: 48.02;
1
1
and 49.2 (–NCH CH N–); 65.4 (–NCH C H); 123.5,
2 2 2 6
2
2
24
3
2
H: 4.40; N: 7.64. Found: C: 48.01; H: 4.37; N: 7.62.
131.6, 132.0, 133.7, 134.1 and 134.8. (Ar–C); 168.3
123

6
34
A. Akta s¸ et al.
(
C=O); 203.3 (2-C). m.p.: 119–120 °C; m(CN)
:
2.8.1 Analytical Data for Dichloro[1-(N-
-
1
1
,667.8 cm
.
Anal. Calcd for C H AgBrN O :
Propylphthalimide)-3-(2-Methylbenzyl)Imidazolidin-
2
5
30
3 2
C: 50.70; H: 5.11; N: 7.07. Found: C: 50.68; H: 5.09; N:
2-Ylidene](p-Cymene)Ruthenium(II), 3b
7
.08.
1
H NMR (300 MHz, CDCI ); d 1.12–1.19 (m, 6H, Ru–
3
2
.7 Synthesis of Dichloro[1-(N-Propylphthalimide)-3-
Benzylimidazolidin-2-Ylidene](p-
C
6
H
4
CH(CH
); 2.05 (s, 3H, C
2.74–2.83 (m, 1H, Ru–C
3
)
2
); 1.92–1.96 (m, 2H, –CH
2
CH
2
CH
2
NC
8
O
H
CH ); 2.23 (s, 3H, Ru–C
H
CH
);
2
6
4
3
6
4
3
Cymene)Ruthenium(II), 3a
6
H
4
CH(CH
NCH CH CH NC O ); 3.44–3.48 (m, 2H, –CH CH
2
) ); 3.37–3.42 (m, 2H,
3 2
–
2
2
2
8
2
2
To a solution of bromo[1-(N-propylphthalimide)-3-benzy-
NC
8
O
2
); 3.67–3.79 (m, 4H, –NCH
C H ); 5.04 and 5.23 (d, 4H, J: 5.7 Hz and 5.1 Hz
2 6 4
2 2
CH N–); 4.59 (s, 2H,
limidazol-2-ylidene]silver(I)(0.150 g, 0.28 mmol) in dichlo-
6
romethane (30 mL), Di-l-chloro-bis[chloro(g -1-isopropyl-
–NCH
Ru–Ar–H); 7.11–7.81 (m, 8H, Ar–H).
(300 MHz, CDCI ); d15.3 (–CH CH CH NC
(C CH(CH ); 21.5 (C CH ); 23.7 (C
28.5 (–NCH CH NC ); 30.5 (Ru–C
(–CH CH NC ); 49.3–50.8 (–NCH
(–NCH 5); 82.1, 82.5, 85.1, 87.1, 98.9 and 108.8. (Ru–
13
C
NMR
4
-methylbenzene)ruthenium(II)] (0.086 g, 0.14 mmol) was
3
2
2
2
8
O
2
); 18.7
added. The reaction mixture was stirred for 24 h at room
temperature in dark condition. The reaction mixture was
filtered through Celite and the solvent were evaporated
under vacuum to afford the product as a red-brown solid.
The crude product was recrystallized from diclorome-
thane:dietylether (1:3) at room temperature. Yield:
6
H
4
3
)
2
6
H
4
3
6
H
4
CH(CH
CH ); 35.6
CH N–); 52.6
2 2
3 2
) );
O
H
4
2
2
8
2
6
3
O
2
2
8
2
C H
2 6
Ar–C); 123.1, 125.0, 126.1, 127.0, 130.7, 132.5, 133.8 and
135.8. (Ar–C); 168.8 (C=O); 209.7(Ru–Ccarb.). m.p.:
-
1
1
50 mg, (82 %).
187–189 °C; m(CN): 1,496.7 cm . Anal. Calc. for RuC33
H Cl N O : C: 57.97; H: 6.04; N: 6.15. Found: C: 57.95;
4
1
2 3 2
2
.7.1 Analytical Data for Dichloro[1-(N-
Propylphthalimide)-3-Benzylimidazolidin-2-
Ylidene](p-Cymene)Ruthenium(II), 3a
H: 6.03; N: 6.13.
2.9 Synthesis of Dichloro[1-(N-Propylphthalimide)-3-
(
3-Methylbenzyl)Imidazolidin-2-Ylidene](p-
1
H NMR (300 MHz, CDCI ); d 1.19–1.24 (m, 6H, Ru–
Cymene)Ruthenium(II), 3c
3
C H CH(CH ) ); 1.96–1.99 (m, 2H, –CH CH CH NC
8
6
4
3 2
2
2
2
O ); 2.18 (s, 3H, Ru–C H CH ); 2.85–2.95 (m, 1H, Ru–
2
The synthesis of 3c was carried out in the same way as
that described for 3a, but bromo[1-(N-propylphthalimide)-
3-(3-methylbenzyl)imidazol-2-ylidene]silver(I)(0.154 g,
0.28 mmol) was used instead of bromo[1-(N-propylph-
6
4
3
C H CH(CH ) ); 3.13–3.20 (m, 2H, –NCH CH CH NC
8
6
4
3 2
2
2
2
O ); 3.46–3.52 (m, 2H, –CH CH NC O ); 3.70–3.77 (m,
2
2
2
8 2
4
H, –NCH CH N–); 5.00 (s, 2H, –NCH C H ); 5.27 and
2 2 2 6 5
5
.32 (d, 4H, J: 5.4 Hz and 6.6 Hz Ru–Ar–H). 7.25–7.90
1
thalimide)-3-benzylimidazol-2-ylidene]silver(I).
150 mg; (84 %).
Yield:
3
(
(
(
m, 9H, Ar–H); C NMR (300 MHz, CDCI ); d15.3
–CH CH CH NC O ); 18.9 (C H CH(CH ) ); 23.3
3 2
3
2
2
2
8
2
6
4
C H CH(CH ) ); 28.5 (–NCH CH NC O );30.5 (Ru–C
8
2.9.1 Analytical Data for Dichloro[1-(N-
6
4
3 2
2
2
2
6
2
H CH ); 35.6 (–CH CH NC O ); 48.8–50.8 (–NCH CH
4
Propylphthalimide)-3-(3-Methylbenzyl)Imidazolidin-
3
2
2
8
2
2
N–); 55.8 (–NCH C H ); 82.2, 85.6, 86.9, 99.4 and 109.3.
2
2-Ylidene](p-Cymene)Ruthenium(II), 3c
6 5
(
Ru–Ar–C); 123.1, 123.5, 127.6, 127.9, 128.6, 131.9,
32.6, 133.8 and 137.0. (Ar–C); 168.8 (C=O); 208.7 (Ru–
1
1
H NMR (300 MHz, CDCI
CH(CH ); 1.98–2.01 (m, 2H, –CH
); 2.18 (s, 3H, Ru–C CH ); 2.34 (s, 3H, C
2.87–2.96 (m, 1H, Ru–C CH(CH
NCH CH CH NC O ); 3.50–3.54 (m, 2H, –CH CH
3
); d 1.21–1.26 (m, 6H, Ru–
-
1
Ccarb.). m.p.: 194–197 °C; m(CN): 1,494.3 cm . Anal. Calc.
for RuC H Cl N O : C: 57.39; H: 5.87; N: 6.27. Found:
C
6
H
4
3
)
2
2
CH
2
CH
2
NC
8
O
H
H
CH
);
3
2
39
2 3 2
2
6
4
3
6
4
3
C: 57.37; H: 5.87; N: 6.26.
6
H
4
) ); 3.12–3.18 (m, 2H,
3 2
–
2
2
2
8
2
2
2-
2
.8 Synthesis of Dichloro[1-(N-Propylphthalimide)-3-
2-Methylbenzyl)Imidazolidin-2-Ylidene](p-
Cymene)Ruthenium(II), 3b
NC
8
O
2
); 3.70–3.77 and 3.85–3.91 (m, 4H, –NCH
2
CH
2
N–);
(
4.80 (s, 2H, –NCH
and 4.8 Hz Ru–Ar–H); 7.07–7.90 (m, 8H, Ar–H).
C H ); 5.26 and 5.33 (d, 4H, J: 5.7 Hz
2 6 5
1
3
C
NMR (300 MHz, CDCI ); d 18.9 (C H CH(CH ) ); 21.5
3
6
4
3 2
The synthesis of 3b was carried out in the same way as that
described for 3a, but bromo[1-(N-propylphthalimide)-3-(2-
methylbenzyl)imidazol-2-ylidene]silver(I)(0.154 g,
(–CH
CH(CH
35.6 (–CH
2
CH
2
CH
2
NC
8
O
2
); 21.8 (C
6
H
4
CH
3
); 23.5 (C H
6 4-
)
); 28.5 (–NCH
CH
); 48.8–50.8 (–NCH
5); 82.0, 82.3, 85.5, 86.9, 99.5 and 109.3. (Ru–
NC O
2 8
); 30.5(Ru–C
2
H CH );
6 4 3
3
2
2
CH
NC
O
CH N–); 55.7
2
2
8
2
2
2
0
.28 mmol) was used instead of bromo[1-(N-propylph-
thalimide)-3-benzylimidazol-2-ylidene]silver(I). Yield: 160 mg,
86 %).
(–NCH
2
C
6
H
Ar–C); 123.1, 124.8, 128.3, 128.5, 128.6, 132.6, 133.8,
137.0 and 138.4. (Ar–C); 168.9 (C=O); 208.7 (Ru–Ccarb.).
(
1
23

Synthesis and Transfer Hydrogenation of Ketones
635
-
1
m.p.: 208–210 °C; m(CN): 1,501.3 cm . Anal. Calc. for
2.11.1 Analytical Data for Dichloro[1-(N-
Propylphthalimide)-3-(2,4,6-
RuC H Cl N O : C: 57.97; H: 6.04; N: 6.15. Found: C:
3
3
41
2 3 2
5
7.96; H: 6.03; N: 6.13.
Trimethylbenzyl)Imidazolidin-2-Ylidene](p-
Cymene)Ruthenium(II), 3e
1
2
.10 Synthesis of Dichloro[1-(N-Propylphthalimide)-3-
H NMR (300 MHz, CDCI ); d 1.20–1.23 (m, 6H, Ru–
3
(4-Methylbenzyl)Imidazolidin-2-ylidene](p-
C H CH(CH ) ); 1.88–1.92 (m, 2H, –CH CH CH NC
8
6
4
3 2
2
2
2
Cymene)Ruthenium(II), 3d
O ); 2.14 (s, 3H, Ru–C H CH ); 2.18 and 2.24 (s, 9H,
2
6
4
3
C H (CH ) ); 2.87–2.91 (m, 1H, Ru–C H CH(CH ) );
6
2
3 3
6
4
3 2
The synthesis of 3d was carried out in the same way as that
described for 3a, but bromo[1-(N-propylphthalimide)-3-(4-
methylbenzyl)imidazol-2-ylidene]silver(I)(0.154 g,
3.02–3.10 (m, 4H, –NCH CH CH NC O ); 3.56–3.76 (m,
2 2 2 8 2
4H, –NCH CH N–); 4.65 (s, 2H, –NCH C H ); 5.25 and
2 6 5
2
2
5.32 (d, 4H, J: 5.7 Hz and 6.2 Hz Ru–Ar–H); 6.76–7.80
1
3
0
.28 mmol) was used instead of bromo[1-(N-propylph-
(m, 6H, Ar–H). C NMR (300 MHz, CDCI ); d15.3
3
thalimide)-3-benzylimidazol-2-ylidene]silver(I). Yield:
(–CH CH CH NC O ); 18.9 (C H CH(CH ) ); 20.1 and
6
2
2
2
8
2
4
3 2
1
70 mg, (90 %).
20.7 (C H (CH ) ); 24.1 (C H CH(CH ) ); 28.5 (–NCH
6 2 3 3 6 4 3 2
2
CH NC O ); 30.6 (Ru–C H CH ); 35.5 (–CH CH NC
2
2
8
2
6
4
3
2
8
O ); 48.3–48.8(–NCH CH N–); 51.0 (–NCH C H ); 81.6,
2
2
2
2 6 5
2
.10.1 Analytical Data for Dichloro[1-(N-
Propylphthalimide)-3-(4-
8
1
3.3, 85.3, 86.4, 100.2 and 108.8. (Ru–Ar–C); 123.0,
29.2, 129.6, 132.6, 133.8, 137.6 and 138.6. (Ar–C); 168.3
Methylbenzyl)Imidazolidin-2-Ylidene](p-
Cymene)Ruthenium(II), 3d
(
C=O); 208.3 (Ru–Ccarb.). m.p.: 156–158 °C; m(CN)
:
-
,494.1 cm . Anal. Calc. for RuC H Cl N O : C:
1
1
35 44 2 3 2
59.06; H: 6.37; N: 5.90. Found: C: 59.04; H: 6.36; N: 5.88.
1
H NMR (300 MHz, CDCI ); d 1.22–1.29 (m, 6H, Ru–
3
C H CH(CH ) ); 1.97–1.99 (m, 2H, –CH CH CH NC
6
4
3 2
2
2
2
8
2.12 Synthesis of Dichloro[1-(N-Propylphthalimide)-3-
(2,3,5,6-Tetramethylbenzyl)Imidazolidin-2-
Ylidene](p-Cymene)Ruthenium(II), 3f
O ); 2.18 (s, 3H, Ru–C H CH ); 2.34 (s, 3H, C H CH );
4
2
6
4
3
6
3
2
2
.86–2.95 (m, 1H, Ru–C H CH(CH ) ); 3.15–3.18 (m,
6 4 3 2
H,–NCH CH CH NC O ); 3.38–3.46 (m, 2H, –CH
2
2
2
2
8
2
CH NC O ); 3.75–3.85 (m, 4H, –NCH CH N–); 5.03 (s,
2
2
8
2
2
The synthesis of 3f was carried out in the same way as that
described for 3a, but bromo[1-(N-propylphthalimide)-3-
2
H, –NCH C H ); 5.24 and 5.32 (d, 4H, J: 7.0 Hz and
2 6 5
1
.0 Hz Ru–Ar–H); 7.12–7.89 (m, 8H, Ar–H). C NMR
3
7
(2,3,5,6-tetramethylbenzyl)imidazol-2-ylidene]sil-
(
300 MHz, CDCI ); d15.5 (–CH CH CH NC O );18.9
2
C H CH(CH ) ); 23.4 (C H CH(CH ) ); 21.9 (C H CH );
6 4 3 2 6 4 3 2 6 4 3
3
2
2
8
2
ver(I)(0.166 g, 0.28 mmol) was used instead of bromo[1-
(N-propylphthalimide)-3-benzylimidazol-2-ylidene]sil-
ver(I). Yield: 170 mg, (85 %).
(
2
8.5 (–NCH CH NC O ); 30.5 (Ru–C H CH ); 35.6
2 2 8 2 6 4 3
(
(
(
–CH CH NC O ); 48.8–50.8 (–NCH CH N–); 55.5
2 2 8 2 2 2
–NCH C H ); 82.2, 82.3, 85.5, 86.9, 99.4 and 109.3.
4
2
6
2.12.1 Analytical Data for Dichloro[1-(N-
Propylphthalimide)-3-(2,3,5,6-
Ru–Ar–C); 123.1, 127.8, 129.3, 132.6, 133.8, 133.9 and
37.2. (Ar–C); 168.8 (C=O); 208.5 (Ru–Ccarb.). m.p.:
1
Tetramethylbenzyl)Imidazolidin-2-Ylidene](p-
Cymene)Ruthenium(II), 3f
-
91–193 °C; m(CN): 1,493.1 cm . Anal. Calc. for RuC33
1
1
H Cl N O : C: 57.97; H: 6.04; N: 6.15. Found: C: 57.95;
1
4
2 3 2
1
H: 6.02; N: 6.14.
H NMR (300 MHz, CDCI ); d 1.25–1.30 (m, 6H, Ru–
3
C H CH(CH ) ); 1.82–1.90 (m, 2H, –CH CH CH NC
8
6
4
3 2
2
2
2
O ); 2.18 and 2.22 (s, 12H, C H(CH ) ); 2.29 (s, 3H, Ru–
2
6
3 4
2
.11 Synthesis of Dichloro[1-(N-Propylphthalimide)-3-
2,4,6-Trimethylbenzyl)Imidazolidin-2-
Ylidene](p-Cymene)Ruthenium(II), 3e
C H CH ); 2.87–2.91 (m, 1H, Ru–C H CH(CH ) );
6
4
3
6
4
3 2
(
2
4
5
6
.93–3.10(m, 4H, –NCH CH CH NC O ); 3.42–3.50 (m,
2 2 2 8 2
H, –NCH CH N–); 4.50 (s, 2H, –NCH C H ); 5.35 and
2
2
2 6 5
.49 (d, 4H, J:5.7 Hz and 6.0 Hz Ru–Ar–H); 6.94–7.87 (m,
13
The synthesis of 3e was carried out in the same way as that
described for 3a, but bromo[1-(N-propylphthalimide)-3-
H, Ar–H). C NMR (300 MHz, CDCI ); d15.4 (–CH
3
2-
CH CH NC O ); 17.9 (C H CH(CH ) ); 19.4 (C H
6
2
2
8
2
6
4
3 2
(
2,4,6-trimethylbenzyl)imidazol-2-ylidene]sil-
ver(I)(0.162 g, 0.28 mmol) was used instead of bromo[1-
N-propylphthalimide)-3-benzylimidazol-2-ylidene]sil-
ver(I). Yield: 170 mg, (87 %).
(
CH ) ); 23.3 (C H CH(CH ) ); 27.5 (–NCH CH NC O );
3 4 6 4 3 2 2 2 8 2
2
9.6 (Ru–C H CH ); 34.5 (–CH CH NC O ); 47.4–48.3
6 4 3 2 2 8 2
(
(–NCH CH N–); 50.0 (–NCH C H); 80.7, 82.8, 84.0, 85.0,
2 2 2 6
9
9.3 and 107.6. (Ru–Ar–C); 122.0, 130.6, 131.4, 131.6,
123

6
36
A. Akta s¸ et al.
1
32.7 and 133.0. (Ar–C); 167.8 (C=O); 207.0 (Ru–Ccarb.).
-
3 Results and Discussion
1
m.p.: 191–193 °C; m(CN): 1,496.4 cm . Anal. Calc. for
RuC H Cl N O : C: 59.58; H: 6.53; N: 5.79. Found: C:
3.1 Synthesis of Ag(I)–NHC Complexes 2a–f
3
3
41
2 3 2
5
9.56; H: 6.52; N: 5.77.
The synthetic route for unsymmetrically N-propylphthali-
mide substituted Ag(I)–NHC complexes and their corre-
sponding Ru(II)–NHC complexes defined in this study
illustrated in Schemes 1 and 2. The unsymmetrically
substituted Ag(I)–NHC complexes 2a–f were prepared by
stirring 1-(N-propylphthalimide)-3-alkylimidazolidinium
2
.13 General Method for the Transfer Hydrogenation
of Ketones
The catalytic hydrogen transfer reactions were carried out
in a closed Schlenk flask under argon atmosphere. Sub-
strate ketone (1 mmol), catalyst Ru(II)–NHC complex 3a–
f (0.01 mmol) and KOH (4 mmol) was heated to reflux in
salts with 0.5 equivalents of Ag O in dichloromethane at
2
room temperature for 24 h. The Ag(I)–NHC complexes as
off white solid in 74–82 % yield. The Ag(I)–NHC com-
plexes were soluble in halogenated solvent and insoluble in
non-polar solvents. The complexes were characterized by
1
0 mL of i-PrOH for 1 h. The solvent was then removed
under vacuum. At the conclusion of the reaction, the
mixture was cooled, extracted with ethyl acetate/hexane
1
13
(
1:5), filtered through a pad of silicagel with copious
spectroscopic techniques ( H, C NMR, IR) and elemental
1
analysis. H and C NMR spectra are consistent with the
13
washings, concentrated, and purified by flash chromatog-
raphy on silicagel. The product distribution was determined
1
by H NMR spectroscopy, GC and GC–MS.
1
13
proposed formulate. In the H NMR and C NMR spectra in
d-DMSO-D6, loss of signals for the imidazolium proton
O
N
O
N
O
O
N
N
AgBr
N
AgBr
N
2d
2a
O
O
O
N
N
O
N
+
O
N
N
O
N
N
N
N
AgBr
AgBr
Br
R
2e
Ag O
2b
2
O
N
O
N
O
O
N
N
N
N
AgBr
AgBr
2f
2c
Scheme 1 Synthesis of Ag(I)–NHC Complexes 2a–f
1
23

Synthesis and Transfer Hydrogenation of Ketones
637
O
O
N
O
N
O
Cl
Ru
Cl
Cl
Ru
Cl
N
N
N
N
3
d
3a
O
O
O
N
N
N
O
O
O
Cl
Ru
Cl
Cl
Ru
Cl
N
N
N
N
N
N
AgBr
R
+
3
e
3b
[
RuCl (Pcym)]2
2
O
O
N
N
O
O
Cl
Ru
Cl
Cl
Ru
Cl
N
N
N
N
3
f
3c
Scheme 2 Synthesis of Ru(II)–NHC Complexes 3a–f
(
NCHN) (8.65–9.65 ppm) and imidazolium carbon (NCHN)
solvents such as chloroform, toluene, dichloromethane. The
Ru(II)–NHC complexes 3a–f were prepared by stirring
bromo[1-(N-propylphthalimide)-3-alkylimidazol-2-ylidene]
silver(I) with 0.5 equivalents of [RuCl (pcym)] in dichlo-
at (157.5–158.4 ppm) showed the formation of the expected
1
3
silver complexes. The C NMR spectra, resonances of the
carbene carbon atoms of complexes appeared in the range
d203.3–204.6 ppm respectively for 2a–f. These signals are
shifted downfield compared to the carbene precursors which
further demonstrates the formation of expected Ag(I)–NHC
complexes. The IR data for Ag(I)–NHC complexes emerge a
characteristic m(C=N) band at 1,503.6–1,508.2 respectively,
for 2a–f. The NMR and FT-IR values are similar to results of
other Ag(I)–NHC complexes.
2
2
romethane at room temperature for 24 h. The Ru(II)–NHC
complexes as a red–brown solid in 82–90 % yield. The
Ru(II)–NHC complexes were soluble in halogenated solvent
and insoluble in non-polar solvents. The Ru(II)–NHC
complexes have been characterized by analytical and
1
spectroscopic techniques. In the H NMR spectra, reso-
nances for the isopropyl and methyl prothons of the
p-cymene group of complexes 3a–f in the range 1.19–1.30
(methyl of izopropyl group), 2.85–3.10 (methyl of izopropyl
group) and 2.18–2.29 ppm (p-methyl of p-cymene group)
respectively showed the formation of the NHC–ruthenium
3
.2 Synthesis of Ru(II)–NHC Complexes 3a–f
The N-propylphthalimide substituted Ru(II)–NHC com-
plexes 3a–f were prepared from synthesized Ag(I)–NHC
complexes via transmetallation method (Scheme 2). The air
and moisture stable Ru(II)–NHC complexes were soluble in
1
3
complexes. The C NMR spectra, resonances of the car-
bene carbon atoms of complexes appeared in the range
d207.0–209.7 ppm respectively for 3a–f. These signals are
123

6
38
A. Akta s¸ et al.
O
OH
1
mol% of 3a-f
eq. base
OH
O
4
R
R1
R
R1
Table 1 Transfer hydrogenation of ketones catalyzed by 3a–f
+
+
5
ml i-PrOH
o
8
0 C, 1h
Entry
R
R
1
Base
Complex
Yield
(%)
1
2
3
4
5
6
7
8
9
H
–CH
–CH
–CH
–CH
–CH
–CH
–CH
–CH
–CH
–CH
–CH
–CH
–CH
–CH
–CH
–CH
–CH
–CH
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
3a
3b
3c
3d
3e
3f
65
77
80
65
78
63
67
60
71
55
60
76
65
66
74
72
65
81
70
96
88
96
87
98
H
H
H
H
H
MeO
MeO
MeO
MeO
MeO
MeO
F
3a
3b
3c
3d
3e
3f
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
a
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
3a
3b
3c
3d
3e
3f
F
F
F
F
F
b
b
b
b
b
b
H
–C
–C
–C
–C
–C
–C
6
H
6
H
6
H
6
H
6
H
6
H
5
5
5
5
5
5
3a
3b
3c
3d
3e
3f
H
H
H
H
H
Determined by GC–MS and yields are based on ketones
b
2
h, 80 °C
shifted downfield compared to corresponding Ag(I)–NHC
complexes of Ru(II)–NHC complexes carbene carbons
signal at the range 203.3–204.6 ppm respectively showed
the formation of the expected Ru(II)–NHC complexes. The
IR data for Ru(II)–NHC complexes exhibit a characteristic
m(C=N) band at 1,493.1–1,501.3 respectively, for 3a–f. The
NMR and FT-IR values are similar to results of other
Ru(II)–NHC complexes.
environmentally benign, and inexpensive. The volatile
acetone by-product can also be easily removed.
We have investigated and compared the catalytic prop-
erties of N-propylphthalimide substituted Ru(II)–NHC
complexes 3a–f in the transfer hydrogenation of various
methyl aryl ketones. The reduction of acetophenone with
2-propanol to 1-phenylethanol was chosen as a model
reaction. The catalytic transfer hydrogenations of ketones
were carried out using ruthenium (II) precatalyst
(0.01 mmol), KOH (4 mmol) and substrate ketone
3
.3 Catalytic Transfer Hydrogenation of Ketones
(1.00 mmol) in 2-propanol at 80 °C. The conversion was
Ruthenium complexes have been used as active catalysts
for transfer hydrogenation using 2-propanol as a hydrogen
source. The reaction conditions for this transformation are
economic, partly mild and environmentally benign
friendly. 2-propanol using as a hydrogen source is a pop-
ular reactive solvent for the catalytic transfer hydrogena-
tion since it is easy to handle and is relatively non-toxic,
monitored by GC and NMR. It is well known that catalytic
transfer hydrogenation is sensitive to the nature of the base.
We surveyed K CO , Cs CO , NaOH, KOH, t-BuOK and
2
3
2
3
NaOAc for the choice of base. The highest rate was
observed when KOH was employed. A variety of ketones by
2-propanol were transformed to the corresponding second-
ary alcohols. Typical results are summarized in Table 1.
1
23

Synthesis and Transfer Hydrogenation of Ketones
639
When compared with similar studies, particularly in
terms of reaction time [39–43], all complexes 3a–f seem to
be reasonably active in transfer hydrogenation reactions.
Generally, all complexes 3a–f are seen to be reasonably
active in hydrogen transfer reactions. Under the reaction
conditions complex 3c turned out to be the active catalyst
in comparison with 3a, 3b, 3d, 3e and 3f. The reduction of
acetophenone with 3c was completed within 1 h reaching
3. Huang J, Stevens ED, Nolan SP, Peterson JL (1999) J Am Chem
Soc 121:2674
4
. Wanzlick HW, Sch o¨ nherr HJ (1968) Angew Chem Int Ed Engl
7
:141
5. O¨ fele K (1968) J Organomet Chem 12:42
6. Arduengo III AJ, Harlow RL, Kline M (1991) J Am Chem Soc
1
13:361
7
8
. Arduengo III AJ, Krafczyk R (1998) Chem Unserer Zeit 32:6
. Hong SH, Day MW, Grubbs RH (2004) J Am Chem Soc
126:7414
8
0 %. In contrast, acetophenone was reduced within 1 h
9. Chatterjee AK, Morgan JP, Scholl M, Grubbs RH (2000) J Am
Chem Soc 122:3783
0. Austin JF, Kim SG, Sinz CJ, Xiao W-J, MacMillan DWC (2004)
Proc Natl Acad Sci 101:548
using 3a, 3b, 3d, 3e and 3f with 65, 77, 65, 78 and 63 %
conversion, respectively (Table 1).
1
A variety of ketones were converted to be corresponding
secondary alcohols. Typical results is illustrated in Table 1.
Under those conditions p-metoxyacetophenone and p-
fluoroacetophenone react neatly and in good yields with
11. Chatterjee AK, Morgan JP, Scholl M, Grubbs RH (2000) J Am
Chem Soc 122:3783
1
1
1
2. JB Lin Ivan, CS Vasam, (2007) Coord Chem Rev 251:642
3. JB Lin Ivan, CS Vasam, (2004) Inorganic Chem 25:75
4. Murahashi S-I, Takaya H, Naota T (2002) Pure Appl Chem 74:19
2
-propanol (Table 1). The existence of electron with-
15. Naota T, Takaya H, Murahashi S-I (1998) Chem Rev 98:2599
16. Bruneau C, Dixneuf PH (1999) Acc Chem Res 32:311
drawing (F) or electron donating (OCH ) substituents on
3
1
1
7. Selegue JP (2004) Coord Chem Rev 248:1543
8. Trost BM, Frederiksen MU, Rudd MT (2005) Angew Chem Int
Ed 44:6030
acetophenone (Table 1) has effect on the reduction of
major of ketones to their corresponding alcohols. The more
conversion of p-flouroacetophenone to secondary alcohol
was obtained at a time 1 h (Table 1).
19. Tfouni E, Ferreira KQ, Doro FG, DaSilva RS, DaRocha ZN
(2005) Coord Chem Rev 249:405
2
0. Distefano AJ, Nishart JF, Isied SS (2005) Coord Chem Rev
49:507
The transformation of ketones with bulky substituents
was not shown or mildly decreased. We tried this reaction
with benzophenone at 1 h. But, we have achieved low yields.
Therefore, we have extended the duration of experiments for
benzophenone to 2 h. The benzophenone was reduced within
2
2
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2
1
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1
h using 3a and 3b with 18 and 20 % conversion, respec-
tively. However, the yields lower than 2 h, for example the
reduction of benzophenone with 3a and 3b was completed
within 70 and 98 % respectively (Table 1).
24. Ung T, Hejl A, Grubbs RH, Schrodi Y (2004) Organometallics
23:5399
2
5. Wong C-Y, Chan MCW, Zhu N, Che C-M (2004) Organome-
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2
2
6. Dragutan V et al (2007) Coordination Chem Rev 251:765
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Conclusions
2
2
3
3
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As a result, we reported the synthesis of the six N-propyl-
phthalimide substituted Ag(I)–NHC complexes 2a–f and six
N-propylphthalimide substituted Ru(II)–NHC complexes
1
18:100
32. Herrmann WA (2002) Angew Chem Int Ed 41:1290
3
a–f. The Ru(II)–NHC complexes were prepared via the
3
3
3
3. Perry MC, Burgess K (2003) Tetrahedron Assymetry 14:951
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Ag(I)–NHC complexes transmetallation route. Catalytic
activities of Ru(II)–NHC complexes were readily accessible
and are effective catalyst precursors for the transfer hydro-
genation of ketones. The catalytic activities of these six N-
propylphthalimide substituted Ru(II)–NHC complexes have
been examined for the transfer hydrogenation of ketones and
exhibited excellent activity in this reaction.
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3
3
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9. Ozdemir I, Ya s¸ ar S (2005) Transit Met Chem 30:831
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