Synthesis, spectral, thermal, X-ray single crystal of new RuCl 2(dppb)diamine complexes and their application in hydrogenation of Cinnamic aldehyde

Article abstract of DOI:10.1016/j.saa.2012.03.089

The preparation of new three trans-[RuCl₂(dppb)(N-N)] with mixed diamine (N-N) and 1,4-bis-(diphenylphosphino)butane (dppb) ligands, starting from RuCl₂(PPh₃)₃ as precursor is presented. The complexes are charac

Full text of DOI:10.1016/j.saa.2012.03.089

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 374–381
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Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
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Synthesis, spectral, thermal, X-ray single crystal of new RuCl2(dppb)diamine
complexes and their application in hydrogenation of Cinnamic aldehyde
a
b
a
c
Ismail Warad a, , Hanan Al-Hussain , Rawhi Al-Far , Refaat Mahfouz , Belkheir Hammouti ,
⇑
Taibi Ben Hadda d
a Department of Chemistry, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
b Department of Applied Sciences, Faculty of Applied Sciences and I.T., Al-Balqa’ Applied University, Salt 19117, Jordan
c LCAE-URAC18, Faculté des Sciences, Université Mohammed Ier, B.P. 717, Oujda 60000, Morocco
d Laboratoire de Chimie Matériaux, FSO, Université Mohammed Ier, Oujda 60000, Morocco
a r t i c l e i n f o
a b s t r a c t
Article history:
The preparation of new three trans-[RuCl2(dppb)(N–N)] with mixed diamine (N–N) and 1,4-bis-(diphen-
ylphosphino)butane (dppb) ligands, starting from RuCl2(PPh3)3 as precursor is presented. The complexes
are characterized on the basis of elemental analysis, IR, 1H, 13C and 31P{1H}NMR, FAB-MS, TG/DTA and
single crystal X-ray diffraction studies. Complex (2L1) crystallizes in the monoclinic unit cells with the
space group P21. The catalysts are evaluated for their Cinnamic aldehyde hydrogenation. The catalysts
show excellent activity and selectivity for the unsaturated carbonyl compound under mild conditions.
Ó 2012 Elsevier B.V. All rights reserved.
Received 9 February 2012
Received in revised form 14 March 2012
Accepted 25 March 2012
Available online 12 April 2012
Keywords:
Ru(II) complexes
Diamines
Diphosphine
Crystal structure
Catalytic hydrogenation
Introduction
due to their remarkable performance as hydrogen transfer catalysts
[8,9] and asymmetric hydrogenation of unsaturated carbonyl com-
Over the years, phosphine ligands have played a very important
role in the design and development of metal complexes-mediated
catalysis [1–8]. Among them, diphosphines have received much atten-
tion because of their tendency to form more stable complexes than
their non chelating phosphine analogs under the harsh reaction condi-
tions required for catalysis [9–13]. Moreover the chelate diphosphine
ligands decreased the number of isomers compared to monodentate
phosphine ligands which de-complicated the structural identification
of synthesized complexes [5–10]. Due to the presence of phosphine
atoms in the backbone of the coordinated ligands, structural and flux-
ional behaviors of such complexes during reaction processes can be
easy monitored by 31P{1H} NMR [14]. Although structural and dy-
namic behaviors of transition metal complexes containing monoden-
tate and bidentate ligands have been often investigated in the last few
years, it still remains an active area of research interest [15,16]. In re-
cent years, many ruthenium/diphosphine complexes have been syn-
thesized and characterized for their applications in the field of
electrocatalysis, photolysis, bioinorganic chemistry, and asymmetrical
catalytic hydrogenation [17–19]. Mixed diamine(phosphine)ruthe-
nium(II) complexes have received much attention in recent years
pounds [5,6,10]. Exchange of the monodentate phosphine such as tri-
phenylphosphine (PPh3) or ether-phosphine (P–O) ligands and the
bidentate phphosphine such as 1,3-bis-diphenylphosphinepropane
(dppp) or 1,1-bis(diphenyl-phosphinomethyl)ethene, (dppme) li-
gands on ruthenium(II) complexes by several types of diamine ligands
to synthesize diamines/diphosphine/ruthenium(II) complexes is cur-
rently one of our ongoing line of investigations [7–9,14,20,21]. In con-
tinuation of our ongoing interest in synthesis and characterization of a
variety of novel diamines/diphosphine/ruthenium(II) complexes and
their applications [7–9]. Herein, we synthesized and characterized
RuCl2(dppb)diamine complexes obtained from 1,4-bis(diphenylphos-
phino)butane and various aliphatic diamines viz., 1,3-diamnopropane
2-methyl-1,2-ethanediamine, and 1,4-diaminobutane. Complexes of
this type proved to be highly selective and effective catalyst in the
hydrogenation of carbonyl group of the Cinnamic aldehyde under mild
conditions.
Experimental
General remarks, materials and physical measurements
⇑
All reactions were carried out in an inert atmosphere (argon)
by using standard high vacuum and Schlenk-line techniques.
Corresponding author. Tel./fax: +966 1 4675992.
E-mail address: warad@ksu.edu.sa (I. Warad).
1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.03.089

I. Warad et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 374–381
375
1,4-bis(diphenylphophino)butane (dppb), 1,4-diaminobutane, 1,3-
diamninopropane and 2-methyldiaminoethane were available
from Merck and used as received. RuCl2(PPh3)3 were previously
prepared in our lab [22]. Elemental analyses were carried out on
an Elementar Varrio EL analyzer. High-resolution 1H, 13C{1H}, DEPT
135, and 31P{1H} NMR spectra were recorded on a Bruker DRX 250
spectrometer at 298 K. FT-IR and FAB-MS data were obtained on a
Bruker IFS 48 FT-IR spectrometer and Finnigan 711A (8 kV), modi-
fied by AMD and reported as mass/charge (m/z), respectively. The
analyses of the hydrogenation experiments were performed on a
GC 6000 Vega Gas 2 (Carlo Erba Instrument) with a FID and capil-
lary columns PS 255 [10 m, carrier gas, He (40 k Pa), integrator
3390 A (Hewlett–Packard)].
Found: C, 55.46; H, 5.60; N, 4.27; Cl, 10.64. Calc. for
C31H38Cl2N2P2Ru: C, 55.42; H, 5.69; N, 4.16; Cl, 10.56%.
2L2: Complex 1 (0.25 g, 0.26 mmol) was treated with dppb li-
gand (0.11 g, 0.27 mmol), then (0.02 g, 0.27 mmol) of L2 diamine li-
gand was added to give 2L2. Yield (95%), yellow powder, mp.
3
296 °C. 1H NMR (CDCl3): o (ppm) 0.91 (d, JHH = 6.02 Hz, 3H,
CH3), 1.78 (m, 4H, PCH2CH2), 2.44-2.68 (3b, 10H, PCH2, NH2,
NCH2), 3.14, (m, 1H, NCH), 7.22-7.7.55 (2 m, 20H –C6H5).
31P{1H}NMR (CDCl3): o (ppm) 46.87, 2.04 (AB Pattern).13C{1H}NMR
(CDCl3): o(ppm) 19.20, 20.51 (2s, PCH2CH2), 20.54 (s, CH3), 25.71,
26.18 (2 m, PCH2),, 49.66 (s, NCH2), 50.96 (s, NCH), 127.97 (m, m-
C6H5), 129.11 (s, p-C6H5), 133.09 (m, o-C6H5), 136.56 (m, i-C6H5).
FAB-MS; (m/z) 672.1 [M+]. Anal. Found: C, 55.34; H, 5.58; N,
4.07; Cl, 10.39. Calc. for C31H38Cl2N2P2Ru: C, 55.42; H, 5.69; N,
4.16; Cl, 10.56%.
Synthesis of the RuCl2(dppb)diamine complexes 2L1–2L3
2L3: Complex 1 (0.25 g, 0.26 mmol) was treated with dppb li-
gand (0.11 g, 0.27 mmol), then (0.024 g, 0.27 mmol) of L2 diamine
ligand was added to give 2L2. Yield (55%), Yellow powder, mp.
195 °C. 1H NMR (CDCl3): o(ppm) 0.75 (m, 4H, CH2CH2N), 1.81 (m,
4H, PCH2CH2), 2.78 (b, 6H,CH2CH2N, PCH2), 3.22 (b, 10H, CH2N,
NH2), 7.19-7.60 (2 m, 20H, C6H5), 31P{1H}NMR (CDCl3): o(ppm)
47.03. 13C{1H}NMR (CDCl3): o (ppm) 19.97 (s, PCH2CH2), 26.23
(m, PCH2), 29.02 (s, NCH2CH2), 38.56 (s, NCH2), 128.20 (m, m-
C6H5), 129.27 (s, p-C6H5), 133.78 (m, o-C6H5), 136.57 (m, i-C6H5).
FAB-MS (m/z), 686.11 [M+]. Anal. Found: C, 55.88; H, 5.72; N,
4.17; Cl, 10.41. Calc. for C32H40Cl2N2P2Ru: C, 55.98; H, 5.87; N,
4.08; Cl, 10.33%.
By treating Cl2Ru(PPh3)3 with one equivalent amount of dppb li-
gand in dichloromethane and inert atmosphere the brown color
turns directly to green one due to the in situ formation of RuCl2/
PPh3/dppb precursor, this precursor served to prepare 2L1–2L3 by
treating it with the equivalent amount of 2L1–2L3 diamines
co-ligand in dichloromethane. The yellow, air sensitive mixed
[(diamine)[bis(diphenylphosphino)butane]ruthenium(II)] complex
es 2L1–2L3 were formed directly in good yields. Even in the presence
of excess of diamine ligands only the monodentate PPh3 ligands
were exchanged which facilitated and reduced the synthesized
complexes number (Scheme 1).
General procedure for the catalytic studies
General procedure for the preparation of complexes 2L1–2L3
(0.02 mmol) of respective complexes 2L1–2L3 and (0.20 mmol)
of the co-catalysts (KOH or K2CO3 and (2.0 mmol) of Cinnamic
aldehyde are placed together in a 100 mL pressure Schlenk tube.
The solid mixture was stirred and warmed during the evacuation
process, during that the Schlenk tube was filled and refilled with
argon several times to insure the inert atmosphere, 40 mL of 2-pro-
panol was added to the reaction mixture then sonicated for 10 min
to complete the dissolving. The mixture was vigorously stirred, de-
gassed by two freeze-thaw cycles, and then pressurized with dihy-
drogen of 3 bar. The reaction mixture was vigorously stirred at RT
for 1 h. During the hydrogenation process samples were taken
from the reaction mixture after the gas was removed to control
the conversion and turnover frequency. The samples were inserted
by a special glass syringe into a gas chromatograph and the kind of
the reaction products was compared with authentic samples.
The corresponding diamine (10% excess of L1–L3) was dissolved
in 10 mL of dichloromethane and the resultant solution was added
dropwise to a stirred solution of (RuCl2/PPh3/dppb) precursor in
10 mL of dichloromethane. The reaction mixture was stirred for
1 min. at room temperature under inert atmosphere resulting in
the change in color from green to light yellow. The resulting yellow
solution was concentrated by vacuum to 1 ml followed by the addi-
tion of 30 mL of diethyl ether to cause precipitation of 2L1–2L3. The
resulting precipitate was collected and re-crystallized from dichlo-
romethane/n-hexane and obtained in analytically pure form.
2L1: Complex 1 (0.25 g, 0.26 mmol) was treated with dppb li-
gand (0.11 g, 0.27 mmol), then (0.02 g, 0.27 mmol) of L1 diamine li-
gand was added to give 2L1. Yield (90%), yellow crystal, mp. 298 °C.
1H NMR (CDCl3): o (ppm) 1.82 (m, 4H, PCH2CH2), 2.88 (b,
6H,CH2CH2N, PCH2), 3.18 (b, 8H, CH2N, NH2), 7.19–7.60 (2 m,
20H, C6H5), 31P{1H}(CDCl3): o (ppm) 46.87. 13C{1H}NMR (CDCl3):o
(ppm) 22.78 (s, PCH2CH2), 26.63 (m, PCH2), 29.19 (s, NCH2CH2),
39.98 (s, NCH2), 128.23 (m, m-C6H5), 129.36 (s, p-C6H5), 133.83
(m, o-C6H5), 136.64 (m, i-C6H5). FAB-MS; (m/z) 672.1 [M+]. Anal.
X-ray structural analyses for complexes 2L1
Crystal of 2L1 was grown by slow diffusion of diethyl ether into a
solution of the complex in dichloromethane. Data were collected at
173(2) Siemens P4 diffractometer operating in the omega scan
Cl
NH2
PPh2
Cl
Ru
Cl
1
mode, using graphite monochromated Mo K
a radiation (k = 0.71
PPh3
PPh3
1- Ph2P(CH2)4PPh2 / CH2Cl2
2- Diamine/ CH2Cl2 - 3PPh3
073°A). Details of crystal data, data collection, and structure refine-
ment are given in Table 1. The structure was solved by direct meth-
ods using the Bruker SHELXS-97 programme and refined by full
matrix least-squares on F2 using the Bruker SHELXL-97 programme
[23,24].
Ph3P
Ru
PPh2
NH2
Cl
2L1-2L3
Diamines
H2N
H2N
H2N
H2N
Result and discussion
Ruthenium(II) complexes synthetic investigation
H2N
H2N
L3
The reason for choosing the C2-symmetric dppb ligand with
two equivalent P atoms was to reduce the number of possible
isomeric metal complexes, as well as the number of different
L2
L1
Scheme 1. Synthesis of new Ru(II) complexes.

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I. Warad et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 374–381
Table 1
Crystal data and structure refinement for complex 2L1.
Empirical formula
Formula weight
Temperature
C31H38Cl2N2P2Ru
672.54
173(2) K
Wavelength
Crystal system
Space group
0.71073 Å
Monoclinic
P 21
Unit cell dimensions
a = 10.0927(15) Å a = 90°
b = 10.6480(9) b = 100.630(13)°
c = 14.1523(18) Å
1494.8(3) Å3
2
c = 90°
Volume
Z
Density (calculated)
Absorption coefficient
F(000)
Crystal size
Theta range for data collection
Index ranges
Reflections collected
Independent reflections
Completeness to theta = 27.50°
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I>2/s (I)]
R indices (all data)
Absolute structure parameter
Extinction coefficient
Largest diff. peak and hole
1.494 mg/cm3
0.834 mmÀ1
692.0
0.5 Â 0.2 Â 0.2 mm3
2.29–27.50°
À13<=h<=1, À13<=k<=13, À18<=l<=18
3618
3618 [R (int) = 0.0240]
99.9%
Numerical
0.835 and 0.805
Full-matrix least-squares on F2
3618/1/344
1.049
R1 = 0.0272, wR2 = 0.0701
R1 = 0.0278, wR2 = 0.0705
0.00(1)
Fig. 1. 31P{1H} NMR spectrum of 2L1 (a) and 2L2 (b) direct dissolved in CDCl3 at RT.
0.0068(7)
0.861 and À1.175 e Å3À
substrate–catalyst arrangements and reaction pathways, when
compared with a nonsymmetrical ligand. The reaction scheme
for the synthesis of new ruthenium(II) complexes is depicted in
Scheme 1. The air-sensitive 2L1–2L3 complexes of the formula
trans-Cl2Ru(dppb)diamines with three different types of diamine
co-ligand were obtained in a very good yield by a substitution reac-
tion starting from Cl2Ru(PPh3)3 (1) with one equivalent mole of
dppb ligand followed by one equivalent mole of the corresponding
diamine co-ligands in dichloromethane. The structure of the de-
sired complexes has been deduced from elemental analysis, infra-
red spectroscopy, FAB-mass spectrometry, 1H, 13C{1H} and 31P{1H}
NMR, spectroscopy TG/DTA, additionally (2L1) was subjected to X-
ray crystallography.
The stepwise formation of these complexes was monitored by
31P{1H} spectroscopy as well as the color changes.
NMR investigations
Fig. 2. 1H NMR (ppm) spectrum of 2L2 in CDCl3 at RT.
The 31P{1H} NMR spectra of the complexes 2L1–2L3 were re-
corded in CDCl3 immediately after dissolution. It is important to
point out that in ruthenium/dppb/diamine complexes, when the
P atoms are trans to nitrogen, the 31P{1H}NMR chemical shifts oc-
cur around 45 ppm [25–27]. The 31P{1H} NMR spectra of com-
plexes with 2L1 and 2L3 showed only one signal at 46.87 and
47.03 ppm, respectively as in Fig. 1a, as expected for symmetrical
arrangements of the P atoms and would be assigned to the forma-
tion of trans-[Cl2Ru(dppb)(diamine)] complexes with C2v symme-
try, where the nitrogen atom is trans to the phosphorus atom as
in Scheme 1. In case of complex 2L2, the asymmetric diamine
causes a loss of the C2 axis which results in splitting of the 31P res-
onances into AB pattern with d (ppm) 46.45, 47.29 (AB pattern,
2JPP = 51.40 Hz). The 31P chemical shifts and the 31P–31P coupling
constants are consistent with a cis arrangement of the P atoms in
dppb (Fig. 1b).
ruthenium and their assignments are given in Section 2. Several
characteristic sets of signals are observed attributed to the dppb
and diamine ligands. The integration of the 1H resonances confirms
that the dppb to diamine ratio is in agreement with the structural
composition of trans-[Cl2Ru(dppb)diamine], 2L1–2L3 complexes.
The 1H NMR spectra of all the complexes present a set of signals
in the region 7.2–7.4 and 1.7–3.3 ppm attributed to aromatic and
aliphatic protons, respectively. Additional double signal for –CH3
protons in 2L2 complex is observed at 0.92 ppm (Fig. 2).
The 13C{1H}NMR spectra also corroborate the structure of de-
sired complexes. Characteristic 13C NMR signals due to the carbons
in diamine and dppb ligands in all the complexes appeared at their
expected positions.
135 dept 13C{1H} NMR spectra, as a typical technique to differ-
entiate the C, CH, CH2 and CH3 carbon types were investigated to
identify the structure of desired complexes, typical example of
2L1 and 2L2 complexes was recorded as in (Fig. 3).
The 1H NMR spectra of 2L1–2L3 complexes have been recorded
in CDCl3 solution to confirm the binding of the ligands to

I. Warad et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 374–381
377
Fig. 3. The 135 Dept 13C{1H} NMR spectra (ppm) corroborates the structures of 2L1 (a) and 2L1 (b).

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I. Warad et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 374–381
high-energy side at 200–280 nm have been assigned to intra-li-
gand
p⁄/n–p⁄ transitions [25–27]. As typical example absorption
p–
bands at 280, 335 and 475 nm of complex 2L1 are depicted in Fig. 4.
Mass spectra
Another strong evidence for the structural elucidation comes
from the mass spectra. The observed molecular ion peak (s) at m/
z 672.1, 672.4 and 687.5 corresponding to complexes 2L1–2L3,
respectively are consistent with the proposed molecular formula.
The FAB-MS spectrum of complex (2L1) shows (Fig. 5) a molecular
ion peak [M+] m/z = 672.1 which is corresponding to its molecular
formula [C31H38Cl2N2P2Ru]+ parent ion with 100% intensity base
peak. The other fragments appeared (Fig. 6) in the spectrum are
as m/z = 637.1 ([C31H38ClN2P2Ru]+, 40%, [M+]-Cl), 584.0
([C31H38N2P2Ru]+, 20%, [M+]-2Cl). It also shows a series of peaks
at 222.3, 243.2, 289.2, 387.2, 329.1, 335.1, 355.1, 429.1, 475.1,
548.1 and 511.1.
Fig. 4. UV–Vis spectrum of 2L1 complex.
Electronic absorption spectral studies
The electronic absorption spectra of 2L1–2L3 were acquired in
dichloromethane at room temperature. The complexes formed
very intense colored solutions and thus very low concentrations
have been used (10-4 M). Ruthenium(II) complexes usually exhibit
IR spectral investigations
intense peaks in the UV region corresponding to ligand based p–
p⁄
transitions with overlapping metal-to-ligand charge transfer
(MLCT) transitions in the visible region [25–27]. An analogous gen-
eral pattern has been observed in the electronic absorption spectra
of complexes under study. The complexes 2L1–2L3 displayed in-
tense transitions in the UV–Vis region. On the basis of its intensity
and position, the lowest energy transitions in the visible region at
The IR spectra of the complexes have been examined in compar-
ison with the spectra of the free dppb and diamine ligands. IR spec-
tra of the 2L1–2L3 in particular show main four sets of
characteristic absorptions in the range 3400–3200, 3190–3000,
2950–2820 and 270–285 cmÀ1, which can be assigned to –NH2,
Ph-CH, alkyl-CH and Ru–Cl stretching vibrations, respectively. All
the other functional group vibrations are appeared at their ex-
pected positions as in Fig. 7.
488–430 and 380–330 nm have been tentatively assigned to Md
–
p
L
p
metal to ligand charge transfer transitions (MLCT). Bands in the
⁄
Fig. 5. FAB-MS spectrum of complex 2L1.
+
+
+
Cl
Cl
.
H2N
Ru
H2N
PPh2
PPh2
PPh2
- Cl
H2N
N
PPh2
H2N
N
PPh2
PPh
.
- Cl
Ru
Ru
Ru
N
N
PPh
2 Cl
H2
PPh
H2
2 Cl
2 Cl
H2
H2
2L1
M+, m/z = 672.1
m/z = 602.1
m/z = 637.1
Fig. 6. Fragmentation path of the first three stable fragments belongs to 2L1.

I. Warad et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 374–381
379
Fig. 7. IR-KBr disk spectrum of complex 2L2.
Fig. 8. TG and DTA thermal curves of complex 2L1.
Thermal studies
plexes revealed a similar thermal behavior. Typical thermal TG
and DTA curves of 2L1 complex were given in Fig. 8. There is no
weight loss in the range 25–260 °C which indicates the absence
of coordinated or uncoordinated water molecule. Such complexes
undergo one step decomposition with weight loss experimentally
The thermal decomposition studies of the 2L1–2L3 complexes
were investigated in the 25–900 °C temperature range under open
atmosphere at a heating rate of 10 °C/min. All the 2L1–2L3 com-

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I. Warad et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 374–381
Table 3
Hydrogenation of Cinnamic aldehyde using 2L1–2L3 complexes.
Trial
Catalyst
Conversion (%)a
TOFb
Selectivity (%)a
A
B
C
1
2
3
4
5
2L1
2L2
2L3
2L3
2L1
>99
96
920
905
520
88
>99
>99
>99
>99
0
0
0
0
0
0
0
0
0
0
0
42
88c
0d
0
a
b
c
Yields and selectivities were determined by GC.
TOF: turnover frequency (molsub molÀ1 hÀ1).
cat
10 h react.
d
20 h react, K2CO3 co-catalyst was investigated instead of KOH.
The crystal data and structural refinement of 2L1 are summa-
rized in Table 1. The selected bond distances and bond angles are
given in Table 2.
The ruthenium atom is coordinated with two chlorine species in
trans form, one diamine co-ligand via the nitrogen atoms and one
dppb ligand via the phosphorus atoms in cis forms as in scheme
1. The coordination environment around the ruthenium center is
slightly distorted octahedral in nature with two Ru–N distances
of 2.199 and 2.203 Å, two Ru–Cl distances of 2.416 and 2.430 Å
and two Ru–P distances equal to 2.294 and 2.284 Å. The diamine
and diphosphine ligands are practically planar. The coordination
angle of the diamine chelate ring results in distinctly N–Ru–N an-
gle of 85.36° that departs from ideal value by up to approximately
4.6°, due to the six-membered ring chelating nature of 1,3-pro-
panediamine ligand, while the P–Ru–P angle is equal to 90.19°
with negligible deviation from ideality due to the seven-membered
ring chelating nature of the dppb ligand. The dichloro ligands are
bent away from their axial positions toward the diamine ligand
forming Cl–Ru–Cl angle of 163.82° with 16o deviation, resonating
to the steric effect of the phenyls in the phosphine ligands. In the
crystal structure there are a number of RuClÁ Á ÁHN contacts smaller
than 3.0 Å, indicating the presence of unconventional intra-hydro-
gen bonds [20,21].
Fig. 9. Labeled ORTEP diagram of 2L1 complex with thermal probability. All
hydrogen atoms were omitted for clarity.
Table 2
Selected bond lengths (Å) and angles (°) for 2L1.
Ru(1)–Cl(1)
Ru(1)–Cl(2)
Ru(1)–N(1)
Ru(1)–N(2)
Ru(1)–P(1)
Ru(1)–P(2)
2.4161(6)
2.4299(6)
2.1994(19)
2.2030(2)
2.2943(6)
2.2842(6)
163.82(2)
85.36(11)
90.19(2)
92.94(9)
177.41(7)
176.87(10)
91.51(6)
88.05(6)
85.65(7)
96.25(2)
91.57(2)
81.43(6)
81.30(7)
96.54(2)
98.26(2)
Cl(1)–Ru(1)–Cl(2)
N(1)–Ru(1)–N(2)
P(2)–Ru(1)–P(1)
N(1)–Ru(1)–P(2)
N(2)–Ru(1)–P(2)
N(1)–Ru(1)–P(1)
N(2)–Ru(1)–P(1)
N(1)–Ru(1)–Cl(1)
N(2)–Ru(1)–Cl(1)
P(2)–Ru(1)–Cl(1)
P(1)–Ru(1)–Cl(1)
N(1)–Ru(1)–Cl(2)
N(2)–Ru(1)–Cl(2)
P(2)–Ru(1)–Cl(2)
P(1)–Ru(1)–Cl(2)
Catalytic activity of complexes 2L1–2L3 in the hydrogenation of
Cinnamic aldehyde
Ruthenium complexes with the formation of [RuCl2(diphos-
phine)diamine] have been used as transfer hydrogen catalysts un-
der H2 atmosphere using strong base as co-catalyst and 2-propanol
as solvent [2–7]. To evaluate the catalytic activity of the 2L1–2L3
complexes, Cinnamic aldehyde (trans-4-phenyl-3-propene-2-al)
was selected, in order to determine the hydrogenation selectivity
and activity of the desired complexes, three different rego-selec-
tive hydrogenation reactions are expected (Scheme 2).
85%, the coordinated chlorides, diamine, dppb ligands have been
moved away from the complex in between 260 and 365 °C with
exothermic DTA peaks at 296.13 °C. The final residue was analyzed
by IR spectra and identified as ruthenium oxide (RuO).
X-ray structural analyses for complex (2L1)
The selective hydrogenation of the carbonyl group affords the
corresponding unsaturated alcohol A. Unwanted and hence of min-
or interest both the hydrogenation of the C@C double bond B, lead-
ing to the full hydrogenation of C@O and C@C bonds C. The
hydrogenation reactions using complexes 2L1–2L3 as catalysts were
carried out under identical conditions: 40 °C with a molar sub-
strate: catalyst (TON, S/C) ratio of 1000/1, under 3 bar of hydrogen
The molecular structure of the 2L1 complex has been deter-
mined by single crystal X-ray diffraction and the ORTEP diagram
is given in Fig. 9. The 2L1 is crystallized as free solvated trans-di-
chloro-cis-(dppb)-cis-(diamine)ruthenium(II) isomer with approxi-
mate C2v symmetry.
OH
O
OH
O
Ru(II) cat
H
H
H
H
+
+
A
B
C
Scheme 2. Different catalytic hydrogenation possibilities of Cinnamic aldehyde.

I. Warad et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 374–381
381
ber CCDC 781815. Copies of this information may be obtained free
of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from
the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223
336033; e-mail: deposit@ccdc.cam.ac.uk).
Acknowledgements
The project was supported by the King Saud University, Dean-
ship of Scientific Research, College of Science Research Center.
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Supplementary material
Crystallographic data have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication num-