Transfer hydrogenation of ketones catalyzed by new rhodium and iridium complexes of aminophosphine containing cyclohexyl moiety and photosensing behaviors of rhodium and iridium based devices

Article abstract of DOI:10.1016/j.jorganchem.2014.01.025

The reaction of [Rh(μ-Cl)(cod)]₂ and Ir(η⁵- C₅Me₅)(μ-Cl)Cl]₂ with aminophosphine ligands Cy₂PNHCH₂-C₄H₃X (X: O; S) gave a range of new monodendate [Rh(Cy₂PNHCH₂-C₄H ₃O)(cod)Cl], (1), [Rh(Cy₂PNHCH₂-C ₄H₃S)(cod)Cl], (2), [Ir(Cy₂PNHCH ₂-C₄H₃O)(η⁵-C₅Me ₅)Cl₂], (3) and [Ir(Cy₂PNHCH₂-C ₄H₃S)(η⁵-C₅Me ₅)Cl₂], (4) complexes, which were characterized by analytical and spectroscopic methods. The new rhodium(I) and iridium(III) catalysts were applied to transfer hydrogenation of acetophenone derivatives using 2-propanol as a hydrogen source. The results showed that the corresponding alcohols could be obtained with high activity (up to 99%) under mild conditions. Notably, [Rh(Cy₂PNHCH₂-C₄H ₃O)(cod)Cl] complex (1) is much more active than the other analogous complexes in the transfer hydrogenation. Moreover, organic-inorganic rectifying contacts were fabricated forming rhodium(I) and iridium(III) complex thin films on n-Si semiconductors and evaporating Au metal on the structures. Electrical properties of the contacts including ideality factor, barrier height and series resistance were determined using their current-voltage (I-V) data. The photoelectrical characteristics of the devices were examined under the light with 40-100 mW/cm² illumination conditions. It was seen that light had strong effects on I-V characteristics of the devices and the ones fabricated using 3 and 4 complexes had unusually forward and reverse bias photoconducting behavior.

Full text of DOI:10.1016/j.jorganchem.2014.01.025

Accepted Manuscript
Transfer hydrogenation of ketones catalyzed by New Rhodium and Iridium
Complexes of Aminophosphine Containing Cyclohexyl Moiety and Photosensing
Behaviors of Rhodium and Iridium Based Devices
Khadichakhan Rafikova, Nurzhamal Kystaubayeva, Murat Aydemir, Cezmi Kayan,
Yusuf Selim Ocak, Hamdi Temel, Alexey Zazybin, Nevin Gürbüz, İsmail Özdemir
PII:
S0022-328X(14)00040-0
10.1016/j.jorganchem.2014.01.025
JOM 18466
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 6 December 2013
Revised Date: 14 January 2014
Accepted Date: 20 January 2014
Please cite this article as: K. Rafikova, N. Kystaubayeva, M. Aydemir, C. Kayan, Y.S. Ocak, H. Temel,
A. Zazybin, N. Gürbüz, İ. Özdemir, Transfer hydrogenation of ketones catalyzed by New Rhodium and
Iridium Complexes of Aminophosphine Containing Cyclohexyl Moiety and Photosensing Behaviors
of Rhodium and Iridium Based Devices, Journal of Organometallic Chemistry (2014), doi: 10.1016/
j.jorganchem.2014.01.025.
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ACCEPTED MANUSCRIPT
RESEARCH HIGHLIGHTS
ꢀ For the first time complexes of aminophosphine carrying cyclohexyl moiety were
synthesized and characterized.
ꢀ [Rh(Cy2PNHCH2-C4H3O)(cod)Cl] was a more efficient catalyst in the transfer
hydrogenation.
ꢀ Fabrication of organic-inorganic heterojunction devices, their electrical properties
including ideality factor, barrier height and series resistance values and photoelectrical
properties are presented.
ꢀ The devices obtained using Ir(III)-aminophosphine complexes have reverse and current
bias photoconduction behavior which have not reported up to now for organic based
devices.

ACCEPTED MANUSCRIPT
Transfer hydrogenation of ketones catalyzed by New Rhodium and Iridium
Complexes of Aminophosphine Containing Cyclohexyl Moiety and Photosensing Behaviors
of Rhodium and Iridium Based Devices
Khadichakhan Rafikovaa, Nurzhamal Kystaubayevaa, Murat Aydemirb , Cezmi Kayanb, Yusuf
Selim Ocakc, Hamdi Temeld, Alexey Zazybina, Nevin Gürbüze, Đsmail Özdemire
a Department of Chemical Engineering, Kazakh-British Technical University, 050000 Almaty, Kazakhstan
b Department of Chemistry, Faculty of Science, University of Dicle, 21280 Diyarbakir, Turkey
c Department of Science, Faculty of Education, University of Dicle, 21280 Diyarbakir, Turkey
d Department of Chemistry, Faculty of Education, University of Dicle, 21280 Diyarbakir, Turkey
e Department of Chemistry, Faculty of Science and Art, University of Đnönü, 44280 Malatya, Turkey
Novel Rh(I) and Ir(III) complexes containing aminophosphine ligands including cyclohexyl
moiety have been synthesized. The use of the new complexes for the reduction of the ketonic
C=O bond under hydrogen transfer conditions was investigated. Surprisingly,
[Rh(Cy2PNHCH2-C4H3O)(cod)Cl] was a more efficient catalyst in the transfer hydrogenation
than the other complexes. In addition, the electrical properties of the devices were analyzed in
dark and under a solar simulator with various illumination conditions. The results showed
excellent reverse and forward bias photosensing behaviors for [Ir(Cy2PNHCH2-C4H3O)(η5-
C5Me5)Cl2] and [Ir(Cy2PNHCH2-C4H3S)(η5-C5Me5)Cl2] complexes.
.

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1
Transfer hydrogenation of ketones catalyzed by New Rhodium and Iridium
2 Complexes of Aminophosphine Containing Cyclohexyl Moiety and Photosensing Behaviors
3
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of Rhodium and Iridium Based Devices
Khadichakhan Rafikovaa, Nurzhamal Kystaubayevaa, Murat Aydemirb,*, Cezmi Kayanb,
Yusuf Selim Ocakc, Hamdi Temeld, Alexey Zazybina, Nevin Gürbüze, Đsmail Özdemire
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a Department of Chemical Engineering, Kazakh-British Technical University, 050000 Almaty, Kazakhstan
b Department of Chemistry, Faculty of Science, University of Dicle, 21280 Diyarbakir, Turkey
c Department of Science, Faculty of Education, University of Dicle, 21280 Diyarbakir, Turkey
d Department of Chemistry, Faculty of Education, University of Dicle, 21280 Diyarbakir, Turkey
e Department of Chemistry, Faculty of Science and Art, University of Đnönü, 44280 Malatya, Turkey
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ABSTRACT
The reaction of [Rh(ꢀ-Cl)(cod)]2 and Ir(η5-C5Me5)(ꢀ-Cl)Cl]2 with aminophosphine ligands
Cy2PNHCH2-C4H3X (X: O; S) gave a range of new monodendate [Rh(Cy2PNHCH2-
C4H3O)(cod)Cl], (1), [Rh(Cy2PNHCH2-C4H3S)(cod)Cl], (2), [Ir(Cy2PNHCH2-C4H3O)(η5-
C5Me5)Cl2], (3) and [Ir(Cy2PNHCH2-C4H3S)(η5-C5Me5)Cl2], (4) complexes, which were
characterized by analytical and spectroscopic methods. The new rhodium(I) and iridium(III)
catalysts were applied to transfer hydrogenation of acetophenone derivatives using 2-propanol
as a hydrogen source. The results showed that the corresponding alcohols could be obtained
with high activity (up to 99 %) under mild conditions. Notably, [Rh(Cy2PNHCH2-
C4H3O)(cod)Cl] complex (1) is much more active than the other analogous complexes in the
transfer hydrogenation. Moreover, organic-inorganic rectifying contacts were fabricated
forming rhodium(I) and iridium(III) complex thin films on n-Si semiconductors and
*
To whom correspondence should be addressed: Department of Chemistry, Dicle University, TR-21280
Diyarbakır, Turkey. Tel: +90 412 248 8550, Fax: +90 412 248 8300, e-mail: aydemir@dicle.edu.tr
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evaporating Au metal on the structures. Electrical properties of the contacts including ideality
factor, barrier height and series resistance were determined using their current-voltage (I-V)
data. The photoelectrical characteristics of the devices were examined under the light with 40-
100 mW/cm2 illumination conditions. It was seen that light had strong effects on I-V
characteristics of the devices and the ones fabricated using 3 and 4 complexes had unusually
forward and reverse bias photoconducting behavior.
Keywords: Aminophosphine; Iridium; Transfer Hydrogenation; Rectifying contact; Electrical
properties; Photoconductor
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1. Introduction
Transition metal complexes are powerful catalysts for organic transformations and when
suitable ligands are bound to a metal center, they can offer chemio, regio or stereo selectivity
under mild conditions [1]. However, the appropriate choice of metal precursors and the
reaction conditions are crucial for catalytic properties [2]. A number of transition metal
complexes are known to catalyze hydrogen transfer from an alcohol to a ketone [3,4,5]. Over
the last three decades, most effort on hydrogenation has been focused on the use of
ruthenium, rhodium and iridium catalysts [6,7,8,9,10]. Rhodium and iridium complexes have
been proven to lead to very efficient processes along with potential industrial applications
[11,12,13,14].
To date, a number of such systems with a variety of backbone frameworks have been
synthesized and their transition metal chemistry has been explored [15,16,17]. Phosphorus-
nitrogen containing ligands have particular use in catalysis where it is necessary for part of
ligand to dissociate to allow an organic fragment to coordinate and undergo transformations
[18,19]. The presence of P-N ligands enables many different and important catalytic processes
to occur [20,21,22]. Especially, aminophosphines are able to stabilize many different metals
in various oxidation states, controlling the performance of metals in a large variety of useful
transformations. Synthesis of new aminophosphines to stabilize transition metals in low
valent states is considered to be a most challenging task in view of their potential utility in a
variety of metal-mediated organic transformations [23].
Hydrogen transfer reactions are mild methodologies for reduction of ketones or imines and
oxidation of alcohols or amines in which a substrate-selective catalyst transfers hydrogen
between the substrate and a hydrogen donor or acceptor, respectively [24,25,26]. From an
industrial point of view, catalytic transfer hydrogenation is an attractive alternative for high
pressure catalytic hydrogenations with molecular hydrogen [27]. Here, hydrogen donors such
as secondary alcohols (e.g., 2-propanol) are applied to convert carbonyl compounds to
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alcohols. The risk associated with the use of molecular hydrogen at high pressures is thereby
eliminated [28,29]. Furthermore, there are several other advantages for use of 2-propanol such
as, it is inexpensive, readily available and has an appropriate boiling point. It is also a good
solvent for many organic compounds. Upon dehydrogenation, 2-propanol is converted to
acetone, which can be easily removed from the reaction mixture, and thus simplifies the
reaction process [30,31].
Organic materials have obtained an important place in the fields of electrical and optical
device industry. They have been preferred in device applications because of their key
advantages including large area coating, using on flexible substrates and low cost [32,33].
Among the other organic compounds, there is a growing interest on metal complexes because
of their mechanical and chemical stabilities [34]. While some studies have concentrated on
finding suitable metal complexes for device technology [35,36], others have focused on the
usage of these compounds in the fabrication of devices including solar cells, Schottky diodes
and light emitting diodes [37,38,39,40]. Studies on metal-semiconductor (MS) devices with
organic semiconductor have shown that these structures presented photovoltaic and
photoconductivity influences when they are exposed to light because of electron and hole
production at the interface [41].
To the best our knowledge, there is no report on the use of these complexes including
aminophosphines having cyclohexyl moiety on phosphorus atom in rhodium and iridium
catalyzed transfer hydrogenation reaction. As part of our research program, we report here
the synthesis and full characterization of four new aminophosphine complexes
[Rh(Cy2PNHCH2-C4H3O)(cod)Cl]
(1),
[Rh(Cy2PNHCH2-C4H3S)(cod)Cl],
(2),
[Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2], (3) and [Ir(Cy2PNHCH2-C4H3S)(η5-C5Me5)Cl2],
(4). We also report their catalytic activity in transfer hydrogenation reactions of ketones with
iso-PrOH. Furthermore, up to know, studies have reported to reverse bias photosensing
properties of organic based devices [39,42,43]. In this study, fabrication of organic-inorganic
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heterojunction devices, their electrical properties including ideality factor, barrier height and
series resistance values and photoelectrical properties are presented. It is also reported that the
devices obtained using 3 and 4 complexes have reverse and current bias photoconduction
behavior which have not reported up to now for organic based devices.
3. Results and discussion
3.1. Synthesis and characterization of the metal complexes
Synthesis
and
characterization
of
the
ligands,
furfuryl-2-(N-
dicyclohexylphosphino)methylamine and thiophene-2-(N-dicyclohexylphosphino)methyla-
mine, were mentioned elsewhere [44]. We examined various coordination chemistry of these
aminophosphines with [Rh(ꢀ-Cl)(cod)]2 precursor. Reaction of furfuryl-2-(N-
dicyclohexylphosphino)methylamine
or
thiophene-2-(N-dicyclohexylphosphino)
methylamine with [Rh(ꢀ-Cl)(cod)]2 in a molar ratio of 2/1 at room temperature for 45 min
afforded [Rh(Cy2PNHCH2-C4H3O)(cod)Cl], (1) and [Rh(Cy2PNHCH2-C4H3S)(cod)Cl] (2),
respectively as crystalline yellow powders (Scheme 1). The complexes of 1 and 2 were
1
isolated as indicated by doublets in the 31P-{1H} NMR spectra at δ 71.98 (d, JRhP: 156.5 Hz)
and 74.39 (d, 1JRhP: 154.1 Hz) ppm, respectively, (Figure 1). In their 1H NMR spectra, 1 and 2
are characterized by CH resonances of cod at δ ~5.35 and 3.55 ppm, whereas in the 13C-{1H}
NMR spectra, resonances at δ ~70 and 104 ppm correspond to CH resonances of cod (for
1
details see Experimental Section). Furthermore, other H and 13C-{1H} NMR data are in
agreement with the proposed structures. The complexes were also characterized by IR and
microanalysis.
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We studied coordination chemistry of aminophosphines including cyclohexyl moiety with
[Ir(η5-C5Me5)(ꢀ-Cl)Cl]2 precursor as well. [Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2], 3 and
[Ir(Cy2PNHCH2-C4H3S)(η5-C5Me5)Cl2], 4 were obtained by the reaction of ligands with
[Ir(η5-C5Me5)(ꢀ-Cl)Cl]2 in a molar ratio of 2/1 at room temperature for 1 h (Scheme 1). In the
31P-{1H} NMR spectra, resonances at δ ~ 43 ppm may be attributed to complexes of 3 and 4
(Figure 1). 13C NMR spectra of the complexes display singlets at δ ~ 10 ppm attributable to
1
methyl carbons of Cp* and doublets at δ ~92 due to carbons of Cp* ring. The H NMR
spectra are consistent with the anticipated structures. The structural compositions of the
complexes 3 and 4 were further confirmed by IR spectroscopy and microanalysis, and found
to be in good agreement with the theoretical values (for details see experimental section).
3.2. Catalytic transfer hydrogenation of ketones
The brilliant catalytic performance of aminophosphine-based transition metal complexes [45,
and references therein] prompted us to develop new Rh(I) and Ir(III) complexes with well-
shaped ligands, since NH unit forms a hydrogen bond with the carbonyl oxygen atom to
stabilize the transition state. Therefore, the presence of an NH moiety in the ligands is
crucially important to determine the catalytic performance of the bifunctional catalysts
[46,47,48]. An important and unprecedented aspect is that the carbonyl compound does not
interact directly with the metal center for its own activation [49]. To this end, we observed the
catalytic activation of complexes 1-4 in the transfer hydrogenation of ketones to the
corresponding alcohols. In a typical experiment, 0.005 mmol of the complex and 0.5 mmol of
ketone were added to a solution of NaOH in iso-PrOH (0.025 mmol of NaOH in 5 mL iso-
PrOH) and refluxed at 82 ºC, the reaction being monitored by GC. In all reactions, these
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complexes catalyzed the reduction of ketones to the corresponding alcohols via hydrogen
transfer from iso-PrOH.
These complexes as catalyst precursors for the transfer hydrogenation of acetophenone have
been tested and typical results are summarized in Table 1. As seen, high conversions can be
achieved with the 1-4 catalytic systems. Conversions of transfer hydrogenation of
acetophenone were negligible either at room temperature with a base and at reflux
temperature in the absence of base in all the reactions (see Table 1). Thus, one can conclude
that high temperature as well as presence of base is necessary to obtain considerable
conversions. Results obtained from the optimization studies indicated clearly that the
excellent conversions were achieved in the reduction of acetophenone to 1-phenylethanol
when 1-4 were used as the catalytic precursor, with a substrate-catalyst molar ratio (100:1) in
iso-PrOH at 82 °C (Table 1, entries 1, 8, 15 and 22). Furthermore, it should be pointed out
that complex [Rh(Cy2PNHCH2-C4H3O)(cod)Cl], (1), is more active than [Rh(Cy2PNHCH2-
C4H3S)(cod)Cl], (2), [Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2], (3) and [Ir(Cy2PNHCH2-C4H3S)(η5-
C5Me5)Cl2], (4) complexes, because, conversion of acetophenone occurred in 15 min and 8 h
by 1 and 2-4, respectively. In addition, the yields gradually decreased on by increasing the
mole ratios of [acetophenone]/[Ru] from 100/1 to 500/1 or 1000/1. Furthermore, performing
the reaction in the presence of small amount of water did not change reaction time, while that
in air slowed down the reaction (Table 1, entries 4, 5, 11, 12, 18, 19, 25 and 26).
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The complexes [Rh(Cy2PNHCH2-C4H3O)(cod)Cl], (1), [Rh(Cy2PNHCH2-C4H3S)(cod)Cl],
(2), [Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2], (3) and [Ir(Cy2PNHCH2-C4H3S)(η5-C5Me5)Cl2],
(4) were also extensively investigated with a variety of substrates. As expected, electronic
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properties (the nature and position) of the substituents on the phenyl ring of the ketone caused
significant changes in the reduction rate. To ensure that the observed results could be
attributed to purely electronic effects [50], substrates involving para- and orto- substituted
acetophenone derivatives were investigated. The results indicated that strong electron
withdrawing substituents, such as F, Cl and Br were capable of higher conversion (Table 2).
Conversely, the most electron-donor substituents, (2-methoxy or 4-methoxy) led to lower
conversion. It is well-known that the presence of an electron withdrawing group has generally
been found to facilitate the hydrogen transfer reaction [51,52] which has been attributed to the
hydridic nature of the reducing species involved. As such, reactions with fluoro proceeded to
higher conversion owing to rapid hydride transfer, while reactions with electron-donating
substituents methoxy proceeded in a slower and more controlled manner [53,54].
Encouraged by the high catalytic activities gained in these preliminary studies, we next
extended our investigations to include hydrogenation of various simple ketones. A variety of
simple ketones (S/C=100/1) can be transformed to the corresponding secondary alcohols with
high conversion, as exemplified in Table 3. The cyclic substrates are convertible to the
corresponding alcohols with a moderate conversion. Furthermore, under identical conditions,
transfer hydrogenation of methyl isobutyl ketone led to 99 % conversion within 1.5 h, while
that of diethyl ketone occurred in 3 h with the same conversion by [Rh(Cy2PNHCH2-
C4H3O)(cod)Cl], 1.
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We also carried out further experiments to examine the effect of bulkiness of the alkyl groups
on the catalytic activity and the results were given in Table 4 (Entries 1–16). As the steric
hindrance of the alkyl group growths from ethyl to isopropyl, the extent of the time is
increasing. Reaction of tert-butyl phenyl ketone possessing a bulky alkyl substituent
proceeded rather slowly and in somewhat increasing time. Hence, it was found that the
activity is highly dependent on the steric bulk of the alkyl group [55] and the reactivity
gradually decreased by increasing the bulkiness of them [56].
3.3. Electrical and photoelectrical properties of Au/metal complex/n-Si devices
I-V measurements of a structure give important information about electrical characteristics of
the device. Main electrical parameters of a diode such as ideality factor, barrier height and
series resistance can be determined using its I-V data in dark. In addition, photoelectrical
parameters of a structure including open circuit voltage (VOC) closed circuit current (ISC) can
be extracted using its I-V data under light. Figure 2 presents I-V measurements of Au/metal
complex/n-Si structures in dark and under a solar simulator with various illumination
conditions. As seen from the figures, all structures have excellent rectification behavior.
When a rectifying diode is taken into account, I-V can be analyzed using thermionic emission
theory.
According to the theory, the ideality factor and the barrier height values of a device can be
extracted from the slope and the current axis intercept of the linear regions of the forward bias
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I-V plots, respectively. The calculated ideality factor and the barrier height values are given in
Table 5. As seen from the table, the ideality factors of the junctions are greater than unity.
According to the theory, ideality factor should be very close to unity (1.03) when image force
lowering is considered. The deviation from ideal diode can be attributed the effects of series
resistance of the structure, existence of interface states at organic-inorganic interface,
recombination-generation at the interface and tunneling [57,58]. The barrier height values of
the structures are very close to each other and vary between 0.76 and 0.80 ev. Up to now,
many kinds of molecules including small organic compounds, metal complexes, polymers and
biological compounds have been used in the fabrication of organic-inorganic devices. For
instance, several researchers [40] have synthesized and characterized Cu(II), Co(III), Ni(II)
and Pd(II) complexes of N2S2O2 thio Schiff base ligand and showed their usage in the
fabrication of organic–inorganic hybrid devices. The calculated barrier heights of the devices
were between 0.75 and 0.88 eV. Other researchers [59] have reported the I-V and capacitance-
voltage (C-V) characteristics of an Al/p-Si/organic semiconductor formed using CoPc thin
film on p-Si semiconductor. They have showed the strong effects of CoPc interlayer on
electrical properties of metal/semiconductor (MS) contact. Therefore, it can be easily said that
the organic thin films have strong impacts on the electrical performance of the organic-
inorganic devices and they behave as an active layer.
The curvature in the higher voltage values of the I-V measurements are because of the series
resistance of the structures. The series resistance of the devices may be caused by contact
wires or bulk resistance of the organic material and semiconductor [60]. Series resistance of a
diode can be calculated by the help of Norde functions [61]. It is also possible to determine
barrier height values using Norde Functions. The obtained barrier height and series resistance
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values are also given in Table 5. As seen from the table, the devices obtained using
[Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2], (3), and [Ir(Cy2PNHCH2-C4H3S)(η5-C5Me5)Cl2],
(4), have lower series resistance compared with ones fabricated using [Rh(Cy2PNHCH2-
C4H3O)(cod)Cl], (1) and [Rh(Cy2PNHCH2-C4H3S)(cod)Cl], (2). The large differences in
series resistance between the compounds can be attributed to the higher conductivity values of
compounds 3 and 4. As it is well known, conjugation is one of the most important properties
increasing the conductivity of organic compounds. Thus, the obtained results are in consistent
with the theory.
Figure 2 also presents the influences of light intensity on I-V properties of the structures.
Although all structures have sensitivity to the light, the devices obtained using 3 and 4 have
reverse bias and forward bias photosensing properties. As seen from the figures, current
values of Au/3/n-Si and Au/4/n-Si are nearly fixed after the series resistance curvatures in
forward bias. The reverse and forward bias photosensing properties of the structures imply the
photoconductivity of [Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2] and [Ir(Cy2PNHCH2-C4H3S)(η5-
C5Me5)Cl2], compounds. There are many papers on the increase of reverse bias current with
the increase of light intensity [39,43,44]. To the best our knowledge, there is no report on the
forward bias photosensing properties of a device. The photovoltaic parameters of all
structures determined under the light with 100 mW/cm2 illumination intensity called one sun
are given in Table 6. The table presents the superior photovoltaic properties of the junctions
formed using compounds 3 and 4. By taking Figure 1 and Table 6 into account, one can easily
say that the [Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2] and [Ir(Cy2PNHCH2-C4H3S)(η5-C5Me5)Cl2]
might be used in the fabrication reverse bias or forward bias photosensor applications.
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3. Conclusion
In conclusion, new rhodium(I) and iridium(III) complexes containing furfuryl-2-(N-
dicyclohexylphosphino)methylamine and thiophene-2-(N-dicyclohexylphosphino)methyl
amine ligands have been synthesized with high yield. All complexes were characterized using
multi nuclear NMR, IR and microanalysis. The use of the new complexes for the reduction of
the ketonic C=O bond of acetophenone derivatives under hydrogen transfer conditions was
investigated. Surprisingly, [Rh(Cy2PNHCH2-C4H3O)(cod)Cl] was a more efficient catalyst in
the transfer hydrogenation reaction than the other complexes. It was also found that these
catalysts containing cyclohexyl moiety exhibited promising catalytic activity compared to
those of containing phenyl moiety. The construction of the catalysts containing cyclohexyl
moiety and their flexibility toward transfer hydrogenation make these encouraging systems to
follow. In addition, organic-inorganic rectifying contacts were formed by spin coating of
complexes on n-Si semiconductor and evaporating Au metal on thin films. The electrical
properties of the devices were analyzed in dark and under a solar simulator with various
illumination conditions and the results showed excellent reverse and forward bias
photosensing behaviors for [Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2] and [Ir(Cy2PNHCH2-
C4H3S)(η5-C5Me5)Cl2] complexes, which were attributed the photoconducting properties of
the complexes.
4. Experimental
4.1. Materials and methods
Unless otherwise stated, all reactions were carried out under an atmosphere of argon using
conventional Schlenk glassware, solvents were dried using established procedures and
distilled under argon immediately prior to use. Analytical grade and deuterated solvents were
purchased from Merck. [Rh(ꢀ-Cl)(cod)]2 and Ir(η5-C5Me5)(ꢀ-Cl)Cl]2 are purchased from
Fluka and were used as received. The IR spectra were recorded on a Mattson 1000 ATI
UNICAM FT-IR spectrometer as KBr pellets. H (400.1 MHz), 13C NMR (100.6 MHz) and
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31P-{1H} NMR spectra (162.0 MHz) were recorded on a Bruker AV400 spectrometer, with δ
referenced to external TMS and 85% H3PO4 respectively. Elemental analysis was carried out
on a Fisons EA 1108 CHNS-O instrument. Melting points were recorded by Gallenkamp
Model apparatus with open capillaries. GC analyses were performed on a Shimadzu 2010
Plus Gas Chromatograph equipped with capillary column (5% biphenyl, 95%
dimethylsiloxane) (30m x 0.32mm x 0.25ꢀm). The GC parameters for transfer hydrogenation
of ketones were as follows; initial temperature, 110 ºC; initial time, 1 min; solvent delay,
4.48 min; temperature ramp 80 ºC/min; final temperature, 200 ºC, 19 min; final time, 21.13
min; injector port temperature, 200 ºC; detector temperature, 200 ºC, injection volume, 2.0
ꢀL.
4.2. General procedure for the transfer hydrogenation of ketones
Typical procedure for the catalytic hydrogen transfer reaction: a solution of complexes
[Rh(Cy2PNHCH2-C4H3O)(cod)Cl],
(1),
[Rh(Cy2PNHCH2-C4H3S)(cod)Cl],
(2),
[Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2], (3) and [Ir(Cy2PNHCH2-C4H3S)(η5-C5Me5)Cl2], (4)
(0.005 mmol), NaOH (0.025 mmol) and the corresponding ketone (0.5 mmol) in degassed
iso-PrOH (5 mL) were refluxed until the reactions were completed. After this period a sample
of the reaction mixture was taken off, diluted with acetone and analyzed immediately by GC.
Conversions obtained are related to the residual unreacted ketone.
4.3. Synthesis of rhodium and iridium complexes
4.3.1. [Rh(Cy2PNHCH2-C4H3O)(cod)Cl], (1)
A mixture of [Rh(ꢀ-Cl)(cod)]2 (0.235 g, 0.48 mmol) and [Cy2PNHCH2-C4H3O] (0.279 g,
0.95 mmol) in 15 mL of tetrahydrofuran was stirred at room temperature for 45 min. The
volume of the solvent was then reduced to 0.5 mL before addition of petroleum ether (10
mL). The precipitated product was filtered and dried in vacuo yielding 1 as a yellow
1
microcrystalline solid. Yield 0.472 g, 91.8 %, m.p. = 148-150°C. H NMR (400.1 MHz,
3
3
CDCl3): δ 7.36 (d, 1H, J = 1.9 Hz, H-5), 6.32 (dd, 1H, J = 1.9 and 3.0 Hz, H-4), 6.19 (d,
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1H, J = 3.0 Hz, H-3), 5.34 (br, 2H, CH of cod), 4.03 (dd, 2H, J = 5.7 and 5.8 Hz, CH2-),
3.55 (br, 2H, CH of cod), 2.78 (dt, 1H, 3J(HH) = 5.7 and 2J(HP) = 12.6 Hz), NH-), 1.23-2.42
(m, 30H, CH2 of cod + protons of cyclohexyl); 13C NMR (100.6 MHz, CDCl3): δ (26.43,
27.14, 27.23, 27.27, 27.33, 27.86, 28.38, 28.81, 29.01, 29.05) (CH2 of cyclohexyl + cod),
35.69 (d, 1J = 25.2 Hz, CH of cyclohexyl), 40.49 (d, 2J = 11.1 Hz, CH2), 68.79 (d, 1J = 15.1
1
Hz, CH of cod (a)), 103.88 (d, J = 6.4 Hz, CH of cod (b)), 106.23 (C-3), 110.26 (C-4),
141.86 (C-5), 153.80 (d, J = 5.0 Hz, C-2); assignment was based on the H-13C HETCOR,
DEPT and 1H-1H COSY spectra; 31P-{1H} NMR (162.0 MHz, CDCl3): δ 71.98 (d, 1J (103Rh-
31P) = 156.5 Hz); IR, (KBr): υ 3320 (N-H), 1076 (P-N), cm-1. C25H40NOPRhCl (539.9 g/mol):
calcd. C 55.61, H 7.47, N 2.59; found C 55.42, H 7.31, N 2.45.
3
1
4.3.2. [Rh(Cy2PNHCH2-C4H3S)(cod)Cl], (2)
A mixture of [Rh(ꢀ-Cl)(cod)]2 (0.208 g, 0.42 mmol) and [Cy2PNHCH2-C4H3S] (0.261 g, 0.84
mmol) in 15 mL of tetrahydrofuran was stirred at room temperature for 45 min. The volume
of the solvent was then reduced to 0.5 mL before addition of petroleum ether (10 mL). The
precipitated product was filtered and dried in vacuo yielding 2 as a yellow microcrystalline
1
solid. Yield 0.418 g, 89.1 %, m.p. = 150-152 °C. H NMR (400.1 MHz, CDCl3): δ 7.23 (dd,
1H, 3J = 1.2, 4.9 Hz, H-5), 6.94-6.97 (m, 2H, H-3 + H-4), 5.35 (br, 2H, CH of cod), 4.25 (dd,
3
3
2
2H, J = 6.7 and 6.8 Hz, CH2-), 3.56 (br, 2H, CH of cod), 3.08 (dt, 1H, J HH) = 6.7 and J
13
HP) = 12.8 Hz, NH), 1.39-2.46 (m, 30H, protons of cyclohexyl + CH2 of cod); C NMR
(100.6 MHz, CDCl3): δ (25.98, 26.43, 27.14, 27.23, 27.27, 27.33, 28.03, 28.40, 29.01, 29.10)
1
2
(CH2 of cyclohexyls + cod), 35.89 (d, J = 25.2 Hz, CH of cyclohexyls), 42.75 (d, J = 9.1
Hz, CH2-), 68.88 (d, 1J = 13.1 Hz, CH of cod, (a)), 104.04 (d, 1J = 9.1 Hz, CH of cod, (b)),
3
126.81, 124.55, 124.38 (C-3, C-4 and C-5), 144.40 (d, J = 5.0 Hz, C-2); assignment was
based on the 1H-13C HETCOR, DEPT and 1H-1H COSY spectra; 31P-{1H} NMR (162.0 MHz,
CDCl3): δ 74.39 (d, J (103Rh-31P) = 154.1 Hz); IR, (KBr): υ 3322 (N-H), 849 (P-N) cm-1.
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C25H40NSPRhCl (556.0 g/mol): calcd. C 54.00, H 7.25, N 2.52; found C 53.82, H 7.19, N
2.41.
4.3.3. [Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2], (3)
A mixture of [Ir(η5-C5Me5)(ꢀ-Cl)Cl]2 (0.379 g, 0.48 mmol) and [Cy2PNHCH2-C4H3O] (0.279
g, 0.95 mmol) in 15 mL of tetrahydrofuran was stirred at room temperature for 1 h. The
volume of the solvent was then reduced to 0.5 mL before addition of petroleum ether (20
mL). The precipitated product was filtered and dried in vacuo yielding 3 as an orange
1
microcrystalline solid. Yield 0.583 g, 88.6 %, m.p. = 189-191°C. H NMR (400.1 MHz,
CDCl3) δ: 7.31 (d, 1H, 3J = 2.6 Hz H-5), 6.43 (dd, 1H, 3J = 1,7 and 2.6 Hz, H-4), 6.30 (d, 1H,
3
3
3J = 1.7 Hz, H-3), 4.15 (dd, 2H, J = 6.2 and 6.4 Hz, CH2-), 3.30 (dt, 1H, J(HH) = 6.2 and
2J(HP) = 12.2 Hz, NH), 1.19-2.24 (m, 37H, protons of cyclohexyls + CH3 of Cp* (C5Me5);
13C NMR (100.6 MHz, CDCl3): δ 9.58 (C5Me5), 26.44, 27.20, 27.32, 27.41, 27.97, 28.37
1
2
(CH2 of cyclohexyls), 39.07 (d, J = 34.2 Hz, CH of cyclohexyls), 41.48 (d, J = 7.0 Hz,
CH2-), 91.92 (d, 2J = 12.0 Hz, C5Me5), 106.53 (C-4), 110.40 (C-3), 141.21 (C-5), 154.51 (C-
2); assignment was based on the 1H-13C HETCOR, DEPT and 1H-1H COSY spectra; 31P-{1H}
NMR (162.0 MHz, CDCl3): δ 43.98 (s); IR, (KBr): υ 3341 (N-H), 852 (P-N) cm-1;
C27H43NOPIrCl2 (691.7 g/mol): calcd. C 46.88, H 6.27, N 2.02; found C 46.73, H 6.21, N
1.98.
4.3.4. [Ir(Cy2PNHCH2-C4H3S)(η5-C5Me5)Cl2], 4
A mixture of [Ir(η5-C5Me5)(ꢀ-Cl)Cl]2 (0.336 g, 0.42 mmol) and [Cy2PNHCH2-C4H3S] (0.261
g, 0.84 mmol) in 15 mL of tetrahydrofuran was stirred at room temperature for 1 h. The
volume of the solvent was then reduced to 0.5 mL before addition of petroleum ether (10
mL). The precipitated product was filtered and dried in vacuo yielding 4 as an orange
1
microcrystalline solid. Yield 0.539 g, 90.3 %, m.p. = 169-171°C. H NMR (400.1 MHz,
3
3
CDCl3): δ 7.15 (d, 1H, J = 2.0 Hz, H-5), 7.12 (dd, 1H, J = 2.0 and 3.2 Hz, H-4), 6.93 (d,
3
3
3
1H, J = 3.2 Hz, H-3), 4.36 (dd, 2H, J = 5.6 and 5.7 Hz, CH2-), 3.39 (dt, 1H, J HH) = 5.6
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and 2J (HP) = 12.8 Hz, NH,), 1.20-2.26 (m, 37H, protons of cyclohexyls + CH3 of Cp*); 13C
NMR (100.6 MHz, CDCl3): δ 9.61 (C5Me5), (26.43, 27.21, 27.30, 27.40, 28.05, 28.42) (CH2-
1
2
of cyclohexyls), 39.06 (d, J = 34.2 Hz, CH of cyclohexyls), 43.50 (d, J = 8.0 Hz, CH2-),
2
91.89 (d, J = 2.0 Hz, C5Me5), 124.45, 123.74 (C-4and C-5), 126.80 (C-3), 144.79 (C-2);
1
1
assignment was based on the H-13C HETCOR and H-1H COSY spectra; 31P-{1H} NMR
(162.0 MHz, CDCl3): δ 43.34 (s). IR, (KBr): υ 3332 (N-H), 1070 (P-N) cm-1; C27H43NSPIrCl2
(707.8 g/mol): calcd. C 45.82, H 6.12, N 1.98; found C 45.71, H 6.03, N 1.85.
4.4. Fabrication and characterization of Au/metal complex/n-Si devices
An n-Si semiconductor with (100) orientation and 1-10 Ωcm resistivity was used in this study
to fabricate Au/metal complex/n-Si devices. The semiconductor was cleaned by boiling in
trichloroethylene and ultrasonically vibrating in acetone and methanol. The native oxide on n-
Si wafer was removed using 0.4 % HF:H2O solution. The wafer was dipped in deionized
water and dried under N2 flow. Au ohmic back contact was formed by evaporation of Au on
n-Si in high vacuum and annealing the n-Si/Au contact in N2 atmosphere at 420 °C. The thin
films of metal complexes were formed on n-Si wafer by means of a SCS G3P-8 spin coater.
Finally, Au metal was evaporated on the structure to obtain the front contact of the devices.
Current-voltage (I-V) measurements were carried out using Keithley 2400 sourcemeter in dark
and under a solar simulator with AM1.5 global filter for various light intensities.
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[44] Furfuryl-(N-dicyclohexylphosphino)amine: Yield 0.279 g, 93.3 %. 1H NMR (400.1 Hz, CDCl3): δ
7.33 (d, 1H, H-5, 3J = 1.6 Hz), 6.29 (dd, 1H, H-4, 3J = 1.6 and 3.0 Hz), 6.13 (d, 1H, H-3, 3J = 3.0 Hz),
4.04 (dd, 2H, CH2-, 3J(HP) = 7.7 and 3J(HH) = 7.6 Hz), 2.42 (dt, -NH-, 1H, 3J(HH) = 7.6 and 2J(HP)
= 7.7 Hz), 1.16-1.77 (m, 22 H, protons of cyclohexyls); 13C NMR (100.6 MHz, CDCl3): δ 26.55,
27.03, 27.16, 27.28, 29.12, 29.30 (CH2- of cyclohexyls), 36.40 (d, CH- of cyclohexyls, 1J = 11.1 Hz),
45.86 (d, CH2-, 2J = 27.2 Hz), 105.56 (C-3), 110.09 (C-4), 141.27 (C-5), 156.23 (d, C-2, 3J= 3.0 Hz),
1
1
assignment was based on the H-13C HETCOR, DEPT and H-1H COSY spectra; 31P-{1H} NMR
(162.0 MHz, CDCl3): δ 61.61 (s, NH-P(Cy)2); IR, (KBr): υ 801 (P-N), 3257 (N-H) cm-1; C17H28NOP
(293.39 g/mol): calcd. C 69.60, H 9.62, N 4.77; found C 69.49, H 9.54, N 4.61 %. Thiophene(N-
dicyclohexylphosphino)amine: Yield 0.261 g, 95.6 %. 1H NMR (400.1 Hz, CDCl3): δ 7.18 (d, 1H, H-
3
3
3
5, J = 5.0 Hz), 6.90-6.94 (m, 2H, H-3 and H-4), 4.27 (dd, 2H, CH2-, J(HP) = 6.4 and J(HH) = 6.3
20

ACCEPTED MANUSCRIPT
Hz), 2.98 (m, 1H, NH), 1.24-1.81 (m, 22H, protons of cyclohexyls); 13C NMR (100.6 MHz, CDCl3): δ
26.01, 26.57, 27.00, 27.70, 29.43, 29.62 (CH2 of cyclohexyls), 36.58 (d, CH of cyclohexyls, 1J = 10.1
Hz), 48.16 (d, CH2, 2J = 4.0 Hz), 123.46 (C-3), 123.67 (C-5), 126.36 (C-4), 147.40 (C-2), assignment
1
1
was based on the H-13C HETCOR, DEPT and H-1H COSY spectra; 31P-{1H} NMR (162.0 MHz,
CDCl3): δ 61.69 (s, NH-P(Cy)2); IR, (KBr): υ 798 (P-N), 3253 (N-H) cm-1; C17H28NSP (309.45 g/mol):
calcd. C 65.98, H 9.12, N 4.53; found C 65.87, H 8.99, N 4.35 %.
[45] M. Aydemir, A. Baysal, N. Meriç, B. Gümgüm. New active ruthenium(II) complexes based
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acid-P,P′-[2,2′-bipyridine]-3,3′-diyl ester ligands for transfer hydrogenation of aromatic ketones
by propan-2-ol J. Organomet. Chem. 694 (2009) 2488-2492.
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R. Noyori, J. Amino alcohol effects on the ruthenium(II)-catalysed asymmetric transfer
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Transition Metal-Based Molecular Catalysts. Acc. Chem. Res. 40 (2007) 1300–1308.
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New York, 1987, Chapter 2.
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[52] M.J. Palmer, M. Wills. Asymmetric transfer hydrogenation of C=O and C=N bonds.
Tetrahedron: Asymmetry 10 (1999) 2045-2061.
[53] D.H. McDaniel, H.C. Brown. An Extended Table of Hammett Substitutent Constants Based on
the Ionization of Substituted Benzoic Acids. J. Org. Chem. 23 (1958) 420-427.
[54] J.W. Faller, A.R. Lavoie. Catalysts for the Asymmetric Transfer Hydrogenation of Ketones
Derived from L-Prolinamide and (p-CymeneRuCl2)2 or (Cp*RhCl2)2. Organometallics 20 (2001)
5245-5247.
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rhodium–aminophosphine complexes for asymmetric transfer hydrogenation of aromatic
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21

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Phys. 50 (1979) 5052.
22

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Captions
Scheme 1 Synthesis of the [Rh(Cy2PNHCH2-C4H3O)(cod)Cl], (1), [Rh(Cy2PNHCH2-
C4H3S)(cod)Cl], (2), [Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2], (3) and [Ir(Cy2PNHCH2-
C4H3S)(η5-C5Me5)Cl2], (4) complexes (i) 1/2 equiv. [Rh(ꢀ-Cl)(cod)]2, thf; (ii) 1/2 equiv.
[Ir(η5-C5Me5)(ꢀ-Cl)Cl]2, thf.
Figure 1 The 31P-{1H} NMR spectra of the complexes [Rh(Cy2PNHCH2-C4H3O)(cod)Cl],
(1), [Rh(Cy2PNHCH2-C4H3S)(cod)Cl], (2), [Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2], (3) and
[Ir(Cy2PNHCH2-C4H3S)(η5-C5Me5)Cl2], (4).
Figure 2 I-V measurements of Au/metal complex/n-Si structures fabricated using a) 1 b) 2 c)
3 and d) 4 compounds.
23

ACCEPTED MANUSCRIPT
Table 1 Transfer hydrogenation of acetophenone with iso-PrOH catalyzed [Rh(Cy2PNHCH2-
C4H3O)(cod)Cl], (1), [Rh(Cy2PNHCH2-C4H3S)(cod)Cl], (2), [Ir(Cy2PNHCH2-C4H3O)(η5-
C5Me5)Cl2], (3) and [Ir(Cy2PNHCH2-C4H3S)(η5-C5Me5)Cl2], (4).
Entry
Catalyst
S/C/NaOH
Time
Conversion(%)[i] TOF(h-1)[k]
[a]
1
100:1:5
100:1:5
100:1
100:1:5
100:1:5
500:1:5
1000:1:5
1
2
3
4
5
6
7
15 min
24 h
24 h
15 min
3 h
98
392
....
....
384
33
132
65
[b]
1
trace
trace
96
98
99
[c]
1
[d]
1
[e]
1
[f]
1
45 min
1.5 h
[g]
1
97
[a]
2
100:1:5
100:1:5
100:1
100:1:5
100:1:5
500:1:5
1000:1:5
8
9
8 h
98
12
....
....
12
<5
<5
<5
[b]
2
24 h
24 h
8 h
30 h
20 h
40 h
trace
trace
96
97
98
[c]
2
10
11
12
13
14
[d]
2
[e]
2
[f]
2
[g]
2
97
[a]
3
100:1:5
100:1:5
100:1
100:1:5
100:1:5
500:1:5
1000:1:5
15
16
17
18
19
20
21
8 h
97
12
....
....
12
<5
<5
<5
[b]
3
trace
trace
97
98
97
24 h
24 h
8 h
30 h
20 h
40 h
[c]
3
[d]
3
[e[
3
[f]
3
[g]
3
96
[a]
4
96
12
....
....
12
<5
<5
<5
100:1:5
100:1:5
100:1
100:1:5
100:1:5
500:1:5
1000:1:5
22
23
24
25
26
27
28
8 h
[b]
4
trace
trace
98
98
98
24 h
24 h
8 h
30 h
20 h
40 h
[c]
4
[d]
4
[e]
4
[f]
4
[g]
4
96
Reaction conditions:
[a]
[b]
Refluxing in iso-PrOH; acetophenone/Ru/NaOH, 100:1:5;
At room temperature;
[c]
acetophenone/Ru/NaOH, 100:1:5;
Refluxing in iso-PrOH; acetophenone/Ru, 100:1, in the absence
[d]
[e]
[f]
of base;
Added 0.1 mL of H2O;
Refluxing the reaction in air;
Refluxing in iso-PrOH;
[g]
[i]
acetophenone/Ru/NaOH, 500:1:5;
Refluxing in iso-PrOH; acetophenone/Ru/NaOH, 1000:1:5;
[k]
Determined by GC (three independent catalytic experiments);
indicated in column; TOF= (mol product/mol Ru(II)Cat.)x h-1.
Referred at the reaction time

ACCEPTED MANUSCRIPT
Table 2 Transfer hydrogenation results for substituted acetophenones with the catalyst
systems,
[Rh(Cy2PNHCH2-C4H3O)(cod)Cl],
(1),
[Rh(Cy2PNHCH2-C4H3S)(cod)Cl],
(2),
[Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2], (3) and [Ir(Cy2PNHCH2-C4H3S)(η5-C5Me5)Cl2], (4).[a]
O
OH
OH
O
Cat 1-4
R
R
+
+
Entry
R
Time
Conversion(%)[b]
TOF(h-1)[c]
Cat:Rh(I) complex 1
10 min
10 min
15 min
25 min
20 min
1
2
3
4
5
4-F
4-Cl
4-Br
2-MeO
4-MeO
96
98
98
97
96
576
588
392
233
288
Cat:Rh(I) complex 2
6 h
6 h
8 h
12 h
96
98
97
98
98
16
16
12
8
6
7
8
9
4-F
4-Cl
4-Br
2-MeO
4-MeO
10 h
10
10
Cat:Ir(III) complex 3
6 h
6 h
8 h
12 h
96
95
95
98
97
16
16
12
8
11
12
13
14
15
4-F
4-Cl
4-Br
2-MeO
4-MeO
10
10 h
Cat:Ir(III) complex 4
6 h
6 h
8 h
12 h
10 h
97
97
95
97
96
16
16
12
8
16
17
18
19
20
4-F
4-Cl
4-Br
2-MeO
4-MeO
10
[a]
Catalyst (0.005 mmol), substrate (0.5 mmol), iso-PrOH (5 mL), NaOH (0.025 mmol %), 82 °C, the
[b]
1
concentration of acetophenone derivatives is 0.1 M;
Purity of compounds is checked by H NMR
[c]
and GC (three independent catalytic experiments), yields are based on methyl aryl ketone;
(mol product/mol Cat.) x h-1.
TOF =

ACCEPTED MANUSCRIPT
Table 3 Transfer hydrogenation of various simple ketones with iso-PrOH catalyzed by
[Rh(Cy2PNHCH2-C4H3O)(cod)Cl],
(1),
[Rh(Cy2PNHCH2-C4H3S)(cod)Cl],
(2),
[Ir(Cy2PNHCH2-C4H3O)(η5-C5Me5)Cl2], (3) and [Ir(Cy2PNHCH2-C4H3S)(η5-C5Me5)Cl2],
(4).[a]
O
O
O
O
a
b
c
d
Entry
Cat
Substrate
Time
Conversion(%)[b]
a
b
c
d
a
b
c
d
a
b
c
d
a
b
c
d
30 min
10 h
10 h
10 h
30 min
10 h
10 h
10 h
3/2 h
20 h
20h
20 h
3h
30 h
30 h
30h
1
2
3
4
5
6
7
8
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
96
98
97
98
96
98
95
97
99
97
98
97
99
96
99
95
9
10
11
12
13
14
15
16
[a]
[b]
Refluxing in iso-PrOH; ketone/Ru/NaOH, 100:1:5;
Determined by GC (three independent
[b]
1
catalytic experiments); Purity of compounds is checked by H NMR and GC (three independent
catalytic experiments), yields are based on methyl aryl ketone.