Syntheses, structures and electrochemical properties of ruthenium(II/III) complexes with tetradentate Schiff base ligands

Article abstract of DOI:10.1080/00958972.2019.1566541

Three unsymmetrical tetradentate Schiff base ligands, H₂salipn, H₂salipn-Br₄ and H₂salipn-Cl₂, have been synthesized from the typical condensation reactions of treating 1,2-diaminopropane with salicylaldehyde, 3,5-dibromosalicylaldehyde and 5-chlorosalicylaldehyde, respectively. Treatment of [RuCl₂(PPh₃)₃] with one equivalent of H₂salipn or H₂salipn-Br₄ in the presence of triethylamine in tetrahydrofuran (THF) afforded the corresponding ruthenium(III) complexes [Ru^IIICl(PPh₃)(salipn)] (1) and [Ru^IIICl(PPh₃)(salipn-Br₄)] (2). Interaction of [RuHCl(CO)(PPh₃)₃] with one equivalent of H₂salipn-Cl₂ or H₂salipn-Br₄ under the same conditions led to isolation of ruthenium(II) complexes [Ru^II(CO)(PPh₃)(salalipn-Cl₂)] (3) and [Ru^II(CO)(PPh₃)(salalipn-Br₄)] (4), respectively, in which one of the imine bonds was nucleophilically attacked by hydride to result in the formation of a mixed imine-amine ligand. The molecular structures of 1?1.5CH₂Cl₂, 2, 3?0.5CH₂Cl₂ and 4 have been determined by single-crystal X-ray crystallography. The electrochemical properties of 1–4 were also investigated. Their cyclic voltammograms displayed quasi-reversible Ru(IV)/Ru(III) and Ru(III)/Ru(II) couples with E^o ranging from 0.67 to 1.05 V and 0.74 to 0.80 V vs. Ag/AgCl (0.1 M), respectively. (Figure presented.).

Full text of DOI:10.1080/00958972.2019.1566541

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Syntheses, structures and electrochemical
properties of ruthenium(II/III) complexes with
tetradentate Schiff base ligands
Jiao Ji, Xin Chen, Chang-Jiu Wang, Ai-Quan Jia & Qian-Feng Zhang
To cite this article: Jiao Ji, Xin Chen, Chang-Jiu Wang, Ai-Quan Jia & Qian-Feng
Zhang (2019): Syntheses, structures and electrochemical properties of ruthenium(II/III)
complexes with tetradentate Schiff base ligands, Journal of Coordination Chemistry, DOI:
10.1080/00958972.2019.1566541
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Syntheses, structures and electrochemical properties of ruthenium(II/III)
complexes with tetradentate Schiff base ligands
JIAO JI, XIN CHEN, CHANG-JIU WANG, AI-QUAN JIA and QIAN-FENG ZHANG*
Institute of Molecular Engineering and Applied Chemistry, Anhui University of Technology,
Ma’anshan, Anhui 243002, P R China
Three unsymmetrical tetradentate Schiff base ligands, H2salipn, H2salipn-Br4 and H2salipn-Cl2,
have been synthesized from the typical condensation reactions of treating 1,2-diaminopropane
with salicylaldehyde, 3,5-dibromosalicylaldehyde and 5-chlorosalicylaldehyde, respectively.
Treatment of [RuCl2(PPh3)3] with one equivalent of H2salipn or H2salipn-Br4 in the presence of
triethylamine in tetrahydrofuran (THF) afforded the corresponding ruthenium(III) complexes
[RuIIICl(PPh3)(salipn)] (1) and [RuIIICl(PPh3)(salipn-Br4)] (2). Interaction of [RuHCl(CO)(PPh3)3]
with one equivalent of H2salipn-Cl2 or H2salipn-Br4 under the same conditions led to isolation of
ruthenium(II) complexes [RuII(CO)(PPh3)(salalipn-Cl2)] (3) and [RuII(CO)(PPh3)(salalipn-Br4)]
(4), respectively, in which one of the imine bonds was nucleophilically attacked by hydride to
result in the formation of a mixed imine-amine ligand. The molecular structures of 11.5CH2Cl2,
2, 30.5CH2Cl2 and 4 have been determined by single-crystal X-ray crystallography. The
electrochemical properties of 1-4 were also investigated. Their cyclic voltammograms displayed
quasi-reversible Ru(IV)/Ru(III) and Ru(III)/Ru(II) couples with Eo ranging from 0.67 to 1.05 V
and ‒0.74 to ‒0.80 V vs. Ag/AgCl (0.1 M), respectively.
Keywords: Ruthenium complex; Schiff base; Salen; Synthesis; Crystal structure;
Electrochemistry
1. Introduction
In recent years, there has been considerable interest in the rational design and synthesis of Schiff
base-based transition metal complexes which can be used as homogeneous catalysts for many
organic transformations [1-3]. In this area, the ruthenium complexes containing
N2,O2-tetradentate Schiff bases have been well documented. For example, Che and coworkers
reported a series of (Schiff base)ruthenium complexes [RuII(Schiff base)(PPh3)2], prepared by
*Corresponding author. Email: zhangqf@ahut.edu.cn
1

treating [RuCl2(PPh3)3] with tetradentate H2(Schiff base) ligands in refluxing methanol solution
containing triethylamine [4]. [RuIIIBr(Nap-o-phd)(PPh3)] was obtained by reaction of
[RuIIIBr3(PPh3)2(MeOH)] with tetradentate Schiff base ligand (H2Nap-o-phd) in a 1:1 molar ratio
(H2Nap-o-phd = N,N′-bis(2-hydroxy-1-naphthaldehyde) o-phenylene diamine) [5]. Nakajima and
coworkers reported the structure of [RuIIICl(PPh3)(salcyn)] (H2salcyn = N,N′-disalicylidene-
(R,R)-1,2-cyclohexanediamine) from sequential reactions of salicylaldehyde, (R,R)-1,2-
cyclohexanediamine and [RuIICl2(PPh3)3] in the presence of triethylamine and air, which
involved the oxidation of ruthenium(II) to ruthenium(III) by air [6]. This oxidation phenomenon
was also reported by the Che, Sessoli and Ouahab research groups, who found that the
coordinated chloride of [RuIII(salen)(PPh3)(Cl)] was labile and easily underwent substitution in
the presence of Ag(I) (where salen2- = N,N-ethan-1,2-diylbis(salicylidenamine) [7-9]. The
N2,O2-tetradentate Schiff base ligands in the above results usually chelate with the ruthenium
center forming a stable co-planar RuN2O2 square. However, as shown in chart 1, when one of the
imine groups is reduced to amine, the resulting salalen ligand will not coordinate to metals
facially due to steric effects. Instead, the salalen ligand adopts a cis-β configuration in its
complexes [10]. Actually, several cis-β metal(ONNO) complexes have been prepared, such as
[Fe(OMe)(salalphen)]2 [11], Ni(salalcyn) [12], Mo(O)2(salalcyn-tBu2) [13] and
[Re(O)(PPh3)(salalphen)](PF6) [14]. Previously, we have synthesized and characterized several
ruthenium(II)/ruthenium(III) complexes with bi-, tri- or tetradentate Schiff-base ligands [15-17].
In this continuing interest, the present report explores the coordination reaction of a series of
tetradentate Schiff base ligands towards ruthenium(II) precursors. We disclose herein syntheses,
structures and electrochemical properties of a series of ruthenium(III)-salipn and ruthenium(II)-
salalipn complexes with tetradentate Schiff base ligands.
2. Experimental
2.1. General considerations
All synthetic manipulations were carried out under dry nitrogen by standard Schlenk techniques.
Solvents were purified by standard procedures and distilled prior to use. Triethylamine,
1,2-diaminopropane, salicylaldehyde, 3,5-dibromosalicylaldehyde and 5-chlorosalicylaldehyde
were purchased from Alfa Aesar Ltd. and used without purification. The N2,O2-tetradentate
Schiff bases were prepared by the condensation between 1,2-diaminopropane and according
2

salicylaldehyde in refluxing ethanol [18]. [Ru(PPh3)3Cl2] [19] and [RuHCl(CO)(PPh3)3] [20]
were prepared according to the literature methods. NMR spectra were recorded on a Bruker ALX
1
31
400 Plus spectrometer operating at 400 MHz for H and 162 MHz for P. Chemical shifts
(, ppm) were reported with reference to SiMe4 (1H) and H3PO4 (31P). Infrared spectra were
recorded on a Perkin-Elmer 16 PC FT-IR spectrophotometer with the use of pressed KBr pellets
and positive FAB mass spectra were recorded on a Finnigan TSQ 7000 spectrometer. Elemental
analyses were carried out using a Perkin-Elmer 2400 CHN analyzer. Cyclic voltammetry was
performed with a CHI 660 electrochemical analyzer. A standard three-electrode cell was used
with a glassy carbon working electrode (Ф = 3 mm), a platinum counter electrode and an
Ag/AgCl reference electrode under nitrogen atmosphere at 25 °C. Formal potentials (Eo) were
measured in CH2Cl2 solutions with 0.1 M [nBu4N]PF6 as supporting electrolyte and reported with
reference to the ferrocenium–ferrocene couple (Cp2Fe+/0, E1/2 = 0.56 V). In the –1.5 to +1.5 V
region, a potential scan rate of 100 mV s–1 was used.
2.2.
Synthesis
of
chloro-(N,N′-bis(salicylidene)-1,2-(1-methyl)ethane
diaminato)-
solvate
triphenylphosphine-ruthenium(III)
dichloromethane
[RuIIICl(PPh3)(salipn)]·1.5CH2Cl2 (1·1.5CH2Cl2)
A mixture of H2salipn (28.2 mg, 0.100 mmol) and [Ru(PPh3)3Cl2] (95.8 mg, 0.100 mmol) in
THF (30 mL) was refluxed with stirring for 6 h, during which there was a color change from
brown to dark green. The solvent was evaporated in vacuo, and the residue was washed with
diethyl ether (5 mL × 2) and hexane (5 mL × 2). Recrystallization from CH2Cl2/hexane afforded
black block crystals of 1·1.5CH2Cl2 in seven days. Yield: 33.4 mg, 55.6% (based on Ru). IR
(KBr disc, cm1): 1594 (C=N), 1314 (ArO); MS (FAB): m/z 679 [M+], 644 [M+  Cl], 417
[M+  PPh3]. Anal. Calcd. for C35H31N2O2PClRu1.5(CH2Cl2) (%): C, 54.41; H, 4.26; N, 3.48.
Found: C, 54.47; H, 4.23; N, 3.50.
2.3. Synthesis of chloro-(N,N′-bis(3,5-dibromosalicylidene)-1,2-(1-methyl)ethane diaminato)-
triphenylphosphine-ruthenium(III) [RuIIICl(PPh3)(salipn-Br4)] (2)
A mixture of H2salipn-Br4 (59.7 mg, 0.100 mmol) and [Ru(PPh3)3Cl2] (95.8 mg, 0.100 mmol) in
THF (30 mL) was refluxed with stirring for 6 h, during which there was a color change from
brown to dark red brown. The solvent was evaporated in vacuo, and the residue was washed with
3

diethyl ether (5 mL×2) and hexane (5 mL×2). Recrystallization from CH2Cl2/hexane afforded
yellow crystals of 2 in five days. Yield: 51.0 mg, 55.6% (based on Ru). IR (KBr disc, cm1):
1654 (C=N), 1261 (ArO); MS (FAB): m/z 991 [M+], 956 [M+  Cl], 729 [M+  PPh3]. Anal.
Calcd. for C35H27N2O2PBr4ClRu (%): C, 42.39; H, 2.75; N, 2.83. Found: C, 42.43; H, 2.73; N,
2.86.
2.4.
Synthesis
of
carbonyl-(4-chloro-6-(((5-chloro-2-oxybenzyl)amino)isopropyl)-
imino)methyl)phenolato)-triphenylphosphine-ruthenium(II)
dichloromethane
solvate
[RuII(CO)(PPh3)(salalipn-Cl2)]0.5CH2Cl2 (30.5CH2Cl2)
To a solution of H2salipn-Cl2 (35.2 mg, 0.100 mmol) in EtOH (15 mL) was added
RuHCl(CO)(PPh3)3 (950 mg, 0.100 mmol) in THF(15 mL), and then triethylamine (Et3N)
(10.1 mg, 0.100 mmol) was introduced. The reaction mixture was stirred for 9 h at 90 °C, during
which the color of solution changed from reddish grey to bright yellow green. After removal of
solvents in vacuo, the residue was washed with diethyl ether (5 mL×2) and hexane (5 mL×2) to
give the desired product. Recrystallization from CH2Cl2/hexane afforded yellow crystals of
1
3·0.5CH2Cl2 for X-ray diffraction in a week. Yield: 37.4 mg, 50.7% (based on Ru). H NMR
(400 MHz, CDCl3): 1.23 (d, J = 8.0 Hz, 3H, CH3), 2.50 (m, 1H, NH), 2.77-3.15 (m, 5H,
2CH2 + CH), 6.606.63 (m, 2H, Ar), 7.067.12 (m, 4H, Ar), 7.387.43 (m, 10H, PPh), 7.94-
8.05 (m, 6H, HC=N + PPh) ppm. 31P NMR (162 MHz, CDCl3): 29.43 ppm. IR (KBr disc, cm1):
1638 (C=N), 1945 (CO), 3280 (N‒H). MS (FAB): m/z 741 [M+], 713 [M+  CO], 479
[M+  PPh3]. Anal. Calcd. for C36H30N2O3PCl2Ru0.5(CH2Cl2) (%): C, 58.30; H, 4.08; N, 3.78.
Found: C, 58.34; H, 4.04; N, 3.81.
2.5. Synthesis of carbonyl-(2,4-dibromo-6-(((3,5-dibromo-2-oxybenzyl)amino)isopropyl)-
imino)methyl)phenolato)-triphenylphosphine-ruthenium(II) [RuII(CO)(PPh3)(salalipn-Br4)]
(4)
To a slurry of [RuHCl(CO)(PPh3)3] (950 mg, 0.100 mmol) in THF (15 mL) was added a solution
of H2salipn-Br4 (59.8 mg, 0.100 mmol) and Et3N (10.1 mg, 0.100 mmol) in EtOH (15 mL), and
then the mixture was heated at 90 °C with stirring 10 h, during which there was a color change
from reddish grey to bright yellow green. After removal of solvents in vacuo, the residue was
washed with diethyl ether (5 mL×2) and hexane (5 mL×2) to give the desired product, which was
4

recrystallized from CH2Cl2/hexane. Yellow block-shaped crystals of 4 were harvested in five
days. Yield: 51.2 mg, 51.8% (based on Ru). 1H NMR (400 MHz, CDCl3):  (d, J = 8.0 Hz,
3H, CH3), 2.52 (br, 1H, NH), 2.78-3.19 (m, 5H, 2CH2 + CH), 6.68 (d, J = 4.0 Hz, 1H, Ar), 7.16
(d, J = 4.0 Hz, 1H, Ar), 7.387.42 (m, 10H, PPh), 7.697.78 (m, 2H, Ar), 7.96-8.05 (m, 6H,
HC=N + PPh) ppm. 31P NMR (162 MHz, CDCl3): 31.15 ppm. IR (KBr disc, cm1): 1640 (C=N),
1947 (CO), 3287 (N‒H). MS (FAB): m/z 986 [M+], 958 [M+  CO], 724 [M+  PPh3]. Anal.
Calcd. for C36H29N2O3PBr4Ru (%): C, 43.82; H, 2.84; N, 3.78. Found: C, 43.86; H, 2.82; N,
3.82.
2.6. X-ray crystallography
A summary of crystallographic data and experimental details for 11.5CH2Cl2, 2, 30.5CH2Cl2
and 4 are summarized in table 1 and their selected bond lengths and angles are collected in
table 2 for comparison. Intensity data were collected on a Bruker SMART APEX 2000 CCD
diffractometer using graphite-monochromated Mo-Kα radiation ( = 0.71073 Å) at 296(2) K.
The collected frames were processed with SAINT [21]. The data was corrected for absorption
using SADABS [22]. Structures were solved by the direct methods and refined by full-matrix
least-squares on F2 using the SHELXTL software package [23, 24]. All non-hydrogen atoms
were refined anisotropically. The positions of all hydrogens were generated geometrically
(Csp3H = 0.96 and Csp2H = 0.93 Å) and included in the structure factor calculations with
assigned isotropic thermal parameters, but were not refined.
3. Results and discussion
As shown in scheme 1, treatment of [RuCl2(PPh3)3] with equal equiv. tetradentate Schiff base
H2Salen or H2Salen-Br4 in the presence of triethylamine in THF afforded the expected
ruthenium(III) complexes [RuIIICl(PPh3)(salipn)] (1) and [RuIIICl(PPh3)(salipn-Br4)] (2),
respectively. Two triphenylphosphine and one chlorido ligand in the starting ruthenium(II)
complex [RuCl2(PPh3)3] were replaced by the salipn-type ligand in the present reaction system,
thus, the tetradentate dianionic O2,N2-ligands bind the ruthenium center facially. Oxidation of
ruthenium(II) to ruthenium(III) by air took place during formation of 1 and 2, similar to that in
preparation of the related complexes [RuCl(PPh3)(salen)], [RuCl(PPh3)(salphen)],
[RuCl(PPh3)(salcyn)], et al. by reaction of [RuCl2(PPh3)3] and respective tetradentate Schiff
5

bases [6-9, 16, 25]. Interactions of [RuHCl(CO)(PPh3)3] with one equivalent of H2salipn-Cl2 or
H2salipn-Br4 in the presence of triethylamine led to isolation of [RuII(CO)(PPh3)(salalipn-Cl2)] (3)
and [RuII(CO)(PPh3)(salalipn-Br4)] (4), respectively, in moderate yields. One of the imine bonds
was nucleophilically attacked by hydride to result in the formation of a mixed imine-amine
ligand salalipn (see chart 1) in complexes 3 and 4, which is similar to that in our previous report
involved in reaction of [RuHCl(CO)(PPh3)3] and N,N'-disalicylidene-1,2-phenylenediamine [25].
It has been noted that this in situ ligand reduction was also observed between reactions of
[M(CO)2(PPh3)2Cl2] (M = Ru, Os) and a carbohydrate derived salen ligand, and the authors
stated that PPh3 may act as a reducing agent [26].
IR spectra of Schiff base ligands in 1-4 showed strong bands in the region of
15991654 cm1 which are characteristic of the CH=N group absorptions. The weak bands at
around 3280 cm1 in the IR spectra of 3 and 4 may be tentatively assigned to the (NH)
absorption. The CO stretching vibration modes were found at ca. 1945 cm1 in the IR spectra of
ruthenium(II) carbonyl complexes 3 and 4, similar to those in related ruthenium(II) carbonyl
triphenylphosphine complexes [27]. Complexes 1 and 2 had no NMR signals, indicating they are
1
paramagnetic species and the oxidation state of the ruthenium center is +3. In the H NMR
spectra of unsymmetrical free ligands H2salipn-Cl2 and H2salipn-Br4, there were two aldimine
(CH=N–) proton resonances at around 8.20 ppm as two singlets. The methyl protons exhibited
as a doublet at about 1.42 ppm with J = 8.0 Hz. The phenolic protons appear at 13.15 ppm for
1
H2salipn-Cl2 and 14.20 ppm for H2salipn-Br4, which could not be observed in the H NMR
spectra of 3 and 4. Some new signals appeared in the region at about 2.50 ppm that correspond to
amine NH protons. This suggests that one of the imine groups in ligands is hydrogenated during
the complex formation [28]. Moreover, the 31P{1H} NMR spectra of 3 and 4 exhibit a singlet at
 29.43 and 31.15 ppm, respectively, which are comparable to that in the starting material
[RuHCl(CO)(PPh3)3] (39.06, 29.11 ppm). The positive ion FAB mass spectra of 1-4 display the
expected peaks corresponding to the molecular ions {[M+], [M+  Cl], [M+  CO] and
[M+  PPh3] with the characteristic isotopic distribution patterns.
The structures of 11.5CH2Cl2, 2, 30.5CH2Cl2 and 4 have been established by X-ray
crystallography. The perspective views of the molecular structures of 1-4 are shown in figures
1-4, respectively, with atom numbering schemes. According to the X-ray structures the salipn
6

ligand in 11.5CH2Cl2 and salipn-Br4 ligand in 2 coordinate to ruthenium atoms in a tetradentate
mode. The two phenolic oxygen atoms and the two imine nitrogen atoms of the Schiff-base
constitute the basal plane in 11.5CH2Cl2 and 2, while the chlorine and phosphine atoms occupy
the axial positions. The ClRuP bond angles are 176.89(4) in 11.5CH2Cl2 and 176.45(14)
in 2, which are comparable to those in related ruthenium-N2,O2 complexes
[RuIIICl(PPh3)(salphen)] (175.08(2)°) [25], [RuIIICl(PPh3)(salcyn)] (173.7(3)°) [6] and similar to
that in the previously reported complex [RuIIICl(PPh3)(salipn)]2CH2Cl2 (176.06(7)) [16]. In
ruthenium(II) carbonyl complexes 30.5CH2Cl2 and 4, the two phenolic oxygen atoms, one imine
nitrogen atom and one amine nitrogen atom of salalipn-Cl2 ligand in 30.5CH2Cl2 and salalipn-
Br4 ligand in 4 also bind ruthenium centers in a tetradentate manner. However, the four atoms of
salalipn-type ligands are not in the equatorial plane; instead it is coordinated in a cis-β fashion
(chart 1) with one of the π-donating phenolato groups coordinated trans to the π-accepting
carbonyl and the other trans to the σ-donating amine. As a result, the σ-donating phosphine is
coordinated trans to the imine. The corresponding PRuN bond angles are 179.57(8) in
30.5CH2Cl2 and 178.50(16) in 4. It has been noted that the carbohydrate derived Ru/Os-Salalen
complexes [26] and the ruthenium complex [Ru(salbinapht)(CO)(Pi-Pr3)] {salbinapht = 2-[({2’-
[(2-hydroxy-benzyl)-amino]-[1,1’-bi-naphthalen]-2-yl}imino)-methyl]phenolato}
[28],
the
phosphine atom and the amine nitrogen atom are trans to each other. The C(8)‒N(1) bond
lengths are 1.488(4) and 1.496(7) Å in 3 and 4, respectively, suggesting their C‒N single bond
character; while the C(12)‒N(2) bond lengths are 1.283(4) Å in 3 and 1.266(7) Å in 4, indicating
their original C=N bond property. Two Ru–N bonds have almost similar bond lengths in
11.5CH2Cl2 (1.983(3) and 2.008(3) Å) and 2 (1.965(6) and 1.981(6) Å), which are a little shorter
than those in Ru-salalipn complexes 30.5CH2Cl2 (2.125(3) and 2.054(3) Å) and 4 (2.145(4) and
2.062(5) Å). The Ru–P of 2.259(2) Å and Ru–Cl of 2.196(4) Å in 2 are shorter than those in
11.5CH2Cl2 (2.3547(13), 2.4587(13) Å) possibly due to the Br4 substitute effect on the salalipn
ligands. The Ru–P bond lengths are 2.3592(9) Å and 2.3697(7) Å in 30.5CH2Cl2 and 4,
respectively, comparable to that in the related ruthenium carbonyl triphenylphosphine complex
[RuII(CO)(PPh3)(salalphen)] (2.345 Å) [25].
Cyclic voltammograms for 1-4 scanning from 1.50 to +1.50 V are shown in figure 5.
Table 3 summarizes the electrochemical data of the ruthenium(III)-salipn and ruthenium(II)-
7

salalipn complexes. The ruthenium(III) complexes 1 and 2 show one quasi-reversible reductive
couple at about –0.80 V and one oxidative couple at around 0.67 V, which are comparable to the
related ruthenium(III) complex [RuCl(PPh3)(salen)] (–0.22 V, 0.95 V) [9]. The ruthenium(II)
complexes 3 and 4 have similar quasi-reversible RuII/RuIII couples (–0.74 V) compared to those
of 1 and 2 (–0.80 V). Complexes 3 and 4 exhibit one weak oxidation couple at about 1.00 V,
which is a little higher than those for 1 and 2 (0.67 V), an indication of the carbonyl stability of
the ruthenium(II) complexes.
In summary, a series of ruthenium(II)/(III) complexes with unsymmetrical tetradentate
Schiff base ligands were synthesized by reactions of ruthenium(II) starting materials
[RuCl2(PPh3)3]/[RuHCl(CO)(PPh3)3] and the corresponding free Schiff bases in the presence of
organic base. Though these salipn ligands have been employed in many transition metal
complexes, such as iron, manganese and vanadium [29-31], they have not yet been used to
coordinate to ruthenium metal. The isolation of ruthenium complexes 1-4 enriched the
exploration of such ligands. Formation of 1 and 2 involved in the oxidation of ruthenium(II) to
ruthenium(III) by air [6]. In situ ligand reduction was observed in the syntheses of 3 and 4; this
imine amine transformation was also reported in other ruthenium-salen complexes [25, 26]. It is
interesting to note that the mixed imine-amine ligands salalipn-Br4 and salalipn-Cl2 in according
complexes 3 and 4 coordinated to ruthenium atoms in a cis-β fashion (chart 1), which resulted in
the carbonyl and the phosphine cis to each other with the bond angles of C–Ru–P being about
87.6°.
Supplementary material
Crystallographic
data
for
[RuIIICl(PPh3)(salipn)]·1.5CH2Cl2
(1·1.5CH2Cl2),
[RuIIICl(PPh3)(salipn-Br4)] (2), [RuII(CO)(PPh3)(salalipn-Cl2)]·0.5CH2Cl2 (3·0.5CH2Cl2) and
[RuII(CO)(PPh3)(salalipn-Br4)] (4) have been deposited with the Cambridge Crystallographic
Data Centre as supplementary publication nos. CCDC 1865332, 1865333, 1865334 and 1865335,
respectively. Copies of the data can be obtained free of charge on application to CCDC,
12 Union Road, Cambridge CB2 1EZ, UK [Fax: (+44)1233-336-033; E-mail:
deposit@ccdc.cam.ac.uk].
8

Acknowledgements
This project was supported by the Natural Science Foundation of China (21372007).
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10

Graphical abstract
N
N
HC
CH
OH
HO
R
R
RuHCl(CO)(PPh3)3
RuCl2(PPh3)3
H2
C
Cl
N
N
N
NH
Ru
HC
HC
CH
Ru
C
O
O
O
O
O
R
PPh3
PPh3
R
R
R
11

salen
salalen
N
N
N
HN
OH HO
OH HO
R
R
R
R
X
N
N Ru
X
N
N Ru
O
O
O
Y
O
Y
trans configuration
cis-β configuration
Chart 1. Structures of salen and salalen ligands and their derivatives.
12

N
N
HC
CH
OH
HO
R
R
RuHCl(CO)(PPh3)3
RuCl2(PPh3)3
H2
C
Cl
N
N
N
NH
Ru
HC
HC
CH
Ru
C
O
O
O
O
O
R
PPh3
PPh3
R
R
R
R = H, 1, RuCl(PPh3)(salipn);
R = 3,5-Br2, 2, RuCl(PPh3)(salipn-Br4)
R = 5-Cl, 3, Ru(CO)(PPh3)(salsalipn-Cl2);
R = 3,5-Br2, 4, Ru(CO)(PPh3)(salsalipn-Br4)
Scheme 1. Syntheses of 1-4.
13

Figure 1. ORTEP diagram of [RuCl(PPh3)(salipn)] (1) showing the atom labeling scheme and 40%
thermal ellipsoids. Hydrogens and solvents are omitted for clarity.
14

Figure 2. ORTEP diagram of [RuCl(PPh3)(salipn-Br4)] (2) showing the atom labeling scheme
and 40% thermal ellipsoids. Hydrogens are omitted for clarity.
15

Figure 3. ORTEP diagram of [Ru(CO)(PPh3)(salalipn-Cl2)] (3) showing the atom labeling
scheme and 40% thermal ellipsoids. Hydrogens and the solvent are omitted for clarity.
16

Figure 4. ORTEP diagram of [Ru(CO)(PPh3)(salalipn-Br4)] (4) showing the atom labeling
scheme and 40% thermal ellipsoids. Hydrogens are omitted for clarity.
17

Figure 5. Cyclic voltammogram of 1-4 (0.001 M) in CH2Cl2 at 25 °C at 100 mV s–1 scan rate
with 0.1 M [nBu4N]PF6 as supporting electrolyte.
18

Table 1. Crystallographic data and experimental details for [RuIIICl(PPh3)(salipn)]·1.5CH2Cl2 (1·1.5CH2Cl2),
[RuIIICl(PPh3)(salipn-Br4)] (2), [RuII(CO)(PPh3)(salalipn-Cl2)]·0.5CH2Cl2 (3·0.5CH2Cl2) and [RuII(CO)(PPh3)(salalipn-Br4)] (4).
Complex
1·1.5CH2Cl2
3·0.5CH2Cl2
2
4
Empirical formula
Formula weight
Crystal system
a (Å)
b (Å)
c (Å)
C36.5H34N2O2PCl4Ru
806.49
Monoclinic
12.896(5)
13.995(6)
21.578(9)
C35H27N2O2PBr4ClRu
994.72
Monoclinic
13.9571(11)
17.5871(15)
14.9296(12)
C36.5H32N2O3PCl3Ru
785.03
Monoclinic
9.138(2)
30.118(8)
13.368(3)
C36H29N2O3PBr4Ru
989.29
Triclinic
12.8542(10)
13.3858(11)
13.6434(11)
100.5026(10)
114.6044(9)
112.1851(10)
1808.6(3)
 (°)
 (°)
98.685(6)
109.0377(11)
100.387(3)
 (°)
V (Å3)
3850(3)
3464.2(5)
3618.7(16)
Space group
Z
P21/n
4
1.392
296(2)
1640
P21/n
4
1.907
296(2)
1932
P21/c
4
1.441
296(2)
1596
Pī
2
1.817
296(2)
964
Dcalc (g cm-3)
Temperature (K)
F(000)
μ(Mo-Kα) (mm-1)
Total reflns.
Independent reflns.
Parameters
Rint
R1a, wR2b (I > 2(I))
R1, wR2 (all data)
GoFc
0.759
23494
8749
5.225
21849
7957
0.736
15123
8274
4.934
11570
8038
434
416
438
429
0.0294
0.0537, 0.1488
0.0775, 0.1698
0.0673
0.0587, 0.1318
0.1388, 0.1649
0.0391
0.0428, 0.1056
0.0650, 0.1183
1.033
0.0182
0.0506, 0.1166
0.0762, 0.1292
1.045
1.044
0.968
2
2 2 1/2
a R1 = ΣFo– Fc/ Σ Fo. b wR2 = [Σw(Fo  – Fc2)2/ΣwFo  ] . c GoF = [Σw(Fo – Fc)2/(Nobs – Nparam)]1/2.
19

Table 2. Selected bond lengths (Å) and angles () for 1·1.5CH2Cl2, 2, 3·0.5CH2Cl2 and 4.
RuN RuO RuP RuCl/C NRuO NRuN ORuO NRuP
1.983(3) 2.008(3) 2.3547(13) 2.4587(13) 170.63(13) 83.05(13) 95.07(11) 96.04(11) 87.72(9)
Complex
ORuP
1
2.008(3) 2.016(3)
91.23(11)
90.67(13)
173.70(12)
92.39(10) 91.59(9)
1.965(6) 2.102(4) 2.259(2)
1.981(6) 2.106(5)
2.196(4)
169.8(2)
90.5(2)
90.6(2)
171.6(2)
84.9(3)
92.82(17) 93.37(18) 96.15(13)
95.23(17) 92.09(14)
2
3
4
2.125(3) 2.071(2) 2.3592(9) 1.812(3)
2.054(3) 2.105(2)
169.35(10) 80.50(11) 85.14(8) 179.57(8) 89.38(6)
90.98(10)
84.83(9)
87.73(10)
99.12(9)
94.95(6)
2.145(4) 2.058(4) 2.3697(12) 1.823(6)
2.062(5) 2.060(3)
165.88(16) 80.46(18) 82.71(14) 178.50(16) 95.61(12)
85.42(16)
91.05(16)
85.9(2)
99.79(12) 88.98(10)
20

Table 3. Electrochemical data for ruthenium-salipn/salalipn
complexes.
Eo,a V vs. Ag/AgCl
Complex
I
II
[RuIIICl(PPh3)(salipn)]
0.67
0.79
0.80
0.74
0.74
[RuIIICl(PPh3)(salipn-Br4)]
[RuII(CO)(PPh3)(salalipn-Cl2)]
[RuII(CO)(PPh3)(salalipn-Br4)]
0.67b
0.96b
1.05
a Glassy carbon working electrode, platinum counter electrode,
Ag/AgCl reference electrode, 0.1 M [nBu4N]PF6 in CH2C12 as
supporting electrode. Ferrocene was added as internal standard.
b Irreversible.
21