Synthesis, structure and catalytic alcohol oxidation by ruthenium(III) supported by Schiff base and triphenylphosphine ligands

Article abstract of DOI:10.1016/j.ica.2018.03.017

Treatment of [RuCl₂(PPh₃)₃] with two equiv. bi-dentate Schiff base N,O-LH-Cl (N,O-LH-Cl = 2[(3-chloro-phenylimino)-methyl]-phenol) or N,O-LH-NO₂ (N,O-LH-NO₂ = 2[(4-nitro-phenylimino)-methyl]-phenol) in the presence of triethylamine afforded cis-[RuCl(PPh₃)(κ²-N,O-L-Cl)₂] (1) and trans-[RuCl(PPh₃)(κ²-N,O-L-NO₂)₂]·Et₂O (2), respectively. Reactions of [RuCl₂(PPh₃)₃] and equal equiv. tetra-dentate Schiff bases gave corresponding ruthenium(III) complexes [RuCl(PPh₃)(salen)] (3) (H₂salen = N,N′-disalicylidene-1,2-ethanediamine), [RuCl(PPh₃)(salipn)]·2CH₂Cl₂ (4) (H₂salipn = N,N′-disalicylidene-1,2-(1-methyl)ethanediamine), [RuCl(PPh₃)(salpn)]·CH₂Cl₂ (5) (H₂salpn = N,N′-disalicylidene-1,2-propanediamine), [RuCl(PPh₃)(salphen)]·CH₂Cl₂ (6) (H₂salphen = N,N′-disalicylidene-1,2-phenyldiamine), [RuCl(PPh₃)(saltoln)]·CH₂Cl₂ (7) (H₂saltoln = N,N′-disalicylidene-1,2-tolyldiamine) and [RuCl(PPh₃)(salcyn)] (8) (H₂salcyn = N,N′-disalicylidene-(R,R)-1,2-cyclohexanediamine). The molecular structures of complexes 1–5 and 7 have been determined by single-crystal X-ray crystallography. The catalytic oxidation properties of ruthenium(III) complexes 1–8 were tested towards alcohols in the presence of N-methylmorpholine-N-oxide.

Full text of DOI:10.1016/j.ica.2018.03.017

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Research paper
Synthesis, structure and catalytic alcohol oxidation by ruthenium(III) supported
by Schiff base and triphenylphosphine ligands
Li-Hua Tang, Fule Wu, Hui Lin, Ai-Quan Jia, Qian-Feng Zhang
PII:
S0020-1693(17)31423-8
https://doi.org/10.1016/j.ica.2018.03.017
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Please cite this article as: L-H. Tang, F. Wu, H. Lin, A-Q. Jia, Q-F. Zhang, Synthesis, structure and catalytic alcohol
oxidation by ruthenium(III) supported by Schiff base and triphenylphosphine ligands, Inorganica Chimica Acta
(2018), doi: https://doi.org/10.1016/j.ica.2018.03.017
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Synthesis, structure and catalytic alcohol oxidation by
ruthenium(III) supported by Schiff base and triphenylphosphine
ligands
Li-Hua Tang, Fule Wu, 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 [RuCl2(PPh3)3] with two equiv. bi-dentate Schiff base N,O-LH-Cl (N,O-LH-
Cl = 2[(3-chloro-phenylimino)-methyl]-phenol) or N,O-LH-NO2 (N,O-LH-NO2 = 2[(4-
nitro-phenylimino)-methyl]-phenol) in the presence of triethylamine afforded cis-
[RuCl(PPh3)(κ2-N,O-L-Cl)2] (1) and trans-[RuCl(PPh3)(κ2-N,O-L-NO2)2]Et2O (2),
respectively. Reactions of [RuCl2(PPh3)3] and equal equiv. tetra-dentate Schiff bases gave
corresponding ruthenium(III) complexes [RuCl(PPh3)(salen)] (3) (H2salen = N,N'-
disalicylidene-1,2-ethanediamine), [RuCl(PPh3)(salipn)]2CH2Cl2 (4) (H2salipn = N,N'-
disalicylidene-1,2-(1-methyl)ethanediamine), [RuCl(PPh3)(salpn)]CH2Cl2 (5) (H2salpn =
N,N'-disalicylidene-1,2-propanediamine), [RuCl(PPh3)(salphen)]CH2Cl2 (6) (H2salphen
= N,N'-disalicylidene-1,2-phenyldiamine), [RuCl(PPh3)(saltoln)]CH2Cl2 (7) (H2saltoln =
N,N'-disalicylidene-1,2-tolyldiamine) and [RuCl(PPh3)(salcyn)] (8) (H2salcyn = N,N'-
disalicylidene-(R,R)-1,2-cyclohexanediamine). The molecular structures of complexes 1–
5 and 7 have been determined by single-crystal X-ray crystallography. The catalytic
oxidation properties of ruthenium(III) complexes 1–8 were tested towards alcohols in the
presence of N-methylmorpholine-N-oxide.
Keywords: Ruthenium(III) complex; Schiff base; Synthesis; Crystal structure; Catalytic
oxidation
___________________
* Corresponding author. E-mail: zhangqf@ahut.edu.cn (Q.-F. Zhang).
1

1. Introduction
Ruthenium complexes are extensively being investigated because of their rich
structural, electrochemical, catalytic and biological properties [1‒3]. In this area, the
ruthenium complexes containing N,O-bidentate and N2,O2-tetradentate Schiff bases have
been well studied, of which the N,O-bidentate Schiff base bonded to the ruthenium center
in a typically chelating manner forming an approximately coplanar RuNC3O six-
membered ring and the N2,O2-tetradentate Schiff base chelated with the ruthenium center
forming a stably co-planar RuN2O2 square [4‒7]. Both bi- and tetra-dentate Schiff bases
used in this study have been easily prepared from salicyaldehyde and the substituted
mono- or bis-amines [8], in which the phenolic groups are of oxidation property
depending on the ruthenium starting materials. The reactions of RuII(PPh3)3Cl2 with the
NO/N2O2-Schiff bases proceeding via oxidative addition are subject to reductive proton
elimination, affording motifs of the according ruthenium(III) complexes with the
chelating Schiff base ligands [9]. When the staring materials are K2RuIIICl5(H2O) and
RuIIICl3xH2O, the trivalent ruthenium(III) is unsuitable for oxidative addition and instead
gets accordingly NO/N2O2-chelated ruthenium(III)/(IV) products at the salicylaldimine
sites [10]. Previously, we have reported a series of ruthenium(II) monocarbonyl
complexes with N,O-bidentate Schiff-base ligands and their catalytic behavior towards
alcohols [11]. As our long-standing research interest in the high-valence ruthenium
complexes, we disclose herein syntheses, structures and catalytic oxidation properties of a
series of ruthenium(III) complexes with the coordination type RuN2O2PCl supported by
Schiff base and triphenylphosphine ligands in this paper.
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, 3-chloro-phenylamine, 4-nitro-phenylamine, 1,2-
ethanediamine, 1-methyl-1,2-ethanediamine, 1,3-propanediamine, 1,2-phenyldiamine, 4-
2

methyl-1,2-phenyldiamine, and 1,2-cyclohexanediamine were purchased from Alfa Aesar
Ltd and used without further purification. The N,O-bidentate and N2,O2-tetradentate
Schiff bases (see Chart 1) were prepared by the condensation between salicyaldehyde and
according mono- or bis-amines in the refluxing ethanol. [Ru(PPh3)3Cl2] was prepared
according to the literature method [12]. 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. The magnetic
moment for the solid sample was measured by a Sherwood magnetic susceptibility
balance at room temperature. 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. Synthesis of cis-[RuCl(PPh3)(κ2-N,O-L-Cl)2] (1)
To a solution of N,O-LH-Cl (930 mg, 4.0 mmol) in THF (20 mL) was added
[Ru(PPh3)3Cl2] (868 mg, 2.0 mmol), which was then stirred under N2 for 15 min.
Triethylamine (Et3N) (404 mg, 4.0 mmol) was introduced, and the reaction mixture was
stirred overnight at room temperature, during which the color of solution changed from
brown to dark green. After removal of solvents in vacuo, the residue was extracted with
CH2Cl2 (5 mL 2) and the solution was filtered. The filtrate was layered with Et2O (20
mL) at room temperature, and dark green block-shaped crystals of cis-[RuCl(PPh3)(κ2-
N,O-L-Cl)2] (1) were harvested in three days. Yield: 1187 mg, 69% (based on Ru). eff =
1.98 B. IR (KBr disc, cm1): 1592 (C=N), 1314 (CO), 1437, 1092 and 698 (PPh3). MS
(FAB): m/z 860 [M+], 825 [M+  Cl], 598 [M+  PPh3], 563 [Ru(κ2-N,O-L-Cl)2]+. Anal.
Calc. for C44H33N2O2Cl3PRu(%): C, 61.44; H, 3.87; N, 3.26. Found: C, 61.47; H, 3.83;
N, 3.24.
2.3. Synthesis of trans-[RuCl(PPh3)(κ2-N,O-L-NO2)2]Et2O (2)
To a solution of [Ru(PPh3)3Cl2] (868 mg, 2.0 mmol) in THF (10 mL) was added a
solution of N,O-LH-NO2 (972 mg, 2.0 mmol) and Et3N (404 mg, 4.0 mmol) in EtOH (5
3

mL), and then the mixture was heated at 90 C with stirring overnight, during which there
was a color change from brown to green. After removal of solvents in vacuo, the residue
was extracted with CH2Cl2 (5 mL 2) and the solution was filtered. The clearly green
filtrate was layered with Et2O (20 mL) at room temperature, and dark green block-shaped
crystals of trans-[RuCl(PPh3)(κ2-N,O-L-NO2)2]Et2O (2) were obtained in three days.
Yield: 1356 mg, 71% (based on Ru). eff = 1.97 B. IR (KBr disc, cm1): 1592 (C=N),
1576, 1373 (NO2), 1312 (CO), 1435, 1098 and 694 (PPh3). MS (FAB): m/z 881 [M+],
846 [M+  Cl], 619 [M+  PPh3], 584 [Ru(κ2-N,O-L-NO2)2]+. Anal. Calc. for
C44H33N4O6ClPRu(C4H10O) (%): C, 60.34; H, 4.54; N, 5.86. Found: C, 60.44; H, 4.51;
N, 5.79.
2.4. Synthesis of [RuCl(PPh3)(salen)] (3)
To a round-bottomed flask with a stir bar was placed with [Ru(PPh3)3Cl2] (868 mg,
2.0 mmol) under the nitrogen. Pre-dried THF (10 mL) was added and the resulting
mixture was stirred at room temperature. Then salen-enH2 (536 mg, 2.0 mmol) and a little
excess of Et3N (252 mg, 2.5 mmol) in THF (5 mL) were added. The reaction mixture was
stirred at room temperature overnight. After removal of solvents, CH2Cl2 (15 mL) was
added and the solution was filtered through cilite. The filtrate was concentrated and the
residue was washed with Et2O (5 mL  2) and hexane (5 mL  2) to give the desired
product. Recrystallization from CH2Cl2/Et2O (1:2) afforded green block-shaped crystals
of [RuCl(PPh3)(salen)] (3) suitable for X-ray diffraction in three days. Yield: 1011 mg,
76% (based on Ru). eff = 1.98 B. IR (KBr disc, cm1): 1599 (C=N), 1317 (CO), 1432,
1085 and 690 (PPh3). MS (FAB): m/z 665 [M+], 630 [M+  Cl], 403 [M+  PPh3], 368
[Ru(salen-en)]+. Anal. Calc. for C34H29N2O2ClPRu (%): C, 59.97; H, 3.77; N, 6.36.
Found: C, 60.05; H, 3.73; N, 6.39.
2.5. Synthesis of [RuCl(PPh3)(salipn)]2CH2Cl2 (4)
The method was similar to that used for 3, employing salen-pnH2 (564 mg, 2.0 mmol)
instead of salen-enH2. Yield: 1070 mg, 63% (based on Ru). eff = 1.95 B. IR (KBr disc,
cm1): 1594 (C=N), 1315 (CO), 1428, 1079 and 692 (PPh3). MS (FAB): m/z 679 [M+],
4

644 [M+  Cl], 417 [M+  PPh3], 382 [Ru(salipn)]+. Anal. Calc. for C35H31N2O2ClPRu-
2(CH2Cl2) (%): C, 59.42; H, 4.72; N, 3.75. Found: C, 59.63; H, 4.75; N, 3.72.
2.6. Synthesis of [RuCl(PPh3)(salpn)]CH2Cl2 (5)
The method was similar to that used for 3, employing salen-tnH2 (564 mg, 2.0 mmol)
instead of salen-enH2. Yield: 963 mg, 63% (based on Ru). eff = 1.96 B. IR (KBr disc,
cm1): 1598 (C=N), 1321 (CO), 1421, 1083 and 699 (PPh3). MS (FAB): m/z 679 [M+],
644 [M+  Cl], 417 [M+  PPh3], 382 [Ru(salpn)]+. Anal. Calc. for C35H31N2O2ClPRu-
(CH2Cl2) (%): C, 56.59; H, 4.35; N, 3.67. Found: C, 56.53; H, 4.38; N, 3.70.
2.7. Synthesis of [RuCl(PPh3)(salphen)]CH2Cl2 (6)
The method was similar to that used for 3, employing salen-phnH2 (632 mg, 2.0
mmol) instead of salen-enH2. Yield: 777 mg, 63% (based on Ru). eff = 1.94 B. IR (KBr
disc, cm1): 1591 (C=N), 1315 (CO), 1428, 1079 and 692 (PPh3). MS (FAB): m/z 711
[M+], 676 [M+  Cl], 449 [M+  PPh3], 416 [Ru(salphen)]+. Anal. Calc. for
C38H29N2O2ClPRu(CH2Cl2) (%): C, 58.69; H, 3.92; N, 3.51. Found: C, 58.74; H, 3.87;
N, 3.48.
2.8. Synthesis of [RuCl(PPh3)(saltoln)]CH2Cl2 (7)
The method was similar to that used for 3, employing salen-tolnH2 (660 mg, 2.0
mmol) instead of salen-enH2. Yield: 1039 mg, 64% (based on Ru). eff = 1.96 B. IR
(KBr disc, cm1): 1591 (C=N), 1318 (CO), 1423, 1071 and 697 (PPh3). MS (FAB): m/z
727 [M+], 692 [M+  Cl], 465 [M+  PPh3], 430 [Ru(saltoln)]+. Anal. Calc. for
C39H31N2O2ClPRu(CH2Cl2) (%): C, 59.16; H, 4.10; N, 3.45. Found: C, 59.13; H, 4.04;
N, 3.51.
2.9. Synthesis of [RuCl(PPh3)(salcyn)] (8)
The method was similar to that used for 3, employing salen-R,R’-cynH2 (644 mg, 2.0
mmol) instead of salen-enH2. Yield: 818 mg, 57% (based on Ru). eff = 1.99 B. IR (KBr
disc, cm1): 1590 (C=N), 1308 (CO), 1411, 1074 and 696 (PPh3). MS (FAB): m/z 718
5

[M+], 683 [M+  Cl], 456 [M+  PPh3], 421 [Ru(salcyn)]+. Anal. Calc. for
C38H34N2O2ClPRu (%): C, 63.55; H, 4.77; N, 3.90. Found: C, 63.53; H, 4.76; N, 3.94.
2.10. X-ray crystallography
A summary of crystallographic data and experimental details for complexes 15
and 7 are summarized in Table 1. Intensity data were collected on a Bruker SMART
APEX 2000 CCD diffractometer using graphite-monochromated Mo-K radiation ( =
0.71073 Å) at 296(2) K. The collected frames were processed with the software SAINT
[13]. The data was corrected for absorption using the program SADABS [14]. Structures
were solved by the direct methods and refined by full-matrix least-squares on F2 using
the SHELXTL software package [15,16]. 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 displacement parameters but were not refined.
2.11. Procedure for catalytic oxidation of alcohols
Oxidations of primary alcohols to aldehydes and secondary ones to ketones were
catalyzed by complexes 18 in the presence of N-methylmorpholine-N-oxide (NMO) as
co-oxidant. A typical reaction using complexes 18 as catalysts is as follows. A solution
of each of complexes 18 (0.01 mmol) in 10 mL of CH2Cl2 was added to the mixture of
substrate (1 mmol) and NMO (2 mmol). The mixture was stirred at room temperature for
12 h and the solvent was evaporated under reduced pressure with a rotary evaporator
resulting in a solid mass. Then it was shaken with petroleum ether (30~40 C) (20 mL).
The oxidized product extracted into petroleum ether was analyzed by GC.
3. Results and discussion
As shown in Scheme 1, interaction of [RuCl2(PPh3)3] with two equiv. Schiff base
ligand N,O-LH-Cl at room temperature in the presence of organic base afforded cis-
[RuCl(PPh3)(κ2-N,O-L-Cl)2] (1), while the similar reaction employing N,O-LH-NO2
compound occurred at 90 C resulted in formation of trans-[RuCl(PPh3)(κ2-N,O-L-
6

NO2)2]Et2O (2). It appears that reaction of [RuCl2(PPh3)3] with N,O-bidentate Schiff
bases may probably depend on thermo-dynamic conditions such as reactive temperature
and solvent, which will be needed more examples to explain the relationship between
reaction conditions and substituted groups of N,O-bidentate Schiff base ligands [17].
Reactions of [RuCl2(PPh3)3] and equal equiv. tetra-dentate Schiff bases gave
corresponding ruthenium(III) complexes with O2,N2-salen ligands, [RuCl(PPh3)(salen)]
(3),
[RuCl(PPh3)(salipn)]2CH2Cl2
(6),
(4),
[RuCl(PPh3)(salpn)]CH2Cl2
(7)
(5),
[RuCl(PPh3)(salphen)]CH2Cl2
[RuCl(PPh3)(saltoln)]CH2Cl2
and
[RuCl(PPh3)(salcyn)] (8). Two PPh3 ligands and one chloride in the starting ruthenium(II)
compound were just replaced by two bidentate O,N-ligands or one tetradentate O2,N2-
ligand in the present reaction system, thus, the anionic bidentate O,N-ligands or
tetradentate O2,N2-ligands bind the ruthenium(III) centre. IR spectra of all Schiff base
ligands showed a strong band in the region 15901599 cm1 which is characteristic of the
-CH=N- group absorptions. Absorption due to phenolic OH was not observed in the IR
spectra of all the complexes, suggesting deprotonation prior to coordination to the
ruthenium atom. The C‒O stretching vibration modes were found at around 1315 cm1 in
the IR spectra of complexes 18. The effective magnetic moment µeff of 1.941.99 µB at
room temperature is consistent with a ruthenium(III) formulation for complexes 1‒8 [18].
The positive ion FAB mass spectra of 18 display the expected peaks corresponding to
the molecular ions {[M+], [M+  Cl] or [M+  PPh3], and [ML2]+, or [ML]+ } with the
characteristic isotopic distribution patterns.
The structures of complexes 15 and 7 have been established by X-ray
crystallography. The perspective views of the molecular structures of 15 and 7 are
shown in Figs. 16, respectively, with atom numbering scheme. Selected bond lengths
and bond angles for complexes 15 and 7 are summarized in Table 2 for the comparison.
The central ruthenium atom in complexes 15 and 7 is in an octahedral coordination
environment, containing two bidentate ligands or one tetradentate ligand with the bite
NRuO angles (av. 90.7(1)). The triphenylphosine ligand and chloro ligand are cis in 1
with the PRuCl angle of 93.51(2), which is compared with that in few reported
7

RuN2O2PCl complexes [Ru(κ2-N,O-L)2(PPh3)Cl] (L = 3-ethyliminomethyl-2-hydroxy-5-
methyl-benzaldehyde, 90.2(1)) [10], [RuCl(bsp)2(PPh3)] (Hbsp [N-(2-
hydroxybenzylidene)-benzothiazole, 92.37) [17], [Ru(PPh3)Cl(PhenoxSQ)2]
=
(HPhenoxSQ = 1-hydroxy-2,4,6,8-tetra-tert-butylphenoxazinyl radical, 99.8(1)) [19].
The PRuCl angles (average value of 176.52(3)) in complexes 25 and 7 are well in
the range of other RuN2O2PCl complexes [RuCl(PPh3){sal-(RR)-chxn}] (H2sal-(RR)-
chxn
=
N,N'-disali-cylidene-(R,R)-1,2-cyclohexanediamine, 173.7(3)) [6] and
[(OL)Ru(PPh3)Cl] (OL = azosalen, 179.07(2)) [20]. The RuP and RuCl bond lengths
in cis-[RuCl(PPh3)(κ2-N,O-L-Cl)2] 1 (2.3489(5) and 2.3691(5) Å) are a little shorter than
those in complex 2 (2.4063(8) and 2.4290(8) Å). The average RuN and RuO bond
lengths in complexes 1 and 2 are 2.094(2) and 1.988(2) Å, respectively, which are similar
to those in salen-type ruthenium(III) complexes 35 and 7 (av. RuN = 2.004(4) Å and
av. RuO = 2.009(3) Å), indicating the bi- and tetra-dentate Schiff base ligands have little
difference in coordinating ability to the ruthenium(III) center.
Ruthenium(III) complexes 18 have been found to catalyze oxidation of primary
alcohols to corresponding aldehydes and secondary alcohols to ketones in dichloro-
methane in the presence of NMO (Scheme 2). Various alcohols have been selectively
converted into corresponding aldehydes or ketones with 1 mol% of the ruthenium(III)-
Schiff complex catalysts. It has been observed that neither the present complex nor NMO
alone causes this organic transformation under identical reaction conditions. The
precursor complex [Ru(PPh3)3Cl2] showed less catalytic property compared with the
present ruthenium(III)-Schiff complexes bearing bi- or tetra-dentate Schiff base and
triphenylphosphine ligands. The TON (%conversion) values are given in Table 3, which
showed that all the substrates were efficiently converted to the corresponding ketones or
aldehydes. Substituted benzylic primary alcohols bearing electron-donating and electron-
withdrawing groups all afforded the corresponding aldehydes in good conversions that
seem no obvious difference. Benzylic secondary alcohols were found to be smoothly
oxidized to the corresponding ketones with moderate yields. No further oxidation of
aldehydes to acids was observed even after extended reaction time. The efficiency of
8

oxidation of benzylic alcohols is higher than already reported catalytic systems of
[RuX(EPh3)L] (where X = Cl/Br; E = P/As; and L = dibasic tetradentate Schiff base
derived by condensation of ethylenediamine with acetoacetanilide/acetoacetotoluidide-
/ethylacetoacetate) [21] and is well compared with binuclear ruthenium(III) bis(thiosemi-
carbazone) complexes [22]. Unlike benzylic alcohols, the conversion was not
encouraging in the case of cyclohexanol and 1-cyclohexylethanol which were converted
into their corresponding ketones in 72%80% yields. The investigations to understand
further catalytic mechanics and properties of the ruthenium(III) complexes containing
bidentate and tetradentate Schiff base ligands are in progress.
In summary, a series of ruthenium(III) complexes with bi- or tetradentate Schiff
base ligands were synthesized and characterized from ruthenium(II) starting compound
[RuCl2(PPh3)3], confirming the much or less oxidative property of Schiff bases towards
[RuCl2(PPh3)3] [9]. The different chloro and nitro substituted groups at bidentate Schiff
base ligands lead to different geometries of the according ruthenium(III) complexes cis-
[RuCl(PPh3)(κ2-N,O-L-Cl)2] 1 and trans-[RuCl(PPh3)(κ2-N,O-L-NO2)2]Et2O 2. The
ruthenium(III) complexes 1‒8 exhibited obviously catalytic performance on oxidation of
alcohols to corresponding aldehydes or ketones in the presence of NMO co-oxidant, and
the Schiff base ligands with different electron-donating and electron-withdrawing groups
have little influence on the catalytic activity. It may provide a simple and alternative
method for the oxidation of different kinds of alcohols under relatively mild conditions.
Supplementary material
Crystallographic data for 1‒5 and 7 have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication nos. CCDC 1573974-
1573979, 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].
Acknowledgements
9

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

Table 1. Crystallographic data and experimental details for cis-[RuCl(PPh3)(κ2-N,O-L-Cl)2] (1), trans-[RuCl(PPh3)(κ2-N,O-L-NO2)2]Et2O (2),
[RuCl(PPh3)(salen)] (3), [RuCl(PPh3)(salipn)]2CH2Cl2 (4), [RuCl(PPh3)(salpn)]CH2Cl2 (5), and [RuCl(PPh3)(saltoln)]CH2Cl2 (7).
Complex
1
2
3
4
5
7
Empirical formula
C44H33N2O2Cl3-
PRu
C48H43N4O7Cl-
PRu
C34H29N2O2Cl-
PRu
C37H35N2O2Cl5-
PRu
C36H33N2O2Cl3- C40H33N2O2Cl3-
PRu
PRu
Formula weight
Crystal system
a (Å)
860.11
955.35
665.08
848.96
764.03
812.07
triclinic
monoclinic
13.823(2)
16.702(3)
20.431(3)
monoclinic
11.0725(4)
21.2498(7)
12.7703(4)
monoclinic
14.629(3)
13.910(2)
18.647(3)
monoclinic
9.2508(3)
34.8344(10)
11.4042(3)
monoclinic
14.2537(18)
13.7095(17)
18.923(2)
8.6244(7)
11.6785(10)
20.768(2)
101.232(1)
96.151(1)
110.548(1)
1885.8(3)
b (Å)
c (Å)
 (°)
107.047(2)
101.966(2)
103.163(4)
112.641(2)
103.596(2)
 (°)
 (°)
V (Å3)
4509.6(12)
2939.41(17)
3694.8(11)
3391.75(17)
3594.1(8)
Space group
Z
P-1
P21/n
4
P21/c
4
P21/n
4
P21/c
4
P21/n
4
2
Dcalc (g cm-3)
Temperature (K)
F(000)
μ(Mo-Kα) (mm-1)
Total refln
Independent refln
1.515
296(2)
874
1.407
296(2)
1964
0.498
26800
10086
1.503
296(2)
1356
0.713
29366
6790
1.526
296(2)
1724
0.865
23173
8322
1.496
296(2)
1556
0.781
32908
7691
1.501
296(2)
1652
0.742
22060
8160
0.712
11850
8354
11

Parameters
Rint
478
561
370
434
406
443
0.0131
0.0237
0.0599
0.0649
0.0434
0.0600
R1a, wR2b (I > 2(I))
R1, wR2 (all data)
GoFc
0.0287, 0.0663
0.0338, 0.0691
1.016
0.0358, 0.0836
0.0606, 0.1020
1.077
0.0428, 0.0789
0.0852, 0.0921
1.016
0.0779, 0.1097
0.1009, 0.1486
1.025
0.0560, 0.1040
0.0673, 0.1253
0.970
0.0562, 0.1377
0.1095, 0.1647
1.035
a R1 = Fo– Fc/Fo.
2
2 2 1/2
b wR2 = [w(Fo  – Fc2)2/wFo  ]
.
c GoF = [w(Fo – Fc)2/(Nobs – Nparam)]1/2.
12

Table 2.
Selected bond lengths (Å) and angles () for complexes 15 and 7.
complex RuN
RuO
RuP
RuCl
NRuO
89.10(6)
88.95(6)
91.07(8)
90.24(8)
90.60(10)
90.36(10)
ClRuP
2.0890(16) 2.0215(13) 2.3489(5)
2.1469(16) 1.9735(13)
2.3691(5)
93.51(2)
1
2
3
4
5
7
2.076(2)
2.062(2)
1.986(3)
1.992(3)
2.009(5)
1.987(6)
2.035(4)
2.052(4)
2.017(4)
2.005(4)
1.9814(17) 2.4063(8)
1.9759(17)
2.4290(8)
2.4423(9)
177.41(3)
177.86(3)
176.06(7)
175.88(4)
176.09(5)
2.011(2)
2.022(2)
2.015(4)
2.015(4)
2.007(3)
2.014(3)
2.004(3)
2.013(3)
2.3507(9)
2.3377(16) 2.4468(18) 90.74(19)
90.8(2)
2.3659(11) 2.4223(12) 89.58(15)
91.10(14)
2.3442(13) 2.4455(13) 92.60(14)
91.08(14)
13

Table 3. Oxidation of alcohols of corresponding aldehydes and ketones with NMO co-oxidant catalyzed by complexes 18a
Entry
Substrate
Product
TONb (% conversionsc)d
1
2
3
4
5
6
7
8
O
OH
1
785(74)
765(72)
801(77)
809(78)
795(75)
823(82)
849(81)
836(80)
O
OH
2
3
772(73)
782(78)
753(70)
779(75)
791(76)
805(79)
804(80)
835(83)
812(78)
830(79)
816(77)
843(84)
902(86)
887(82)
892(85)
875(82)
O
OH
H CO
3
H CO
3
O
OH
4
5
782(78)
802(81)
779(75)
841(84)
805(79)
837(83)
835(83)
896(87)
830(79)
821(82)
843(84)
809(80)
887(82)
892(86)
875(82)
883(85)
Cl
Cl
O
OH
O N
2
O N
2
CHO
CHO
6
7
8
1004(90) 1012(92) 992(91)
1102(94) 998(89)
926(88)
996(93)
1006(89) 1108(93)
1162(92) 1247(95)
OH
1220(93) 1158(95) 1109(94) 1004(91) 972(90)
OH
CHO
1215(91) 1126(92) 1002(91) 985(89)
994(92)
992(91)
1019(95) 1271(95) 1118(91)
1006(93) 1126(92) 1083(90)
OH
H3CO
H3CO
Cl
CHO
9
980(88)
1073(90) 972(86)
959(87)
OH
Cl
14

CHO
10
11
1124(92) 1233(93) 1039(90) 974(88)
987(93)
949(91)
1234(95) 1089(93) 1025(91)
OH
O2N
O N
2
OH
O
891(85)
899(86)
810(82)
852(84)
883(87)
819(83)
928(90)
902(91)
910(89)
903(86)
916(85)
913(87)
887(88)
854(84)
OH
OH
O
O
12
13
915(88)
692(79)
627(73)
637(77)
610(74)
784(79)
604(72)
814(80)
783(77)
825(80)
793(80)
810(80)
629(75)
721(79)
637(76)
713(78)
794(79)
14
OH
O
a Reaction conditions: alcohol (1 mmol), NMO (2 mmol), catalyst (0.01 mmol), dichloromethane (20 mL), stirring for 12 h, room temperature.
b TON is a ratio of mmol of product/mmol of catalyst.
c Conversions (%) are measured relative to the starting alcohol after 12 h.
d Yield is determined by GC with area normalization.
15

Chart 1. Schematic of N,O-LH-Cl, N,O-LH-NO2, and series salen-type ligands.
OH
N
OH
N
HO
N
X
N
N
N
N
N
N
N
N
N
N
N
N
X = 3-Cl
4-NO
=
N,O-L-Cl
N,O-L-NO
N
N
2
2
salcyn
saltoln
salen
salipn
salpn
salphen
Scheme 1. Synthesis of ruthenium(III) complexes 1‒8.
NO
2
Cl
Ph P
PPh
3
PPh
3
3
N
N
O
N
Cl
Cl
Ru
Ru
Cl
Ph P
3
Ru
O
O
O
Cl
PPh
3
N
Cl
O N
2
Cl
N
O
N
O
trans-[RuCl(PPh )(N,O-L-Cl) ] 2
3
2
cis-[RuCl(PPh )(N,O-L-Cl) ] 1
3
2
Ru
PPh
3
[RuCl(PPh )(salen)] 3
[RuCl(PPh )(salphen)] 6
3
3
[RuCl(PPh )(salipn)] 4
[RuCl(PPh )(saltoln)] 7
3
3
[RuCl(PPh )(salpn)]
5
[RuCl(PPh )(salcyn)] 8
3
3
Scheme 2. Catalytic oxidation reactions of alcohols to aldehydes/ketones.
OH
O
Ru(III) catalyst (1 mol%)
NMO /CH Cl , r.t., 12 h
R
R'
R'
R
2
2
R = R' = Alkyl (or) aryl (or) H
16

Fig. 1. Molecular structure of cis-[RuCl(PPh3)(κ2-N,O-L-Cl)2] (1), showing the
atom labeling scheme and 40% displacement parameters. Hydrogen atoms are
omitted for clarity.
Fig. 2. Molecular structure of trans-[RuCl(PPh3)(κ2-N,O-L-NO2)2]Et2O (2),
showing the atom labeling scheme and 40% displacement parameters. Hydrogen
atoms and solvent are omitted for clarity.
17

Fig. 3. Molecular structure of [RuCl(PPh3)(salen)] (3), showing the atom labeling
scheme and 40% displacement parameters. Hydrogen atoms are omitted for clarity.
Fig. 4. Molecular structure of [RuCl(PPh3)(salipn)]2CH2Cl2 (4), showing the atom
labeling scheme and 40% displacement parameters. Hydrogen atoms and solvent
are omitted for clarity.
18

Fig. 5. Molecular structure of [RuCl(PPh3)(salpn)]CH2Cl2 (5), showing the atom
labeling scheme and 40% displacement parameters. Hydrogen atoms and solvent
are omitted for clarity.
Fig. 6. Molecular structure of [RuCl(PPh3)(saltoln)]CH2Cl2 (7), showing the atom
labeling scheme and 40% displacement parameters. Hydrogen atoms and solvent
are omitted for clarity.
19

Graphical Abstract
Synthesis, structure and catalytic alcohol oxidation by ruthenium(III) supported by
Schiff base and triphenylphosphine ligands
Li-Hua Tang, Fule Wu, Hui Lin, Ai-Quan Jia, and Qian-Feng Zhang*
Ruthenium(III) complexes with N,O-bidentate and N2,O2-tetradentate Schiff base ligands are
synthesized from [Ru(PPh3)3Cl2] in the refluxing tetrahydrofuran. The catalytic oxidation
properties of these ruthenium(III) complexes were tested towards the substituted alcohols.
20

Highlights
► Reactions of [RuCl2(PPh3)3] and Schiff bases afford a series of Ru(III) complexes. ►
Ruthenium complexes with bi- and tetra-dentate Schiff bases were fully characterized. ►
The ruthenium(III) complexes were tested as catalyst for oxidation of alcohols.
21