Synthesis, structural characterization and catalytic activity of chlororuthenium(II) complexes with substituted Schiff base/phosphine ancillary ligands

Article abstract of DOI:10.1515/znb-2020-0110

Treatment of [(η 6-p-cymene)RuCl2]2 with one equivalent of chlorodiphenylphosphine in tetrahydrofuran at reflux afforded a neutral complex [(η 6-p-cymene)RuCl2(κ 1-P-PPh2OH)] (1). Similarly, the reaction of [Ru(bpy)2Cl2·2H2O] (bpy = 2,2′-bipyridine) and chlorodiphenylphosphine in methanol gave a cationic complex [Ru(bpy)2Cl(κ 1-P-PPh2OCH3)](PF6) (2), while treatment of [RuCl2(PPh3)3] with [2-(C5H4N)CH=N(CH2)2N(CH3)2] (L1) in tetrahydrofuran at room temperature afforded a ruthenium(II) complex [Ru(PPh3)Cl2(κ 3-N,N,N-L1)] (3). Interaction of the chloro-bridged complex [Ru(CO)2Cl2] n with one equivalent of [Ph2P(o-C6H4)CH=N(CH2)2N(CH3)2] (L2) led to the isolation of [Ru(CO)Cl2(κ 3-P,N,N-L2)] (4). The molecular structures of the ruthenium(II) complexes 1-4 have been determined by single-crystal X-ray crystallography. The properties of the ruthenium(II) complex 4 as a hydrogenation catalyst for acetophenone were also tested.

Full text of DOI:10.1515/znb-2020-0110

Z. Naturforsch. 2020; 75(9–10)b: 851–857
Chong Chen, Fule Wu, Jiao Ji, Ai-Quan Jia and Qian-Feng Zhang*
Synthesis, structural characterization and
catalytic activity of chlororuthenium(II)
complexes with substituted Schiff base/
phosphine ancillary ligands
https://doi.org/10.1515/znb-2020-0110
Received June 15, 2020; accepted September 27, 2020;
published online October 29, 2020
coordinating ligands [4, 5]. In particular, a series of metal
catalysts of ruthenium(II) complexes containing mono-
1
2
2
dentate (κ -P), bidentate (κ -P,P, κ -P,N) or tetradentate
4
4
(
κ -P N , κ -P O ) phosphine ligands have been reported
6
2
2
2 2
Abstract: Treatment of [(η -p-cymene)RuCl ] with one
2
2
[
6–8]. Meanwhile, it has been demonstrated that ruth-
equivalent of chlorodiphenylphosphine in tetrahydrofuran at
enium(II) complexes bearing Schiff base ligands are also
excellent catalysts in organic synthesis [9]. Contrary to the
frequently studied phosphine ligands, Schiff base ligands
are not only available by a relatively simple single-step
synthetic procedure, but also offer a valuable structural
ligand diversity. We extend our interest to Schiff base
ligands which contain two nitrogen atoms, with the
expectation of exploiting their new reactivity. Moreover, it
may be interesting to develop nitrogen-containing ruth-
enium(II) complexes in which phosphorus atoms are
offered in ancillary ligands for chelation. Previously, we have
reported a series of ruthenium complexes bearing phosphine
ligands with methoxysilyl groups [10]. We herein describe
syntheses and structures of four novel ruthenium(II) com-
6
1
reflux afforded a neutral complex [(η -p-cymene)RuCl (κ -P-
2
PPh OH)] (1). Similarly, the reaction of [Ru(bpy) Cl ·2H O]
2
2
2
2
(bpy = 2,2′-bipyridine) and chlorodiphenylphosphine in
1
methanol gave
a
cationic complex [Ru(bpy) Cl(κ -P-
2
PPh OCH )](PF ) (2), while treatment of [RuCl (PPh ) ] with
2
3
6
2
3 3
[
2-(C H N)CH=N(CH ) N(CH ) ] (L1) in tetrahydrofuran at
5 4 2 2 3 2
room temperature afforded
a ruthenium(II) complex
3
[
Ru(PPh )Cl (κ -N,N,N-L1)] (3). Interaction of the chloro-
3
2
bridged complex [Ru(CO) Cl ] with one equivalent of
2
2 n
[
Ph P(o-C H )CH=N(CH ) N(CH ) ] (L2) led to the isolation of
2 6 4 2 2 3 2
3
[Ru(CO)Cl (κ -P,N,N-L2)] (4). The molecular structures of the
2
ruthenium(II) complexes 1–4 have been determined by
single-crystal X-ray crystallography. The properties of the
ruthenium(II) complex 4 as a hydrogenation catalyst for
acetophenone were also tested.
6
1
plexes [(η -p-cymene)RuCl (κ -P-PPh OH)] (1), [Ru(bpy) Cl
2
2
2
1
3
(
κ -P-PPh OCH )](PF ) (2), [Ru(PPh )Cl (κ -N,N,N-L1)] (3) and
2
3
6
3
2
3
Keywords: catalytic hydrogenation; crystal structure; [Ru(CO)Cl
(κ -P,N,N-L2)] (4). The catalytic activity of complex
2
phosphine ligand; ruthenium; Schiff base; synthesis.
4 in hydrogenation reactions was also investigated.
1
Introduction
2
Experimental section
Organic phosphines are a very important and widely used
class of ligands in coordination chemistry, materials
chemistry and organic synthesis [1–3]. Transition metal
complexes with phosphine ligands are among the most
common and efficient catalysts due to the possibility of
fine-tuning the electronic and steric properties of the
2
.1 General
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, N,N-dimethylethylenediamine,
2-pyridinecarboxaldehyde, 2-(diphenylphosphino)benzal-
dehyde and chlorodiphenylphosphine were purchased
*
Corresponding author: Qian-Feng Zhang, Institute of Molecular
from Alfa Aesar Ltd and used without further purification.
Engineering and Applied Chemistry, Anhui University of Technology,
Ma’anshan, Anhui 243002, PR China, E-mail: zhangqf@ahut.edu.cn
Chong Chen, Fule Wu, Jiao Ji and Ai-Quan Jia, Institute of Molecular
Engineering and Applied Chemistry, Anhui University of Technology,
Ma’anshan, Anhui 243002, PR China
6
The starting ruthenium complexes [(η -p-cymene)RuCl ]
2
2
[
11], [Ru(bpy) Cl ·2H O] (bpy
=
2,2′-bipyridine) [12],
2
2
2
[
RuCl (PPh ) ] [13] and [Ru(CO) Cl ] [14] were prepared
2
3 3
2
2 n
according to literature methods. NMR spectra were

8
52
C. Chen et al.: Schiff base/phosphine ancillary ligands
recorded on a Bruker ALX 400 Plus spectrometer operating J = 6.9 Hz, 2H, CH ), 2.39 (d, J = 3.3 Hz, 2H, CH ), 2.17
2
2
1
31
31
at 400 and 162 MHz for H and P, respectively. Chemical (d, J = 2.0 Hz, 6H, N(CH ) ). – P NMR (162 MHz, CDCl ,
shifts (δ, ppm) were reported with reference to SiMe ( H) ppm): δ = −13.62 (s, PPh ). – IR (KBr disc, cm ): ν(C=N)
and H PO ( P). Infrared spectra (KBr) were recorded on a 1640 (s), ν(C−N) 1092 (vs), 1024 (vs). – Anal. calc. for
3
2
3
1
−1
4
2
31
3
4
Perkin-Elmer 16 PC FT-IR spectrophotometer with use of C H N P: C 76.64, H 6.99, N 7.77; found C 76.65, H 6.98, N
23 25 2
pressed KBr pellets. Gas chromatographic analyses 7.76%.
were performed with an FID detector on a Shimadzu
GC-2010 Plus spectrometer using the RTX-5 column
6
2
.4 Synthesis of [(η -p-cymene)RuCl
(
15 m × 0.25 mm, film thickness 0.25 µm). The initial tem-
2
1
perature of the column was 110 °C and increased to 260 °C
with a rate of 20 K min . Elemental analyses were carried
out using a Perkin-Elmer 2400 CHN analyzer.
(κ -P-PPh OH)] (1)
2
−1
6
To a solution of [(η -p-cymene)RuCl ] (62 mg, 0.10 mmol)
2
2
in tetrahydrofuran (30 mL) was added a solution of chlor-
odiphenylphosphine (44 mg, 0.20 mmol) in tetrahydro-
furan (5 mL), and then the mixture was heated at 90 °C for
4 h, during which time there was a color change from or-
ange to dark red. After removal of solvent in vacuo, the
2
.2 Synthesis of [2-(C H N)CH=N(CH ) N(CH ) ]
5 4 2 2 3 2
(L1)
An oven-dried glass flask charged with 2-pyridinecarbox residue was washed with diethyl ether (2 × 5 mL) and
aldehyde (107 mg, 1.0 mmol) and N,N-dimethylethylene- n-hexane (2 × 5 mL) and dissolved in dichloromethane
diamine (88 mg, 1.0 mmol) in toluene (30 mL), was heated (4 mL). The filtrate was layered with n-hexane (20 mL) at
at reflux with stirring overnight, during which time there room temperature, and dark red block-shaped crystals of
was a color change from yellow-brown to dark red. After product (1) were obtained in five days. Yield: 38 mg, 75%
1
removal of solvent in vacuo, the residue was washed with (based on ruthenium). – H NMR (400 MHz, CDCl , ppm):
3
diethyl ether (3 ×
5 mL). Recrystallization from δ = 7.75–7.64 (m, 5H, Ar-H), 7.56–7.40 (m, 5H, Ar-H), 6.62
dichloromethane-diethyl ether afforded a dark red solid (s, 1H, PO−H), 5.40 (d, J = 6.9 Hz, 2H, p-cymene), 5.26
1
(
L1). Yield: 158 mg, 89%. – H NMR (400 MHz, CDCl , ppm): (d, J = 6.0 Hz, 2H, p-cymene), 2.51 (s, 1H, CH), 2.01 (s, 3H,
3
31
δ = 8.56 (dd, J = 4.8, 0.7 Hz, 1H, pyridine), 8.34 (s, 1H, CH ), 0.98 (d, J = 7.0 Hz, 6H, CH(CH ) ). – P NMR (162 MHz,
CH=N), 7.91 (d, J = 7.9 Hz, 1H, pyridine), 7.64 (m, 1H, pyr- CDCl , ppm): δ = 105.7 (s, (OH)PPh ). – IR (KBr disc, cm ):
3
3 2
−1
3
2
idine), 7.21 (dd, J = 7.5, 1.2 Hz, 1H, pyridine), 3.74 (td, 7.1, ν(O−H) 3223 (m), ν(P−O) 860 (w). – Anal. calc. for
.4 Hz, 2H, CH ), 2.62 (t, J = 6.9 Hz, 2H, CH ), 2.37 (s, 6H, C H OCl PRu: C 51.98, H 4.96; found C 51.95, H 4.96%.
1
2
2
22 25
2
−1
N(CH ) ). – IR (KBr disc, cm ): ν(C=N) 1648 (s), ν(C−N) 1089
3
2
(
2
vs), 1082 (s). – Anal. calc. for C H N : C 67.76, H 8.53, N
3.71; found C 67.77, H 8.51, N 23.72%.
10 15 3
1
2
.5 Synthesis of [Ru(bpy) Cl(κ -P-
2
PPh OCH )](PF ) (2)
2
3
6
2
.3 Synthesis of [Ph P(o-C H )
2 6 4
To a solution of [Ru(bpy) Cl ·2H O] (52 mg, 0.10 mmol) in
2 2 2
CH=N(CH ) N(CH ) ] (L2)
methanol (20 mL) was added a solution of chlor-
odiphenylphosphine (44 mg, 0.20 mmol) in methanol
2
2
3 2
A toluene (25 mL) solution of N,N-dimethylethylenedi- (10 mL), and then the mixture was heated at reflux with
amine (88 mg, 1.0 mmol) was added to 2-(diphenylphos- stirring for 8 h, during which time there was a color change
phino)benzaldehyde (290 mg, 1.0 mmol) in a round- from purple-red to dark purple-red. After the reaction mixture
bottomed flask equipped with a condenser. The reaction was cooled to room temperature, an excess of KPF (20 mg,
6
mixture was stirred at reflux for 12 h. After the completion 0.11 mmol) was added to the flask and stirred for 30 min. After
of reaction, the solvent was pumped off and the residue filtering, the solvent was removed in vacuo, and the residue
was washed with diethyl ether (3 × 5 mL). Recrystallization was washed with diethyl ether (2 × 5 mL). Dark purple-red
from dichloromethane-diethyl ether gave a red solid (L2). block crystals suitable for X-ray diffraction were obtained by
1
Yield: 318 mg, 88%. – H NMR (400 MHz, CDCl , ppm): slow evaporation of a mixed dichloromethane-n-hexane (1:6)
3
δ = 8.82 (d, J = 4.8 Hz, 1H, CH=N), 7.88 (d, J = 7.2 Hz, 1H, Ar- solvent in three days. Yield: 63 mg, 64% (based on ruthe-
1
H), 7.68 (d, J = 3.6 Hz, 1H, Ar-H), 7.60–7.53 (m, 1H, Ar-H), nium). – H NMR (400 MHz, CDCl , ppm): δ = 9.29–8.12 (dd,
3
7
.50–7.44 (m, 1H, Ar-H), 7.42–7.36 (m, 1H, Ar-H), 7.25–7.16 J = 8.3, 5.4 Hz, 6H, bpy-H), 8.03–6.77 (dd, J = 7.8, 6.7 Hz, 6H,
(
m, 8H, Ar-H), 6.78 (d, J = 7.7 Hz, 1H, Ar-H), 3.57 (d, bpy-H), 7.44–7.31 (m, 10H, PPh ), 7.17 (m, 4H, bpy-H), 3.55 (s,
3

C. Chen et al.: Schiff base/phosphine ancillary ligands
853
3
1
−1
3
(
H, OCH ). – P NMR (162 MHz, CDCl , ppm): δ = 45.43 (s, disc, cm ): ν(C≡O) 1989 (s), ν(C=N) 1615 (s), ν(C−N) 1225
3
3
−1
CH O)PPh ). – IR (KBr disc, cm ): ν(C−N) 1195 (m), ν(C−O) (s). – Anal. calc. for C H N OCl PRu: C 51.44, H 4.50, N
3
2
24 25
2
2
1
054 (m), ν(P−O) 859 (w). – Anal. calc. for C H N OCl F - 5.00; found C 51.43, H 4.48, N 5.01%.
35
33
4
5 6
P Ru·2CH Cl : C 42.90, H 3.39; found C 42.92, H 3.38%.
2
2
2
2
.8 X-Ray crystallography
2
.6 Synthesis of [Ru(PPh )Cl
3 2
3
(κ -N,N,N-L1)] (3)
A summary of crystallographic data and experimental de-
tails for the ruthenium(II) complexes 1–4 is presented in
A mixture of [RuCl (PPh ) ] (96 mg, 0.10 mmol) and L1 Table 1. Intensity data was collected on a Bruker SMART
2
3 3
(
18 mg, 0.10 mmol) was stirred in tetrahydrofuran (25 mL) APEX 2000 CCD diffractometer using graphite-
for 4 h at room temperature, during which time the color of monochromatized MoKα radiation (λ = 0.71073 Å) at
solution changed from brown to red-brown. After removal T = 296(2) K. The collected frames were processed with the
of the solvent in vacuo, dichloromethane (20 mL) was software SAINT [15]. The data was corrected for absorption
added and the solution was filtered. The filtrate was using the program SADABS [16]. Structures were solved by
concentrated and the residue was washed with diethyl Direct Methods and refined by full-matrix least-squares on
2
ether (2 × 5 mL) and hexane (2 × 5 mL). Recrystallization F using the SHELXTL software package [17, 18]. All non-
from dichloromethane-hexane (1:3) afforded after three hydrogen atoms were refined anisotropically. The posi-
days dark red block crystals of (3) suitable for X-ray tions of all hydrogen atoms were generated geometrically
1
diffraction. Yield: 44 mg, 72% (based on ruthenium). – H (Csp3−H = 0.96 and Csp2−H = 0.93 Å) and included in the
NMR (400 MHz, CDCl , ppm): δ = 8.98 (s, 1H, Ar-H), 8.50 structure factor calculations with assigned isotropic
3
(
d, J = 4.8 Hz, 1H, CH=N), 7.72–7.62 (m, 6H, Ar-H), 7.62–7.51 displacement parameters but were not refined. The
(
m, 7H, Ar-H), 7.47–7.21 (m, 5H, Ar-H), 3.94 (d, J = 10.6 Hz, dichloromethane molecules in 2 were isotropically refined
2
H, CH ), 3.15 (s, 3H, N−CH ), 2.89 (s, 2H, CH ), 2.56 (s, 3H, without hydrogen atoms due to disorder, which resulted in
2
3
2
31
N−CH ). – P NMR (162 MHz, CDCl , ppm): δ = 29.28 a relatively high R value in the final refinement.
3
3
−1
6
1
(
(
s, PPh ). – IR (KBr disc, cm ): ν(C=N) 1626 (s), ν(C−N) 1182
CCDC 1991983 (for [(η -p-cymene)RuCl
2
(κ -P-PPh
2
OH)]
) (2)),
2
1
m). – Anal. calc. for C H N Cl PRu: C 55.00, H 4.95, N (1)), 1991984 (for [Ru(bpy)
Cl(κ -P-PPh
OCH
)](PF
2
8
30
3
2
2
3
2
3
6
6
.87; found C 55.01, H 4.94, N 6.88%.
1991985 (for [Ru(PPh
3
)Cl
2
(κ -N,N,N-L1)] (3)) and 1991986
3
(
for [Ru(CO)Cl (κ -P,N,N-L2)] (4)) contain the supplemen-
2
tary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
2
.7 Synthesis of [Ru(CO)Cl2
3
(
κ -P,N,N-L2)] (4)
To a slurry of [Ru(CO) Cl2]n (46 mg, 0.20 mmol) in
2
N,N-dimethylformamide-tetrahydrofuran (1:9, v/v) (20 mL)
was added a solution of L2 (72 mg, 0.20 mmol) and trie-
thylamine (22 mg, 0.20 mmol) in tetrahydrofuran (5 mL),
and then the mixture was heated at 90 °C with stirring
overnight, during which time there was a color change
from light yellow to yellow. After removal of the solvent in
vacuo, the residue was washed with diethyl ether (2 × 5 mL)
and n-hexane (2 × 5 mL). The residue was extracted with
dichloromethane (5 mL) and yellow crystals of (4) were
obtained after layering the filtrate with hexane (15 mL) at
2
.9 Catalytic testing
In a typical experiment, a testing tube was filled with
acetophenone (1 mmol), KOH in PrOH (0.05 mmol KOH in
degassed PrOH (10 mL)) and the homogeneous catalyst 4
i
i
(
0.01 mmol). The mixture was stirred at T = 70 °C for 10 h
under hydrogen atmosphere. After cooling and filtering,
the filtrate was diluted with acetone and then analyzed
immediately by GC. The conversions are related to the re-
sidual unreacted ketone.
room temperature for five days. Yield: 67 mg, 59% (based
1
on ruthenium). – H NMR (400 MHz, CDCl , ppm): δ = 8.68
3
(s, 1H, CH=N), 7.72 (d, J = 4.0 Hz, 1H, Ar-H), 7.66–7.61 (m,
1
H, Ar-H), 7.54 (d, J = 7.5 Hz, 1H, Ar-H), 7.50–7.44 (m, 4H, 3 Results and discussion
Ar-H), 7.42–7.30 (m, 7H, Ar-H), 4.29–4.23 (m, 2H, CH ), 3.05
2
31
(d, J = 1.9 Hz, 6H, N(CH ) ), 2.79–2.75 (m, 2H, CH ). –
P
The synthesis of the Schiff base ligands L1, L2 and of
3
2
2
NMR (162 MHz, CDCl , ppm): δ = 58.69 (s, PPh ). – IR (KBr the ruthenium(II) complexes 1–4 are summarized in
3
2

854
C. Chen et al.: Schiff base/phosphine ancillary ligands



Table : Crystallographic data and experimental details for ruthenium(II) complexes [(η -p-cymene)RuCl

(κ -P-PPh

OH)] (), [Ru(bpy)

Cl(κ -P-


   
PPh OCH )](PF ) (), [Ru(PPh )Cl

(κ -N,N,N-L)] () and [Ru(CO)Cl

(κ -P,N,N-L)] ().
Complex


·CH Cl



Empirical formula
Formula weight
Crystal system
Space group
a, Å
C

H
Cl

OPRu
C

H
Cl
.
monoclinic
P /c

F

 
N OP Ru
C

H
Cl

N

PRu
C

H
Cl
.
monoclinic
P /n

N OPRu

.
monoclinic
P /c
.()
.()
.()
.()
.()

.
orthorhombic
Pca
.()
.()
.()





.()
.()
.()
.()
()

.()
.()
.()
.()
.()

b, Å
c, Å
β, deg

V, Å
()

Z
D
calc, g cm−

.
.
.
.
Temperature, K
F (), e
()

()

()

()

μ(MoKα), mm−
Total refln

.

.

.

.

Independent refln




R
int
.

.

.

.

Ref. Parameters
a
b
R /wR (I > σ(I))
R/wR (all data)
Flack x
./.
./.
–
.
./−.
./.
./.
–
.
./−.
./.
./.
−.()
.
./.
./.
–
.
./−.
c
GoF
Δρfin (max/min), e Å−

./−.
−
/

a
b


c

o



o

o

c
R = Σ||F
o
|–|F
c
||/Σ|F
o
|. wR ꢀ ꢀ∑w(F − F )/∑w(F ) ꢁ , ꢀw ꢀ ꢀσ ꢂF ꢃ + ꢂAPꢃ + BPꢁ , where P ꢀ (Max(F , ) + F )/ and A and B are
o

/
c

o


constants adjusted by the program. GoF ꢀ S ꢀ ꢀ∑w(F − F ) /(nobs − nparam)ꢁ , where nobs is the number of data and nparam the number of
c
refined parameters.
equiv. L1 in tetrahydrofuran at room temperature afforded
3
dark red block crystals of [Ru(PPh )Cl (κ -N,N,N-L1)] (3). Two
3
2
PPh ligands were replaced by one tridentate N,N′,Nʺ-ligand
3
in this reaction. Interaction of [Ru(CO) Cl ] with one equiv-
2
2 n
alent L2 in the presence of triethylamine gave a ruthenium(II)
3
complex [Ru(CO)Cl (κ -P,N,N-L2)] (4). It is interesting to find
2
that the two chloro ligands were not eliminated in complexes
3
and 4, and the tridentate L1 serves as a N,N′,Nʺ-chelating
ligand in complex 3, whereas the tridentate L2 serves as a P,N,
N′-chelating ligand in complex 4. The IR spectra of the Schiff
base ligands L1, L2 and of the complexes 3 and 4 all showed a
characteristic band of CH=N groups in the region of 1615–
Scheme 1: Synthetic routes to the Schiff base ligands L1 and L2.
Schemes 1 and 2, respectively. The ligands [2-(C H N)
5
4
−1
1648 cm , which is characteristic of the azomethine group
CH=N(CH ) N(CH ) ] (L1) and [Ph P(o-C H )CH=N(CH )
2 2
2
2
3 2
2
6
4
absorptions [19]. In complex 4, the stretching vibration mode
of the terminal C≡O group was found at 1989 cm , which is
similar to that of other ruthenium carbonyl complexes with
N(CH ) ] (L2) were synthesized from the condensation of N,N-
dimethylethylenediamine with 2-pyridinecarboxaldehyde
and 2-(diphenylphosphino)benzaldehyde in toluene,
3
2
−1
phosphine ancillary ligands [Ru(CO) Cl (P∩S] (P∩S =
P,S-chelating diphosphane ligands) (1956–2059 cm ) [20].
respectively. Treatment of chlorodiphenylphosphine with
2
2
−1
6
[
(η -p-cymene)RuCl ] and [Ru(bpy) Cl ·2H O] afforded the
2
2
6
2
2
1
2
The proton resonance of POH in 1 and of OCH in 2 appeared
neutral complex [(η -p-cymene)RuCl (κ -P-PPh OH)] (1) and
the cationic complex [Ru(bpy) Cl(κ -P-PPh OCH )](PF ) (2),
3
2
2
1
at δ = 6.62 and 3.55 ppm, respectively, similar to those of
2
2
3
6
6
ruthenium complexes [RuCl (η -p-cymene)(tert-BuPhPOH)]
respectively, which both have “RuPO” fragments in their
2
(
δ = 6.20 ppm) [21] and [Ru (μ -Se) (CO) (P(OMe)Ph ) ]
molecular structures. Treatment of [RuCl (PPh ) ] with one
3
3
2
7
2 2
2
3 3

C. Chen et al.: Schiff base/phosphine ancillary ligands
855
Scheme 2: Synthetic routes for the ruthenium(II) complexes 1–4.
3
1
6
1
Figure 1: Molecular structure of [(η -p-cymene)RuCl
(
2
(κ -P-PPh
2
OH)]
(
δ = 3.42 and 3.59 ppm), respectively [22]. The P NMR spectra
1) in the crystal. Displacement ellipsoids are shown at the 35%
probability level. Selected bond lengths (Å) and angles (deg):Ru(1)–
C(1) 2.177(5), Ru(1)–C(2) 2.185(6), Ru(1)–C(3) 2.220(5), Ru(1)–C(4)
of complexes 1and 2showed a singlet at 105.7 and 45.43 ppm,
respectively, consistent with a P-coordinated diphenylphos-
phinous acid [23].
2
.245(5), Ru(1)–C(5) 2.221(5), Ru(1)–C(6) 2.221(5), Ru(1)–Cl(1)
The structures of ruthenium(II) complexes 1–4 have 2.4139(15), Ru(1)–Cl(2) 2.4150(16), Ru(1)–P(1) 2.3087(16), P(1)–O(1)
been established by X-ray crystallography. The perspective 1.601(3); P(1)–Ru(1)–Cl(1) 83.22(5), P(1)–Ru(1)–Cl(2) 84.38(6), Cl(1)–
Ru(1)–Cl(2) 87.29(6), O(1)–P(1)–Ru(1) 113.34(13).
views of the molecular structures of complexes 1–4 are
shown in Figures 1–4, with their atom numbering schemes.
It should be noted that the structure of complex 1 has been
determined before and the conversion of complexed
chlorodiphenylphosphine into the PPh OH ligand has
2
precedent [21, 24, 25]. This adventitious hydrolysis is an
alternative procedure for the synthesis of metal complexes
with phosphinous acid PR OH ligands (Scheme 3). It is
2
probably due to the high temperature of the reaction and
the presence of small amounts of water in the reaction
system [26, 27]. The P−O bond lengths are 1.601(3) and
1
.617(5) Å in complexes 1 and 2, respectively, which
6
compare well with those in [RuCl (η -p-cymene)
2
(
PPh (OCH CH NMe ))][SbF ] (1.612(2) Å) [28] and
2
2
3
2
3
6
3
[
RuCl (η :η -C H )(PPh OH)] (1.6040(18) Å) [29]. Complex
2
10
6
2
1
+
2
comprises of one cation [Ru(bpy) Cl(κ -P-PPh OCH )] ,
2
2
3
−
one [PF ] anion, and two CH Cl solvent molecules. In the
octahedral [PF ] anion, the P‒F distances span the range
6
2
2
−
6
of 1.454(9)–1.563(7) Å. The Ru‒N bond lengths are
2.060(6)–2.128(6) Å, together with the bipyridine chelate
1
+
3
2 2
Figure 2: Molecular structureof cations [Ru(bpy) Cl(κ -P-PPh OCH )]
bite angles of 77.8(2)–78.8(2)°, which compare well with in crystals of (2). The anion is omitted for clarity. Displacement
II
those in [Ru (bpy) fla][BF ] (fla = flavonolate) (2.023(3)– ellipsoids are shown at the 40% probability level. Selected bond
2
4
lengths (Å) and angles (deg): Ru(1)–N(1) 2.105(6), Ru(1)–N(2) 2.128(6),
Ru(1)–N(3) 2.061(6), Ru(1)–N(4) 2.060(6), Ru(1)–P(1) 2.285(2), Ru(1)–
Cl(1) 2.425(2), P(1)–O(1) 1.617(5); N(1)–Ru(1)–N(2) 77.8(2), N(4)–Ru(1)–
N(3) 78.8(2), N(4)–Ru(1)–N(2) 93.7(2), N(3)–Ru(1)–N(1) 167.9(2), N(2)–
Ru(1)–P(1) 176.69(18), N(4)–Ru(1)–Cl(1) 172.74(17), P(1)–Ru(1)–Cl(1)
2
.055(3) Å, 79.48(13)–79.51(13)°) [30]. The Ru−P and Ru−Cl
bond lengths are 2.285(2) and 2.425(2) Å, respectively,
similar to those in complex 1. In the distorted octahedral
coordination sphere of complex 3 bearing tridentate Schiff
base ligands, the Ru‒N(N,N-dimethylethylenediamine) 95.78(8), O(1)–P(1)–Ru(1) 108.4(2).

856
C. Chen et al.: Schiff base/phosphine ancillary ligands
Scheme 3: Alternative procedure to generate complexes with
PR OH ligands.
2
bond lengths are 1.950(4) and 2.226(4) Å, together with the
N,N-chelate bite angles of 82.26(16)°, similar to those in
complex 4 (2.102(2) and 2.262(2) Å, 81.06(8)°). The average
Ru‒Cl bond length is 2.461(1) Å in complex 3, which is a
little longer than in the complexes 1 (2.4145(16) Å), 2
(
2.425(2) Å) and 4 (2.408(7) Å). In complex 4, however, the
Cl−Ru−Cl bond angle is 172.75(2)°, indicating the trans-
configuration of the two chloro ligands. The C≡O bond
length is 1.111(3) Å and the Ru−C−O bond angle is 178.7(3)°,
which are normal for ruthenium(II) carbonyl complexes
3
Figure 3: Molecular structure of [Ru(PPh
3
)Cl
2
(κ -N,N,N-L1)] (3) in the
crystal. Displacement ellipsoids are shown at the 35% probability
level. Selected bond lengths (Å) and angles (deg): Ru(1)–N(1)
.054(4), Ru(1)–N(2) 1.950(4), Ru(1)–N(3) 2.226(4), Ru(1)–P(1)
.3087(16), Ru(1)–Cl(1) 2.4955(17), Ru(1)–Cl(2) 2.4261(18); N(2)–
Ru(1)–N(1) 79.08(16), N(2)–Ru(1)–N(3) 82.26(16), N(1)–Ru(1)–N(3)
60.30(15), Cl(2)–Ru(1)–Cl(1) 86.53(7), P(1)–Ru(1)–Cl(1) 171.93(4),
[
31, 32].
3
Complex [Ru(CO)Cl (κ -P,N,N-L2)] (4) was selected to
2
2
2
3
explore the catalytic activity, since it has a κ -P,N,N Schiff
base ligand. Recently, the catalytic hydrogenation of ace-
tophenone by ruthenium(II) complexes containing mixed
donor (PˆN) ligands has been reported [33, 34]. Under
similar conditions, complex 4 gave about 68% conversion,
compared with those obtained with pyrazolylphosphite-
and pyrazolylphosphinite-ruthenium(II) complexes with
PˆN ligands (69, 42, 61, 68, 61, 31 and 65%) and the parent
complex[Ru(p-cymene)Cl ] (21%) [33]. The yield was not
1
P(1)–Ru(1)–Cl(2) 90.86(7), N(2)–Ru(1)–Cl(2) 172.43(12).
2
2
improved after longer reaction times. In a similar work
done by Günnaz and co-workers [35] with tridentate tri-
amine NˆNˆN-ruthenium(II) complexes, the conversions
were from 3 to 73% together with the formation of
2-phenylethanol, which was not observed in the process
using 4, indicating good selectivity of complex 4. In-
vestigations to understand further the catalytic mechanism
are in progress.
In summary, four ruthenium(II) complexes with Ru−Cl
functions and substituted Schiff base/phosphine ancillary
ligands were synthesized and characterized. Their molec-
ular structures have been determined by single-crystal
X-ray crystallography. Ruthenium(II) carbonyl complex 4
3
Figure 4: Molecular structure of [Ru(CO)Cl
2
(κ -P,N,N-L2)] (4) in the
3
crystal. Displacement ellipsoids are shown at the 35% probability
with a tridentate κ -P,N,N Schiff base ligand exhibited good
level. Selected bond lengths (Å) and angles (deg): Ru(1)–C(1)
catalytic performance in the hydrogenation of acetophe-
none to 1-phenylethanol with good yield and selectivity.
1
.860(3), Ru(1)–N(1) 2.102(2), Ru(1)–N(2) 2.262(2), Ru(1)–P(1)
.2718(6), Ru(1)–Cl(1) 2.4122(7), Ru(1)–Cl(2) 2.4038(7); C(1)–Ru(1)–
N(1) 177.20(10), C(1)–Ru(1)–N(2) 96.14(10), N(1)–Ru(1)–N(2)
1.06(8), C(1)–Ru(1)–P(1) 92.67(8), N(2)–Ru(1)–P(1) 170.57(6), Cl(2)–
Ru(1)–Cl(1) 172.75(2), O(1)–C(1)–Ru(1) 178.7(3), C(1)–Ru(1)–Cl(1)
4.56(8), C(1)–Ru(1)–Cl(2) 92.65(8).
2
Author contribution: All the authors have accepted
responsibility for the entire content of this submitted
manuscript and approved submission.
8
9

C. Chen et al.: Schiff base/phosphine ancillary ligands
857
Research funding: This project was supported by the
Natural Science Foundation of China (20771003).
Conflict of interest statement: The authors declare no
conflicts of interest regarding this article.
15. SMART, SAINT+ for Windows NT (version 6.02a). Area Detector
Control and Integration Software; Bruker AXS Inc.: Madison,
Wisconsin (USA), 1998.
1
6. Sheldrick G. M. SADABS (version 2.03). Program for Empirical
Absorption Correction of Area Detector Data; University of
Göttingen: Göttingen (Germany), 1996.
1
7. Sheldrick G. M. SHELXTL (version 5.1). Software Reference Manual;
Bruker AXS Inc.: Madison, Wisconsin (USA), 1997.
8. Sheldrick G. M. Acta Crystallogr. 2015, C 71, 3.
9. Brunner H., Zwack T., Zabel M. Organometallics 2003, 22, 1741.
References
1
1
1
2
3
4
. Queff e´ lec C., Petit M., Janvier P., Knight D. A., Bujoli B. Chem. Rev. 20. Deb B., Sarmah P. P., Dutta D. K. Eur. J. Inorg. Chem. 2010, 11,
015, 112, 3777.
1710.
2
. Zhan X.-C., Hei Y.-Y., Song J.-L., Qian P.-C., Zhang X.-G., Deng C.-L.
Org. Chem. Front. 2019, 6, 1453.
21. Graux L. V., Giorgi M., Buono G., Clavier H. Dalton Trans. 2016, 45,
6491.
. Keskin S. G., Mejia M. L., Cowley A. H., Holliday S. J. Macromol.
Chem. Phys. 2018, 219, 1800262.
. Hussein S., Priester D., Beet P., Cottom J., Hart S. J., James T.,
Thatcher R. J., Whitwood A. C., Slattery J. M. Chem. Eur J. 2019, 25,
22. Cauzzi D., Graiff C., Pattacini R., Predieri G., Tiripicchio A.,
Kahlal S., Saillard J. Y. Eur. J. Inorg. Chem. 2004, 5, 1063.
23. Tribó R., Pons J., Yáñez R., Piniella J. F., Alvarez-Larena A., Ros J.
Inorg. Chem. 2000, 3, 545.
2
262.
24. Pandiakumar A. K., Samuelson A. G. J. Chem. Sci. 2015, 127, 1329.
25. González-Fernández R., Crochet P., Cadierno V., Men e´ ndez M. I.,
5
6
7
. Trindade A. F., Coelho J. A. S., Afonso C. A. M., Veiros L. F.,
Gois P. M. P. ACS Catal. 2012, 2, 370.
. Biancalana L., Zacchini S., Ferri N., Lupo M. G., Pampaloni G.,
Marchetti F. Dalton Trans. 2017, 46, 16589.
López R. Chem. Eur J. 2017, 23, 15210.
26. Pandiakumar A. K., Samuelson A. G. J. Chem. Sci. 2015, 127, 1329.
27. González-Fernández R., González P.J., Borge J., Crochet P.,
Cadierno V. Catal. Sci. Technol. 2016, 6, 4398.
28. Crochet P., Díez J., Fernández-Zúmel M. A., Gimeno J. Adv. Synth.
Catal. 2006, 348, 93.
. Schotes C., Ranocchiari M., Mezzetti A. Organometallics 2011, 30,
3
596.
8
9
. Geldbach T. J., Chaplin A. B., Hänni K. D., Scopelliti R., Dyson P. J.
Organometallics 2005, 24, 4974.
29. Tomás-Mendivil E., Suárez F. J., Díez J., Cadierno V. Chem.
Commun. 2014, 50, 9661.
. Habermehl N. C., Angus P. M., Kilah N. L., Nor e´ n L., Rae A. D.,
Willis A. C., Wild S. B. Inorg. Chem. 2006, 45, 1445.
0. Ji J., Wu F.-L., Shi L.-M., Jia A.-Q., Zhang Q.-F. J. Organomet. Chem.
30. Han X.-Z., Klausmeyer K. K., Farmer P. J. Inorg. Chem. 2016, 55,
7320.
1
2
019, 885, 1.
31. Wang C.-J., Lin H., Chen X., Jia A.-Q., Zhang Q.-F. Inorg. Chem. Acta
2017, 467, 198.
1
1. Bennett M. A., Huang T. N., Matheson T. W., Smith A. K. Inorg.
Synth. 1982, 21, 75.
2. Lay P. A., Sargeson A. M., Taube H. Inorg. Synth. 1986, 24, 291.
3. Stephenson T. A., Wilkinson G. J. Inorg. Nucl. Chem. 1996, 28,
32. Tamizh M. M., Mereiter K., Kirchner K., Karvembu R. J. Organomet.
Chem. 2012, 700, 194.
33. Amenuvor G., Obuah C., Nordlander E., Darkwa J. Dalton Trans.
2016, 45, 13514.
1
1
9
45.
1
4. Anderson P. A., Deacon G. B., Haarmann K. H., Keene F. R.,
Meyer T. J., Reitsma D. A., Skelton B. W., Strouse G. F., Thomas N. C.,
Treadway J. A., White A. H. Inorg. Chem. 1995, 34, 6145.
34. Wang L.-D., Liu T.-T. Chin. J. Catal. 2018, 39, 327.
35. Günnaz S., Özdemir N., Dayan S., Dayan O., Çetinkaya B.
Organometallics 2011, 30, 4165.