Syntheses, structures and catalytic properties of ruthenium(II) nitrosyl complexes with bidentate and tetradentate Schiff base ligands

Article abstract of DOI:10.1016/j.ica.2017.12.004

Treatment of Ru(NO)Cl₃·xH₂O with 1 equiv. bidentate Schiff bases in the presence of triethylamine in DMF/THF afforded a series of anionic ruthenium(II) nitrosyl complexes of the type [Et₃NH][Ru(κ²-N,O-L^R)(NO)Cl₃] (HL^R = 2-butyliminomethyl-phenol 1, 2-(benzylimino-methyl)-phenol 2, 2-[(4-chloro-phenylimino)-methyl]-phenol 3, 2-[(4-nitro-phenylimino)-methyl]-phenol 4, 2-[(2,6-diisopropyl-phenylimino)-methyl]-phenol 5). Interaction of Ru(NO)Cl₃·xH₂O and 1 equiv. tetradentate Schiff bases under the same condition led to isolation of an anionic complex [Et₃NH][Ru(κ²-N,O-L-CH₂CH₂-NOH)-(NO)Cl₃] (HL-CH₂CH₂-NOH = N,N′-disalicylidene-1,2-ethanediamine 6) and a neutral complex [Ru(salen-phn)(NO)Cl] (H₂salen-phn = N,N′-disalicylidene-1,2-phenyldiamine 7). The molecular structures of 1·?C₂H₅OH, 2–6, and 7·CH₂Cl₂ have been determined by single-crystal X-ray crystallography. Investigation of the catalytic properties of ruthenium(II) nitrosyl complexes 1–7 showed that they are efficient catalytic precursors for the transfer hydrogenation of acetophenone.

Full text of DOI:10.1016/j.ica.2017.12.004

Accepted Manuscript
Research paper
Syntheses, structures and catalytic properties of ruthenium(II) nitrosyl com-
plexes with bidentate and tetradentate Schiff base ligands
Fule Wu, Chang-Jiu Wang, Hui Lin, Ai-Quan Jia, Qian-Feng Zhang
PII:
S0020-1693(17)31356-7
https://doi.org/10.1016/j.ica.2017.12.004
ICA 18038
DOI:
Reference:
Inorganica Chimica Acta
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1 November 2017
2 December 2017
Please cite this article as: F. Wu, C-J. Wang, H. Lin, A-Q. Jia, Q-F. Zhang, Syntheses, structures and catalytic
properties of ruthenium(II) nitrosyl complexes with bidentate and tetradentate Schiff base ligands, Inorganica
Chimica Acta (2017), doi: https://doi.org/10.1016/j.ica.2017.12.004
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Syntheses, structures and catalytic properties of ruthenium(II)
nitrosyl complexes with bidentate and tetradentate Schiff base
ligands
Fule Wu, Chang-Jiu Wang, Hui Lin, 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
Treatment of Ru(NO)Cl3⋅xH2O with 1 equiv. bidentate Schiff bases in the presence of
triethylamine in DMF/THF afforded a series of anionic ruthenium(II) nitrosyl complexes
of the type [Et3NH][Ru(κ2-N,O-LR)(NO)Cl3] (HLR = 2-butyliminomethyl-phenol 1, 2-
(benzylimino-methyl)-phenol 2, 2-[(4-chloro-phenylimino)-methyl]-phenol 3, 2-[(4-nitro-
phenylimino)-methyl]-phenol 4, 2-[(2,6-diisopropyl-phenylimino)-methyl]-phenol 5).
Interaction of Ru(NO)Cl3⋅xH2O and 1 equiv. tetradentate Schiff bases under the same
condition led to isolation of an anionic complex [Et3NH][Ru(κ2-N,O-L-CH2CH2-NOH)-
(NO)Cl3] (HL-CH2CH2-NOH = N,N'-disalicylidene-1,2-ethanediamine 6) and a neutral
complex [Ru(salen-phn)(NO)Cl] (H2salen-phn = N,N'-disalicylidene-1,2-phenyldiamine
7). The molecular structures of 1⋅½C2H5OH, 2‒6, and 7⋅CH2Cl2 have been determined by
single-crystal X-ray crystallography. Investigation of the catalytic properties of
ruthenium(II) nitrosyl complexes 1–7 showed that they are efficient catalytic precursors
for the transfer hydrogenation of acetophenone.
Keywords: Ruthenium complex; Schiff base; Nitrosyl ligand; Synthesis; Crystal structure
___________________
* Corresponding author. E-mail: zhangqf@ahut.edu.cn (Q. F. Zhang).
1

1. Introduction
It has been well-known that nitric oxide plays fundamental roles in biochemical
processes and catalytic application [1,2]. The interests in nitric oxide in chemical and
biochemical studies are its reactions and interactions with the metal centers. Normally,
nitrogen monoxide bonds to a metal center via two types of coordinating modes, linearly
and bend bonding: a linearly bonded nitrosyl ligand functions as a poor σ-donor and a
strong π-acceptor, and a bend one as a strong σ-donor [3]. As a matter of the fact, the
transition metal nitrosyl chemistry occupies the major areas in nitric oxide chemistry and
biochemistry [4]. Up to now, ruthenium(II) nitrosyl complexes have been well
documented and there are quite a few well-characterized complexes with biological and
environmental applications, such as metalloprotein or metalloenzyme participates in the
physiological processes [5,6]. It has been noted that the {ruthenium(II)-NO+} type of
nitrosylruthenium complexes is one of the compounds suitable for developing the metal
nitrosyl chemistry and investigating the biological role of NO+ because the
{ruthenium(II)-NO+} moiety tends to form stable-coordinate complexes [7]. For
examples, a series of nitrosylruthenium complexes with bidentate chelating substituted 8-
quinolinolato, 2-pyridinemethanol and pyridine-2-carboxylato ligands were found to
show reversible thermal isomerization [8–10], the biological studies of a new
nitrosylruthenium complex with the formula [RuCl2(NO)(BPA)] [BPA = (2-
hydroxybenzyl)(2-methylpyridyl)amine ion] revealed the activity against two different
tumor cell lines [11], and nitrosylruthenium complexes with the chiral quadridentate
Schiff base ligands may be acted as catalysts for asymmetric trimethyl-silylcyanation of
aldehydes [12]. Previously, we have reported a series of ruthenium(II)/ruthenium(III)
complexes with bi-, tri- or tetra-dentate Schiff-base ligands [13–15], as our long-standing
research interest in ruthenium complexes with the correspondingly catalytic properties,
we disclose herein syntheses, structures and catalytic properties of a series of
ruthenium(II) nitrosyl complexes with bidentate and tetradentate Schiff base ligands in
this paper.
2

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, salicyaldehyde, n-butylamine, benzylamine, 4-chloro-phenylamine,
4-nitro-phenylamine, 2,6-di-iso-propylo-phenylamine, 1,2-ethanediamine (en) and 1,2-
phenyldiamine (phn) were purchased from Alfa Aesar Ltd. and used without further
purification. The N,O-bidentate and N2,O2-tetradentate Schiff bases were prepared by the
condensation between salicyaldehyde and according mono- or bis-amines in the refluxing
ethanol [15]. Ru(NO)Cl3⋅xH2O was prepared according to the literature method [16].
NMR spectra were recorded on a Bruker ALX 400 Plus spectrometer operating at 400
1
MHz for H and chemical shifts (δ, ppm) were reported with reference to SiMe4 (1H).
Infrared spectra (KBr) were recorded on a Perkin-Elmer 16 PC FT-IR spectrophotometer
with 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. Gas chromatography (GC) experiments were performed on a
Shimadzu GC-16A instrument using a 2 m column packed with silicon DC-200 or
Carbowax 20M. n-Decane was used as internal standard and yields were determined by
using peak area during the GC testing experiments.
2.2. General procedure for preparation of ruthenium(II) nitrosyl complexes 1−7
To a slurry of Ru(NO)Cl3⋅xH2O (68.4 mg, 0.25 mmol) in N,N’-dimethylformamide
(5 mL) was added a solution of the bidentate N,O-Schiff base (0.25 mmol) or the
tetradentate N2,O2-Schiff base (0.25 mmol) and a little excess of triethylamine (33.0 mg,
0.30 mmol) in tetrahydrofuran (8 mL), and then the reaction mixture was heated at 95 °C
with stirring for ca. 4 h, during which time there was a colour change from orange-red to
dark red. Addition of 35 mL diethyl ether to the reaction solution gave red precipitate
which was filtered and washed with diethyl ether and hexane. The red precipitate was
dissolved in dichloromethane (10 mL). The clearly red filtrate was layered with ethanol
(5 mL) and diethyl ether (15 mL) at room temperature, and red block-shaped crystals
3

were harvested in three or four days.
2.3. [Et3NH][Ru(κ2-N,O-L-Bun)(NO)Cl3]⋅½C2H5OH (1⋅½C2H5OH)
Yield: 72 mg, 56%. IR (KBr disc, cm−1): 3427 (vN−H), 1845 (νN=O), 1614 (νC=N),
1245 (νAr−O); 1H NMR (CDCl3, 400 MHz): δ 0.93 (s, 3H, CH3), 0.99 (s, 9H, CH3), 1.30 (t,
2H, J = 2.6 Hz, CH2), 1.67 (t, 2H, J = 2.8 Hz, CH2), 1.96 (s, 1H, NH), 2.62 (t, 6H, J =
3.1 Hz, CH2), 3.49 (t, 2H, J = 3.4 Hz, CH2), 6.74 (t, 1H, J = 5.9 Hz, ArH), 6.87 (t, 1H, J =
5.6 Hz, ArH), 7.14 (d, 1H, J = 6.2 Hz, ArH), 7.46 (d, 1H, J = 6.0 Hz, ArH), 8.32 (s, 1H, -
CH=N) ppm. MS (FAB): m/z 413 [Ru(κ2-N,O-L-Bun)(NO)Cl3]+, 378 [Ru(κ2-N,O-L-
Bun)(NO)Cl2]+, 343 [Ru(κ2-N,O-L-Bun)(NO)Cl]+, 308 [Ru(κ2-N,O-L-Bun)(NO)]+, 278
[Ru(κ2-N,O-L-Bun)]+. Anal. Calc. for C17H30N3O2Cl3Ru⋅½(C2H6O) (%): C, 40.12; H, 6.17;
N, 7.80. Found: C, 40.07; H, 6.13; N, 7.84.
2.3. [Et3NH][Ru(κ2-N,O-L-CH2Ph)(NO)Cl3] (2)
Yield: 92 mg, 67%. IR (KBr disc, cm−1): 3431 (vN−H), 1852 (νN=O), 1612 (νC=N),
1
1249 (νAr−O); H NMR (CDCl3, 400 MHz): δ 1.01 (s, 9H, CH3), 2.57 (t, 6H, J = 3.0 Hz,
CH2), 4.85 (s, 2H, CH2), 6.79 (t, 2H, J = 4.8 Hz, ArH), 7.04 (dd, 3H, J = 6.2 Hz, ArH),
7.12 (d, 1H, J = 5.0 Hz, ArH), 7.18 (t, 1H, J = 5.7 Hz, ArH), 7.46 (d, 1H, J = 6.0 Hz,
ArH), 8.16 (s, 1H, -CH=N) ppm. MS (FAB): m/z 422 [Ru(κ2-N,O-L-CH2Ph)(NO)Cl3]+,
387 [Ru(κ2-N,O-L-CH2Ph)(NO)Cl2]+, 382 [Ru(κ2-N,O-L-CH2Ph)(NO)Cl]+, 347 [Ru(κ2-
N,O-L-CH2Ph)(NO)]+, 317 [Ru(κ2-N,O-L-CH2Ph)]+. Anal. Calc. for C20H28N3O2Cl3Ru
(%): C, 43.68; H, 5.13; N, 7.64. Found: C, 43.47; H, 5.15; N, 7.61.
2.4. [Et3NH][Ru(κ2-N,O-L-C6H4-4-Cl)(NO)Cl3] (3)
Yield: 91 mg, 64%. IR (KBr disc, cm−1): 3437 (vN−H), 1855 (νN=O), 1623 (νC=N),
1
1253 (νAr−O); H NMR (CDCl3, 400 MHz): δ 1.02 (s, 9H, CH3), 2.54 (t, 6H, J = 3.0 Hz,
CH2), 6.75 (t, 1H, J = 4.6 Hz, ArH), 6.88 (t, 1H, J = 5.1 Hz, ArH), 7.13 (d, 1H, J = 5.0 Hz,
ArH), 7.22 (d, 2H, J = 5.8 Hz, ArH), 7.35 (d, 2H, J = 5.9 Hz, ArH), 7.49 (d, 1H, J = 6.0
Hz, ArH), 8.35 (s, 1H, -CH=N) ppm. MS (FAB): m/z 468 [Ru(κ2-N,O-L-C6H4-4-
Cl)(NO)Cl3]+, 433 [Ru(κ2-N,O-L-C6H4-4-Cl)(NO)Cl2]+, 398 [Ru(κ2-N,O-L-C6H4-4-Cl)-
(NO)Cl]+, 363 [Ru(κ2-N,O-L-C6H4-4-Cl)(NO)]+, 360 [Ru(κ2-N,O-L-C6H4-4-Cl)]+. Anal.
4

Calc. for C19H25N3O2Cl4Ru (%): C, 40.01; H, 4.42; N, 7.37. Found: C, 40.06; H, 4.36; N,
7.32.
2.5. [Et3NH][Ru(κ2-N,O-L-C6H4-4-NO2)(NO)Cl3] (4)
Yield: 106 mg, 73%. IR (KBr disc, cm−1): 3441 (vN−H), 1848 (νN=O), 1619 (νC=N),
1
1571, 1365 (νNO2), 1247 (νAr−O); H NMR (CDCl3, 400 MHz): δ 1.03 (s, 9H, CH3), 2.51
(t, 6H, J = 3.0 Hz, CH2), 6.77 (t, 1H, J = 4.7 Hz, ArH), 6.86 (t, 1H, J = 4.8 Hz, ArH),
7.15 (d, 1H, J = 4.8 Hz, ArH), 7.46 (d, 1H, J = 5.6 Hz, ArH), 7.46 (d, 2H, J = 5.9 Hz,
ArH), 8.17 (d, 2H, J = 5.8 Hz, ArH), 8.38 (s, 1H, -CH=N) ppm. MS (FAB): m/z 478
[Ru(κ2-N,O-L-C6H4-4-NO2)(NO)Cl3]+, 443 [Ru(κ2-N,O-L-C6H4-4-NO2)(NO)Cl2]+, 408 [Ru(κ2-
N,O-L-C6H4-4-NO2)(NO)Cl]+, 373 [Ru(κ2-N,O-L-C6H4-4-NO2)(NO)]+, 343 [Ru(κ2-N,O-L-
C6H4-4-NO2)]+. Anal. Calc. for C19H25N4O4Cl3Ru (%): C, 39.29; H, 4.34; N, 9.65. Found:
C, 39.42; H, 4.31; N, 9.63.
2.6. [Et3NH][Ru(κ2-N,O-L-C6H3-2,6-Pri2)(NO)Cl3] (5)
Yield: 94 mg, 61%. IR (KBr disc, cm−1): 3449 (vN−H), 1852 (νN=O), 1621 (νC=N),
1249 (νAr−O); 1H NMR (CDCl3, 400 MHz): δ 1.04 (s, 9H, CH3), 1.04 (s, 12H, CH3 in Pri),
2.53 (t, 6H, J = 3.0 Hz, CH2), 3.17 (m, 2H, CH in Pri), 6.74 (t, 1H, J = 4.8 Hz, ArH), 6.83
(t, 1H, J = 4.6 Hz, ArH), 6.95 (dd, 2H, J = 4.8 Hz, ArH), 7.14 (tt, 2H, J = 5.2 Hz, ArH),
7.48 (d, 1H, J = 5.6 Hz, ArH), 8.33 (s, 1H, -CH=N) ppm. MS (FAB): m/z 517 [Ru(κ2-N,O-
L-C6H3-2,6-Pri2)(NO)Cl3]+, 482 [Ru(κ2-N,O-L-C6H3-2,6-Pri2)(NO)Cl2]+, 447 [Ru(κ2-N,O-L-
C6H3-2,6-Pri2)(NO)Cl]+, 412 [Ru(κ2-N,O-L-C6H3-2,6-Pri2)(NO)]+, 382 [Ru(κ2-N,O-L-C6H3-
2,6-Pri2)]+. Anal. Calc. for C25H38N3O2Cl3Ru (%): C, 48.43; H, 6.18; N, 6.78. Found: C,
48.31; H, 6.15; N, 6.82.
2.7. [Et3NH][Ru(κ2-N,O-L-CH2CH2-NOH)(NO)Cl3] (6)
Yield: 79 mg, 52%. IR (KBr disc, cm−1): 3456 (vN−H), 3125 (vO−H), 1847 (νN=O),
1
1630, 1617 (νC=N), 1242 (νAr−O); H NMR (CDCl3, 400 MHz): δ 1.03 (s, 9H, CH3), 2.51
(t, 6H, J = 3.0 Hz, CH2), 3.86 (dd, 4H, J = 3.8 Hz, CH2), 4.92 (br, 1H, OH), 6.76 (t, 1H,
J = 4.6 Hz, ArH), 6.81 (dd, 3H, J = 4.8 Hz, ArH), 7.16 (tt, 2H, J = 5.1 Hz, ArH), 7.48 (dd,
2H, J = 5.2 Hz, ArH), 8.09 (s, 1H, -CH=N), 8.15 (s, 1H, -CH=N) ppm. MS (FAB): m/z
5

504 [Ru(κ2-N,O-L-CH2CH2-NOH)(NO)Cl3]+, 469 [Ru(κ2-N,O-L-CH2CH2-NOH)(NO)Cl2]+, 434
[Ru(κ2-N,O-L-CH2CH2-NOH)(NO)Cl]+, 399 [Ru(κ2-N,O-L-CH2CH2-NOH)(NO)]+, 369 [Ru(κ2-
N,O-L-CH2CH2-NOH)]+. Anal. Calc. for C22H31N4O3Cl3Ru (%): C, 43.54; H, 5.15; N, 9.23.
Found: C, 43.42; H, 5.12; N, 9.17.
2.8. [Ru(salen-phn)(NO)Cl]⋅CH2Cl2 (7⋅CH2Cl2)
Yield: 88 mg, 73%. IR (KBr disc, cm−1): 1859 (νN=O), 1625 (νC=N), 1239 (νAr−O); 1H
NMR (CDCl3, 400 MHz): δ 5.11 (s, 2H, CH2Cl2), 6.73 (d, 2H, J = 4.9 Hz, ArH), 6.82 (t,
2H, J = 4.8 Hz, ArH), 7.13 (t, 2H, J = 5.2 Hz, ArH), 7.32 (m, 4H, ArH), 7.46 (d, 2H, J =
5.2 Hz, ArH), 8.26 (s, 2H, -CH=N) ppm. MS (FAB): m/z 480 [Ru(salen-phn)(NO)Cl]+,
445 [Ru(salen-phn)(NO)]+, 415 [Ru(salen-phn)]+. Anal. Calc. for C20H14N3O3ClRu-
⋅(CH2Cl2) (%): C, 44.58; H, 2.85; N, 7.43. Found: C, 44.52; H, 2.87; N, 7.51.
2.9. X-ray crystallography
A summary of crystallographic data and experimental details for complexes 1−7 are
summarized in Table 1. Intensity data were collected on a Bruker SMART APEX 2000
CCD diffractometer using graphite-monochromated Mo-K radiation (λ = 0.71073 Å) at
296(2) K. The collected frames were processed with the software SAINT [17]. The data
was corrected for absorption using the program SADABS [18]. Structures were solved by
the direct methods and refined by full-matrix least-squares on F2 using the SHELXTL
software package [19,20]. All non-hydrogen atoms were refined anisotropically. The
positions of all hydrogen atoms 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. The largest peaks in the final difference maps had
heights of 2.034 (for 3), 2.083 (for 4) and 1.194 e Å−3 (for 5) are in the vicinities of the
ruthenium atoms. The Flack parameter value of −0.05(4) indicates that the correct
enantiomorph has been selected in the structure of complex 1 (space group P21).
2.10. Catalytic hydrogen transfer reactions
Under a high pure dinitrogen atmosphere, the tested ruthenium(II) nitrosyl
complex (0.004 mmol) and potassium hydroxide (10 mL, 0.012 M in iso-propanol) were
6

introduced into a Schlenk tube. The solution was heated to 75 °C for 30 min.
Subsequently, acetophenone (2 mmol) was added. The reaction process was monitored by
GC analysis.
3. Results and discussion
As shown in Scheme 1, treatment of Ru(NO)Cl3⋅xH2O with equal equivalent
bidentate Schiff bases in the presence of Et3N in DMF/THF afforded a series of anionic
ruthenium(II) nitrosyl complexes of the type [Et3NH][Ru(κ2-N,O-LR)(NO)Cl3] (1–5) in
moderate yields. The water molecules in the starting ruthenium(III) compound was just
replaced by one bidentate O,N-ligand in the present reaction system, thus, the anionic
bidentate O,N-ligands bind the ruthenium centre facially. Similar reaction between
Ru(NO)Cl3⋅xH2O and 1 equiv. tetradentate Schiff base of N,N'-disalicylidene-1,2-
ethanediamine (H2salen-en) led to isolation of an anionic complex [Et3NH][Ru(κ2-N,O-L-
CH2CH2-NOH)(NO)Cl3] (6), leaving one nitrogen and one oxygen atoms coordination-
free. Preparation of the related complex [Ru(salen-en)(NO)Cl] has been previously,
reported by reaction of RuCl3⋅3H2O, [Na2(salen-en)] and nitric oxide gas in
ethanol/acetonitrile, but the ruthenium(II) nitrosyl complex [Ru(salen-en)(NO)Cl] was
obtained in a relatively low yield [21]. Interaction of Ru(NO)Cl3⋅xH2O and N,N'-
salicylidene-1,2-phenyldiamine (H2salen-phn) gave the expected neutral complex
[Ru(salen-phn)(NO)Cl] (7) in a good yield of 73%.
IR spectra of Schiff base ligands in all complexes showed a strong band in the
region of 1612−1625 cm−1 which is characteristic of the azomethine group absorptions.
The characteristic band for NO+ group in the ruthenium(II) nitrosyl complexes 1–7 are
found at 1845−1859 cm-1 (νN≡O), compared with that in other reported ruthenium(II)
nitrosyl complex with Schiff base ligand [Ru(salen-en)(NO)Cl] (1844 cm-1) [22], but
much lower than that of the bend N=O group in the typical ruthenium starting material
[Ru(NO)(PPh3)2Cl3] (1881 cm-1) [23]. The aldimine (–CH=N–) proton resonances of
complexes 1–7 appeared at around 8.20 ppm as a singlet. The positive ion FAB mass
spectra of complexes 1−7 display the expected peaks corresponding to the molecular ions
7

{[M+], [M+ − Cl] or [M+ − 2Cl] or [M+ − 3Cl], and [M+ − Cl − NO] or [M+ − 2Cl − NO]
or [M+ − 3Cl − NO] with the characteristic isotopic distribution patterns.
The structures of complexes 1⋅½C2H5OH, 2‒6, and 7⋅CH2Cl2 have been established
by X-ray crystallography. The perspective views of the molecular structures of
complexes 1−7 are shown in Figs. 1−7, respectively, with atom numbering scheme. The
central ruthenium atoms in 1⋅½C2H5OH and 2‒5 are in an octahedral coordination
environment, containing one bidentate Schiff base ligand with the bite N−Ru−O angle
ranging from 88.6(1)° to 90.7(4)°, which is similar to that in the related ruthenium(II)
nitrosyl complex with two bidentate N,O-Schiff base ligands cis-[Ru(NO)(Cl)L2] (HL =
2,4-dibromo-6-[(2,6-diisopropyl-phenylimino)-methyl]-phenol, 89.64°, 90.43°) [24]. The
Ru–N(NO) (1.709(5)–1.779(15) Å) and N≡O (1.053(16)–1.169(7) Å) bond lengths in
1⋅½C2H5OH and 2‒5 are compared with those in other ruthenium(II) nitrosyl complexes
[22−24]. In addition, the Ru–N–O bond angles in complexes 1−5 range from 169.4(16)°
to 176.0(4)°, clearly indicating the linear N≡O coordination where RuII–NO+ is the
electronic structure. The Ru–Cl bond lengths in the range of 2.3550(14)–2.3986(15) Å for
complexes 1‒5 are normal in the related ruthenium(II)-chloride complexes [15].
The bite N−Ru−O angle of 90.31(9)º in complex 6 is similar to those in complexes
1⋅½C2H5OH and 2‒5, whereas the bite N−Ru−O angles of 94.89(12)º and 95.36(13)º in
the neutral salen-ruthenium(II) nitrosyl complex 7⋅CH2Cl2 are obviously larger than that
in the anionic salen-ruthenium(II) nitrosyl complex 6 (90.31(9)º). The bite N−Ru−O
angles in complex 7⋅CH2Cl2 are quite in agreement with those in complex
[Ru(tBu2salophen)(Cl)(NO)] (tBu2salophen = N,N′-1,2-phenylenediaminebis(3-tert-butyl-
salicylideneiminato), 94.16(7)º and 94.17(6)º) [22]. The Ru–N(NO) bond length of
1.748(4) Å in complex 7⋅CH2Cl2 is slight longer than that in complex 6 (1.722(3) Å),
though the N≡O bond lengths of 1.124(5) Å in complex 7⋅CH2Cl2 is slightly shorter than
that in complex 6 (1.144(3) Å). All the Ru−O and Ru−N bond lengths in 1⋅½C2H5OH,
2‒6, and 7⋅CH2Cl2 are similar, indicating the substituents have little effect on the crystal
structures in the present system.
8

The classical transfer hydrogenation of acetophenone by iso-propanol was used as a
testing reaction to explore the catalytic performance of the ruthenium(II)-nitrosyl catalyst
precursors 1‒7 in the transfer hydrogenation. The activities of complexes 2 (75%), 3
(70%) and 4 (74%) are moderate. When the reaction time was extended to two hours, the
yields were not improved. Complex 5, with 2,6-diisopropylphenyl substituent groups in
the R-imine ligand, was the most efficient in the transfer hydrogenation, the conversion
reached 92%. While the activities of complexes 1 (85%), 6 (80%) and 7 (84%) are also
good. These comparisons further suggest that the catalytic activities of ruthenium(II)-
nitrosyl complexes with Schiff bases are affected by the peripheral ligands [25,26].
In summary, a series of anionic and neutral ruthenium(II) nitrosyl complexes with
bi- or tetra-dentate Schiff base ligands were synthesized by reactions of ruthenium(III)
starting material Ru(NO)Cl3⋅xH2O and the corresponding free Schiff bases in the
presence of organic base. The different substituted groups of -n-Bu, -CH2Ph, -4-ClC6H4, -
4-NO2C6H4 and -2,6-iPr2C6H3 at bidentate Schiff base ligands led to the same geometries
of the according ruthenium complexes 1–5, which enriches the structures of ruthenium(II)
nitrosyl complexes with bidentate Schiff base ligands [24]. Similar reactions employing
tetradetate Schiff base ligand H2salen-en or H2salen-phn led to isolation of ruthenium(II)
nitrosyl complexes 6 and 7 with different structural geometries. The catalytic properties
of the transfer hydrogenation of the ruthenium(II)-nitrosyl complexes with Schiff bases
are affected by the supporting ligands.
Supplementary material
Crystallographic
data
for
[Et3NH][Ru(κ2-N,O-L-Bun)(NO)Cl3]⋅½C2H5OH
(1⋅½C2H5OH), [Et3NH][Ru(κ2-N,O-L-CH2Ph)(NO)Cl3] (2), [Et3NH][Ru(κ2-N,O-L-C6H4-
4-Cl)(NO)Cl3] (3), [Et3NH][Ru(κ2-N,O-L-C6H4-4-NO2)(NO)Cl3] (4), [Et3NH][Ru(κ2-
N,O-L-C6H3-2,6-Pri2)(NO)Cl3] (5), [Et3NH][Ru(κ2-N,O-L-CH2CH2-NOH)(NO)Cl3] (6),
and [Ru(salen-phn)(NO)Cl]⋅CH2Cl2 (7⋅CH2Cl2) have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication nos. CCDC 1571301-
1571307, respectively. Copies of the data can be obtained free of charge on application to
9

CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax: (+44)1233-336-033; e-mail:
deposit@ccdc.cam.ac.uk].
Acknowledgements
This project was supported by the Natural Science Foundation of China
(21372007).
References
[1] S. Hossain, L.-M. Nisbett, E.M. Boon. Acc. Chem. Res., 50, 1633 (2017).
[2] Y. Iwamoto, M. Kodera, Y. Hitomi. Chem. Commun., 46, 9539 (2015).
[3] T. Hirano, T. Oi, H. Nagao, K. Morokuma. Inorg. Chem., 42, 6575 (2003).
[4] A. Franke, R. Van Eldik. Eur. J. Inorg. Chem., 4, 460 (2013).
[5] F.G. Doro, K.Q. Kleber, Z.N. da Rocha, G.F. Caramori, A.J. Gomes, E. Tfouni. Coord. Chem.
Rev., 306, 652 (2016).
[6] E. Tfouni, D.R. Truzzi, A. Tavares, A.J. Gomes, L.E. Figueiredo, D.W. Franco. Nitric Oxide-
Biol. Ch., 26, 38 (2012).
[7] F.P. Rodrigues, Z.A. Carneiro, P. Mascharak, C. Curti, R.S. da Silva. Coord. Chem. Rev., 306,
701 (2016).
[8] H. Ikezawa, Y. Ikezawa, E. Miki, K. Mizumachi, T. Ishimori. Inorg. Chim. Acta, 238, 89 (1995).
[9] Y. Suzuki, H. Tomizawa, E. Miki. Inorg. Chim. Acta, 290, 36 (1999).
[10] F. Bottomley, E. Hahn, J. Pickardt, H. Schumann, M. Mukaida, H. Kakihana. J. Chem. Soc.,
Dalton Trans., 2427 (1985).
[11] T.A. Heinrich, G.V. Poelhsitz, R.I. Reis, E.E. Castellano, A. Neves, M. Lanznaster, S.P.
Machado, A.A. Batista, C.M. Costa-Neto. Eur. J. Med. Chem., 46, 3616 (2011).
[12] X.-G. Zhou, J.-S. Huang, P.-H. Ko, K.-K. Cheung, C.-M. Che. J. Chem. Soc., Dalton Trans.,
3303 (1999).
[13] C.-J. Wang, W.-F. Xu, B.-H. Tong, A.-Q. Jia, Q.-F. Zhang, J. Coord. Chem., 70, 1617 (2017).
[14] L.-M. Shi, X.-X. Wang, X.-F. Ma, A.-Q. Jia, Q.-F. Zhang, J. Coord. Chem., 69, 2630 (2016).
[15] X.-F. Yin, H. Lin, A.-Q. Jia, Q. Chen, Q.-F. Zhang. J. Coord. Chem., 66, 3229 (2013).
[16] A.A. Batista, C. Pereira, S.L. Queiroz, L.A.A. Oliveira, R.H.A. Santos, M.T.P. Gambardella.
Polyhedron, 16, 927 (1997).
[17] SMART and SAINT+ for Windows NT Version 6.02a. Bruker Analytical X-ray Instruments Inc.,
Madison, Wisconsin, USA (1998).
10

[18] G.M. Sheldrick. SADABS. University of Göttingen, Germany (1996).
[19] G.M. Sheldrick. SHELXTL Software Reference Manual. Version 5.1. Bruker AXS Inc., Madison,
Wisconsin, USA (1997).
[20] G.M. Sheldrick. Acta Crystallogr. A, 64, 112 (2008).
[21] J. Bordini, D.L. Hughes, J.D.D.M. Neto, C.J. da Cunha. Inorg. Chem., 41, 5410 (2002).
[22] C.F. Works, C.J. Jocher, G.D. Bart, X. Bu, P.C. Ford. Inorg. Chem., 41, 3728 (2002)
[23] B.L. Haymore, J.A. Ibers. Inorg. Chem., 14, 3060 (1975).
[24] H.-Y. Ng, N.-M. Lam, M. Yang, X.-Y. Yi, I.D. Williams, W.-H. Leung. Inorg. Chim. Acta, 394,
171 (2013).
[25] H.-J. Xu, X.-Y. Lu, Y. Cheng, J.-F. Sun, X.-T. Chen, Z.-L. Xue. Organometallics, 28, 6687
(2009).
[26] T. Liu, H. Chai, L. Wang, Z. Yu. Organometallics, 36, 2914 (2017).
11

Table 1. Crystallographic data and experimental details for [Et3NH][Ru(κ2-N,O-L-Bun)(NO)Cl3]⋅½C2H5OH (1⋅½C2H5OH), [Et3NH][Ru(κ2-N,O-L-
CH2Ph)(NO)Cl3] (2), [Et3NH][Ru(κ2-N,O-L-Ph-4-Cl)(NO)Cl3] (3), [Et3NH][Ru(κ2-N,O-L-Ph-4-NO2)(NO)Cl3] (4), [Et3NH][Ru(κ2-N,O-L-Ph-2,6-
Pri2)(NO)Cl3] (5), [Et3NH][Ru(κ2-N,O-L-CH2CH2-NOH)(NO)Cl3] (6), and [Ru(salen-phn)(NO)Cl]⋅CH2Cl2 (7⋅CH2Cl2).
Complex
1
2
3
4
5
6
7
Empirical formula
C18H33N3O2.5-
Cl3Ru
C20H28N3O2-
Cl3Ru
C19H25N3O2-
Cl4Ru
C19H25N4O4-
Cl3Ru
C25H38N3O2-
Cl3Ru
C22H31N4O3-
Cl3Ru
C21H16N3O3-
Cl3Ru
Formula weight
Crystal system
a (Å)
538.89
549.87
570.29
580.85
620.00
606.93
565.79
monoclinic
11.6099(7)
13.6795(9)
16.8793(11)
monoclinic
9.9737(9)
13.623(3)
17.889(3)
monoclinic
9.6895(15)
23.903(4)
10.1597(16)
monoclinic
9.543(4)
23.865(9)
10.434(4)
triclinic
monoclinic
39.033(2)
10.4250(6)
13.5242(7)
monoclinic
12.159(2)
18.852(3)
9.9010(17)
10.1289(13)
10.2066(13)
16.757(3)
101.574(4)
95.961(4)
117.986(2)
1458.9(4)
b (Å)
c (Å)
α
β
γ
(°)
(°)
(°)
105.754(1)
95.002(2)
91.459(4)
90.794(8)
104.737(1)
105.967(4)
V (Å3)
2580.0(3)
2421.4(8)
2352.3(7)
2401.1(15)
5322.2(5)
2182.0(7)
Space group
Z
P21
P21/n
4
P21/n
4
P21/n
4
P-1
C2/c
8
P21/c
4
4
2
Dcalc (g cm-3)
Temperature (K)
F(000)
1.387
296(2)
1108
0.937
16149
1.508
296(2)
1120
0.999
14772
1.610
296(2)
1152
1.141
15123
1.607
296(2)
1176
1.019
14785
1.411
296(2)
640
1.515
296(2)
2480
0.920
17312
1.722
296(2)
1128
1.115
14232
µ(Mo-Kα) (mm-1)
0.837
9472
Total refln
12

Independent refln
Parameters
Rint
10130
486
5530
265
5505
265
8322
271
6287
314
6082
306
4939
280
0.0218
0.0210
0.0794
0.0267
0.0324
0.0457
0.0535
R1a, wR2b (I > 2
σ(I))
0.0422, 0.1059 0.0274, 0.0639 0.0696, 0.1521 0.0696, 0.0896 0.0552, 0.1376 0.0380, 0.0684 0.0471, 0.1021
0.0577, 0.1166 0.0361, 0.0683 0.1382, 0.1835 0.1404, 0.1659 0.0752, 0.1552 0.0737, 0.0805 0.0844, 0.1175
R1, wR2 (all data)
GoFc
1.006
1.020
1.017
1.006
1.030
0.963
1.000
Flack parameter
−0.05(4)
−
−
−
−
−
−
c
2
a R1 = ΣFo– Fc/ΣFo. b wR2 = [Σw(Fo  – Fc2)2/ΣwFo22]1/2 . GoF = [Σw(Fo – Fc) /(Nobs – Nparam)]1/2.
2
13

Table 2. Selected bond lengths (Å) and angles (°) for complexes 1⋅½C2H5OH, 2‒6, and 7⋅CH2Cl2.
complex
Ru
−N(NO) Ru
−O
Ru
−N
Ru
−Cl
N≡O
Ru
−N−O
N−Ru
−O(chelate) N(NO)−Ru−O/Cl
1.709(5)
1.971(4)
2.053(4)
2.3550(14) 1.169(7)
2.3805(16)
175.7(6)
89.10(6)
174.4(2)
1
2.3986(15)
1.7241(19) 1.9618(16) 2.0549(17) 2.3538(6)
1.154(3)
172.18(19) 89.96(7)
171.52(8)
172.7(2)
2
3
4
5
6
7
2.3842(6)
2.4135(7)
1.731(6)
1.779(15)
1.726(4)
1.722(3)
1.748(4)
1.973(5)
1.906(10)
1.977(3)
1.953(2)
2.050(6)
2.044(11)
2.081(3)
2.058(2)
2.3695(19) 1.151(8)
2.3821(18)
174.3(6)
169.4(16)
176.0(4)
175.5(3)
176.3(4)
90.6(2)
2.3933(18)
2.363(5)
2.365(4)
2.380(5)
1.053(16)
90.7(4)
171.9(6)
2.3627(12) 1.144(5)
2.3650(11)
88.63(12)
90.31(9)
175.47(15)
172.38(11)
176.60(12)
2.3906(12)
2.3616(9)
2.3872(8)
2.4011(8)
1.144(3)
2.025(3)
2.023(3)
2.020(3)
2.022(3)
2.3629(13) 1.124(5)
94.89(12)
95.36(13)
14

Scheme 1 Syntheses of complexes 1‒7.
OH N R
O
Cl
N
Cl Ru Cl
R = n-Bu (1), CH2Ph (2), 4-ClC6H4 (3),
4-NO2C6H4 (4), 2,6-i-Pr2-C6H3 (5)
R
O
N
DMF-THF, Et3N
N
N
O
Cl
N
Cl Ru Cl
OH HO
.
Ru(NO)Cl3 xH2O
O
N
DMF-THF, Et3N
6
N
HO
N
N
Cl
N
N
OH HO
Ru
7
O
O
DMF-THF, Et3N
N
O
15

Fig. 1. ORTEP diagram of [Ru(κ2-N,O-L-Bun)(NO)Cl3]− in 1, showing the atom
labeling scheme and 40% thermal ellipsoids. Hydrogen atoms are omitted for
clarity.
Fig. 2. ORTEP diagram of [Ru(κ2-N,O-L-CH2Ph)(NO)Cl3]− in 2, showing the atom
labeling scheme and 40% thermal ellipsoids. Hydrogen atoms are omitted for
clarity.
16

Fig. 3. ORTEP diagram of [Ru(κ2-N,O-L-Ph-4-Cl)(NO)Cl3]− in 3, showing the
atom labeling scheme and 40% thermal ellipsoids. Hydrogen atoms are omitted for
clarity.
Fig. 4. ORTEP diagram of [Ru(κ2-N,O-L-Ph-4-NO2)(NO)Cl3]− in 4, showing the
atom labeling scheme and 40% thermal ellipsoids. Hydrogen atoms are omitted for
clarity.
17

Fig. 5. ORTEP diagram of [Ru(κ2-N,O-L-Ph-2,6-Pri2)(NO)Cl3]− in 5, showing the
atom labeling scheme and 40% thermal ellipsoids. Hydrogen atoms are omitted for
clarity.
Fig. 6. ORTEP diagram of [Ru(κ2-N,O-L-CH2CH2-NOH)(NO)Cl3]− in 6, showing
the atom labeling scheme and 40% thermal ellipsoids. Hydrogen atoms are omitted
for clarity.
18

Fig. 7. ORTEP diagram of [Ru(salen-phn)(NO)Cl] 7, showing the atom labeling
scheme and 40% thermal ellipsoids. Hydrogen atoms are omitted for clarity.
19

Graphical Abstract
Syntheses, structures and catalytic properties of ruthenium(II) nitrosyl complexes
with bidentate and tetradentate Schiff base ligands
Fule Wu, Chang-Jiu Wang, Hui Lin, Ai-Quan Jia, and Qian-Feng Zhang*
Treatment of Ru(NO)Cl3⋅xH2O with bi- or tetra-dentate Schiff base ligands afforded the
corresponding ruthenium(II) nitrosyl complexes in the refluxing DMF/THF. Molecular structures
of all ruthenium(II) nitrosyl complexes have been established by X-ray crystallography and their
catalytic properties of the transfer hydrogenation of acetophenone were also investigated.
20

Highlights
► A series of anionic and neutral ruthenium(II) nitrosyl complexes were synthesized.
►All the synthesized complexes were characterized by X-ray crystallography. ► The
ruthenium complexes were tested as catalyst for the transfer hydrogenation.
21