Synthesis, characterization, and substituent effects of mononuclear ruthenium complexes [RuCl(CO)(PMe3)3(CH{double bond, long}CH-C6H4-R-p)] (R = H, CH3, OCH3, NO2, NH2

Article abstract of DOI:10.1016/j.jorganchem.2009.01.024

A series of mononuclear ruthenium complexes [RuCl(CO)(PMe₃)₃(CH{double bond, long}CH-C₆H₄-R-p)] (R = H (2a), CH₃ (2b), OCH₃ (2c), NO₂ (2d), NH₂ (2e), NMe₂ (

Full text of DOI:10.1016/j.jorganchem.2009.01.024

Journal of Organometallic Chemistry 694 (2009) 1877–1883
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis, characterization, and substituent effects of mononuclear ruthenium
complexes [RuCl(CO)(PMe3)3(CH@CH-C6H4-R-p)]
(R = H, CH3, OCH3, NO2, NH2, NMe2)
*
*
Xianghua Wu, Tanqing Weng, Shan Jin , Jinghua Liang, Rui Guo, Guang-ao Yu, Sheng Hua Liu
Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of mononuclear ruthenium complexes [RuCl(CO)(PMe3)3(CH@CH-C6H4-R-p)] (R = H (2a), CH3
(2b), OCH3 (2c), NO2 (2d), NH2 (2e), NMe2 (2f)) has been prepared. The respective products have been
characterized by elemental analyses, NMR spectrometry, and UV–Vis spectrophotometry. The structures
of complexes 2c and 2d have been established by X-ray crystallography. Electrochemical studies have
revealed that electron-releasing substituents facilitate monometallic ruthenium complex oxidation,
Received 4 December 2008
Received in revised form 15 January 2009
Accepted 15 January 2009
Available online 22 January 2009
and the substituent parameter values (
or oxidation peak potentials of the complexes.
r) show a strong linear correlation with the anodic half-wave
Keywords:
Monometallic ruthenium complex
Redox-active
Ó 2009 Elsevier B.V. All rights reserved.
Substituent effects
Hammett
1. Introduction
studied [11–26]. For example, as model complexes to aid under-
standing of the influence of substituents on the bonding properties
In the emerging field of molecular electronics, the promise of
‘‘tuning” the electronic properties of materials has motivated
investigations into the dependence of electronic structure on the
functional groups present. For example, molecular wires exhibiting
highly variable electronic properties have been investigated [1].
Electron-transfer in these organometallic complexes can be
perturbed to different extents by electroactive end groups in
conjunction with various saturated or conjugated bridges. The
extent to which electron-transfer is perturbed is highly dependent
on the medium, the molecular topology, the nature of the metal
complexes, and various characteristics of the connecting bridge
groups.
within the metal-acetylide backbone, mononuclear metal
r-aryl-
acetylides [(
g
2-dppe)( 5-C5Me5)M(C„C)-1,4-(C6H4)X] (M = Fe or
g
Ru) have recently been reported by Paul and Bruce et al. [4]. Chen
et al. have also shown that the electronic properties of binuclear
ruthenium polyynediyl complexes largely depend on the ancillary
ligands, they found that introducing an electron-donating substitu-
ent favored intermetallic electronic communication, whereas an
electron-withdrawing substituent attenuated the intermetallic
electronic communication [5a].
In contrast, few studies have been carried out on mono- and
bimetallic complexes with oligoenediyl bridges. This is despite
the fact that many conjugated organic materials (e.g. polyacetyl-
enes, push/pull stilbenes) having only sp2-hybridized carbon
atoms in their backbones display high electrical conductivities
(up to 105 S cmꢀ1) upon doping [23] and efficient electronic cou-
pling that exceeds the performances of their oligoynediyl counter-
parts [24]. Previously, particular attention has been focused on
(CH)x-bridged bimetallic complexes [5,25,26]. In fact, the redox
processes of complexes are not dominated by the metal, but are
also influenced by the organic fragments. Recently, Winter et al. re-
ported that the redox processes of the divinylphenylene-bridged
Mono- and polynuclear metal complexes with conjugated car-
bon bridges have attracted much attention recently with regard
to their potential applications in molecular electronics [2–4].
Highly unsaturated, rigid –(C„C)n– and –(C@C)n– bridges offer
an extended p-system and have been recognized as being particu-
larly efficient in mediating electronic transfer [5–10]. In this
context, a vast number of mono- and bimetallic complexes with
polyynediyl or polyacetylene bridges have been extensively
diruthenium complexes [{(PR3)2(CO)Cl(L0)Ru}2{
l-C6H4(CH@CH)2-
1,3 or -1,4}] (R = Ph, L0 = 4-substituted pyridine; R = iPr, L0 = none)
and the corresponding mononuclear complexes of vinyl ligands
* Corresponding authors.
E-mail addresses: jinshan@mail.ccnu.edu.cn (S. Jin), chshliu@mail.ccnu.edu.cn
(S.H. Liu).
with extended
p-systems were dominated by the unsaturated
organic bridge [27].
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.01.024

1878
X. Wu et al. / Journal of Organometallic Chemistry 694 (2009) 1877–1883
Understanding and quantifying the principal factors that govern
washed with hexane, and dried under vacuum. Yield: 0.301 g, 68
%. Anal. Calc. for C19H36ClOP3Ru: C, 44.75; H, 7.12. Found: C,
electron-transfer through ruthenium complexes with vinyl
bridges, and tuning and predicting the electronic properties of
mono- and bimetallic complexes, may serve as an efficient and
economical screening tool for selecting appropriate molecular
wires to fabricate nanoscale electronic devices. However, dinuclear
systems present the added complexity of possible metal–metal
interactions across the bridging ligands, hence we have focussed
on the mononuclear complexes [27a].
In the work described herein, several mononuclear ruthenium
complexes [RuCl(CO)(PMe3)3(CH@CH-C6H4-R-p)] have been syn-
thesized. Their electrochemical properties have been investigated
by voltammetric techniques in order to study the influence of the
substituents on their electrochemical behavior, with a view to
delineating correlations between the anodic potentials of the com-
45.13; H, 6.95%. 1H NMR (400 MHz, CDCl3): d 1.38 (t, JP–H
=
3.2 Hz, 18H, PMe3), 1.47 (d, JP–H = 6.4 Hz, 9H, PMe3), 2.29 (s, 3H,
CH3), 6.53 (m, 1H, Ar-CH@), 7.06 (d, 2H, JH–H = 7.6 Hz, Ar-H), 7.24
(d, JH–H = 7.6 Hz, Ar-H), 8.02 (ddt, 1H, JH–H = 17.2 Hz, JP–H = 8.0 Hz,
JP–H = 4.0 Hz, Ru-CH@). 13C NMR (100 MHz, CDCl3): d 16.57 (t,
JP–C = 15.3 Hz, PMe3), 20.12 (d, JP–C = 20.6 Hz, PMe3), 20.89,
124.23, 128.93, 133.46, 134.39, 138.93, 164.17, 202.51 (CO). 31P
NMR (160 MHz, CDCl3): d ꢀ19.22 (t, JP–P = 21.1 Hz, PMe3), ꢀ7.41
(d, JP–P = 21.1 Hz, PMe3). IR (KBr, cmꢀ1) 1910 (CO), 1573, 1543,
1506 (C@C (aryl, vinyl)).
2.2. Preparation of complex [ RuCl(CO)(PMe3)3(CH@CH-C6H4-OCH3-
p)] (2c)
plexes and the electronic substituent parameters (r).
The synthesis is similar to 2b, with 1-ethynyl-4-methylbenzene
being replaced by 1-ethynyl-4-methoxybenzene. Yield: 0.202 g, 96
%. Anal. Calc. for C19H36ClO2P3Ru: C, 43.39; H, 6.90. Found: C,
2. Experimental
43.06; H, 7.06%. 1H NMR (400 MHz, CDCl3): d 1.39 (t, JP–H
=
All manipulations were carried out at room temperature under
a nitrogen atmosphere using standard Schlenk techniques, unless
otherwise stated. Solvents were distilled under nitrogen from
sodium benzophenone (hexane, THF) or calcium hydride (dichloro-
methane). The starting materials [RuHCl(CO)(PPh3)3] [28],
1-ethynyl-4-methoxybenzene and 4-ethynylbenzenamine [29],
1-ethynyl-4- nitrobenzene [30], 4-ethynyl-N,N-dimethylbenzen-
amine [31], and [RuCl(CO)(PMe3)3(CH@CH-C6H5)] (2a) [32] were
prepared by the procedures described in the literature procedures.
Elemental analyses (C, H, N) were performed by Vario ElIII Chnso.
1H (400 MHz), 13C (100 MHz), and 31P NMR (160 MHz) spectra
were collected on a Varian MERCURY Plus 400 spectrometer, ex-
cept for the 13C NMR (150 MHz) of complexes 2d and 2e being col-
lected on an UNITY INOVA-600 spectrometer. 1H, 13C NMR
chemical shifts are relative to TMS, and 31P NMR chemical shifts
are relative to 85% H3PO4.
3.2 Hz, 18H, PMe3), 1.47 (d, JP–H = 6.4 Hz, 9H, PMe3), 3.78 (s, 3H,
OCH3), 6.47 (m, 1H, Ar-CH@), 6.82 (d, 2H, JH–H = 8.4 Hz, Ar-H),
7.26 (d, 2H, JH–H = 8.4 Hz, Ar-H), 7.85 (ddt, 1H, JH–H = 17.2 Hz, JP–H
= 8.0 Hz, JP–H = 4.0 Hz, Ru-CH@). 13C NMR (100 MHz, CDCl3): d
16.59 (t, JP–C = 15.3 Hz, PMe3), 20.14 (d, JP–C = 20.6 Hz, PMe3),
55.25, 113.67, 125.14, 133.67, 135.15, 156.69, 161.98, 202.42
(CO). 31P NMR (160 MHz, CDCl3): d ꢀ18.85 (t, JP–P = 21.2 Hz,
PMe3), ꢀ7.25 (d, JP–P = 21.2 Hz, PMe3). IR (KBr, cmꢀ1) 1905 (CO),
1602, 1547, 1504, 1506 (C@C (aryl, vinyl)).
2.3. Preparation of complex [RuCl(CO)(PMe3)3(CH@CH-C6H4-NO2-p)]
(2d)
The synthesis is similar to 2b, with 1-ethynyl-4-methylbenzene
being replaced by 1-ethynyl-4-nitrobenzene. Yield: 0.150 g, 69 %.
Anal. Calc. for C18H33ClNO3P3Ru: C, 39.97; H, 6.15; N, 2.59. Found:
C, 40.76; H, 6.15; N, 2.59%. 1H NMR (400 MHz, CDCl3): d 1.39 (t,
JP–H = 3.2 Hz, 18H, PMe3), 1.47 (d, JP–H = 6.4 Hz, 9H, PMe3), 6.74
(m, 1H, Ar-CH@), 7.36 (d, 2H, JH–H = 8.8 Hz, Ar-H), 8.11 (d, 2H,
JH–H = 8.8 Hz, Ar-H), 8.85 (ddt, 1H, JH–H = 17.6 Hz, JP–H = 7.2 Hz,
JP–H = 3.6 Hz, Ru-CH@). 13C NMR (150 MHz, CDCl3): d 16.44 (t,
JP–C = 11.4 Hz, PMe3), 19.67 (d, JP–C = 21.8 Hz, PMe3), 124.06,
124.29, 133.34, 143.99, 146. 41, 180.99, 201.98 (CO). 31P NMR
(160 MHz, CDCl3): d ꢀ18.93 (t, JP–P = 24.0 Hz, PMe3), ꢀ7.28 (d, JP–P
= 24.0 Hz, PMe3). IR (KBr, cmꢀ1) 1916 (CO), 1583, 1536, 1500
(C@C (aryl, vinyl)).
Infrared spectra were obtained on a Nicolet AVATAR 360 FT-IR
instrument. UV–Vis spectra were obtained on a photodiode array
spectrometer (S-3100). Electrochemical measurements were per-
formed on a CHI660C potentiostat (CH Instruments Company,
USA). A three-electrode one-compartment cell was used to contain
the solution of the compound and supporting electrolyte in dry
CH2Cl2. Deaeration of the solution was achieved by argon bubbling
through the solution for about 10 min. before measurement. The li-
gand and electrolyte (Bu4NPF6) concentrations were typically
0.001 and 0.1 mol dmꢀ3, respectively. A 500
lm diameter platinum
disc working electrode, a platinum wire counter electrode, and an
Ag|Ag+ reference electrode were used. The Ag|Ag+ reference elec-
trode contained an internal solution of 0.01 mol dmꢀ3 AgNO3 in
acetonitrile and was incorporated to the cell with a salt bridge con-
taining 0.1 mol dmꢀ3 Bu4NPF6 in CH2Cl2. All electrochemical exper-
iments were carried out under ambient conditions.
2.4. Preparation of complex [RuCl(CO)(PMe3)3(CH@CH-C6H4-NH2-p)]
(2e)
The synthesis is similar to 2b, with 1-ethynyl-4-methylbenzene
being replaced by 4-ethynylbenzenamine. The product was further
purified by recrystallization in CH2Cl2 and hexane. Yield: 0.106 g,
52%. Anal. Calc. for C18H35ClNOP3Ru: C, 42.32; H, 6.91; N, 2.74.
Found: C, 42.65; H, 7.17; N, 2.43%. 1H NMR (400 MHz, CDCl3): d
1.39 (t, JP–H = 3.2 Hz, 18H, PMe3), 1.47 (d, JP–H = 6.8 Hz, 9H, PMe3),
3.51 (s, 2H, NH2), 6.41 (m, 1H, Ar-CH@), 6.65 (d, 2H, JH–H = 8.0 Hz,
2.1. Preparation of complex [RuCl(CO)(PMe3)3(CH@CH-C6H4-CH3-p)]
(2b)
To suspension of [RuHCl(CO)(PPh3)3] (0.762 g, 0.80 mmol) in
CH2Cl2 (30 mL) was slowly added a solution of 1-ethynyl-4-meth-
ylbenzene (0.116 g, 1.00 mmol) in CH2Cl2. The reaction mixture
was stirred for 30 min to give a red solution. Then a 1 M THF solu-
tion of PMe3 (8.00 mL, 8.00 mmol) was added to the red solution.
The mixture was stirred for another 15 h. The solution was filtered
through a column of Celite. The volume of the filtrate was reduced
to ca. 2 mL under vacuum. Addition of hexane (30 mL) to the resi-
due produced a yellow solid, which was collected by filtration,
Ar-H), 7.16 (d, 2H, JH–H = 8.0 Hz, Ar-H), 7.73 (ddt, 1H, JH–H
=
17.0 Hz, JP–H = 7.6 Hz, JP–H = 3.8 Hz, Ru-CH@). 13C NMR (150 MHz,
CDCl3): d 16.61 (t, JP–C = 15.0 Hz, PMe3), 20.19 (d, JP–C = 20.5 Hz,
PMe3), 115.36, 119.85, 125.23, 134.12, 143.03, 168.66, 202.52
(CO). 31P NMR (160 MHz, CDCl3): d ꢀ18.80 (t, JP–P = 21.1 Hz,
PMe3), ꢀ7.12 (d, JP–P = 21.1 Hz, PMe3). IR (KBr, cmꢀ1) 1913 (CO),
1625, 1607, 1546 (C@C (aryl, vinyl)).

X. Wu et al. / Journal of Organometallic Chemistry 694 (2009) 1877–1883
1879
Table 2
2.5. Preparation of complex [RuCl(CO)(PMe3)3(CH@CH-C6H4-NMe2-p)]
(2f)
Selected bond lengths (Å) and angles (°) for 2c and 2d.
2c (X = OCH3)
2d (X = NO2)
The synthesis is similar to 2b, with 1-ethynyl-4-methylbenzene
Selected bond lengths
being replaced by 4-ethynyl-N,N-dimethylbenzenamine.Yield:
0.180 g, 83%. Anal. Calc. for C20H39ClNOP3Ru: C, 44.57; H, 7.29; N,
2.60. Found: C, 44.85; H, 7.43; N, 2.39%. 1H NMR (400 MHz, CDCl3):
d 1.38 (t, JP–H = 3.2 Hz, 18H, PMe3), 1.47 (d, JP–H = 6.4 Hz, 9H, PMe3),
C(11)–C(12)
C(12)–C(13)
C(16)–N(1)
N(1)–O(2)
N(1)–O(3)
C(16)–O(2)
O(2)–C(19)
Ru(1)–Cl(1)
Ru(1)–P(1)
Ru(1)–P(2)
Ru(1)–P(3)
1.318(4)
1.488(4)
1.316(4)
1.482(4)
1.453(5)
1.207(5)
1.213(5)
2.91 (s, 6H, N(CH3)2), 6.46 (m, 1H, Ar-CH@), 6.71 (d, 2H, JH–H
=
1.373(4)
1.376(4)
2.4893(8)
2.4050(7)
2.3591(8)
2.3592(8)
8.8 Hz, Ar-H), 7.26 (d, 2H, JH–H = 8.8 Hz, Ar-H), 7.73 (ddt, 1H,
JH–H = 17.0 Hz, JP–H = 7.6 Hz, JP–H = 3.8 Hz, Ru-CH@). 13C NMR
(100 MHz, CDCl3): d 16.61 (t, JP–C = 15.2 Hz, PMe3), 20.21 (d,
JP–C = 20.2 Hz, PMe3), 41.04, 113.18, 125.05, 131,92, 134.14,
148.05, 158.79, 202.66 (CO). 31P NMR (160 MHz, CDCl3): d ꢀ19.28
(t, JP–P = 21.1 Hz, PMe3), ꢀ7.62 (d, JP–P = 21.1 Hz, PMe3). IR (KBr,
cmꢀ1) 1906 (CO), 1606, 1576, 1541 (C@C (aryl, vinyl)).
2.4833(9)
2.3991(8)
2.3698(10)
2.3707(9)
Selected bond angles
C(11)–C(12)–C(13)
C(12)–C(13)–C(14)
C(15)–C(16)–O(2)
C(16)–O(2)–C(19)
C(15)–(16)–N(1)
C(16)–N(1)–O(2)
C(16)–N(1)–O(3)
O(2)–N(1)–O(3)
Ru(1)–C(11)–C(12)
P(1)–Ru(1)–P(2)
P(1)–Ru(1)–P(3)
P(2)–Ru(1)–P(3)
126.0(2)
120.4(2)
125.7(2)
118.1(3)
127.0(3)
123.4(3)
2.6. X-ray crystal structure determinations for [RuCl(CO)(PMe3)3
(CH@CH-C6H4-OCH3-p)] (2c) and RuCl(CO)(PMe3)3(CH@CH-C6H4-NO2
-p)] (2d)
119.2(3)
118.5(4)
118.7(4)
122.9(4)
131.6(3)
95.13(3)
95.55(3)
167.57(3)
135.3(2)
95.57(3)
95.09(3)
167.68(3)
Crystals suitable for X-ray diffraction were grown from a dichlo-
romethane solution layered with hexane. A crystal with approxi-
mate dimensions of 0.30 ꢁ 0.20 ꢁ 0.10 mm3 for 2c and
0.23 ꢁ 0.13 ꢁ 0.10 mm3 for 2d was mounted on a glass fiber for
diffraction experiment. Intensity data were collected on a Nonius
Kappa CCD diffractometer with Mo K
a radiation (0.71073 Å) at
Table 3
298 K. The structures were solved by a combination of direct meth-
ods (SHELXS-97 [33]) and Fourier difference techniques and refined
by full-matrix least-squares (SHELXL-97 [34]). All non-H atoms were
refined anisotropically. The hydrogen atoms were placed in the
ideal positions and refined as riding atoms. Further crystal data
UV–Vis data for RuCl(CO)(PMe3)3(CH@CH-C6H4-R-p) complexes in CH2Cl2.
R
Abs, nm (10ꢀ3 , Mꢀ1 cmꢀ1
e )
H (2a)
299 (11.2)
296 (9.3)
293 (10.8)
260 (6.7), 413 (13.2)
297 (9.5)
CH3 (2b)
OCH3 (2c)
NO2 (2d)
NH2 (2e)
NMe2 (2f)
Table 1
301 (10.3)
Crystal data, date collection and refinement parameters for the crystal structures of 2c
and 2d.
Complex 2c
Complex 2d
and details of the data collection are summarized in Table 1. Se-
lected bond distances and angles are given in Tables 2 and 3,
respectively.
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
C19H36ClO2P3Ru
525.91
Monoclinic
P2(1)/n
14.5104(15)
12.9606(13)
14.5104(15)
90.00
110.58
90.00
2554.7(5)
4
1.367
C18H33ClNO3P3Ru
540.88
Monoclinic
P2(1)/n
14.3967(5)
12.8524(4)
14.7721(5)
90.00
110.858(10)
90.00
2554.19(15)
4
1.407
1112
0.71073
0.923
3. Results and discussion
b (Å)
c (Å)
a
(°)
3.1. Synthesis and characterization of [RuCl(CO)(PMe3)3(CH@CH-C6H4
-R-p)]
b (°)
c
(°)
V (Åꢀ3
)
The general synthetic route for the preparation of the mononu-
clear ruthenium complexes is outlined in Scheme 1. Treatment of
HC„C-C6H4-R-p (1) with the ruthenium hydride complex [RuHCl-
(CO)(PPh3)3] in dichloromethane gave the insertion products
[RuCl(CO)(PPh3)2(CH@CH-C6H4-R-p)], which were not isolated be-
cause they are air-sensitive, especially in solution. PMe3 was then
added to give the corresponding six-coordinated complexes 2.
These complexes were characterized by NMR. The PMe3 ligands
in 2 are meridionally coordinated to the ruthenium, as indicated
by an AM2 pattern in the 31P{1H} NMR spectrum. The 1H NMR spec-
trum (in CDCl3) of 2b showed the Ru–CH proton signal at
d = 8.02 ppm (ddt, JH–H = 17.2 Hz, JP–H = 8.0 Hz, JP–H = 4.0 Hz), this
chemical shift being similar to those in the complexes [{RuCl-
Z
Dcalcd (g cmꢀ3
F(000)
)
1088
0.71073
0.917
Radiation, Mo K
Absorption coefficient
(mmꢀ1
a
(Å)
)
h Range (°)
Reflection collected
Independent reflections
2.17–27.50
24146
5821 (0.0425)
1.70–27.50
24135
5824 (0.0478)
[R(int)
]
Data/restraints/parameters
Observed reflections
Final R indices (I > 2r(I))
5821/0/245
5824/0/253
4841 (I > 2r(I))
4380 (I > 2r(I))
R1 = 0.0357,
wR2 = 0.0969
0.0426
0.1006
1.063
R1 = 0.0426,
wR2 = 0.1035
0.0582
0.1109
1.001
R1 (observed data)
wR2 (all date)
(CO)(PMe3)3}2{l-(CH@CH)n}] (n = 2 [35], 3 [5g], 4 [5h], 5 [5d], 7
Goodness-of-fit (GOF)
Largest difference peak
[5b]), [Fc(CH@CH)3RuCl(CO)(PMe3)3] [5c], and [1,3,5-{Cl(CO)(P-
Me3)3RuCH@CH}3C6H3] [5f]. The magnitude of the J(HH)coupling
constant indicates that the two vinylic protons (Ru–CH@CH) are
in a trans geometry and that the acetylene is cis-inserted into the
0.649
0.769,
(e Åꢀ3
)
Largest difference hole
ꢀ0.379
ꢀ0.317
(e Åꢀ3
)

1880
X. Wu et al. / Journal of Organometallic Chemistry 694 (2009) 1877–1883
PMe3
R
Cl
1. RuHCl(CO)(PPh3)3
Ru
R
2. PMe3
Me3P
CO
PMe3
1
2
R = H
1a
1b
R = H
2a
CH3
CH3 2b
OCH3 2c
NO2 2d
NH2 2e
NMe2 2f
OCH3 1c
NO2 1d
NH2 1e
NMe2 1f
Scheme 1.
Ru–H bond. The 1H NMR spectra (in CDCl3) of 2c, 2d, 2e and 2f
showed the Ru–CH proton signal at d = 7.85, 8.85, 7.73, 7.73 ppm
with similar coupling constant. These features were confirmed by
the X-ray structures of 2c and 2d (Figs. 1 and 2). Similar mononu-
clear complexes [RuCl(CO)(L)(PPh3)2{(CH@CH)2C6H4-R-p}] (L =
PhPy, PMP) [36] and [OsCl(CO)(PPh3)3{(CH@CH)C6H4-R-p}] [5f]
have recently been reported.
depicted in Figs. 1 and 2, respectively, and the crystallographic de-
tails are given in Table 1. Selected bond distances and angles in 2c
and 2d are presented in Table 2. As shown in Fig. 1, the complex
contains a p-anisyl moiety linked via a trans-CH@CH group to the
ruthenium center. The structure displays an extended conforma-
tion, in which the C(11)–C(12) double bond, O(2), and the benzene
ring are nearly coplanar, with maximum deviations from the least-
squares plane of 0.0042 Å for C(12) and 0.0133 Å for O(2), respec-
tively. The coordination sphere about the ruthenium center is a
The molecular structures of 2c and 2d were determined by
X-ray crystallography. The molecular structures of 2c and 2d are
Fig. 1. Molecular structure for [RuCl(CO)(PMe3)3(CH@CH-C6H4-p-OCH3)] (2c).
Fig. 2. Molecular structure for [RuCl(CO)(PMe3)3(CH@CH-C6H4-p-NO2)] (2d).

X. Wu et al. / Journal of Organometallic Chemistry 694 (2009) 1877–1883
1881
distorted octahedron with three meridionally bound PMe3 ligands.
The vinyl group is trans to a PMe3 ligand, and the CO group is trans
to the chloride group, as suggested by the NMR data. The overall
geometry about the ruthenium center closely resembles that in
the heterobimetallic complex [Fc(CH@CH)3RuCl(CO)(PMe3)3] [5c].
The molecular structure of 2d is similar to that of complex 2c. It
is worth noting that the vinyl groups are essentially coplanar with
Cl–Ru–CO. Coplanarity of the vinyl group and CO is to be expected,
values of about 0.628, 0.556, and 0.800 V, respectively. However,
when the substituent group is a strongly electron-donating group,
mononuclear complexes 2c, 2e, and 2f undergo a quasi-reversible
one-electron oxidation at moderately positive potentials with E1/2
values of about 0.464, 0.188, and 0.084 V, respectively. As expected,
electron-releasing substituents facilitate this process, with the re-
dox potential shifting to more negative values by ca. 716 mV on
going from the nitro (2d) to the N,N-dimethylamino complex (2f).
Similar features have been observed for a series of analogous Ru(II)
due to the strong p-interactions between CO and vinyl and the me-
tal center in this conformation. The two complexes have the same
crystal system and space group, as can be seen in Table 1.
The electronic properties of this series of vinyl complexes have
been investigated by optical absorption spectroscopy. Compared
with the absorption spectrum of the unsubstituted complex 2a,
the absorption maxima of the substituted complexes 2b, 2c, 2e,
and 2f do not show significant differences. However, 2d shows a
significant bathochromic shift owing to the attachment of a strong
chromophore on benzene ring (Table 3).
complexes [(g g
2-dppe)( 5-C5Me5)Ru(C„C)-1,4-(C6H4)X], for which
a shift in redox potential of 350 mV was measured on going from
the nitro to the amino complex [4b]. As the electron-donating effect
of the ligands is increased, the [2]/[2]+ redox process changes from
irreversible to quasi-reversible, which can be rationalized in terms
of stabilization of the radical cation by the electron-rich ligand, at
least on the voltammetric time scale.
3.3. Correlation between the substituent effect and the oxidation
potential
3.2. Electrochemistry
The Hammett methodology is often criticized because of its
essentially empirical foundation, but it constitutes an interesting
way of investigating more specifically the influence of the R substi-
tuent on the various electronic properties of the complexes [RuCl-
(CO)(PMe3)3(CH@CH-C6H4-R-p)] (R = H, CH3, OCH3, NO2, NH2,
NMe2) [4b,37,38]. Therefore, we have sought linear redox potential
relationships with the electronic substituent parameters. A moder-
ately good linear correlation (R2 = 0.935, Eq. (1)) was found between
The redox behavior of the mononuclear complexes 2af (1 mM in
CH2Cl2) has been investigated by cyclic voltammetry and square-
wave voltammetry techniques with 0.1 m n-Bu4NPF6 as the sup-
porting electrolyte, and pertinent data are compiled in Table 4. All
of the complexes 2af display a one-electron wave (Table 4) in the
range 0.0840.800 V, corresponding to [2]/[2]+ oxidation. Represen-
tative voltammograms of complexes 2c and 2d are shown in Fig. 3.
Interestingly, a comparison of the voltammetric features for these
mononuclear complexes reveals an apparent dependence on the ef-
fects of the substituents on the ligands. When the substituent group
is a weakly electron-donating or electron-withdrawing group,
mononuclear complexes 2a, 2b, and 2d undergo a completely irre-
versible one-electron oxidation at high positive potentials with E1/2
the
r
valuesand theredox potentials corresponding to the[2]/[2]+ of
2af (Fig. 4a). The positive slope reflects the fact that an electron-
releasing substituent renders the [2]/[2]+ oxidation more facile.
E1=2ðIÞðVÞ ¼ 0:56 þ 0:49
r
ð1Þ
However, a much better linear correlation (R2 = 0.980, Eq. (2)) was
obtained between the redox potentials corresponding to the [2]/
Table 4
Electrochemical data for RuCl(CO)(PPh3)2(CH@CH-C6H4-R-p) complexes.a
[2]+ oxidation of 2af and Brown’s + values, which measure primar-
r
ily resonance effects and neglect inductive effects (Fig. 4b). Thus,
R
Ep (V)
E1/2 (V)
ipc/ipa
the oxidation potentials of [2]/[2]+ do not correlate so well with
H (2a)
0.674
0.610
0.512
0.856
0.231
0.134
0.628
0.556
0.464
0.800
0.188
0.084
nr.
nr.
0.57
nr.
0.52
0.65
Hammett’s
r
values, but a good correlation with Brown’s r+ values
CH3 (2b)
OCH3 (2c)
NO2 (2d)
NH2 (2e)
NMe2 (2f)
is found. This clearly indicates that the primary mode of interaction
is mainly through a resonance effect rather than an inductive effect.
With increasing electron-donating ability of the ligand, this reso-
nance has a significant stabilizing effect on [2]+, and hence the re-
dox process of the mononuclear complexes changes from an
irreversible to a quasi-reversible or reversible one-electron process.
a
Mean potential: E1/2 = (Epa + Epc)/2. All potential data were determined in CH2Cl2
containing 1 mmol dmꢀ3 compound and 0.1 mol dmꢀ3 Bu4NPF6. The Ag|Ag+ elec-
trode (internal solution: 0.01 mol dmꢀ3 AgNO3 + 0.1 mol dmꢀ3 Bu4NPF6 in aceto-
nitrile; salt bridge: 0.1 mol dmꢀ3 Bu4NPF6 in CH2Cl2) was used as a reference.
E1=2ðIÞðVÞ ¼ 0:63 þ 0:31rþ
ð2Þ
1600
a
1500
b
1200
800
1000
500
0
Me3
P
Cl
Ru
CO
400
0
Me3P
Cl
Ru
Me3
P
Me3P
Me3
OCH3
Me3
P
NO2
CO
P
2c
2d
0.25
0.50
0.75
1.00
1.25
1.50
0.00
0.25
0.50
Potential (V)
0.75
1.00
Potential (V)
Fig. 3. Cyclic voltammograms of (a) complex 2d, and (b) complex 2c in CH2Cl2/ Bu4NPF6 at
t
= 0.1 V sꢀ1. Potentials are given relative to the Ag|Ag+ standard.

1882
X. Wu et al. / Journal of Organometallic Chemistry 694 (2009) 1877–1883
(c) M.I. Bruce, K. Costuas, T. Davin, B.G. Ellis, J.-F. Halet, C. Lapinte, P.J. Low,
1.6
1.2
0.8
0.4
0.0
a
M.E. Smith, B.W. Skelton, L. Toupet, A.H. White, Organometallics 24 (2005)
3864;
(d) R.T. Farley, Q. Zheng, J.A. Gladysz, K.S. Schanze, Inorg. Chem. 47 (2008)
2955;
E1/2 (V)
(e) J. Stahl, W. Mohr, L. de Quadras, T.B. Peters, J.C. Bohling, J.M. Martín-
Alvarez, G.R. Owen, F. Hampel, J.A. Gladysz, J. Am. Chem. Soc. 129 (2007) 8282;
(f) J. Maurer, B. Sarkar, B. Schwederski, W. Kaim, R.F. Winter, S. Záliš,
Organometallics 25 (2006) 3701;
(g) Y. Fan, L.-Y. Zhang, F.-R. Dai, L.-X. Shi, Z.-N. Chen, Inorg. Chem. 47 (2008)
2811;
NO2
R2 = 0.935
H
CH3
OCH3
(h) L.-B. Gao, S.-H. Liu, L.-Y. Zhang, L.-X. Shi, Z.-N. Chen, Organometallics 25
(2006) 506.
[2] (a) K. Venkatesan, O. Blacque, T. Fox, M. Alfonso, H.W. Schmalle, H. Berke,
Organometallics 23 (2004) 1183;
NH2
NMe2
(b) S. Rigaut, J. Massue, D. Touchard, J.-L. Fillaut, S. Golhen, P.H. Dixneuf,
Angew. Chem., Int. Ed. 41 (2002) 4513.
σ
[3] (a) F. Paul, C. Lapinte, in: M. Gielen, R. Willem, B. Wrackmeyer (Eds.), Unusual
Structures and Physical Properties in Organometallic Chemistry, Wiley & Sons
Ltd., San-Francisco, 2002, pp. 219–295;
-1.0
-0.5
0.0
0.5
1.0
(b) M.I. Bruce, Coord. Chem. Rev. 166 (1997) 91.
[4] (a) F. Paul, G. da Costa, A. Bondon, N. Gauthier, S. Sinbandhit, L. Toupet, T.
Costuas, J.-F. Halet, C. Lapinte, Organometallics 26 (2007) 874;
(b) F. Paul, B.G. Ellis, M.I. Bruce, L. Toupet, T. Costuas, J.-F. Halet, C. Lapinte,
Organometallics 25 (2006) 649;
1.6
1.2
0.8
0.4
0.0
b
E1/2 (V)
(c) F. Paul, L. Toupet, J.-Y. Thepot, K. Costuas, J.-F. Halet, C. Lapinte,
Organometallics 24 (2005) 5464;
(d) F. Paul, L. Toupet, T. Roisnel, P. Hamon, C. Lapinte, C.R. Chimie 8 (2005)
1174;
(e) K. Costuas, F. Paul, L. Toupet, J.-F. Halet, C. Lapinte, Organometallics 23
(2004) 2053;
(f) J. Courmarcel, G.L. Gland, L. Toupet, F. Paul, C. Lapinte, J. Organomet. Chem.
670 (2003) 108;
(g) F. Paul, K. Costuas, I. Ledoux, S. Deveau, J. Zyss, J.-F. Halet, C. Lapinte,
Organometallics 21 (2002) 5229;
(h) R. Denis, L. Toupet, F. Paul, C. Lapinte, Organometallics 19 (2000) 4240;
(i) R. Denis, T. Weyland, F. Paul, C. Lapinte, J. Organomet. Chem. 545–546
(1997) 615.
NO2
H
CH3
OCH3
R2 = 0.980
NH2
NMe2
σ+
[5] (a) L.-B. Gao, J. Kan, Y. Fan, L.-Y. Zhang, S.-H. Liu, Z.-N. Chen, Inorg. Chem. 46
(2007) 5651;
(b) P. Yuan, X.H. Wu, G. Yu, D. Du, S.H. Liu, J. Organomet. Chem. 692 (2007)
3588;
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
(c) P. Yuan, S.H. Liu, W. Xiong, J. Yin, G. Yu, H.Y. Sung, I.D. Williams, G. Jia,
Organometallics 24 (2005) 1452;
(d) S.H. Liu, Q.Y. Hu, P. Xue, T.B. Wen, I.D. Williams, G. Jia, Organometallics 24
(2005) 769;
Fig. 4. [2]/[2]+ oxidation potentials (V) (s) vs. (a) Hammett substituent constant
), and (b) Brown substituent constant ( +) in CH2Cl2.
(r
r
(e) Q.Y. Hu, W.X. Lu, H.D. Tang, H.H.Y. Sung, T.B. Wen, I.D. Williams, G.K.L.
Wong, Z. Lin, G. Jia, Organometallics 24 (2005) 3966;
(f) H. Xia, T.B. Wen, Q.Y. Hu, X. Wang, X. Chen, L.Y. Shek, I.D. William, K.S.
Wong, G.K.L. Wong, G. Jia, Organometallics 24 (2005) 562;
(g) S.H. Liu, H. Xia, T.B. Wen, Z.Y. Zhou, G. Jia, Organometallics 22 (2003) 737;
(h) S.H. Liu, Y. Chen, K.L. Wan, T.B. Wen, Z. Zhou, M.F. Lo, I.D. Williams, G. Jia,
Organometallics 21 (2002) 4984;
(i) H.P. Xia, W.S. Ng, J.S. Ye, X.Y. Li, W.T. Wong, Z. Lin, C. Yang, G. Jia,
Organometallics 18 (1999) 4552;
(j) H.P. Xia, W.F. Wu, W.S. Ng, I.D. Williams, G. Jia, Organometallics 16 (1997)
2940.
4. Conclusions
We have reported the synthesis, characterization, and electro-
chemical properties of a series of mononuclear ruthenium com-
plexes [RuCl(CO)(PMe3)3(CH@CH-C6H4-R-p)]. Electrochemical
studies have demonstrated that electron-releasing substituents
facilitate mononuclear ruthenium complexes oxidation. As the
electron-donating effect of the ligands is increased, the one-elec-
tron redox process of [2]/[2]+ changes from irreversible to quasi-
reversible. A good linear correlation between the oxidation poten-
tials and Brown’s r+ values has been found for these Ru(II)
complexes.
[6] S. Szafert, F. Paul, W.E. Meyer, J.A. Gladysz, C. Lapinte, C.R. Chimie 11 (2008) 693.
[7] F. Paul, W.E. Meyer, L. Toupet, H. Jiao, J.A. Gladysz, C. Lapinte, J. Am. Chem. Soc.
122 (2000) 9405.
[8] C.R. Horn, J.M. Martin-Alvarez, J.A. Gladysz, Organometallics 21 (2002) 5386.
[9] S. Rigaut, C. Olivier, K. Costuas, S. Choua, O. Fadhel, J. Massue, P. Turek, J.Y.
Saillard, P.H. Dixneuf, D. Touchard, J. Am. Chem. Soc. 128 (2006) 5859.
[10] (a) M.I. Bruce, P.J. Low, K. Costuas, J.-F. Halet, S.P. Best, G.A. Heath, J. Am. Chem.
Soc. 122 (2000) 1949;
5. Supplementary material
(b) M.I. Bruce, B.C. Hall, B.D. Kelly, P.J. Low, B.W. Skelton, A.H. White, J. Chem.
Soc., Dalton Trans. (1999) 3719;
(c) M.I. Bruce, P. Hinterding, E.R.T. Tiekink, B.W. Skelton, A.H. White, J.
Organomet. Chem. 450 (1993) 209;
(d) M.I. Bruce, M. Cole, M. Gaudio, B.W. Skelton, A.H. White, J. Organomet.
Chem. 691 (2006) 4601;
(e) A.B. Antonova, M.I. Bruce, P.A. Humphrey, M. Gaudio, B.K. Nicholson, N.
Scoleri, B.W. Skelton, A.H. White, N.N. Zaitseva, J. Organomet. Chem. 691
(2006) 4696;
CCDC 709777 and 709778 contain the supplementary crystallo-
graphic data for 2d and 2c. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgement
(f) M.I. Bruce, B.G. Ellis, P.J. Low, B.W. Skelton, A.H. White, Organometallics 22
(2003) 3184;
The authors acknowledge financial support from National Nat-
ural Science Foundation of China (Nos. 20572029, 20772039,
20803027).
(g) M.I. Bruce, K. Costuas, T. Davin, B.G. Ellis, J.-F. Halet, C. Lapinte, P.J. Low, M.E.
Smith, B.W. Skelton, L. Toupet, A.H. White, Organometallics 24 (2005) 3684;
(h) M.I. Bruce, P.J. Low, F. Hartl, P.A. Humphrey, F.D. Montigny, M. Jevric, C.
Lapinte, G.J. Perkins, R.L. Roberts, B.W. Skelton, A.H. White, Organometallics 24
(2005) 5241;
(i) M.I. Bruce, K. Costuas, B.G. Ellis, J.-F. Halet, P.J. Low, B. Moubaraki, K.S. Murray,
N. Oudda, G.J. Perkins, B.W. Skelton, A.H. White, Organometallics 26 (2007)
3735.
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