Transfer hydrogenation of ketones catalyzed by 1-alkylbenzimidazole ruthenium(II) complexes

Article abstract of DOI:10.1007/s00706-007-0590-9

Six [RuCl₂(1-alkylbenzimidazole)(p-cymene)] complexes have been prepared and the new compounds characterized by C, H, N analyses, ¹H NMR, and ¹³C NMR. The reduction of ketones to alcohols via transfer hydrogenation was ach

Full text of DOI:10.1007/s00706-007-0590-9

Monatshefte fu¨r Chemie 138, 205–209 (2007)
DOI 10.1007/s00706-007-0590-9
Printed in The Netherlands
Transfer Hydrogenation of Ketones Catalyzed by 1-Alkylbenzimidazole
Ruthenium(II) Complexes
1;ꢀ
Ismail Ozdemir , Neslihan S¸ahin2, and Bekir C
°
etinkaya3
_
¨
1
2
3
¨ ¨
Department of Chemistry, Inonu University Faculty Science and Art, Malatya, Turkey
Department of Chemistry, Cumhuriyet University Faculty Science and Art, Sivas, Turkey
_
Department of Chemistry, Ege University, Bornova-Izmir, Turkey
Received June 21, 2006; accepted (revised) August 28, 2006; published online February 22, 2007
# Springer-Verlag 2007
Summary. Six [RuCl2(1-alkylbenzimidazole)(p-cymene)]
complexes have been prepared and the new compounds
economy [2]. Especially, a variety of [RuX2(arene)-
(L)] complexes are promoting catalytic reactions
such as nucleophilic addition to triple bonds to form
furans (L ¼ imidazoline, tetrahydropyrimidine [3],
benzimidazole [4]), hydrogen transfer (L ¼ amino
acid [5], amino alcohol [6]), cyclopropanation (L ¼
diamine [7]), or Diels-Alder cycloaddition and
Claisen rearrangement (L ¼ bisoxazoline [8, 9]). It
is also well established that [RuCl2(arene)(L)] com-
plexes can easily be transformed via activation of
propargylic alcohols into cationic ruthenium allenyl-
idene complexes, which have shown catalytic prop-
erties in olefin metathesis [10]. These discoveries
motivate the search for the new metal complexes
with N-coordinated ligands and the evaluation of
their catalytic properties.
Our contribution to this field has started with
syntheses of 2-imidazoline and benzimidazole com-
plexes of Pt(II), Rh(I), Ru(II), and Pd(II) which are
capable of catalyzing the cyclopropanation of styr-
ene with ethyl diazoacetate and intramolecular cy-
clization of (Z)-3-methylpent-2-en-4-yn-1-ol into
2,3-dimethylfuran in good yields [11–14]. Recently,
we have developed improved procedures for Suzuki
reactions of aryl chlorides making use of novel
ligands 1-alkylimidazoline and 1-alkylbenzimida-
zole [15, 16]. The 1-alkybenzimidazole complexes
are insensitive to air and moisture and are thermally
stable in both the solid state and in solution.
1
characterized by C, H, N analyses, H NMR, and 13C NMR.
The reduction of ketones to alcohols via transfer hydrogena-
tion was achieved with catalytic amounts of the complexes in
the presence of t-BuOK.
Keywords. Ruthenium; Benzimidazole ligands; Transfer
hydrogenation; Homogeneous catalysis.
Introduction
The design of new ligands for promoting high reac-
tivity and selectivity in metal-catalyzed synthesis is
a field of constant ongoing research. Nitrogen-con-
taining heterocyclic ligands are receiving more and
more attention in the fields of coordination chemis-
try, homogeneous catalysis, and organic synthesis
because organometallic complexes containing nitro-
gen donor ligands usually exhibit high reactivities
[1]. The coordination chemistry of imidazole and
related compounds, including benzimidazoles, ben-
zoxazoles, and benzothiazoles, has been extensively
studied in part because of their role in aspects
of catalysis and biomimetics. Also transition metal
complexes with nitrogen-containing ligands have
recently shown their potential to perform selective
catalytic transformations of molecules with atom
ꢀ
Corresponding author. E-mail: iozdemir@inonu.edu.tr

_ ¨
I. Ozdemir et al.
206
The reduction of organic compounds is a subject
Results and Discussion
of remarkable interest from both academic and in-
dustrial perspectives. Several viable methodologies
have been established for this purpose, and most of
them make use of a metal, in either stoichiometric or
catalytic amounts, to promote the reaction between
the reducing agent and the substrate. Transfer hydro-
genation is a further one of these methodologies, and
transition-metal catalyzed transfer hydrogenation of
ketones is currently considered as a promising alter-
native to the widely used catalytic hydrogenation
[17]. The reaction conditions for this important pro-
cess are economic, relatively mild and environmen-
tally friendly. The most commonly used catalysts for
this reaction are ruthenium(II) complexes, but some
rhodium and iridium derivatives have also been used
[18]. Exploration of new ligands for construction of
ruthenium(II) catalysts has been one of the greatest
motivations for work in this area.
The reaction of 1-alkylbenzimidazole with the
binuclear [RuCl2(p-cymene)]2 complex proceeded
smoothly in refluxing toluene to give the [RuCl2(1-
alkylbenzimidazole)(p-cymene)] complexes 1–6 as
crystalline solids in 78–92% yields (Scheme 1).
The complexes 1–6 which are very stable in the
solid state, were characterized by analytical and
spectroscopic data. The spectroscopic properties in-
dicate that they all are N(3)-bonded.
The nature of the bonding in the benzimidazole
complexes 1–6 was readily shown by NMR spectro-
scopy. 13C NMR spectroscopy was the most useful
tool for structure elucidation.
Thus, from our previous experience [19–21] we
expected that C-coordination would result in a shift
of the carbene carbon nucleus signal toward low
field i.e., 190–212 ppm, while N-coordination would
result in a high field shift towards 155 ppm. 13C
NMR chemical shifts were consistent with the pro-
posed structure, the imino carbon appeared as a ty-
Based on these findings and our, continuing inter-
est in developing more efficient and stable catalysts,
we wished to examine whether we could influence
the catalytic activity of ruthenium-benzimidazole
complexes for the transfer hydrogenation of ketones.
1
pical singlet in the H-decoupled mode at 145.7,
145.8, 145.8, 145.7, 145.7, and 145.2 ppm for 1–6.
The 1H NMR spectra of the complexes further
Scheme 1. Synthesis of 1-alkylbenzimidazoleruthenium(II) complexes

Transfer Hydrogenation of Ketones
207
supported the assigned structures; the resonances
for C(2)–H were observed as sharp singlets at
8.43, 8.43, 8.50, 8.47, 8.45, and 8.30 ppm for 1–6.
The IR data for 1–6 clearly indicate the presence
of the –C¼N– group with a ꢀꢀ(C¼N) vibration at
1510, 1509, 1515, 1516, 1514, and 1511 cmꢁ1 for
1–6. The NMR and IR values are similar to those
found for N-coordinated metal complexes [3, 4,
11–14].
Catalytic reduction is preferred to stochiometric
reduction for large scale industrial processes of
ketones hydrogenation and they are well known
[22]. Hydrogen gas presents considerable safety
hazards especially for large scale reactions [23].
The use of a solvent that can donate hydrogen over-
comes these difficulties. 2-Propanol is a popular
reactive solvent for transfer hydrogenation reac-
tions since it is easy to handle (bp 82ꢂC) and is
relatively non-toxic, environmentally benign, and
inexpensive. The volatile acetone by-product can
also be easily removed to shift unfavourable
equilibria.
Transfer hydrogenations of ketones were carried
out in 2-propanol at 80ꢂC with in situ prepared com-
plexes 10–60, which were obtained from 1–6 by
exchanging a chloro ligand to a triflate group, as
the catalysts and tBuOK as the base. The results
were summarized in Table 1.
Complexes 3–6 showed high activity for most of
the ketones listed in Table 1 (entries: 3, 4, 8, 9, 11, 13,
15, and 21). The introduction of electron-withdrawing
substituents, such as Cl and Br to the para position of
the aryl ring of the ketone decreased the electron den-
sity on the C¼O bond so that the activity (entries 3, 15)
was improved giving rise to easier hydrogenation.
In conclusion, from readily available starting ma-
terials, such as 1-alkylbenzimidazole, six ruthenium-
benzimidazole complexes 1–6 were prepared and
characterized. In situ prepared [RuCl(1-alkylbenzimi-
dazole)(p-cymene)]OTf (10–60) complexes exhibited
very high catalytic efficiency in the transfer hydroge-
nation of ketones. The procedure is simple and efficient
towards various aryl ketones. Studies on the reactivity
of the new complexes, extension of the methodology
Table 1. Catalytic transfer hydrogenation of acetophenones with 1-benzimidazole ruthenium(II) complexes
Entry
Catalyst
Substrate
Product
Yield=%a,b
1
2
3
4
5
6
1
2
3
4
5
6
91
90
95
88
95
96
7
8
9
10
11
12
1
2
3
4
5
6
97
98
100
98
98
96
13
14
15
16
17
18
1
2
3
4
5
6
95
96
98
91
86
88
19
20
21
22
23
24
1
2
3
4
5
6
82
88
90
86
87
84
a
Catalyst (0.01 mmol), AgOTf (0.01 mmol in 2 cm3 CH2Cl2), substrate (1 mmol), iPrOH (10cm3), KOBut (5mmol%), 80ꢂC, 12 h
Purity of compounds is checked by NMR and GC, and yields are based on methyl aryl ketone
b

_ ¨
I. Ozdemir et al.
208
78% yield, mp 204.5–205ꢂC. IR: ꢀꢀ(CN) ¼ 1509 cmꢁ1
;
1H
to other transition metals and the synthesis of other
functionalised 1-alkylbenzimidazole and imidazoline
ligands with a variety of other donor functionalities
is under way. Future investigations are aiming at the
development of an asymmetric version of this process.
NMR (CDCl3): ꢁ ¼ 1.84 (d, J ¼ 7.0 Hz, 6H, (CH3)2CHC6H4
CH3-p), 2.09 and 2.77 (m, 8H, pyrrolidin), 2.56 (s, 3H, (CH3)2
CHC6H4CH3-p), 2.86 and 4.09 (t, J ¼ 6.0 Hz, 2H, NCH2
CH2N), 2.89 (hept, J ¼ 6.0 Hz, 1H, (CH3)2CHC6H4CH3-p),
5.37 and 5.53 (d, J ¼ 6.0 Hz, 4H, (CH3)2CHC6H4CH3-p),
7.31–8.04 (m, 4H, C6H4-o), 8.43 (s, 1H, 2-CH) ppm; 13C
NMR (CDCl3): ꢁ ¼ 18.9, 22.8, 31.1 ((CH3)2CHC6H4CH3-p),
15.5, 23.8 (pyrrolidin), 23.9, 54.3 (NCH2CH2N), 81.6, 83.3,
98.0, 103.1 ((CH3)2CHC6H4CH3-p), 111.4, 120.9, 123.8,
124.5, 132.7, 133.9 (C6H4-o), 145.8 (2-CH) ppm.
Experimental
Methylene chloride was purchased from Merck and distilled
from P2O5 prior to use. Toluene and n-hexane were purchased
from Aldrich or Merck and distilled from Na=benzophenone.
2-Propanol was purchased from Aldrich or Acros Chemicals.
AgOTf was purchased from Aldrich. All manipulations were
carried out using standard Schlenk techniques under an inert
atmosphere of N2 or Ar. The complex [RuCl2(p-cymene)]2 [24]
and 1-alkylbenzimidazoles were prepared according to known
methods [16]. FT-IR spectra were recorded as KBr pellets in
which 10 mg samples were mixed with KBr and pelleted
under 5 ton cmꢁ2 pressure in the range of 400–4000 cmꢁ1 on
Preparation of RuCl2(p-cymene)1-(piperidinoethyl)
benzimidazole (3)
Compound 3 was prepared in the same way as 1 from 0.245g
1-piperidinoethylbenzimidazole (1.0mmol) and 0.31 g
[RuCl2(p-cymene)]2 (0.5mmol) to give 0.46 g orange crystals
of 3, 86% yield, mp 211–211.5ꢂC. IR: ꢀꢀ(CN) ¼ 1515cmꢁ1; 1H
NMR (CDCl3): ꢁ ¼ 1.42, 1.47 and 2.36 (m, 10H, piperidin),
1.46 (d, J ¼ 6.8 Hz, 6H, (CH3)2CHC6H4CH3-p), 2.11 (s, 3H,
(CH3)2CHC6H4CH3-p), 2.52 and 4.19 (m, 4H, NCH2CH2N),
2.89 (hept, J ¼ 6.8 Hz, 1H, (CH3)2CHC6H4CH3-p), 5.41 and
5.56 (d, J ¼ 5.8 Hz, 4H, (CH3)2CHC6H4CH3-p), 7.01–8.03
(m, 4H, C6H4-o), 8.50 (s, 1H, 2-CH) ppm; 13C NMR (CDCl3):
ꢁ ¼ 18.9, 22.8, 31.1 ((CH3)2 CHC6H4CH3-p), 18.8, 22.7, 35.1
(piperidin), 53.8, 57.4 (NCH2CH2N), 81.6, 83.4, 97.9, 103.1
((CH3)2CHC6H4CH3-p), 110.9, 120.8, 120.9, 123.8, 124.3,
132.5 (C6H4-o), 145.8 (2-CH) ppm.
1
a ATI UNICAM 2000 model spectrometer. All H and 13C
NMR were recorded in CDCl3 on a Bruker AM 400 WB FT
1
spectrometer. H NMR spectra were collected at 400.0 MHz
using a 6000 Hz spectral width, a relaxation delay of 3s, 30k
data points, a pulse width of 35ꢂ, and 13C NMR spectra were
collected at 100.0 MHz and chemical shifts were referenced to
residual solvent CDCl3. All NMR samples were prepared under
an Ar atmosphere prior to the analyses. Microanalyses were
¨
performed by the TUBITAK Analyses Center; results agreed
with calculated values. Gas chromatographic analyses were
performed on an Agilent 6890N instrument equipped with a
30m capillary column of 5% phenylmethylsilicone.
Preparation of RuCl2(p-cymene)1-(morpholinoethyl)
benzimidazole (4)
Compound 4 was prepared in the same way as 1 from 0.231g
1-morpholinoethylbenzimidazole (1.0mmol) and 0.31 g
[RuCl2(p-cymene)]2 (0.5mmol) to give 0.43 g orange crystals
of 4, 80% yield, mp 232–232.5ꢂC. IR: ꢀꢀ(CN) ¼ 1516cmꢁ1; 1H
NMR (CDCl3): ꢁ ¼ 1.28 (d, J ¼ 7.0 Hz, 6H, (CH3)2
CH C6H4CH3-p), 2.11 (s, 3H, (CH3)2CHC6H4CH3-p), 2.44 and
3.66 (m, 8H, CH2CH2-morpholin), 2.63 and 3.99 (m, 4H,
CH2CH2-morpholin), 2.89 (hept, J ¼ 7.0 Hz, 1H, (CH3)2
CHC6H4CH3-p), 5.40 and 5.56 (d, J ¼ 5.6 Hz, 4H, (CH3)2
CHC6H4CH3-p), 7.28–7.99 (m, 4H, C6H4-o), 8.47 (s, 1H,
2-CH) ppm; 13C NMR (CDCl3): ꢁ ¼ 18.9, 22.7, 31.1
((CH3)2CH C6H4CH3-p), 42.9, 53.9, 57.4, 67.1 (CH2CH2
N(CH2CH2)2O), 81.7, 83.3, 97.9, 103.1 ((CH3)2CHC6
H4CH3-p), 111.3, 120.8, 123.5, 124.4, 132.6, 142.5 (C6H4-o),
145.7 (2-CH) ppm.
Preparation of RuCl2(p-cymene)(1-(2-diisopropylaminoethyl)
benzimidazole) (1)
A solution of 0.276 g 1-(2-diisopropylaminoethyl)benzimid-
azole (1.0 mmol) and 0.31g [RuCl2(p-cymene)]2 ( 0.5 mmol)
in 10 cm3 toluene was heated under reflux for 4 h. Upon cool-
ing to room temperature, orange crystals of 1 were obtained.
The crystals were filtered off, washed with diethyl ether (3ꢃ
10cm3), and dried under vacuum. The yield was 0.51 g, 92%,
1
mp 215.5–216ꢂC. IR: ꢀꢀ(CN) ¼ 1510 cmꢁ1; H NMR (CDCl3):
ꢁ ¼ 0.92 (d, J ¼ 12.8 Hz, 12H, NCH2CH2N(CH(CH3)2)2), 1.31
(d, J ¼ 13.6Hz, 6H, (CH3)2CHC6H4CH3-p), 2.16 (s, 3H,
(CH3)2CHC6H4CH3-p), 2.98 (hept, J ¼ 12.7Hz, 2H, NCH2
CH2N(CH(CH3)2)2), 2.98 (hept, J ¼ 12.7 Hz, 1H, (CH3)2
CHC6H4CH3-p), 2.81 and 4.04 (t, J ¼ 20.4Hz, 4H, NCH2
CH2N(CH(CH3)2)2), 5.38 and 5.54 (d, J ¼ 12Hz, 4H, (CH3)2
CHC6H4CH3-p), 7.36–8.20 (m, 4H, C6H4-o), 8.43 (s, 1H, 2-
CH) ppm; 13C NMR (CDCl3): ꢁ ¼ 19.0, 22.8, 31.1 ((CH3)2
CHC6H4CH3-p), 21.3, 44.9, 47.3, 49 (NCH2CH2N-(CH
(CH3)2)2), 81.6, 83.2, 97.8, 103.2 ((CH3)2CHC6H4CH3-p),
111, 121.1, 123.7, 124.3, 142.8 (C6H4-o), 145.7 (2-CH) ppm.
Preparation of RuCl2(p-cymene)(1-(3,4,5-trimethoxybenzyl)
benzimidazole) (5)
Compound 5 was prepared in the same way as 1 from 0.247g
1-(3,4,5-trimethoxybenzyl)benzimidazole (1.0mmol) and
0.31g [RuCl2(p-cymene)]2 (0.5mmol) to give 0.56 g orange
crystals of 5, 92% yield, mp 228.5–229ꢂC. IR: ꢀꢀ(CN)
¼
Preparation of RuCl2(p-cymene)1-(pyrrolidinoethyl)
benzimidazole (2)
1
1514cmꢁ1; H NMR (CDCl3): ꢁ ¼ 1.21 (d, J ¼ 6.8 Hz, 6H,
(CH3)2CH C6H4CH3-p), 2.07 (s, 3H, (CH3)2CHC6H4CH3-p),
2.52 and 4.19 (m, 4H, NCH2CH2N), 2.71 (hept, J ¼ 6.8 Hz,
1H, (CH3)2CHC6H4CH3-p), 3.77 and 3.79 (s, 9H, 3,4,5-
Compound 2 was prepared in the same way as 1 from 0.229 g
1-pyrrolidinoethylbenzimidazole (1.0mmol) and 0.31 g [RuCl2
(p-cymene)]2 (0.5mmol) to give 0.41 g orange crystals of 2,

Transfer Hydrogenation of Ketones
209
(H3CO)3 C6H2CH2), 4.99 (s, 2H, 3,4,5-(H3CO)3C6H2CH2),
5.37 and 5.53 (d, J ¼ 5.8 Hz, 4H, (CH3)2 CHC6H4CH3-p),
6.42 (s, 2H, 3,4,5-(H3CO)3C6H2CH2), 7.28–8.04 (m, 4H,
C6H4-o), 8.45 (s, 1H, 2-CH) ppm; 13C NMR (CDCl3):
ꢁ ¼ 18.9, 22.7, 31.1 ((CH3)2CHC6H4CH3-p), 50.1, 56.8, 61.3
(3,4,5-(H3CO)3 C6H2CH2), 81.4, 83.6, 98.2, 102.7
((CH3)2CHC6H4CH3-p), 105.3, 130.7, 138.5, 145.3 (3,4,5-
(H3CO)3C6H2CH2), 111.9, 120.8, 123.9, 124.8, 134.1, 142.9
(C6H4-o), 154.1 (2-CH) ppm.
13: 891; (c) Fache F, Schulz E, Tommasino ML, Lemaire
M (2000) Chem Rev 100: 2159
¨
_
[3] C°etinkaya B, Alıcı B, Ozdemir I, Bruneau C, Dixneuf
PH (1999) J Organomet Chem 575: 187
¨
_
[4] Ozdemir I, C°etinkaya E, C°etinkaya B, C°ic°ek M,
´
Semeril D, Bruneau C, Dixneuf PH (2004) Eur J Inorg
Chem 418
[5] Carmona D, Lamata MP, Viguri F, Dobrinovich I, Lahoz
FJ, Oro LA (2002) Adv Synth Catal 344: 499
[6] (a) Everaere K, Mortreux A, Carpentier JF (2003)
Adv Synth Catal 345: 67; (b) Alonso DA, Brandt P,
Nordin SJM, Andersson PG (1999) J Am Chem Soc
121: 9580
[7] Simal F, Demonceau A, Noels AF (1998) Tetrahedron
Lett 39: 3493
[8] Faller JW, Lavoie A (2001) J Organomet Chem 630: 17
Preparation of RuCl2(p-cymene) (1-naphthalenomethyl)
benzimidazole (6)
Compound 6 was prepared in the same way as 1 from 0.298 g
1-naphthalenomethylbenzimidazole (1.0mmol) and 0.31g
[RuCl2(p-cymene)]2 (0.5mmol) to give 0.50g orange crys-
tals of 6, 89% yield, mp 248.5–249ꢂC. IR: ꢀꢀ(CN) ¼ 1511 cmꢁ1
;
1H NMR (CDCl3): ꢁ ¼ 0.97 (d, J ¼ 6.4 Hz, 6H, (CH3)2CH
C6H4CH3-p), 2.03 (s, 3H, (CH3)2CHC6H4CH3-p), 2.49 (hept,
J ¼ 6.4 Hz, 1H, (CH3)2CHC6H4CH3-p), 5.28 and 5.37 (d, J ¼
6.4 Hz, 4H, (CH3)2CHC6H4CH3-p), 5.66 (s, 2H, C10H7CH2),
7.31–8.10 (m, 11H, C6H4-o and C10H7CH2), 8.30 (s, 1H, 2-CH)
ppm; 13C NMR (CDCl3): ꢁ ¼ 18.6, 22.5, 30.7 ((CH3)2 CHC6
H4CH3-p), 47.8 (C10H7CH2), 81.1, 83.2, 98.4, 102.2 ((CH3)2
CHC6H4CH3-p), 111.2, 121.1, 123.9, 124.6, 134.1, 142.8
(C6H4-o), 122.4, 125.8, 126.5, 127.3, 127.4, 129.5, 129.6,
130.0, 130.9, 134.2 (C10H7CH2), 145.2 (2-CH) ppm.
^
[9] Ben Ammar H, Le Notre J, Salem M, Kaddachi MT,
Dixneuf PH (2002) J Organomet Chem 662: 63
[10] (a) Picquet M, Touchard D, Bruneau C, Dixneuf PH
´
(1999) New J Chem 141; (b) Castarlenas R, Semeril D,
Noels AF, Demonceau A, Dixneuf PH (2002) J Orga-
nomet Chem 663: 235
[11] C°
etinkaya B, Cetinkaya E, Hitchcock PB, Lappert MF,
Ozdemir I (1997) J Chem Soc Dalton Trans 1359
°
¨
_
¨
_
¨
°etinkaya B, Ozdemir I, Tahir MN, Ulku¨ D (1998)
[12] C
J Organomet Chem 561: 7
¨
_
[13] Sec
44: 47
[14] Cetinkaya B, Ozdemir I, Bruneau C, Dixneuf PH (2000)
Eur J Inorg Chem 29
°kin T, C°etinkaya B, Ozdemir I (2000) Polymer Bull
Typical Procedure for the Transfer Hydrogenation of Ketones
The complexes [RuCl2(1-alkylbenzimidazole)(p-cymene)]
1–6 (0.01 mmol) and AgOTf (0.01 mmol, 2.57 mg) were intro-
duced into a Schlenk tube under Ar. Dry and degassed CH2Cl2
(3cm3) was added, the suspension were stirred at room tem-
perature for 30 min, and the solvent was removed by vacuum
to give [RuCl(1-alkylbenzimidazole)(p-cymene)]OTf (10–60).
After that 10cm3 2-propanol, t-BuOK (5mmol%), and
1 mmol of the substrate were added to 10–60. The resulting
solution was heated at 80ꢂC for 12h. The solvent was then
removed under reduced pressure and product distribution was
¨
_
°
¨
_
¨
[15] Ozdemir I, S¸ahin N, Gu¨rbu¨z N, Demir S, Gok Y,
etinkaya B, Cetinkaya E (2005) Syn React Inorg
Metal-Organic Nano-Metal Chem 35: 541
C°
°
¨
_
¨
[16] Ozdemir I, S¸ahin N, Gok Y, Demir S, C
°etinkaya B
(2005) J Mol Catal A Chem 234: 181
[17] (a) Zassinovich G, Mestroni G, Gladiali S (1992) Chem
Rev 1051; (b) Noyori R, Hashiguchi S (1997) Acc Chem
Res 30: 97; (c) Haixia D, Zhengkun Y, Jinhua D,
Sizhong W (2005) Organometallics 24: 4110
[18] (a) Evans DA, Nelson SG, Gangne MR, Muci AR
(1993) J Am Chem Soc 115: 9800; (b) Nishibayasni
Y, Takei I, Uemnura S, Hidai M (1999) Organometal-
lics 18: 2291
1
determined by H NMR spectroscopy and GC.
Acknowledgements
¨ ¨
Inonu University Research Fund (BAP 2004=23, BAP 2005=
42) and the Technological and Scientific Research Council
¨
_
[19] C
Bruneau C, Dixneuf PH (2001) New J Chem 25: 519
°etinkaya B, Demir S, Ozdemir I, Toupet L, Semeril D,
¨
_
of Turkey TUBITAK TBAG-2474 (104T085) are gratefully
acknowledged for support of this work.
¨
_
[20] C
Organomet Chem 534: 153
[21] Cetinkaya B, Gu¨rbu¨z N, Sec
J Mol Catal A 184: 31
°etinkaya B, Ozdemir I, Dixneuf PH (1997) J
¨
_
°kin T, Ozdemir I (2002)
°
References
[22] Genet JP (2003) Acc Chem Res 36: 908
[23] Johnstone RAW, Wilby AH, Entwistle ID (1985)
Chem Rev 85: 129
[1] Togni A, Venanzi LM (1994) Angew Chem Int Ed Engl
33: 497
[2] (a) Abuhijleh AL (1996) Polyhedron 15: 285; (b)
Noyama K, Mori W, Nonoyama M (1994) Polyhedron
[24] Bennett MA, Huang TN, Matheson ATW, Smith K
(1982) Inorg Synth 21: 74