Supported and non-supported ruthenium(II)/phosphine/[3-(2-aminoethyl) aminopropyl]trimethoxysilane complexes and their activities in the chemoselective hydrogenation of trans-4-phenyl-3-butene-2-al

Article abstract of DOI:10.3390/molecules15074652

Syntheses of four new ruthenium(II) complexes of the [RuCl ₂(P)₂(N)₂] type using 2-(diphenylphosphino) ethyl methyl ether (PO) as ether-phosphine and triphenylphosphine (PPh₃) as monodentate phosphine ligands in

Full text of DOI:10.3390/molecules15074652

Molecules 2010, 15, 4652-4669; doi:10.3390/molecules15074652
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Supported and Non-Supported Ruthenium(II)/Phosphine/[3-(2-
Aminoethyl)aminopropyl]trimethoxysilane Complexes and
Their Activities in the Chemoselective Hydrogenation of trans-4-
Phenyl-3-butene-2-al
Ismail Warad
Petrochemical Research Chair, Department of Chemistry, King Saud University, P. O. Box 2455,
Riyadh 11451, Saudi Arabia; E-Mail: warad@ksu.edu.sa; Tel./Fax: +96-61-4675992
Received: 21 May 2010; in revised form: 22 June 2010 / Accepted: 25 June 2010 /
Published: 30 June 2010
Abstract: Syntheses of four new ruthenium(II) complexes of the [RuCl2(P)2(N)2] type
using 2-(diphenylphosphino)ethyl methyl ether (P~O) as ether-phosphine and
triphenylphosphine (PPh3) as monodentate phosphine ligands in the presence of [3-(2-
aminoethyl)aminopropyl]trimethoxysilane as diamine co-ligand are presented for the first
time. The reactions were conducted at room temperature and under an inert atmosphere.
Due to the presence of the trimethoxysilane group in the backbone of complexes 1 and 2
they were subjected to an immobilization process using the sol-gel technique in the
presence of tetraethoxysilane as cross-linker. The structural behavior of the phosphine
ligands in the desired complexes during synthesis were monitored by 31P{1H}-NMR.
1
Desired complexes were deduced from elemental analyses, Infrared, FAB-MS and H-,
31
13
13C- and P-NMR spectroscopy, xerogels X1 and X2 were subjected to solid state, C-,
29Si- and 31P-NMR spectroscopy, Infrared and EXAF. These complexes served as
hydrogenation catalysts in homogenous and heterogeneous phases, and chemoselective
hydrogenation of the carbonyl function group in trans-4-phenyl-3-butene-2-al was
successfully carried out under mild basic conditions.
Keywords: Ru(II) complexes; hydrogenation; interphase; ether-phosphine; sol-gel; NMR

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1. Introduction
Reduction of aldehydes and ketones to the corresponding alcohols is a core technology in fine
chemicals synthesis, particularly for pharmaceuticals, agrochemicals, flavors and fragrances, which
requires a high degree of stereochemical precision [1–3]. Asymmetric hydrogenations of C=C, C=O,
and C=N functionalities have found important applications in organic synthesis and in the fine
chemical business [3–8]. A high turnover frequency (TOF) can be obtained by designing suitable
molecular catalysts and reaction conditions. Preferential reduction of a C=O function over a coexisting
C=C linkage is an important and difficult task. Although there are many examples of highly efficient
catalysts for olefin and ketone reduction, imine hydrogenation is still a challenge in terms of both the
turnover frequency and the lifespan of the active catalyst [9–25]. One of the best transition-metal
complexes for ketone hydrogenation that has been discovered is the chiral Ru(II)–diphosphine/1,2-
diamine complex, which was developed by Noyori [3]. This system was found to be active in the
chemoselective hydrogenation of carbonyl functional groups in the presence of olefins and in the
reduction of imines [5–8]. The immobilization of metal complexes enables the longterm use of
expensive or toxic catalysts and provides a clean and straightforward separation of the product [26–
33].
It is interesting to investigate the chemical properties and structures of new ruthenium(II) complexes
containing C=C functional groups in the backbone of the phosphine ligand and indirect to the
phosphorus atom [1,1-bis(diphenylphosphinomethyl)ethane, dppme] ligands to see how these
31
properties are related to the chemical behavior of complexes by monitoring any changes by P{1H}-
NMR spectroscopy [21].
Phosphorus–oxygen hemilabile ligands like 2-(diphenylphosphino)ethyl methyl ether ( P~O), reacts
with various metals of catalytic relevance due to their ability to act as both a chelate ligand, stabilizing
the metal complex, and a monodentate ligand providing a free coordination site for an incoming
substrate (through the labilization of the weakly bonded oxygen atom) [12–19].
By the introduction of T-functionalized into the diamine ligands coordinated complexes, these
complexes can be easily immobilized as atypical interphase to a polysiloxane matrix by sol-gel process
[9,10,17,26–33]. In such interphases the stationary phase (comprising active centers, polymer and
spacer) and a mobile component (gas, liquid or dissolved reactants) penetrate each other on a
molecular scale without forming a homogeneous phase [26–33]. When such interphases are provided
with a swellable polymer, they may imitate homogeneous conditions as the active centers become
highly mobile, simulating the properties of a solution [9,10,17,26–33].
Recently we have synthesized a number of ruthenium(II) complexes of the [RuCl2(P)2(N)2] type
using both mondentate or bidentate phodsphine and amine ligands, and these complexes were tested as
hydrogenation catalysts for functionalized carbonyl compounds. Our ongoing research interest is in
synthesizing supported and non-supported phosphine/diamine Ru(II) complexes, then examining their
activity for catalytic hydrogenation in both homogenous and heterogeneous phase [9,10,17].
In this work a set of ruthenium(II)/phosphine/diamine complexes were made available by using
monodentate triphenylphosphine and monodetate/bidentate ether-phosphine ligands in the presence of
the [3-(2-aminoethyl)aminopropyl]trimethoxysilane as diamine co-ligand. The presence of Si(OEt)3
anchoring groups in the backbone of the these complexes enabled the immobilization process through

Molecules 2010, 15
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a simple sol-gel reaction using Si(OEt)4 as cross-linker. The desired complexes served as catalysts for
selectivity hydrogenation of trans-4-phenyl-3-butene-2-al in both homogenous and heterogeneous
phases under mild conditions.
2. Results and Discussion
2.1. Ruthenium(II) complexes 1 and 2 synthetic investigation and structural behavior
Treating each of Cl2Ru(P∩O)2 and Cl2Ru(PPh3)3 individually with an equivalent amount of [3-(2-
aminoethyl)aminopropyl]trimethoxysilane in dichloromethane resulted in the formation of complexes
1 and 2, respectively, as shown in Scheme 1.
Scheme 1. The synthetic route to prepare complexes 1-2 and xerogels X1 and X2.
polysilyoxane xerogel
O
O
O
Si
Cl
Ru
Cl
Ph2
P
Ph2
P
Ph2
P
Cl
Cl
H2
N
Ph2
P
O
O
O
NH
ii
Ru
Cl
1
Ru
O
O
O
i
NH
P
Ph2
N
H2
P
Ph2
(MeO)3Si
Cl
X1
(MeO)3Si
Si(OMe)3
Cl
H2
N
HN
Ph3P
iv
Ru
Cl
NH2
Cl
iii
Ph3P
Ph3P
HN
NH
Ph3P
Cl
Ru
PPh3
PPh3
NH2
Cl
Ph3P
Ru
Cl
X2
Si
2
O
O
O
polysilyoxane xerogel
Reagents and conditions: i, iii) CH2Cl2, 25 °C, 20 min. stirring ii; iv) THF, H2O, Si(OEt)4, 25 °C,
24 h stirring.
High melting yellow powders were obtained in very good yields. These complexes are soluble in
chlorinated solvents such as chloroform or dichloromethane and insoluble in polar or non-polar
solvents like water, methanol, diethyl ether and n-hexane. The structures of the desired complexes have
been deduced from elemental analysis, infrared spectroscopy, FAB-mass spectrometry, 1H-,
13C{1H}− and 31P{1H}−NMR spectroscopy data.

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31
The stepwise formation of complex 1 is monitored by P{1H}-NMR spectroscopy, in an NMR
tube experiment, where addition of [3-(2-aminoethyl)aminopropyl]trimethoxysilane to a CDCl3
solution containing Cl2Ru(P∩O)2 complex as starting material leads to the disappearance of the red
color of the Cl2Ru(P∩O)2 complex and the singlet of this complex at δp = 64.40 ppm and the
appearance of a new AB 31P{1H}-NMR pattern at δp = 38.87, 35.64 ppm due to the formation of
complex 1 with a trans-Cl2Ru(dppme)NN formula, together with the appearance of the yellow color of
the latter, confirming the hemilabile cleavage of 2Ru-O to form the 2Ru-N complex 1 in a very short
time and without side products, as seen in Figure 1.
∩
31
Figure 1. Time-dependent P{1H}-NMR spectroscopic of Cl2Ru(P O)2 at δp = 64.4 ppm
mixed with equivalent of diamine co-ligand in CDCl3 in the NMR tube to produce complex
1 at δp = 38.87, 35.64 ppm a) before co-ligand addition, b) the first shot ~ 0.5 min. and c)
the second shot ~1 min. after the co-ligand addition.
31P{1H}-NMR of Cl2Ru(P∩O)2 at δp
= 64.4 ppm disappearing
a)
AB 31P{1H} NMR pattern of complex
1 at δp = 38.87, 35.64 ppm appeared
35.80
38.69
b)
39.05
35.44
c)
The weak ruthenium-oxygen bonds in bis(chelate)ruthenium(II) complexes of the Cl2Ru(P∩O)2 type
are easily cleaved by an incoming molecule such as the [3-(2-aminoethyl)aminopropyl]-

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trimethoxysilane co-ligand. Due to the hemilabile character the oxygen donor in the ether-phosphine
ligand is regarded as an intramolecular solvent impeding decomposition of the complex by protection
of vacant coordination sites, which accelerates and stabilizes the synthesis of complex 1 without any
side products.
2.2. Oxidative decomposition of complexes 1 and 2 by oxygen or H2O2
The desired complexes showed some sensitivity toward oxygen in solution, and the colour changed
from yellow to green if oxygen allowed to enter the reaction, or if the reactions were carried out in an
open atmosphere. To examine the stability of complex 1 toward oxygen, 0.10 g was dissolved in
20 mL of dichloromethane in an open atmosphere, and several samples were taken over time and
31
subjected to P{1H}-NMR. The spectra showed that complex 1 (indicated by peaks at δp = 38.9, 35.6
ppm) was decomposed to form phosphine oxide [Ph2P(=O)CH2CH2OCH3] with δp = 30.8 ppm and
other green oily ruthenium complexes in around one hour, as shown in Figure 2. These complexes are
mostly free of phosphine or paramagnetic ruthenium(III) species because nothing except the phosphine
oxide were detected by 31P{1H}-NMR.
Figure 2. Time-dependent 31P{1H} NMR spectroscopic of complex 1 at δp = 38.9, 35.6
ppm in an open atmosphere a) fresh synthesis b) after 25 min. c) after 60 min.
AB 31P{1H} NMR pattern of complex 1
at δp = 38.87, 35.64 ppm appeared
31P{1H} NMR of free phosphine
oxide at δp = 30.8 ppm disappearing

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Under identical conditions complex 2 displayed more stability toward oxygen compared with
complex 1, 2 hours are required to decompose the same quantity of complex 2 completely, which
confirmed that phosphine complexes were more stable than the ether-phophine ones. The oxidatative
decomposition processes of complexes 1 and 2 were accelerated by addition of H2O2 as another
oxidizing agent. By adding very small testing drop of H2O2 to solution of the same quantity of
complexes 1 or 2 the colors changed to green immediately. In general, only seconds were required to
ensure the complete decomposition of the more stable phosphine complex 2 when 1:1 (mole:mole) of
[H2O2:complex] were mixed.
2.3. Ruthenium(II) complexes 1 and 2 and synthetic investigation of xerogels X1 and X2
Complexes 1 and 2 are very important in interphase chemistry. They can be converted as primary
complexes to prepare stationary phases via the sol gel technique in order to support complexes that
transform the system from homogenous to heterogeneous phase or interphase catalysts [33–35].
Complexes 1 and 2 were subjected to a typical sol-gel polymerization process at room temperature in
the presence of 10 equivalents of Si(OEt)4 as cross-linker using methanol/THF/water to prepare
polysiloxane xerogels X1 and X2, as shown in Scheme 1. Due to the poor solubility of the xerogels X1
and X2 they were subjected to solid state measurements like NMR, IR and EXAF.
2.4. 31P-NMR investigation of complexes 1 and 2 and Xerogels X1 and X2
The use of an asymmetric diamine co-ligand such as [3-(2-aminoethyl)aminopropyl]trimethoxy-
silane caused the loss of the C
axis, resulting in a splitting of the 31P{1H}-NMR resonances of 1, 2, X1
2
and X2 into AB patterns [14,27]. The phosphorous chemical shifts and the 31P - 31P coupling constants
(Jpp = 30–36 Hz) of the desired complexes suggest that the phosphine ligand was positioned trans to
the diamine, with trans dichloro atoms, to form the kinetically favored trans-Cl Ru(II) isomer, as seen
2
in Figure 3.
Figure 3. 31P{1H}-NMR spectroscopic data of complex 2 at δp = 39.9, 44.1 ppm and their
coupling constant Jpp = 31.6 Hz.
Jpp = 31.6 Hz
(MeO)3Si
43.93
40.0
44.2
39.76
B
Ph3P
Cl
HN
Ru
NH2
Cl
Ph3P
A
PB
PA

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2.5. 1H and 13C-NMR investigations
In the 1H-NMR spectra of complexes 1 and 2 characteristic sets of signals were observed, which are
attributable to the phosphine as well as [3-(2-aminoethyl)aminopropyl]trimethoxysilane ligands. Their
1
1
assignment was supported by a free ligand H-NMR study. The integration of the H resonances
confirms that the phosphine to diamine ratios are in agreement with the compositions of the desired
complexes. A comparison the 1H-NMR spectra of the free diamine co-ligand [3-(2-aminoethyl)amino-
propyl]trimethoxysilane, individual starting material Cl2Ru(P∩O)2 complex and complex 1 (after
mixing Cl2Ru(P∩O)2 with [3-(2-aminoethyl)aminopropyl]trimethoxysilane) is shown in Figure 4.
1
Figure 4. H-NMR of: a) free ligand [3-(2-aminoethyl)aminopropyl]trimethoxysilane; b)
complex Cl2Ru(P∩O)2 starting material and c) complex 1 in CDCl3 at room temperature.
a)
b)
c)
In the 13C-NMR spectra of complexes 1 and 2 and xerogels X1 and X2 characteristic sets of signals
were observed, which are attributed to the PPh3 and P~O phosphine ligands as well as the [3-(2-amino-

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ethyl)aminopropyl]trimethoxysilane diamine co-ligand. Their assignment was supported by free ligand
13C-NMR studies. Several sets of aliphatic and aromatic carbons related to the phosphine and diamine
were assigned with the help of 135 DEPT 13C-NMR to differentiate between the odd and even C-types,
CH, CH3 up axis singlet, CH2 down axis singlet, and C no singlet. As a typical example, the 135 DEPT
13C-NMR spectra of the free [3-(2-aminoethyl)-aminopropyl]trimethoxysilane, complex 1, complex 2,
and solid state 13C-CP-MAS-NMR of xerogels X2 are shown in Figure 5.
13
Figure 5. Dept 135 C-NMR of: a) free [3-(2-aminoethyl)aminopropyl]trimethoxysilane;
b) complex 1 in CDCl3; c) complex 2 in CDCl3; compared by solid state 13C-CP-MAS-
NMR; d)X2 xerogel.
Examination of the 13C-CP-MAS-NMR spectrum of the modified solids along with the solution
phase spectrum of the corresponding molecular precursor led to the conclusion that the organic

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4660
fragments in complex 2 and xerogel X2 remained intact during the grafting and subsequent workup
without measurable decomposition (Figure 5d). The absence of the CH3O peak at δC = 49.92 belonging
to (CH3O)3Si in the [3-(2-aminoethyl)aminopropyl]trimethoxysilane co-ligand after the sol-gel process
of complex 2 to furnish xerogel X2, were the major differences noted between spectra, which
supported the immobilization of the desired hybrid Ru(II) complexes. The total disappearance of
groups in X2 (Figure 5b), compared by complex 2 (Figure 5c and 5d), provides good confirmation of a
sol-gel process gone to full completion [9,10,17].
Solid-state 29Si-NMR provided further information about the silicon environment and the degree of
functionalization [9,10,17,27–33]. In all cases, the organometallic/organic fragment of the precursor
molecule was covalently grafted onto the solid, and the precursors were, in general, attached to the
surface of the polysiloxane by multiple siloxane bridges. The presence of Tm sites in case of xerogel
X1 and X2 in the spectral region of T2 at δSi = -56.8 ppm and T3 at δSi = - 69.1 ppm as expected, Q
silicon sites due to Si(OEt)4 condensation agent were also recorded to Q3 at δSi = -101.2 and Q4 at
δSi = -109.5 ppm silicon sites of the silica framework, as seen in Figure 6.
Figure 6. 29Si CP/MAS NMR spectrum of X2, prepared by condensate of complex 2 with
10 equivalent of Si(OEt)4 cross-linkers.
2.6. FAB mass spectra of the complex 1 and 2
Complexes 1 and 2 were subjected to FAB-MS, which showed molecular ion peaks M+
[Cl2Ru(PP)NN]+ at m/z 972.2 and 882.1 respectively, which revealed their exact calculated mass. For
comparison the FAB-MS spectrum of complex 1 is presented in Figure 7.
The first three fragments are the most important and were assigned as M+ = [Cl2Ru(P~O)2NN]+ at
m/z 882.1, the second molecular ion was formed by the loss of HCl to give a fragment ion peak at m/z
847.2 belonging to M+-HCl =[RuCl2(P~O)2NN-HCl]+, the third fragment at m/z 662.0, which was the
most stable one, was formed by loss of diamine ligand from the structure of complex 1 to give the
starting material M+ -NN = [Cl2Ru(P∩O)2]+, as seen in Figure 7.

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Figure 7. FAB-Mass spectrum of complex 1.
2.7. IR investigations of ruthenium complexes 1 and 2
The IR spectra of the desired complexes in particular show several peaks which attributed to
stretching vibrations of the main function group, in the ranges 3,490–3,300 cm-1 (vNH),
3,280–3,010 cm-1 (vPhH) and 3,090–2,740 cm-1 (vCH). All other characteristic bands due to the other
function groups are also present in the expected regions, as seen in Figure 8. The IR spectrum which
contained the chemical shifts of the main fragments represented the well-known function groups of
complex 1 as an example was illustrated in Figure 8.
Figure 8. Infra-red spectrum cm-1 per well-known function group of complex 1.

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4662
2.8. EXAFS measurement of xerogel X2
The xerogel X2 was chosen as an example to determine the bond lengths between the metal center
and the coordinating atoms of the ligand. The k3 weighted EXAFS function of xerogel X2 can be
described best by six different atom shells. The first intensive peak in the corresponding Fourier
transform (Figure 9a) is mainly due to the nitrogen atoms. Chlorine and phosphorus atoms were found
in the case of the most intense peak. For the most intense peak of the Fourier Transform, two
equivalent phosphorus, two nitrogen atoms and two chlorine atoms with Ru-P, Ru-N and Ru-Cl bond
distances of 2.27, 2.17 and 2.42 Å, respectively, were found (Figure 9b and Table 1). These results
reveal a good agreement between the experimental and the calculated functions.
Figure 9. Experimental (solid line) and calculated (dotted line) EXAFS functions (a) and
their Fourier transforms (b) for xerogel X2 measured at Ru K-edge.
Table 1. EXAFS determined structural parameters of xerogel X2.
e
A-Bsa
Ru – N
Ru – P
Ru – Cl
Nb
2
2
2
rc [Å]
σd [Å]
∆E0 [eV]
k-range [Å-1] Fit-Index
2.17 0.02 0.050 0.005
2.27 0.02 0.067 0.007
2.42 0.03 0.054 0.006
22.26
3.0–18.0 22.06
a absorber (A) – backscatterers (Bs), coordination number N, interatomic distance r, Debye-
Waller factor σ with its calculated deviation and e shift of the threshold energy ∆E0.
b
c
d
2.9. Catalytic activity of complexes 1, 2, X1 and X2 in the hydrogenation of trans-4-phenyl-3-butene-
2-al
To study the catalytic activity of the ruthenium(II) complexes, trans-4-phenyl-3-propene-2-al was
selected, because three different rego-selective hydrogenation are expected (Scheme 2). The selective
hydrogenation of the carbonyl group affords the corresponding unsaturated alcohol A. Unwanted and
hence of minor interest both the hydrogenation of the C=C double bond, leading to the saturated
aldehyde B and the full hydrogenation of C=O and C=C bonds resulting the formation of saturated
alcohol C. The hydrogenation reactions using complexes 1 and 2, and xerogel X1 and X2 as catalysts
were carried out under identical conditions: 35 °C with a molar substrate:catalyst (TON, S/C) ratio of
1,000:1, under 2 bar of hydrogen pressure, in 50 mL of 2-propanol [Ru: Co-catalysts (KOH, tBuOK
and K2CO3): trans-4-phenyl-3-butene-2-al] [1:10:1,000], the results are listed in Table 2.

Molecules 2010, 15
Scheme 2. Different hydrogenation possibilities of trans-4-phenyl-3-butene-2-al: Selective
4663
carbonyl function group hydrogenation to produce A, selective C=C function group
hydrogenation to produce B, full hydrogenation path with no selectivity to produce C.
OH
H
O
O
OH
Ruthenium(II) catalysts
H
H
H
+
+
A
B
C
Table 2. Hydrogenation of trans-4-phenyl-3-butene-2-al by Ru(II) complexes.
Run Catalyst Co-catalyst Conversion (%)a Selectivity (%) a
TOF b
1,160
1,050
1,210
1,070
-
1
2
3
4
5
6
7
8
9
t
BuOK
BuOK
KOH
>
99 c
>
>
>
>
99
99
99
99
-
A
A
A
A
1
2
1
t
>
>
>
99 c
99 c
99 c
KOH
2
1
or
X1
X2
X1
X2
2
K2CO3
t
0 d
BuOK
BuOK
KOH
95 d
90 d
94 d
93
A
80
75
78
76
t
90
92
91
A
A
A
KOH
92 d
a Yield and selectivity were determined by GC. Turnover frequency: mole of product per mole of
b
c
d
catalyst per hour, h-1. The reaction was conducted to the hydrogenation for one hour. The
reaction was conducted to the hydrogenation for 12 hours
These catalysts were only effective in the presence of excess hydrogen in 2-propanol and a strong
basic co-catalyst like KOH and BuOK, since when weakly basic K2CO3 was used as co-catalyst, no
hydrogenation reaction was observed, even after longer reaction times. Complexes and are highly
active under these mild conditions and gave rise to 99% conversion and selective hydrogenation of the
C=O group in the presence of a C=C function. Complex was slightly less active under identical
conditions compared to complex , which can be attributed to the hemilability of the ether-phosphine
t
1
2
2
1
ligand in the diamine/ruthenium(II) system.
The other ruthenium(II) precursors, xerogels X1 and X2, displayed high conversion ratios and
selectivity (~ 90%) in the C=O selective hydrogenation of the trans-4-phenyl-3-butene-2-al using
strong basic conditions. Expected constant decrease in the activity and the selectivity were observed by
comparing the homogenous
1
and
2
with the heterogeneous X1 and X2 precursors under identical
as catalyst was
conditions. The hydrogenation reaction under the above conditions using complex
1
finished within one hour, as seen in Figure 10a, while xerogel X1 under the same condition takes ~ 12
hours to react to 95% conversion, as evident in Figure 10b. The GC-conversion of the hydrogenation
process was plotted vs. reaction time in minutes as illustrated in Figure 10.

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Figure 10. Hydrogenation reaction of trans-4-phenyl-3-butene-2-al using complex
xerogel X1 catalysts under the above mild conditions.
1 and
105
105
a)
b)
90
75
60
45
30
15
0
90
75
60
45
30
15
0
0
10
20
30
40
50
60
70
0
150
300
450
600
Time (min.)
750
Time (min.)
3. Experimental
3.1. General
All reactions were carried out in an inert atmosphere (argon) by using standard high vacuum and
Schlenk-line techniques, unless otherwise noted. Prior to use CH2Cl2, -hexane, and Et2O were
n
distilled from CaH2, LiAlH4, and from sodium/benzophenone, respectively, ether-phosphine ligand,
Cl2Ru(P∩O)2 and Cl2Ru(PPh3)2 were prepared according to literature methods [9–13]. [3-(2-
aminoethyl)aminopropyl]trimethoxysilane and tetramethoxysilyl were purchased from Acros.
1
Elemental analyses were carried out on an Elementar Vario EL analyzer. High-resolution liquid H-,
13C{1H}-, DEPT 135, and 31P{1H}-NMR spectra were recorded on a Bruker DRX 250 spectrometer at
1
13
31
298 K. Frequencies are as follows: H-NMR: 250.12 MHz, C{1H}-NMR: 62.9 MHz, and P{1H}-
NMR 101.25 MHz. Chemical shifts in the H- and C{1H- NMR spectra were measured relative to
1
13
31
partially deuterated solvent peaks which are reported relative to TMS. P-NMR chemical shifts were
measured relative to 85% H3PO4. CP/MAS solid-state NMR spectra were recorded on Bruker DSX
200 (4.7 T) and Bruker ASX 300 (7.05 T) multinuclear spectrometers equipped with wide-bore
31
magnets. Magic angel spinning was applied at 4 kHz (29Si) and 10 kHz (13C, P) using (4 mm ZrO2
rotors). Frequencies and standards: 31P, 81.961 MHz (4.7 T), 121.442 MHz (7.05 T) [85% H3PO4,
NH4H2PO4 (
carbonyl resonance of glycine (
δ
= 0.8) as second standard]; 13C, 50.228 MHz (4.7 T), 75.432 MHz (7.05 T) [TMS,
δ
= 176.05) as second standard]; 29Si, 39.73 MHz (4.7 T), 59.595 MHz
(7.05 T, (Q8M8 as second standard). All samples were prepared with exclusion of molecular oxygen. .
IR data were obtained on a Bruker IFS 48 FT-IR spectrometer. Mass spectra: EI-MS, Finnigan TSQ70
(200 °C) and FAB-MS, Finnigan 711A (8 kV), modified by AMD and reported as mass/charge (m/z).
The analyses of the hydrogenation experiments were performed on a GC 6000 Vega Gas 2 (Carlo Erba
Instrument) with a FID and capillary column PS 255 [10 m, carrier gas, He (40 kPa), integrator 3390 A

Molecules 2010
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4665
(Hewlett Packard)]. The EXAFS measurements were performed at the ruthenium K–edge (22118 eV)
at the beam line X1.1 of the Hamburger Synchrotronstrahlungslabor (HASYLAB) at DESY Hamburg,
under ambient conditions, energy 4.5 GeV, and initial beam current 120 mA. For harmonic rejection,
the second crystal of the Si(311) double crystal monochromator was tilted to 30%. Data were collected
in transmission mode with the ion chambers flushed with argon. The energy was calibrated with a
ruthenium metal foil of 20
polyethylene.
µm thickness. The samples were prepared of a mixture of the samples and
3.2. General procedure for the preparation of the complex 1 and
2
Diamine (0.23 mmol, 5% excess) was dissolved in dichloromethane (5 mL), the solution was added
dropwise to a stirred solution of Cl2Ru(P∩O)2 and Cl2Ru(PPh3)3 (0.22 mmol) in dichloromethane
(10 mL) within 2 min. The mixture was stirred for ca. 2 h at room temperature while the color changed
from brown to yellow, then the volume of the solution was concentrated to about 2 mL under reduced
pressure. Addition of diethyl ether (40 mL) caused the precipitation of a solid which was filtered (P4),
then dissolved again in dichloromethane (40 mL) and concentrated again under vacuum to a volume of
5 mL. Addition of n-hexane (80 mL) caused the precipitation of a solid which was filtered (P4), well
washed with
pure form in very good yields. m.p. > 340 °C (dec.). Complex 1: H-NMR (CDCl3):
2H, CH2Si), 0.57 (m, 2H, SiCH2CH2), 1.45 (br, 2H, SiCH2CH2CH2N), 2.02 (m, 2H, CH2NCH2CH2N),
2.34 (m, 2H, CH2N H2CH2N), 2.44 (br, 4H, PCH2), 2.88, 2.92 (2s, 6H, CH3OCH2), 3.08 (m, 4H,
CH2O), 3.48 (br, 9H, CH3OSi), 3.55 (s, 3H, NH2), 6.90–7.90 (m, 20H, C6H5); 31P{1H}-NMR (CDCl3):
(ppm) 35.64, 38.87, dd, AB pattern with (ppm) 6.67 (s, C,
pp = 35.6 Hz, 13C{1H}-NMR (CDCl3):
CH2Si), 21.11 (s, SiCH2CH2 ), 26.12, 27.03 (2m, 2C, PCH2), 43.82 (s, C, HNCH2CH2NH2), 48.43 (s,
n
-hexane each and dried under vacuum. Complex
1
1
and
2
were obtained in analytically
δ
(ppm) 0.11 (m,
C
δ
J
δ
C, HNCH2CH2NH2), 50.32 (s, 3C, SiOCH3), 55.45 (s, C, SiCH2CH2CH2NH), 57.93, 58.01 (2s, 2C,
OCH3), 69.31, 69.40 (2s, 2C, OCH2), 127.20-134.0 (m, 24C, C6H5); FAB–MS; (m/z): 882.2 (M+);
Yield 92% related to Ru(II); Anal. Calc. C, 51.70; H, 6.39; Cl, 8.03; N, 3.17; for
C38H56Cl2N2O5P2RuSi: Found C, 51.55; H, 6.24; Cl, 8.23; N, 3.54 %. Complex 2: 1H-NMR (CDCl3):
δ
(ppm) 0.12 (m, 2H, CH2Si), 0.82 (m, 2H, SiCH2CH2), 1.32 (br, 2H, SiCH2CH2CH2N), 2.41 (m, 2H,
CH2NCH2CH2N), 2.81 (m, 2H, CH2N H2CH2N), 3.29 (s, 3H, NH2), 3.46 (br, 9H, CH3OSi), 6.90-7.60
(m, 30H, C6H5); 31P{1H}-NMR (CDCl3):
(ppm) 39.9 , 44.1 dd, AB pattern with pp = 31.6 Hz,
13C{1H}-NMR (CDCl3):
(ppm) 6.69 (s, C, CH2Si), 21.82 (s, SiCH2CH2 ), 43.01 (s, C,
HNCH2CH2NH2), 49.17 (s, C, HN H2CH2NH2), 50.86 (s, 3C, SiOCH3), 54.92 (s, C,
C
δ
J
δ
C
SiCH2CH2CH2NH), 127.20-135.60 (3m, 36C, C6H5); FAB–MS; (m/z): 918.1 (M+); Yield 83% related
to Ru(II); Anal. Calc. C, 57.25; H, 7.01; Cl, 7.59; N, 3.08; for C48H58Cl2N2O3P2RuSi: Found C, 57.51;
H, 5.70; Cl, 7.72; N, 3.05%.
3.3. General procedure for sol–gel processing of xerogels X1 and X2
Complexes
1 and 2 (0.100 mmol) and Si(OEt)4 (1 mmol,10 equivalents) in THF (5 mL) were mixed
together. The sol–gel took place when a methanol/water mixture (2 mL, 1:1 v/v) was added to the
solution. After 24 h stirring at room temperature, the precipitated gel was washed with toluene and
diethyl ether (30 mL of each), and petroleum ether (20 mL). Finally the xerogel was ground and dried

Molecules 2010
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4666
under vacuum for 24 h to afford after workup ~ 300 mg [yield ~45% based on Ru(II)] of a pale yellow
powder were collected.
31
13
Xerogel X1: P-CP/MAS-NMR:
NMR: (ppm) 5.44 (br, 1C, CH2Si), 20.65 (m, 1C,
NH2CH2CH2NH), 48.32 (br, 1C, NH2CH2), 55.72 (s, 1C, NH
δ
= 35.64, 38.87, dd, AB pattern with Jpp = 35.6 Hz; C-CP/MAS
H2CH2Si), 27.25 (m, 2C, PCH2), 43,87 (br, 1C,
H2CH2CH2), 57.21 (br, 2C, OCH3),
δ
C
C
69.77 (br, 2C, OCH2), 120.00-140.00 (m, 24C, C6H5); 29Si CP/MAS NMR:
ppm (T2), -101.8 ppm (Q3), -109.3 ppm (Q4).
δ
= –67.2 ppm (T3), –57.4
13
Xerogel X2: 31P-CP/MAS-NMR:
6.68 (br, 1C, CH2Si), 22.12 (m, 1C,
NH2CH2), 54.82 (s, 1C, NH
H2CH2CH2), 120.00-140.00 (m, 36C, C6H5); 29Si CP/MAS NMR:
= –69.1 ppm (T3), –56.8 ppm (T2), -101.2 ppm (Q3), -109.5 ppm (Q4).
δ
= 39.9 , 44.1 ppm. dd, Jpp =31.6 Hz; C-CP/MAS NMR:
δ
(ppm)
C
H2CH2Si), 42.31 (s, 1C, NH2CH2CH2NH), 48.44 (br, 1C,
C
δ
4. Conclusions
Four new diamine/phosphine/ruthenium(II) complexes were prepared. Complexes
1
and 2 were
prepared by ligand exchange and hemilable cleavage methods, respectively. The presence of T-silyl
functions on the diamine co-ligand backbone enabled the hybridization of these complexes in order to
support them on a polysiloxane matrix through the sol-gel technique in order to produce xerogels X1
and X2. The structural behaviors of the phosphine ligands in the desired complexes during synthesis
31
were monitored by P{1H}-NMR. The structure of complexes
1 and 2 described herein have been
deduced from elemental analyses, infrared, FAB-MS and H-, 13C-, H, and 31P-NMR spectroscopy
data. The xerogel structuresof X1 and X2 were determined by solid state 13C-, 29Si- and 31P-NMR
spectroscopy, infrared spectroscopy and EXAFS. When these complexes were tested as catalysts for
the hydrogenation of trans-4-phenyl-3-butene-2-al in both homogenous and heterogeneous phases, they
showed a high degree of stability and activity as well as an excellent degree of carbonyl hydrogenation
selectivity under mild conditions.
1
Acknowledgements
The author would like to thank Sabic Company for its financial support through project no. SCI-30-
14, 2010.
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Sample Availability: Samples of the compounds are available from the author.
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