Synthesis, structure, spectroscopic properties, electrochemistry, and DFT correlative studies of trans-[Ru(P-P)2Cl2] complexes

Article abstract of DOI:10.1016/j.poly.2013.06.024

Five trans-[Ru(P-P)₂Cl₂] complexes were prepared by reacting RuCl₂(PPh₃)₃ with P-P ligands {P-P = 3-hexyl-1,3-bis(diphenylphosphino)propane (hdppp) (1); = 1,3- bis(diphenylphosphino)propane (dppp) (2); = 1,2-bis(diphenylphosphino)ethane (dppe) (3); 1.1′-bis(diphenylphosphino)methane (dppm) (4); 1,2-bis(diphenylphosphino)ethylene (depe) (5)}. The complexes were characterized by an elemental analysis, IR, ¹H, ¹³C and ³¹P{1H}NMR, FAB-MS and TG/DTA. These Ru(II) complexes showed Ru(III)/Ru(II) quasireversible redox couple. The molecular structures of the complexes 1 and 3 were determined by X-ray crystallography, and their spectroscopic properties were studied. Another polymorph of 3 was reported in literature, the reported polymorph of 3 in this work crystallizes in P1 space group, whereas, the previously reported polymorph crystallizes in C2/c space group. The two complexes adopt a distorted trans octahedral coordination and ruthenium(II) ions are located on a crystallographic centre of symmetry. Based on the optimized structures, computational investigations were carried out in order to determine the electronic structures of the complexes. The electronic spectra of 1 and 1⁺ in dichloromethane were calculated with the use of time-dependent DFT methods, and the electronic spectra of the transitions were correlated with the molecular orbitals of the complexes.

Full text of DOI:10.1016/j.poly.2013.06.024

Polyhedron 62 (2013) 110–119
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, structure, spectroscopic properties, electrochemistry,
and DFT correlative studies of trans-[Ru(P-P)2Cl2] complexes
b,
c
d
Mousa Al-Noaimi a, , Ismail Warad , Obadah S. Abdel-Rahman , Firas F. Awwadi ,
⇑
⇑
Salim F. Haddad d, Taibi B. Hadda e
a Department of Chemistry, Hashemite University, P.O. Box 150459, Zarqa 13115, Jordan
b Department of Chemistry, AN-Najah National University, Nablus, Occupied Palestinian Territory
c Fachbereich Chemie der Universität Konstanz, Universitätstraße 10, D-78457 Konstanz, Germany
d Chemistry Department, Faculty of Science, The University of Jordan, Amman 11942, Jordan
e Laboratoire LCM, Faculty of Sciences, University Mohammed 1er, Oujda 60000, Morocco
a r t i c l e i n f o
a b s t r a c t
Article history:
Five trans-[Ru(P-P)2Cl2] complexes were prepared by reacting RuCl2(PPh3)3 with P-P ligands
{P-P = 3-hexyl-1,3-bis(diphenylphosphino)propane (hdppp) (1); = 1,3-bis(diphenylphosphino)propane
(dppp) (2); = 1,2-bis(diphenylphosphino)ethane (dppe) (3); 1.10-bis(diphenylphosphino)methane
(dppm) (4); 1,2-bis(diphenylphosphino)ethylene (depe) (5)}. The complexes were characterized by an
elemental analysis, IR, 1H, 13C and 31P{1H}NMR, FAB-MS and TG/DTA. These Ru(II) complexes showed
Ru(III)/Ru(II) quasireversible redox couple. The molecular structures of the complexes 1 and 3 were
determined by X-ray crystallography, and their spectroscopic properties were studied. Another poly-
Received 22 April 2013
Accepted 16 June 2013
Available online 27 June 2013
Keywords:
Ruthenium
Diphosphine
Electrochemistry
DFT calculation
ꢀ
morph of 3 was reported in literature, the reported polymorph of 3 in this work crystallizes in P1 space
group, whereas, the previously reported polymorph crystallizes in C2/c space group. The two complexes
adopt a distorted trans octahedral coordination and ruthenium(II) ions are located on a crystallographic
centre of symmetry. Based on the optimized structures, computational investigations were carried out in
order to determine the electronic structures of the complexes. The electronic spectra of 1 and 1+ in
dichloromethane were calculated with the use of time-dependent DFT methods, and the electronic spec-
tra of the transitions were correlated with the molecular orbitals of the complexes.
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
of five ruthenium(II) complexes with diphosphine ligands. The
trans-[Ru(P-P)2Cl2] complexes, (P-P) {P-P = (Hdppp) = 3-hexyl-1,3-
Ruthenium(II) complexes with polydentade phosphines ligands
have received much attention in the last decades due to their
application in the field of homogeneous catalysis [1,2]. Several
complexes of the general formula cis- and trans-[M(P-P)2X2]
(P-P = C2H4(PR2)2 (R = Me, Et or Ph), CH2(PPh2)2, and o-C6H4(PEt2)2;
X = halogen, SCNꢀ1, Hꢀ1, CNꢀ1) (M = Ru, Os) were prepared by
Chatt and Hayter [3,4]. These complexes, trans-[Ru(P-P)2Cl2], could
be used as starting materials to prepare bi- and pronuclear com-
plexes [5,6]. Classical procedures for the syntheses of these com-
plexes require the reflux conditions in acidic media [7] or the
aqueous solution of K2[RuCl5(H2O)] [8]. Poor yields of complexes
are obtained by these preparation procedures. For this reason, a
study of the electronic structures of such complexes is valuable
as a mean to predict their properties [9–11].
bis(diphenylphosphino)propane (1); (dppp) = 1,3-bis(diphenyl-
phosphino)propane (2); (dppe) = 1,2-bis(diphenylphosphino)eth-
ane (3) (dppe); (dppm) 1.10-bis(diphenylphosphino)methane (4);
1,2-bis(diphenylphosphino)ethylene (5)}, were prepared from the
reaction RuCl2(PPh3)3 and the corresponding P-P ligand. These
trans complexes have a poor solubility in many organic solvents.
The solubility can be improved by modification of the diphospine
backbone chelating ligand with alkyl group. Hdppp is a newly pre-
pared diphosphine ligand to improve the solubility of the trans-
[Ru(P-P)Cl2] complexes. To probe the effect of the size of chelating
ring of P-P on the electronic behavior trans-[RuCl2(P-P)2] com-
plexes. In this work, we present and discuss the spectroscopic
(IR, UV–Vis, 1HNMR and 31PNMR) and electrochemical (cyclic vol-
tammetry) behavior of 1–5, and report the X-ray structures for 1
and 3. The absorption spectrum of complex 1 and 1+ in dichloro-
methane have been modeled by time-dependent density func-
tional theory (TD-DFT) using a mixed basis set, MWB/6-31+g(d,p)
to correlate experimental findings with theoretical predictions.
In this paper, we present the synthesis, crystal, molecular,
the electronic structures, and the spectroscopic characterization
⇑
Corresponding authors.
E-mail address: manoaimi@hu.edu.jo (M. Al-Noaimi).
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2013.06.024

M. Al-Noaimi et al. / Polyhedron 62 (2013) 110–119
111
2.2.2.2. trans-[Ru(dppp)2Cl2] (2). Yield (0.86 g, 87%). UV–Vis in
2. Experimental
dichloromethane: kmax (nm) (
e
max, Mꢀ1 cmꢀ1): 475 (3.88 ꢁ 102),
375 (4.75 ꢁ 102), 350 (2.097 ꢁ 103). IR (KBr, cmꢀ1): 3166 (vPhH
)
2.1. Materials
and 2964 (vCH), 1525 (vC@C), 454(vRu–). 2.7 (m, 12 H, PCH2, PCH2),
7.01 (t, 16 H, PC6H5), 7.19 (t, 8 H, PC6H5), 7.37 (d, 16 H, PC6H5),
31P {1H}(CDCl3): d (ppm), 5.1. FAB-MS; [M+] 996.7 (m/z) Elemental
Anal. Calc. for C54H52Cl2P4Ru: C, 65.06; H, 5.26. Found: C, 65.22; H,
5.40%.
The reagents: ruthenium trichloride hydrate, 1,3-bis(diphenyl-
phosphino)propane (dppp), 1,2-bis(diphenylphosphino)ethane
(dppe), 1.10-bis(diphenylphosphino)methane (dppm); 1,2- cis-
1,2-bis(diphenylphosphino)ethylene (depe), n-Butyllithium solu-
tion 1.6 M in hexane, Diphenylphosphine, and solvents (reagent
grade) were purchased from Aldrich and were used as received,
1-chloro-2-(chloromethyl)octane was purchased from MolPort,
Tetrabutylammonium hexafluorophosphate (TBAHF), purchased
from Aldrich, was recrystallized twice from 1:1 ethanol/water
solution and then vacuum dried at 110 °C. The synthesis of
RuCl2(PPh3)3 has been previously described [6].
2.2.2.3. trans-[Ru(dppe)2Cl2] (3). Yield (0.87 g, 90%). UV–Vis in
dichloromethane: kmax (nm) (
e
max, Mꢀ1 cmꢀ1): 447 (1.70 ꢁ 102),
380 (3.4 ꢁ 102), 312 nm (2.7 ꢁ 104). IR (KBr, cm-1): 3155 (vPhH
)
and 2957 (vCH), 1517 (vC@C), 445 (v
Ru–P). 1H NMR (CDCl3): d
(ppm) 7.02–7.22 (3 m, 28 H, PC6H5), 2.73 (m, 8 H, 4 CH2), 31P
{1H}(CDCl3): d (ppm) 44.9. FAB-MS; [M+] 968.8 (m/z). Elemental
Anal. Calc. for C52H48Cl2P4Ru: C, 64.47; H, 4.99. Found: C, 64.56;
H, 4.70%.
2.2. Syntheses
2.2.2.4. trans-[Ru(dppm)2Cl2] (4). Yield. (0.77 g, 82%). UV–Vis in
max, Mꢀ1 cmꢀ1): 483 (1.95 ꢁ 102),
2.2.1. Synthesis of 2-hexyl-1,3-bis(diphenylphosphino)propane
(Hdppp) ligand
dichloromethane: kmax (nm) (
e
429 (2.8 ꢁ 102), 320 (2.4 ꢁ 103). IR (KBr, cmꢀ1): 3150 (
vPhH) and
2955 (vCH), 1525 (vC@C), 455 (v
Ru–P). 1H NMR (CDCl3): d (ppm) 4.0
The new ligand was prepared following published procedures
[12,13]. A solution of n-BuLi in n-hexane (25 mL of a 1.6 M solu-
tion, 2.56 g) was added dropwise to a solution of diphenylphos-
phine, Ph2PH (7.44 g, 40.0 mmol) in dry THF (20 ml) at ꢀ5 °C
over 5 h. The prepared red solution consisting of Ph2PLi was stirred
for 2 hours at ambient temperature. Then a solution of 1-chloro-2-
(chloromethyl)octane (3.94 g, 20.0 mmol) in dry THF (20 mL) was
added dropwise within 40 min until all the red color was disap-
peared. The reaction temperature was kept at 0 °C during the addi-
tion and the solution was stirred for another 4 h to ensure that the
reaction went to completion. To the colorless mixture, a degassed
aqueous solution saturated with NH4Cl (100 mL) was added and
the organic layer was separated. The solution was dried with Na2-
SO4 and separated from the solid residue. After the evaporation of
the volatile materials under vacuum, the crude product was dis-
tilled to yield highly viscous colorless air sensitive oil. Yield
(8.0 g, 81%). UV–Vis in dichloromethane: kmax = 237 nm. 1H NMR
(CDCl3): d (ppm), 0.7 (br, 3H, 1CH3), 1.0–2.1 (3 br, 11H, 5CH2 and
1CH), 2.4 (m, 4H, 2PCH2), 6.8–7.9 (3 m, 20H, Phs). 31P{1H} NMR
(CDCl3): d (ppm) ꢀ21.5. MS (EI): M+ 496.2 (m/z). IR (KBr, cmꢀ1):
(m, 4 H, PCH2), 7.01 (t, 16 H, PC6H5), 7.18 (t, 8 H, PC6H5), 7.41 (m,
16 H, PC6H5), 31P{1H}(CDCl3): d (ppm) ꢀ7.1. FAB-MS; [M+] 940.5
(m/z). Elemental Anal. Calc. for C50H44Cl2P4Ru: C, 63.84; H, 4.71.
Found: C, 63.56; H, 4.50%.
2.2.2.5. trans-[Ru(depe)2Cl2] (5). Yield. (0.77 g, 82%). UV–Vis in
dichloromethane: kmax (nm) (
e
max, Mꢀ1 cmꢀ1): 400 (3.96 ꢁ 102),
350 (2.54 ꢁ 103). IR (KBr, cmꢀ1): 3155 (
vPhH) and 2955 (vCH),
1517 (vC@C), 447 (vRu–P), 318 (v
Ru–Cl). 1H NMR (CDCl3): d (ppm)
6.80 (d, 4 H, PCH), 7.0–7.21 (3m, 20 H, PC6H5), 31P {1H}(CDCl3): d
(ppm) 53.7 FAB-MS; [M+] 964.7 (m/z). Elemental Anal. Calc. for C52-
H44Cl2P4Ru: C, 64.74; H, 4.60. Found: C, 64.56; H, 4.40%.
2.3. Instrumentation
1H NMR (400 MHz) and 31P NMR (162 MHz) spectra were mea-
sured on a Bruker Avance III 400 spectrometer as CDCl3 solutions at
room temperature. All chemical shifts are reported in ppm down-
field of TMS (1H) or 85% phosphoric acid (31P) and referenced using
the chemical shifts of residual solvent resonances. IR spectra were
measured by FT-IR JASCO model 420. Elemental analyses were car-
ried out on an Eurovector E.A.3000 instrument using copper sam-
ple-tubes. FAB-MS data were obtained on a Bruker IFS 48 FT-IR
spectrometer and Finnigan 711A (8 kV), modified by AMD and re-
ported as mass/charge (m/z), respectively. UV–Vis/NIR spectra
were recorded on a TIDAS fiberorptic diode array spectrometer
(combined MCS UV/NIR and PGS NIR instrumentation) from j &
m in HELLMA quartz cuvettes with 0.1 cm optical path lengths.
Electrochemical measurements were performed in dichlorometh-
ane (Aldrich, HPLC grade) using BAS CV-27. All electrochemical
experiments were done in a home-built cylindrical vacuum-tight
one-compartment cell. A spiral-shaped Pt wire and an Ag wire as
the counter and thin pseudo-reference electrodes are sealed into
glass capillaries via standard joints and fixed by Quickfit screws.
A platinum electrode is introduced as the working electrode
through the top central port via a Teflon screw cap with a suitable
3180 (
vPhH) and 2970 (vCH). 1520 (vC@C). Elemental Anal. Calc. for
C33H38P2: C, 79.81; H, 7.71. Found: C, 79.63; H, 7.65%.
2.2.2. General procedure for the syntheses of trans-[Ru(P-P)2Cl2] (1–5)
complexes
Diphosphine ligand (2.0 mmol) was dissolved in 10 mL of
dichloromethane and the solution was added dropwise to a stirred
solution of RuCl2(PPh3)3 (1.0 mmol) in 10 mL of dichloromethane.
The reaction mixture was stirred approximately for 50 min at room
temperature. The brown solution was filtered to remove the insol-
uble impurities. The solvent was reduced by a vacuum and the
product was then precipitated by adding n-hexane. The yellow so-
lid was filtered and washed three times with 20 mL of diethyl
ether.
2.2.2.1. trans-[Ru(Hdppp)2Cl2] (1). Yield (1.06 g, 91%). UV–Vis in
dichloromethane: kmax(nm) (
e
max, Mꢀ1 cmꢀ1): 465 (4.21 ꢁ 102),
fitting. It is polished with first 1 lm and then 0.25 lm diamond
365 (4.95 ꢁ 102), 340 (2.320 ꢁ 103). IR (KBr, cmꢀ1): 3160 (vPhH
)
pastes before measurements. The cell was attached to a conven-
tional Schlenk line via a side arm equipped with a Teflon screw
valve and allows experiments to be performed under argon atmo-
sphere with approximately 5 mL of analyte solution. Tetrabutyl-
ammonium hexafurophosphate (0.1 M) was twice recrystallized
and vacuum dried at 120 °C, and used as the supporting electrolyte.
The temperature was controlled (at 25.0 0.1 °C) by a Haake D8-G
and 2960 (vCH), 1520 (vC@C), 450 (v
Ru–P).1H NMR (CDCl3): d
(ppm), 0.6 (2 br, 6 H, 2 CH3), 0.7–3.1 (4 br, 22 H, 10 CH2 and 2
CH), 2.9 (m,
8
H,
4
PCH2), 6.5 ꢀ7.8 (4 m, 20 H, PC6H5).
31P{1H}(CDCl3): d (ppm) 2.2. FAB-MS: M+ 1165.3 (m/z). Elemental
Anal. Calc. for C66H76Cl2P4Ru: C, 68.71; H, 7.61. Found: C, 68.83;
H, 7.41%.

112
M. Al-Noaimi et al. / Polyhedron 62 (2013) 110–119
refrigerator. Referencing was done with an addition of one crystal
of decamethylferrocene (Cp⁄2Fe) as an internal standard to the
analyte solution after all data of interest had been acquired. Repre-
sentative sets of scans were repeated with the added standard. Fi-
nal referencing was done against the ferrocene/ferrocenium
Molecular graphics and publication material were generated using
SHELXTL package.
The structure for complex 1 was solved by direct methods as
P2(1)/n and refined by least squares on F2 to R1 = 0.0503 [I P 2
r(I)]
with h = 2.02° to 27.50°. Goodness-of-fit on F2 = 1.021. All nonhy-
drogen atoms were refined anisotropically except the six C atoms
in the central part of the 2-methyloctane bridging moiety. The
thermal parameters for these atoms are very high and anisotropic
refinement generates some short bond distances. The hydrogen
atoms, other than H14 and H63, were positioned constrained and
assigned isotropic thermal parameters of 1.2 times that of the rid-
ing atoms. (1.5 times for methyl hydrogen atoms). H14 and H63
were located in a difference Fourier map and refined fully, for
otherwise the data did not converge. Largest diffraction peak and
hole were 1.865 and ꢀ0.73 e Åꢀ3. There are two independent half
molecules in the asymmetric unit, one containing Ru1 and the
other Ru2. ORTEP diagram [19] showing the numbering scheme
are for the Ru1 molecule (Fig. 1).
(Cp2Fe0/+) couple with E Cp⁄2Fe0/+ = ꢀ542 mV versus Cp2Fe0/
½
+[14,15]. Spectroelectrochemistry of a representative complex 1
was performed by using an optically transparent thin layer electro-
chemistry (OTTLE) cell [16]. OTTLE cell was home-built and com-
prises a Pt working and counter electrode and a thin silver wire
as a pseudo-reference electrode sandwiched between two CaF2
windows of a conventional liquid IR cell. The working electrode
is positioned in the center of the spectrometer beam. The potential
was controlled by the same BAS CV-27 that was used for cyclic vol-
tammetry. At any given potential, the system was allowed to come
to equilibrium (i ꢂ0 A) before the spectrum was taken.
ꢀ
2.4. X-ray crystallography
The structure for complex 3 was solved by direct methods as P1
and refined by least squares on F2 to R1 = 0.0503 [I P 2
r(I)] with
Crystals were grown by a slow diffusion of diethyl ether into a
solution of the complex in dichloromethane. Suitable yellow pris-
matic crystal of complexes 1 and 3 were mounted with epoxy on
glass fiber and the data collected at room temperature employing
Mo radiation, k = 0.71073 Å and Bruker P4 diffractometer. For com-
plex 1 cell measurements were based on 36 reflections between
theta 4.5° and 15.0°, while for complex 3 on 66 reflections between
h = 2.10–27.50°. Goodness-of-fit on F2 = 1.027. All nonhydrogen
atoms were refined anisotropically. The hydrogen atoms were lo-
cated on the calculated positions using riding model and assigned
isotropic thermal parameters of 1.2 times that of the riding atoms
except methyl hydrogen atoms (1.5 times). The H atoms on C of the
dichloromethane solvent were not locatable in a difference Fourier
map, nor was it possible to position them due to the proximity of
the C atom of the solvent, with 0.5 occupancy, at x, y, z with the
symmetry related one at 1 ꢀ x, 1 ꢀ y, ꢀz. Largest differaction peak
and hole are 0.996 and ꢀ1.111 e Åꢀ3. Fig. 2 is an ORTEP diagram
showing the numbering scheme in the molecular unit made from
two inversions related asymmetric units. Selected bond distances
and angles for both complexes 1 and 3 are listed in Table 2.
4.8° and 12.7°. Data was collected by
x scans. Two standard reflec-
tions recorded after each 98 counts showed no decay. Data collec-
tion and empirical absorption correction were performed by
XSCANS [17] and data reduction by SHELXTL [18]. SHELXS [18] was
used for structure solution and SHELXL [18] for structure refinement.
Details of data collection and refinement are given in Table 1.
Table 1
Crystal data and structure refinement for complex 1 and 3.
Complex
1
3
Empirical formula
Formula weight
T (K)
C
66H76Cl2P4Ru
C53H50Cl4P4Ru1
1053.68
298(2)
1165.12
293(2)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
0.71073
monoclinic
P2(1)/n
0.71073
triclinic
ꢀ
P1
13.909(2)
22.443(3)
18.705(2)
90
91.095(11)
90
5837.9(13)
4
1.326
10.0823(12)
10.4860(9)
13.0002(13)
68.263(9)
70.648(13)
88.262(14)
1197.8(2)
1
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (Mg/m3)
1.461
0.721
540
Absorption coefficient (mmꢀ1
F(000)
)
0.510
2440
Crystal size (mm3)
h (°)
0. 0.6 ꢁ 0.4 ꢁ 0.4
0.3 ꢁ 0.3 ꢁ 0.2
2.02–27.50
2.10–27.50
Index ranges
Reflections collected
ꢀ1 6 h 6 18, ꢀ29 6 k 6 1, ꢀ24 6 l 6 24
15755
ꢀ13 6 h 6 13, ꢀ12 6 k 6 12, ꢀ16 6 l 6 16
10734
Independent reflections (Rint
)
13368 (0.0214)
5368 (0.0210)
Completeness to theta = 27.50° (%)
Maximum and minimum transmission
Refinement method
99.8
97.5
0.3437 and 0.3163
full-matrix least-squares on F2
13368/0/612
0.5339 and 0.4951
full-matrix least-squares on F2
5368/2/287
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
1.021
1.027
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0503, wR2 = 0.1284
R1 = 0.0645, wR2 = 0.1383
1.865 and ꢀ0.731
R1 = 0.0333, wR2 = 0.0893
R1 = 0.0364, wR2 = 0.0922
0.996 and ꢀ1.111
Largest difference in peak and hole (e Åꢀ3
)
P
P
P
|Fo|; wR2 = { [ w(Fo ꢀ Fc2)2]/ [w(Fo2)2]}1/2
.
2
R1
=
||Fo| ꢀ |Fc||/
R

M. Al-Noaimi et al. / Polyhedron 62 (2013) 110–119
113
Fig. 1. Thermal ellipsoid drawing (30%) of complex 1.
2.5. Computational methods
3. Results and discussion
Full geometry optimization of 1 was carried out using density
functional theory (DFT) at the B3LYP level [20]. All calculations
were carried out using the GAUSSIAN 03 program package [21] with
the aid of the GaussView visualization program [22]. For C, H, Cl
and P the 6-31G(d) basis set were assigned, while for Ru, the
MWB basis set with effective core potential were employed [23].
Vertical electronic excitations based on B3LYP optimized
geometries were computed using the time-dependent density
functional theory (TD-DFT) formalism [24–27] in dichloromethane
using conductor-like polarizable continuum model (CPCM) [25].
Gauss Sum was used to calculate the fractional contributions of
various groups to each molecular orbital [28].
3.1. Synthesis
The reaction scheme for the synthesis of ruthenium (II) com-
plexes is depicted in Scheme 1. The yellow complexes of the for-
mula trans-[Ru(P-P)2Cl2] (1–5) were obtained in a good yield by a
substitution reaction of starting complex Ru(PPh)3Cl2 with two
equivalent mole of P-P ligands in dichloromethane. For complex
1, both up-up and up-down of the alkyl chain on the propyl of
the Hdppp ligand can give two possible isomers. 1H, 31P n.m.r.
spectra and X-ray structure confirm that there is only one product.
thus we suggest that this complex is a more stable up-down alkyl
chain isomer.
The structure of the desired complexes has been deduced from
elemental analysis, infrared spectroscopy, FAB-mass spectrometry,
1H, and 31P n.m.r. spectra, TG/DTA spectroscopy. Additionally, the
crystal structures of the complexes 1 and 3 were determined by
X-ray crystallography. The 1H NMR spectra of complexes 1–5 have
been recorded in CDCl3 solution to confirm the binding of the li-
gands to ruthenium and their assignments are given in Section 2.1.
The 1H NMR spectra of all the complexes present a set of signals in
the region 7.0–7.2 and 1.7–3.3 ppm attributed to aromatic and ali-
phatic protons, respectively. The integration of the 1H resonances
confirms that the P-P ratio is in agreement with the structural
composition of trans-[Ru(P-P)2Cl2] (1–5) complexes.
The 31P n.m.r. spectra of these complexes (in CDCl3) show one
resonance; the obvious implication is that the four P atoms of each
P-P are equivalent and the complexes are in octahedral geomety
with trans-chloro ligands and non-exchanging phosphorus nuclei
[29]. There are significant differences in the phosphorus chemical
shifts between the complexes trans-[Ru(P-P)2Cl2] (1–5), which
contains a five-membered chelate ring (complexes 3 and 5), and
those based on four (complex 4) and six-membered chelate rings
(complexes 1 and 2). In the four-membered chelate complex the
phosphorus resonates at lowest field, whereas the resonances of
five-membered rings are observed at highest field (Table 3). The
signals of six-membered rings (1–2) are positioned in between
these two extremes, with that of slightly at higher field compared
to that of four-member ring. Table 3 shows the Millikan charge for
the phosphorus atom in addition the shift of the 31P n.m.r. Millikan
charges for phosphorus atom can be obtained from the DFT theo-
retical calculation (vide infra) and can be used as an indication
Fig. 2. Thermal ellipsoid drawing (30%) of complex 3, solvent dichlormethane
remove for clarity.

114
M. Al-Noaimi et al. / Polyhedron 62 (2013) 110–119
Table 2
Selected bond length (Å) and bond angles (°) for complex 1 and 3.
Complex 1
Complex 3
Molecule (Ru1)
Bond angles (°) (experimental, optimized)
Molecule (Ru2)
Bond lengths (Å)
Bond lengths (Å)
Ru(1)–P(1A)
Ru(1)–P(1)
Ru(1)–P(2)
Ru(1)–P(2A)
Ru(1)–Cl(1A)
Ru(1)–Cl(1)
2.4182(9), 2.45159
2.4182(9), 2.45104
2.4212(8), 2.47365
2.4212(8), 2.48146
2.4377(8), 2.22869
2.4377(8), 2.23117
Ru(2)–P(3)
Ru(2)–P(3A)
Ru(2)–P(4A)
Ru(2)–P(4)
Ru(2)–Cl(2)
Ru(2)–Cl(2A)
2.4224(8)
2.4224(8)
2.4303(8)
2.4303(8)
2.4339(8)
2.4339(8)
Ru1–P(2)
2.3597(6)
2.3597(6)
2.3889(6)
2.3889(6)
2.4288(6)
2.4288(6)
Ru1–P(2A)
Ru1–P(1A)
Ru1–P(1)
Ru1–Cl(1)
Ru1–Cl(1A)
Bond angles (°) (experimental, optimized)
Bond angles (°)
Bond angles (°)
P(2)–Ru1–P(2A)
P(2)–Ru1–P(1A)
P(2A)–Ru1–P(1A)
P(2)–Ru1–P(1)
P(2A)–Ru1–P(1)
P(1A)–Ru1–P(1)
P(2)–Ru1–Cl(1)
P(2A)–Ru1–Cl(1)
P(1A)–Ru1–Cl(1)
P(1)–Ru1–Cl(1)
P(2)–Ru1–Cl(1A)
P(2A)–Ru1–Cl(1A)
P(1A)–Ru1–Cl(1A)
P(1)–Ru1–Cl(1A)
Cl(1)–Ru1–Cl(1A)
P(1A)–Ru(1)–P(1)
P(1A)–Ru(1)–P(2)
P(1)–Ru(1)–P(2)
180.0, 178.456
P(3)–Ru(2)–P(3A)
P(3)–Ru(2)–P(4A)
P(3A)–Ru(2)–P(4A)
P(3)–Ru(2)–P(4)
180.0
180.0
94.05(3), 93.652
85.95(3), 84.659
85.95(3), 84.698
94.05(3), 95.653
180.0, 179.658
97.73(3), 96.486
82.27(3), 81.368
84.15(3), 83.659
95.85(3), 96.068
82.27(3), 81.658
97.73(3), 96.658
95.85(3), 94.859
84.15(3), 83.598
180.0, 179.258
92.99(3)
87.01(3)
87.01(3)
92.99(3)
180.0
83.93(3)
96.07(3)
97.50(3)
82.50(3)
96.07(3)
83.93(3)
82.50(3)
97.50(3)
180.0
98.00(2)
82.00(2)
82.00(2)
98.00(2)
180.0
94.92(3)
85.08(3)
82.88(2)
97.12(2)
85.08(3)
94.92(3)
97.12(2)
82.88(2)
180.00(3)
P(1A)–Ru(1)–P(2A)
P(1)–Ru(1)–P(2A)
P(2)–Ru(1)–P(2A)
P(1A)–Ru(1)–Cl(1A)
P(1)–Ru(1)–Cl(1A)
P(2)–Ru(1)–Cl(1A)
P(2A)–Ru(1)–Cl(1A)
P(1A)–Ru(1)–Cl(1)
P(1)–Ru(1)–Cl(1)
P(2)–Ru(1)–Cl(1)
P(2A)–Ru(1)–Cl(1)
Cl(1A)–Ru(1)–Cl(1)
P(3A)–Ru(2)–P(4)
P(4A)–Ru(2)–P(4)
P(3)–Ru(2)–Cl(2)
P(3A)–Ru(2)–Cl(2)
P(4A)–Ru(2)–Cl(2)
P(4)–Ru(2)–Cl(2)
P(3)–Ru(2)–Cl(2A)
P(3A)–Ru(2)–Cl(2A)
P(4A)–Ru(2)–Cl(2A)
P(4)–Ru(2)–Cl(2A)
Cl(2)–Ru(2)–Cl(2A)
for the shielding and the power of the
r
-donation of the phospho-
tungsten [30,31]. The double bond between the two P-P atoms in
the five-membered ring (depe) makes the phosphorus atoms more
deshielded compared to dppe and appears at 53.8 ppm for 5. A
similar effect has been observed in the series [Pd(S2CNEt2)(P-P)]+
[32], trans-[RuCl2(P-P)2] [7] and fac-[RuCl3(NO)(P-P)] [33].
Further strong evidence for the structural elucidation comes
from FAB-MS spectra. For example, complex 1 shows a molecular
ion peak [M+] m/z = 1165.3 which is corresponding to its molecular
formula [C66H76Cl2P4Ru]+ parent ion. The other fragments ap-
peared in the spectrum are as m/z = 667 for ([C33H38P2Cl2Ru]+
and m/z = 597 [C33H38P2Ru]+.
rus atom. The calculated negative charges on the ruthenium and
positive charges in phosphorus atoms which are obtained from
natural population analysis are shown in Table 3. The negative
charge on ruthenium is a result from the charge donation from
the P-P and chloride ligands to the metal center. Also, the more
positively charged phosphorus atom the more deshielded it is. So
the phosphorous atoms of complex 4 with a four-membered ring
is shielded more than six and five-membered rings. Similar data
are to hand for complexes of Pd chromium, molybdenum and
The thermal decomposition studies of the 1-5 complexes were
investigated in the 25–800 °C temperature range under open
atmosphere at a heating rate of 10 °C/min. All the 1–5 complexes
undergo one step decomposition with weight loss experimentally
86%, the coordinated chlorides, and P-P ligands have been moved
away from the complex in between 260 and 400 °C with exother-
mic DTA peaks at 276.85 °C. The final residue was analyzed by IR
spectra and identified as ruthenium oxide (RuO).
Cl
P
P
P
RuCl2(PPh3)3
+
Ru
Cl
P
P
P
P-P ligand Hdppp dppp dppe dppm depe
3.2. Crystal structures
Complex
1
2
3
4
5
The ruthenium atoms in the two complexes 1, 3 (Figs. 1 and 2)
are coordinated in a distorted octahedral with two chloride and
two diphosphine (P-P) ligands are in a trans form and sited on a
crystallographic centre of inversion. The asymmetric unit of 1 con-
sisted of two halves of crystallographically different molecules.
Other structures trans-[Ru(dppm)2Cl2](C1) [34] and trans-
[Ru(dppp)2Cl2] (C2) [35] have been described in literature. In all
structures the Ru–Cl distances are very similar: 2.426(1) in (Cl),
2.435(1) in (C2) and 2.426(1) in 2.436 (8) Å in the complex 1 and
2.4288 (6) for complex 3. It is noticeable that structures of all the
diphosphine complexes are symmetric, the Ru–P bond distances
are 2.354(1) in (Cl), 2.4197(9) in C2 and 2.429(1) Å in C2 while
the corresponding Ru-P bond distances are 2.3743(6) for 1 and
2.3743(6) for complex 3. As expected, the Ru–P bond distances
are directly proportionally to the length of the hydrocarbon chain
between the diphosphines, due to the steric constraints imposed
by the linkage on the conformation of the bidentate ligand.
Scheme 1.
Table 3
Cyclic Voltammetrya, Electronic spectroscopy, 31P{1H} and Millikan charge for trans-
[Ru(P-P)2Cl2](1–5).
b
Complexes (E°1/2, V)
kmax (nm)a
31P{1H}(CDCl3) Millikan charge
(Ru, P)
1
2
3
4
5
0.29
0.30
0.37
0.02
0.45
465, 425, 330 2.2
(ꢀ1.06, 0.66)
(ꢀ1.03, 0.66)
(ꢀ1.10, 0.70)
(ꢀ1.13, 0.644)
(ꢀ1.31, 0.710)
475, 375, 340 ꢀ5.1
447, 429,320
44.9
483, 429, 320 ꢀ7.1
445, 350 29.0
a
Solvent dichloromethane.
b
In volts vs. ferrocenium/ferrocene at 25 °C and scan rate of 0.1 V/s, 0.1 M TBAHF
electrolyte.

M. Al-Noaimi et al. / Polyhedron 62 (2013) 110–119
115
20 mv/s
60 mv/s
100 mv/s
200 mv/s
400 mv/s
600 mv/s
800 mv/s
1 v/s
5
μA
1 μA
0,50
0,45
0,40
0,35
0,30
in
0,25
vs Cp2Fe0/+
0,20
0,15
0,10
0,05
0,00
E
V
0,50
0,45
0,40
0,35
0,30
0,25
0,20
0,15
0,10
E in v vs. Cp2Fe0/+
Fig. 3. Cyclic voltammogram for complex 1 in dichloromethane 0.1 M TBAH at 25 °C, data reported in V vs. ferocine with scan rate of 0.1 V/s, inset shows.
A different polymorph of trans-[Ru(dppe)2Cl2] (3) was prepared
previously and was crystallized in C2/c group [36], whereas, the re-
ported polymorph in this paper is crystallized in P1 space group.
between E°1/2 values for the anodic and cathodic waves from cyclic
voltammetry. Decamethylferrocene was added as an internal stan-
dard near the end of the experiment1. The analyte potential was
referenced to a ferrocene by subtracting 0.62 V [37]. This value can
then be referenced to the NHE by adding 0.66 V [38]. As a represen-
tative example, the cyclic voltammogram for complex 1 is shown in
Fig. 3. A one electron oxidation quasi reversible wave is observed at
0.29 V versus Fc0/ꢀ. This wave is assigned to Ru(III/II) couple. This
couple was quasi reversible with an anodic to cathodic peak separa-
tion of 80 mV. This separation was generally variant at scan rates
from 20 to 1000 mV/s (inset Fig. 3).
Consequently, the less stable complex is easier to oxidize. There
are significant differences in the E°1/2 between the complexes
Ru(P-P)2Cl2, which contain a five-membered chelate ring (com-
plexes 3 and 4) and those based on six-membered chelate rings
(complexes 1 and 2). In the four-membered chelate (complex 4)
the Ru(II) oxidized at lower potential, whereas the Ru (III/II) of
five-membered rings (complex 3 and 5) are observed at a highest
potential (Table 3, Fig. 3). The Ru (III/II) of six-membered rings
(complexes 1 and 2) is positioned in between the four and five-
membered rings. Adding a double bond to the dppe ligand (com-
plex 3) to generate depe (complex 5) expected to increases the
rigidity and the electronic delocalization between the two phos-
phorous atoms. These two factors stabilize the ruthenium center
and thus increase its redox potential. A similar behaviour was ob-
served for the [Ru(Cp)(P-P)(NO2)] series, P-P = dppe, dppm or dmpe
[39] on which the ruthenium (III/II) shifted to more anodic poten-
tials when the more stable complex (P-P = dppe, dppm) is replaced
with less stable [Ru(Cp)(dmpe)(NO2)] complex [40].
ꢀ
Both phases are solvates, with disordered dichlorometane, the
ꢀ
C2/c phase was grown by a slow evaporation of CH2Cl2, while, P1
was grown by a slow diffusion of diethyl ether into a solution of
the complex in dichloromethane (vide supra). According to the den-
ꢀ
sity rule the P1 phase is the thermodynamically stable one; densi-
ties of the two polymorphs are 1.461 and 1.411 Mg/m3 for P1 and
ꢀ
C2/c phases, respectively. The difference in the asymmetric units of
the two polymorphs is minimal, excluding the dichloromethane
molecule. However, the supramolecular structure of the two poly-
morphs differs significantly. The C9–Hꢃ ꢃ ꢃCl1 non-classical hydro-
gen bonding interactions connect the molecular units to form
linear chains run parallel to a-axis. Hydrogen bonding parameters
are 2.894, 3.599 Å and 133.64° for Hꢃ ꢃ ꢃCl1, C9ꢃ ꢃ ꢃCl1 and
C9–Hꢃ ꢃ ꢃCl1, respectively. Selected bond distances and angles are
given in Table 2.
For complex 1 (Fig. 1), the Cl–Ru–Cl angle is linear and the
P–Ru–P angle of the chelate ring is 85.95(3) for Ru1 and 87.01(3)
for Ru2. The coordination angle P–Ru–P angles of the chelate ring
is 85.95(3)° for Ru1 and 87.01(3)° for Ru2 with negligible deviation
from ideality due to seven-membered dppb chelate. For both com-
plexes the plane of the phosphorus atoms are not perpendicular to
the Cl–Ru–Cl. For example, Ru1 in complex 1, the angles Cl(l)–Ru–
P(1) and Cl(l)–Ru–P(2) have two different values (97.73(3),
95.85(3)) which means that the pseudo plane made by P(l)–P(2)–
P(lA)–P(2A) is not perpendicular to the Cl–Ru–Cl axis.
In trans-[RuCl2(dppm)2] [34], the trans P–Ru–P angle is 71.4°.
This angle is well-compared with the P–Ru–P angle for the com-
plexes 1 and 3 in the present study. The P–Ru–P cone angle is
83.98°, 82.00(2)° for complexes 1 and 3, respectively. In cases of
dppm acting as a bidentate ligand coordinated to a single metal
ion, contraction of the tetrahedral angle of the methylene carbon
connecting the two phosphorus atoms occurs.
3.4. UV–Vis and spectroelectrochemical studies
UV–Vis electronic absorption spectra of all the complexes were
measured in dichloromethane. The changes in kmax values based on
a change of the phosphine ligand are tabulated in Table 3. The elec-
tronic absorption spectra of the trans-[Ru(P-P)2Cl2] (1–5) com-
plexes are very similar, all have two weak absorption bands
around 483–400 nm with a molar absorption coefficient of the or-
der of 102 Mꢀ1 cmꢀ1, and an intense high energy absorption
3.3. Electrochemistry
The electron-transfer behaviour of the complexes in dichloro-
methane solution was examined by cyclic voltammetry and the
corresponding results are summarized in Table 3. The E°1/2, values
for the reversible couples were calculated from half the difference
1
The ferrocene potential was too close to that of Ru(III/II) so decamethylferrocene
was used as the internal standard.

116
M. Al-Noaimi et al. / Polyhedron 62 (2013) 110–119
25000
20000
15000
10000
5000
0
300
350
400
450
500
550
600
Wavelength (nm)
Fig. 4. UV-Vis. spectrum for 1 in dichloromethane. Inset shows simulated absorption spectrum. (black line) based on TD-DFT calculations, compared to excitation energies
and oscillator strengths.
Table 4
around 300–290 nm. Complex 1 as a representative example
(Fig. 4) has three bands, two weak transitions around k = 547 and
375 nm and a strong transition around 326 nm.
DFT energies and composition of selected highest occupied and lowest unoccupied
molecular orbitals of complex 1 and 1+ expressed in terms of composing fragments.
Complex
MO
E(eV)
Ru
Hdppp
Cl
The electronic transitions for complex 1 in dichloromethane
have been assigned based on the DFT and TDDFT calculation. Since
the two molecules of complex 1 exhibit similar bond lengths and
angles (Table 2), and for the sake of simplicity, molecule 1 was
used for the present calculations. DFT calculation has been per-
formed for the complexes 1 and 1+. The optimized structure of this
molecule is developed using GAUSSIAN 03 analyses package. The
structural agreement has been observed from the comparison of
bond distances and angles between calculated and X-ray deter-
mined structure (Table 2). The DFT calculated values for the bond
angles were in closest agreement. The orbital energies along with
contributions from the ligands and metal are given in Table 4
which depicts selected occupied and unoccupied frontier orbitals.
Moreover, the isodensity plots for the HOMOs and LUMOs orbitals
for complex 1 are shown in Fig. 5. The HOMO and HOMOꢀ1 is con-
stituted by >70% contribution from Ru where is HOMOꢀ3 to
HOMOꢀ10 are mainly chloride in character. The LUMO is com-
posed of 48% Ru and 38% of diphosphine ligand. This large contbu-
tion from the metal d-orbital in the LUMO suggests a significant
1
L+5
L+4
L+3
L+2
L+1
L
ꢀ0.47
ꢀ0.52
ꢀ0.59
ꢀ0.67
ꢀ0.90
ꢀ1.06
ꢀ5.18
ꢀ5.22
5.91
5
0
4
0
24
48
70
70
81
2
0
0
1
0
95
100
95
100
76
38
5
0
14
25
25
0
14
19
0
H
Hꢀ1
Hꢀ2
Hꢀ3
Hꢀ4
Hꢀ5
5
19
84
78
97
ꢀ6.18
ꢀ6.2
3
2
ꢀ6.51
1+
a
MO
L+3
L+2
L+1
L
ꢀ1.16
ꢀ1.23
ꢀ2.33
ꢀ3.23
ꢀ6.86
ꢀ7.02
ꢀ7.02
ꢀ7.08
3
0
34
49
2
2
4
0
97
100
66
23
97
97
94
98
0
0
0
27
1
1
2
0
H
Hꢀ1
Hꢀ2
Hꢀ3
b MO
L+3
L+2
L+1
L
ꢀ1.23
ꢀ2.09
ꢀ2.93
ꢀ4.84
ꢀ6.87
ꢀ6.98
ꢀ7.01
ꢀ7.03
3
0
97
100
64
24
6
97
28
92
0
0
0
24
17
1
28
5
back donation [41] from the Ru(dp) ? P(dp)). LUMO+ is composed
from 24% from Ru and 76% from diphosphine ligand. LUMO+2 to
LUMO+10 are composed mainly from diphosphine ligands. The full
theoretical absorption spectra were obtained from the calculation
of the singlet excited states with TD-DFT at the B3LYP/MWB/6-
31+g(d,p) level in the dichloromethane solution. Computation of
40 excited states of complex 1 allowed the interpretation of the
experimental spectra in the 300–800 nm range (Fig. 4). The calcu-
lated energy of excitation states and transition oscillator strength
(f) are shown in Table 5. The absorption spectrum of 1 was simu-
lated using Gaussian Sum software [28] based on the obtained
TD-DFT results. Each excited state was interpolated by a Gaussian
convolution with the full width at half-maximum (fwhm) of
3000 cmꢀ1. Both the experimental UV–Vis spectrum of complex 1
36
52
77
2
44
3
H
Hꢀ1
Hꢀ2
Hꢀ3
reported in dichloromethane and its simulated absorption spec-
trum shown in Fig. 6 were in acceptable agreement. On the basis
of its intensity and position, a weak broad band at 465 nm
and 425, nm (ꢄ303 and 288 nm (calculated)) resulted from
HOMO ? LUMO+1 (96%) and HOMOꢀ2, HOMOꢀ ? LUMO thus
band is assigned to d–d t2(Ru) ? e(Ru) transition [41]. The bands

M. Al-Noaimi et al. / Polyhedron 62 (2013) 110–119
117
Fig. 5. Isodensity plots of the HOMO and LUMO orbitals of complex 1.
Table 5
Computed excitation energies (nm), electronic transition configurations and oscillator strengths (f) for the optical transitions in the visible region of complex 1 and 1+ transitions
with f P 0.006 are listed).
Complex
f
Composition
1
306.0 (4.06)
303.7 (4.09)
300.9 (4.13)
290.4 (4.28)
288.9 (4.30)
270.8 (4.59)
268.8 (4.62)
266.9 (4.66)
1056.6 (1.18)
761.4 (1.63)
726.7 (1.71)
661.7 (1.88)
605.5 (2.05)
585.4 (2.12)
457.7 (2.71)
444.9 (2.79)
433.1 (2.87)
402.6 (3.09)
395.3 (3.14)
0.0067
0.0098
0.0105
0.0154
0.0768
0.0223
0.205
0.3183
0.0052
0.0024
0.0022
0.0029
0.0034
0.0042
0.0039
0.0172
0.028
Hꢀ1 ? L+4 (98%)
H ? L+6 (96%)
Hꢀ1 ? L+6 (95%)
H ? L+8 (79%)
Hꢀ4 ? L (38%), Hꢀ3 ? L (37%)
Hꢀ4 ? L+1 (18%), Hꢀ2 ? L+2 (65%)
Hꢀ3 ? L+1 (35%), Hꢀ2 ? L+2 (32%)
Hꢀ4 ? L+1 (46%), Hꢀ3 ? L+1 (43%)
Hꢀ1(b) ? L (b) (89%)
1+
Hꢀ7(b) ? L (b) (82%)
Hꢀ11(b) ? L (b) (52%), Hꢀ8 (b) ? L (b) (33%)
Hꢀ15 (b) ? L (b) (76%)
Hꢀ19 (b) ? L (b) (30%), Hꢀ18 (b) ? L (b) (46%)
Hꢀ19 (b) ? L (b) (54%), Hꢀ18 (b) ? L (b) (36%)
Hꢀ30 (b) ? L (b) (32%), Hꢀ23 (b) ? L (b) (31%)
H (a
) ? L (a) (89%)
Hꢀ1 (
a
) ? L (a) (64%), Hꢀ24 (b) ? L (b) (11%)
0.0223
0.0884
H (b) ? L+1 (b) (81%)
Hꢀ1 (b) ? L+1 (b) (72%)
in the high-energy side at 330 (ꢄ269 and 266 nm (calculated)) nm
which is resulted from two transitions, HOMOꢀ3 ? LUMO+1
(35%), HOMOꢀ2 ? LUMO+2 (32%) and HOMOꢀ4 ? LUMO+1
(46%), HOMOꢀ3 ? LUMO+1 (43%), is assigned to ligand–ligand
were reversible having greater than 90% recovery of the starting
spectrum. Upon oxidation of 1, the weak low energy d–d transition
bands at 490–510 and 330–380 nm absorption band moving to-
wards the ultraviolet (ca. 410 and 460 nm) and increasing in inten-
sity. The intense high-energy band at 310 nm is shifted to lower
energy and appears at 340 nm and a new a broad absorption band
which appears at low energy and with an absorbance maximum at
704 nm.
charge transfer (Cl(pp) ?P(dp)) charge transfer transitions [42].
Spectroelectrochemical study for complex 1 was performed in
order to obtain the electronic absorption spectra of the complexes
in their Ru(III) oxidation state (Fig. 6). The spectral transformations

118
M. Al-Noaimi et al. / Polyhedron 62 (2013) 110–119
12000
10000
8000
6000
4000
2000
0
300
400
500
600
700
800
Wavelength(nm)
Fig. 6. Spectroelectrochemical experiment showing the absorption spectrum changes upon oxidation of a Dichloromethane solution of complex 1 and 0.1 M TBAH.
Theoretical calculations were performed on 1+; the calculations
utilize both and b occupied molecular orbitals. Relative percent-
ages of atomic contributions to the lowest unoccupied and highest
occupied molecular orbitals have been placed in Table 4. The
Ruthenium (III) contributes to the HOMOs and in the range from
NMR is also related to Millikan charge for phosphorus atom which
can be obtained from the dft theoretical calculation. Also, the more
positively charged phosphorus atom the more deshielded it is. The
absorption spectra of 1 and 1+ in dichloromethane were calculated
with use of TD-DFT, and the transition characters were assigned
using basis set, MWB/6-31+g(d,p) in connection with the molecu-
lar orbitals of the complexes.
a
LUMO/+1 with
with b spin. The Hdppp ligand contributes to LUMO+1 to LUMO+18
and HOMOꢀ3 to HOMOꢀ20 with and b spin. TD-DFT calculations
a
spin and in the HOMO, HOMOꢀ2 and LUMO/+1
a
(Fig. 6) shows that the band centered at kmax = 330 nm (ꢄ395 nm
(calculated)) resulted from Hꢀ1(b) which have sizable contribu-
tions of Hdppp and chloride ion to L+1 (b) which have sizable con-
tributions of Hdppp and Ru(III). Thus this band is assigned to LLCT
(ligand to ligand charge transfer). The two bands centered at 410
and 460 nm (ꢄ433.1 and 444.9 nm (calculated)) reseluted from
Acknowledgements
Warad and M. Al-Noaimi would like to thank AN-Najah
National University and The Hashemite University, Jordan for their
research support.
the overlap of several transitions, H(
ger contribution of Hdppp to L ( ) which has a larger contribution
of Ru(III), thus this band is assigned to Hdppp (P(d )) ? Ru(III) li-
a) and H-1(a) which has a lar-
Appendix A. Supplementary material
a
p
Crystallographic data have been deposited with the Cambridge
Crystallographic Data Center, CCDC No. 782386 complex 1 and
714308 complex 3 Copies of this information may be obtained
from the director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK.
Tel.: +44 1223 762910; fax: +44 1223 336 033; e-mail: depos-
it@ccdc.cam.ac.uk or on the web http://www.ccdc.cam.ac.uk/
deposit.
gand-to-metal charge transfer (LMCT) transition. The low energy
transition around 700 nm probably assigned to Chloride
(pp) ? Ru(III) (dp) LMCT transition.
4. Conclusions
Five neutral Ru(II) complexes with the formula trans-[Ru(P-
P)2Cl2] (1–5) were prepared by reacting RuCl2(PPh3)3 with P-P.
Molecular structures of the complexes were determined by
X-ray, and the spectroscopic properties were studied. The opti-
mized structures were used for DFT calculations in order to deter-
mine the electronic properties of the complexes. The differences in
the Ru(III/II) and the shift in the 31P n.m.r. spectra are related to
Ru(P-P) chelating ring and explain based on dft calculation. In
the four-membered chelate complex the phosphorus resonates at
lowest field and oxidized at lower potential, whereas the reso-
nances of five-membered rings are observed at highest field and
oxidized at higher potential. The signals of the phosphorous and
Ru(III/II) of six-membered rings (1–2) are positioned in between
these two extremer. The shift in the E1/2 values for the trans-
[Ru(P-P)2Cl2] (1–5) are related to the stability of the diphosphine
complexes. The shielding and the chemical shift of the 31P{1H}
References
[1] C.C. Tai, J. Pitts, J.C. Linehan, A.D. Main, P. Munshi, P.G. Jessop, Inorg. Chem. 41
(2002) 1606.
[2] (a) I. Warad, E. Lindner, K. Eichele, H.A. Mayor, Inorg. Chim. Acta 357 (2004)
1847;
(b) E. Lindner, I. Warad, K. Eichele, H.A. Mayor, Inorg. Chim. Acta 350 (2003)
49;
(c) E. Lindner, H.A. Mayor, I. Warad, K. Eichele, J. Organomet. Chem. 665 (2003)
176.
[3] J. Chatt, R.G. Hayter, J. Chem. Soc. (1961) 896.
[4] J. Chatt, R.G. Hayter, J. Chem. Soc. (1961) 2605.
[5] (a) J.N. Anderson, N.J. Brookes, B.J. Coe, S.J. Coles, M.E. Light, M.B. Hursthouse,
Acta Crystallogr., Sect. C 59 (2003) m215;
(b) S. Rigaut, J. Perruchon, L. Le Pichon, D. Touchard, P.H. Dixneuf, J.
Organomet. Chem. 670 (2003) 37.
[6] T.A. Stephenson, G. Wilkinson, J. Inorg. Nucl. Chem. 28 (1966) 945.
[7] J.C. Briggs, C.A. McAuliffe, J. Chem. Soc., Dalton Trans. (1984) 423.
[8] M.M.T. Khan, R. Mohiuddin, Polyhedron 2 (1983) 1247.

M. Al-Noaimi et al. / Polyhedron 62 (2013) 110–119
119
[9] M. Al-Noaimi, M. Sunjuk, M. El-khateeb, S.F. Haddad, A. Haniyeh, Polyhedron
42 (2012) 66.
[10] M. Al-Noaimi, M.I. El-Barghouthi, O.S. Abdel-Rahman, S.F. Haddad, A.
Rewashed, Polyhedron 30 (2011) 1884.
Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M.
Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A.
Pople, GAUSSIAN 03 Revision D 01, GAUSSIAN Inc., Wallingford, CT, 2004.
[22] GaussView3.0, Gaussian, Pittsburgh, PA.
[11] M. Al-Noaimi, M. El-Barghouthi, M. El-khateeb, O. Abdel-Rahman, H. Goröls,
R.J. Crutchley, Polyhedron 27 (12) (2008) 2698.
[12] E. Lindner, A. Enderle, A. Baumann, J. Organomet. Chem. 558 (1998) 235.
[13] I. Warad, M. Azam, U. Karama, S. Al-Resayes, A. Aouissi, B. Hammouti, J. Mol.
Struct. 1002 (2011) 107.
[14] M. Krejcik, M. Danek, F. Hartl, J. Electroanal. Chem. 317 (1991) 179.
[15] C. Nataro, A.N. Campbell, M.A. Ferguson, C.D. Incarvito, A.L. Rheingold, J.
Organomet. Chem. 673 (2003) 47.
[16] T. Gennett, D.F. Milner, M.J. Weaver, J. Phys. Chem. 89 (1985) 2787.
[17] Siemens, XSCANS. Siemens Analytical X-ray Instruments Inc., Madison,
Wisconsin, USA, 1994.
[23] P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 270.
[24] R. Bauernschmitt, R. Ahlrichs, Chem. Phys. Lett. 256 (1996) 454.
[25] M.K. Casida, C. Jamorski, K.C. Casida, D.R. Salahub, J. Chem. Phys. 108 (1998)
4439.
[26] R.E. Stratmann, G.E. Scuseria, M.J. Frisch, J. Chem. Phys. 109 (1998) 8218.
[27] M. Cossi, N. Rega, G. Scalmani, V. Barone, Comput. Chem. 24 (2003) 669.
[28] N.M. O’Boyle, A.L. Tenderholt, K.M. Langner, J. Comput. Chem. 29 (2008) 839.
[29] R. Mason, D.W. Meek, G.R. Scollary, Inorg. Chim. Acta 16 (1976) L11.
[30] S.O. Grim, W.L. Briggs, R.C. Barth, C.A. Tolman, J.P. Jesson, Inorg. Chem. 13
(1974) 1095.
[31] P.E. Garrou, Inorg. Chem. 14 (1975) 1435.
[18] G.M. Sheldrick, Acta Crystallogr., Sect. A 64 (2008) 112.
[19] C.K. Johnson, ORTEPII. Report ORNL-5138, Oak Ridge National Laboratory,
Tennessee, USA, 1976.
[32] G. Exarchos, S.D. Robinson, J.W. Steed, Polyhedron 19 (2000) 1511.
[33] A.A. Batista, C. Pereira, S.L. Queiroz, L.A.A. de Oliveira, R.H.D. Santos, M.T.D.
Gambardella, Polyhedron 16 (1997) 927.
[20] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[34] A.R. Chakravarty, F.A. Cotton, W. Schwotzer, Inorg. Chim. Acta 84 (1984) 1979.
[35] M.R. Fontes, G. Oliva, L. Acácio, C. Cordeiro, A.A. Batista, J. Coord. Chem. 30
(1993) 125.
[36] T.S. Lobana, R. Singh, E.R.T. Tiekink, J. Coord. Chem. 21 (1990) 199.
[37] N. Camire, U.T. Mueller-Westerhoff, W.E. Geiger, J. Organomet. Chem. 637–639
(2001) 823.
[38] S. Lu, V.V. Strelets, M.F. Ryan, W.J. Pietro, A.B.P. Lever, Inorg. Chem. 35 (1996)
1013.
[39] B.K. Ghosh, A. Chakravorty, Coord. Chem. Rev. 95 (1989) 239.
[40] L.F. Szczepura, K.J. Takeuchi, Inorg. Chem. 29 (1990) 1772.
[41] S.I. Gorelsky, A.B.P. Lever, M. Ebadi, Coord. Chem. Rev. 230 (2002) 97.
[42] D.M. Massen, G.A. Crosby, J. Mol. Spectrosc. 25 (1968) 398.
[21] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
J.A. Montgomery, Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox,
H.P. Hratchian, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E.
Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y.
Ayala, K. Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S.
Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J.
Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L.