Ruthenium(II) carbonyl complexes containing tetradentate schiff bases and their catalytic activities

Article abstract of DOI:10.1080/15533170600732619

The reactions of ruthenium(II) complexes, [RuHX(CO) (EPh 3 ) 2 (B)] [X=H or Cl; E=P or As; B=PPh 3 , AsPh 3 or pyridine(Py)] with tetradentate Schiff base ligands derived by condensing o -aminophenol or o -aminothiophenol with gloxyal or benzil have been carried out. The new complexes have been characterised by analytical, IR, electronic, 1 H NMR spectral studies and are formulated as [Ru(CO)(B)(L)] [L=Schiff base anion; B=PPh 3 , AsPh 3 or pyridine(Py)]. An octahedral structure has been tentatively proposed for the new complexes. The new complexes were found to be effective catalysts for the oxidation of benzyl alcohol to benzaldehyde using N-methylmorpholine-N-oxide as a co-oxidant. Copyright

Full text of DOI:10.1080/15533170600732619

This article was downloaded by: [Texas A & M International University]
On: 07 October 2014, At: 23:40
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,
37-41 Mortimer Street, London W1T 3JH, UK
Synthesis and Reactivity in Inorganic, Metal-Organic,
and Nano-Metal Chemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/lsrt20
Ruthenium(II) Carbonyl Complexes Containing
Tetradentate Schiff Bases and Their Catalytic Activities
P. Viswanathamurthi a & K. Natarajan b
a Department of Chemistry , Periyar University , Salem, India
b Department of Chemistry , Bharathiar University , Coimbatore, India
Published online: 15 Feb 2007.
To cite this article: P. Viswanathamurthi & K. Natarajan (2006) Ruthenium(II) Carbonyl Complexes Containing Tetradentate
Schiff Bases and Their Catalytic Activities, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry,
36:5, 415-418
To link to this article: http://dx.doi.org/10.1080/15533170600732619
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the
Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and
should be independently verified with primary sources of information. Taylor and Francis shall not be liable for
any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever
or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of
the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry, 36:415–418, 2006
Copyright # 2006 Taylor & Francis Group, LLC
ISSN: 0094-5714 print/1532-2440 online
DOI: 10.1080/15533170600732619
Ruthenium(II) Carbonyl Complexes Containing Tetradentate
Schiff Bases and Their Catalytic Activities
P. Viswanathamurthi
Department of Chemistry, Periyar University, Salem, India
K. Natarajan
Department of Chemistry, Bharathiar University, Coimbatore, India
complexes. The general structure of the Schiff base ligands
The reactions of ruthenium(II) complexes, [RuHX(CO) used in this study is shown in Figure 1.
(EPh3)2(B)] [X5H or Cl; E5P or As; B 5 PPh3, AsPh3 or pyridi-
ne(Py)] with tetradentate Schiff base ligands derived by conden-
EXPERIMENTAL
sing o-aminophenol or o-aminothiophenol with gloxyal or benzil
have been carried out. The new complexes have been character-
.
RuCl3 3H2O was purchased from Loba-chemie and was
1
ised by analytical, IR, electronic, H NMR spectral studies and
used without further purification. Solvents were purified and
dried according to standard procedure.[7] Microanalyses
(C, H and N) were performed at the Central Drug Research
are formulated as [Ru(CO)(B)(L)] [L 5 Schiff base anion;
B 5 PPh3, AsPh3 or pyridine(Py)]. An octahedral structure has
been tentatively proposed for the new complexes. The new com-
plexes were found to be effective catalysts for the oxidation of Institute, Lucknow. IR spectra of the ligands and complexes
benzyl alcohol to benzaldehyde using N-methylmorpholine-N-
oxide as a co-oxidant.
were recorded in KBr pellets with a Perkin-Elmer 597
infrared diffraction grating spectrophotometer in the 4000–
250 cm21 range. Electronic spectra of the complexes were
Keywords ruthenium(II) Schiff base, triphenylphosphine, tripheny-
larsine, N-methylmorpholine-N-oxide, catalytic activity
recorded in dichloromethane using a Systronics 119 spectro-
meter in the 750–200 nm range. 1H NMR spectra were
recorded on a Bruker WM 400 instrument using tetramethylsi-
lane (TMS) as an internal standard. Melting points were
recorded on a Boetius microheating table and are uncorrected.
The starting complexes [RuHCl(CO)(PPh3)3], [RuH2(CO)
(PPh3)3],[8] [RuHCl(CO)(AsPh3)3],[9] [RuHCl(CO)(PPh3)2
(Py)][10] and the Schiff base ligands[11] were prepared accord-
ing to published procedures.
INTRODUCTION
Schiff bases and their metal complexes play a key role in the
understanding of the coordination chemistry of transition metal
ions. They may serve as models in biologically important
species, finding applications in biological, clinical, analytical
and catalytic activities.[1–4] Earlier work has shown that
some drugs showed increased activity when administered as
metal chelates rather than as organic compounds.[1] Ruthenium
Schiff base complexes, particularly those containing oxygen
and nitrogen as donor atoms were found to be very efficient cat-
alysts in the oxidation of alcohols using N-methylmorpholine-
N-oxide as co-oxidant.[5,6]
Preparation of New Ruthenium(II) Complexes,
[Ru(CO)(B)(L)]
(B ¼ PPh3, AsPh3 or pyridine(Py); L ¼ Schiff base ligand
dianion)
All the new complexes were prepared by the following
general procedure. To a solution of [RuHX(CO)(EPh3)2(B)]
[X¼H or Cl; E¼P or As; B ¼ PPh3, AsPh3 or pyridine(Py)]
(0.1 g, 0.1–0.13 mmol) in benzene (25 mL), was added the
appropriate Schiff base (0.021–0.051 g, 0.1–0.13 mmol)
(molar ratio of ruthenium complex:Schiff base was 1 : 1).
The solution was heated under reflux for 6 h. Then, it was
concentrated to a small volume (3 mL) and the new complex
was separated from it by the addition of a small quantity
(6 mL) of light petroleum (60–80 8C). The product was
filtered, washed with light petroleum and recrystallised from
As a part of our continuing efforts to synthesis and
characterise ruthenium chelates using simple and inexpensive
Schiff base ligands, in this paper we describe the synthesis,
characterisation and catalytic studies of stable ruthenium(II)
Received 8 March 2006; accepted 30 March 2006.
Address correspondence to P. Viswanathamurthi, Department of
Chemistry, Periyar University, Salem 636 011, India. E-mail:
viswanathamurthi@yahoo.com
415

416
P. VISWANATHAMURTHI AND K. NATARAJAN
The analytical data for the new complexes (Table 1) agrees
very well with the proposed molecular formulae. The reactions
of [RuHCl(CO)(PPh3)3] and [RuH2(CO)(PPh3)3] with Schiff
bases yielded similar complexes.[12] In all of the above reac-
tions, the Schiff bases behave as binegative tetradentate
ligands.
Infrared Spectra
The infrared spectra of the ligands did not exhibit any
absorption corresponding to n(C55N), n(O-H) or n(S–H)
because the condensation of glyoxal or benzil with o-amino-
phenol or o-aminobenzene thiol does not give the expected
Schiff bases. These reactions involve ring closure with the for-
mation of heterocyclic compounds. The hetrocyclic com-
pounds rearrange to give Schiff base complexes in the
presence of metal ions.[11] The equilibrium (I–III) between
the heterocyclic compound and the corresponding Schiff base
takes place in the presence of metal ions.
FIG. 1. Structure of the Schiff base ligands.
CH2Cl2/light petroleum (60–80 8C) mixture and dried in
vacuo. Yields: 71–80%.
Catalytic Studies
To a solution of alcohol (1 mmol) in CH2Cl2 (20 mL) was
added N-methylmorpholine-N-oxide (3 mmol) and the ruthe-
nium complex (0.01 mmol). The solution was heated under
reflux for 3 h. The mixture was evaporated to dryness and
extracted with light petroleum (60–80 8C) (3 ꢀ 10 mL). The
combined light petroleum extracts were filtered and evaporated
to give the corresponding aldehyde that was quantified as the 2,
4–dinitrophenyl hydrazone derivative.
The IR spectra of all the complexes showed a strong band at
1627–1629 cm21 (Table 2), which has been assigned to the
coordinated azomethine group.[13] The phenolic C–O stretch-
ing at 1342–1343 cm21 and the phenolic C–S stretching at
747–749 cm21 showed that the other coordination is through
oxygen or sulphur.[14,15] The strong absorption around 1941–
1961 cm21 has been assigned to the coordinated terminal
carbonyl group in the new ruthenium complexes. In the com-
plexes containing coordinated pyridine, a weak band is
RESULTS AND DISCUSSION
New
hexa-coordinated
ruthenium(II)
complexes
[Ru(CO)(B)(L)] [L ¼ Schiff base anion; B ¼ PPh3, AsPh3 or
pyridine(Py)] have been prepared from [RuHX(CO)(EPh3)2
(B)] [X ¼ H or Cl; E ¼ P or As; B ¼ PPh3, AsPh3 or pyridi-
ne(Py)] and the respective Schiff bases (molar ratio 1 : 1) in
dry benzene as shown next.
observed around 1020 cm21 [16]
In addition, characteristic
.
absorptions of triphenylphosphine / arsine were also present
in the expected regions.
Electronic Spectra
The new ruthenium(II) Schiff base complexes are diamag-
netic, indicating the presence of ruthenium in the þ2 oxidation
state. The ground state of ruthenium(II) is 1A1g arising from the
t62g configuration in an octahedral environment. The excited
3
3
state corresponding to the t52g eg1 configuration are T1g, T2g,
1
1T1g and T2g. Hence, four bands corresponding to the
3
3
1
transitions
1A1g ! T1g,
1A1g ! T2g,
1A1g ! T1g,
1A1g ! T2g are possible in the order of increasing energy.
The electronic spectra of all the complexes in dichloromethane
showed a band in the 275–295 nm region (Table 2). This band
has been assigned to the charge-transfer transition arising from
the excitation of an electron from the metal t2g level to the
unfilled m.o.’s derived from the pꢁ level of the ligands, in
accordance with the assignments made for other similar
octahedral ruthenium(II) complexes.[17,18]
1

RUTHENIUM(II) CARBONYL COMPLEXES
417
TABLE 1
Analytical and physical data of the Ru(II) Schiffbase complexes
Elemental analyses, (%) found (calc.)
M.p.
( 8C)
Complex
Color
C
H
N
[Ru(CO)(PPh3)(apg)]
[Ru(CO)(PPh3)(apb)]
[Ru(CO)(PPh3)(atg)]
[Ru(CO)(AsPh3)(apg)]
[Ru(CO)(AsPh3)(apb)]
[Ru(CO)(AsPh3)(atg)]
[Ru(CO)(Py)(apg)]
[Ru(CO)(Py)(apb)]
[Ru(CO)(Py)(atg)]
Green
Brown
Green
Green
Brown
Green
Green
Brown
Green
149
202
165
162
152
223
207
165
210
62.51(62.93)
69.07(69.16)
59.52(59.83)
58.44(58.88)
65.14(65.43)
55.82(56.19)
53.71(53.82)
64.08(64.14)
49.93(50.14)
3.73(4.06)
4.15(4.28)
3.64(3.81)
3.53(3.77)
4.28(4.08)
3.65(3.52)
3.34(3.38)
3.53(3.82)
3.06(3.16)
4.22(4.48)
3.37(3.54)
4.36(4.20)
4.08(4.12)
3.11(3.35)
3.73(3.91)
9.35(9.42)
7.07(7.05)
8.52(8.72)
Nuclear Magnetic Resonance Spectra
turnover were found to vary with the different calalysts used
(Table 3). From the yield of the oxidation products, it has
been found that there is no appreciable change in the catalytic
activity of the complexes due to the change in PPh3 or AsPh3 or
Schiff bases.
On the basis of elemental analyses, IR, electronic, 1H NMR
spectral data, the following octahedral structure (Figure 2)
has been tentatively proposed for all the new ruthenium(II)
complexes.
Coordition of the Schiff bases in the new ruthenium(II)
complexes is further confirmed by NMR spectra of the com-
plexes. The peak observed at 3.71 and 3.89 ppm has been
assigned as due to the glyoxal protons of the Schiff base
ligands. The signal for aromatic protons appeared as multiplet
in the 7.26–8.00 ppm region in all the complexes.
Catalytic Studies
The oxidation of benzyl alcohol was carried out with ruthe-
nium(II) Schiff base complexes in the presence of N-methyl-
morpholine-N-oxide as co-oxidant and dichloromethane as
CONCLUSION
New ruthenium(II) complexes of the type [Ru(CO)(B)(L)]
solvent at room temperature. There is no detectable oxidation [L ¼ Schiff base anion; B ¼ PPh3, AsPh3 or pyridine(Py)]
of alcohol in the presence of N-methylmorpholine-N-oxide were prepared by a simple procedure. Elemental analysis of
alone without the ruthenium complex. All the synthesised the complexes agrees well with the molecular formula
ruthenium Schiff base complexes were found to catalyse the proposed. The coordination of Schiff base through the azo-
oxidation of alcohol to aldehydes but the yield and the methine nitrogen, phenolic oxygen and thiol sulphur were
TABLE 2
R and electronic spectral data for the Ru(II) Schiff base complexes
n(C55O) or
n(C–S)
;;
n(C O)
Complex
n(C55N)
lmax
[Ru(CO)(PPh3)(apg)]
[Ru(CO)(PPh3)(apb)]
[Ru(CO)(PPh3)(atg)]
[Ru(CO)(AsPh3)(apg)]
[Ru(CO)(AsPh3)(apb)]
[Ru(CO)(AsPh3)(atg)]
[Ru(CO)(Py)(apg)]
[Ru(CO)(Py)(apb)]
[Ru(CO)(Py)(atg)]
1628
1629
1628
1629
1627
1628
1627
1628
1628
1342
1343
749
1949
1953
1948
1959
1949
1964
1942
1941
1949
290
295
292
291
292
275
293
296
297
1343
1342
748
1342
1343
747
n in cm21; l in nm.

418
P. VISWANATHAMURTHI AND K. NATARAJAN
new manganese(II) and manganese(III) complexes of tetradentate
TABLE 3
Catalytic oxidation of the Ru(II) Schiff base complexes
Schiff-base ligands and their reaction with molecular oxygen.
Synthesis and characterisation of some new manganese(II) and
manganese(III) complexes of tetradentate Schiff-base ligands
and their reaction with molecular oxygen. J. Chem. Soc. Dalton
Trans. 1987, 2009–2012.
Catalyst
% yielda
Turnoverb
Without catalyst
0.15
3.47
4.64
3.92
4.53
3.52
4.62
3.92
3.72
4.12
1.74
33.18
45.43
38.25
44.26
32.95
43.15
36.66
35.35
37.25
[Ru(CO)(PPh3)(apg)]
[Ru(CO)(PPh3)(apb)]
[Ru(CO)(PPh3)(atg)]
[Ru(CO)(AsPh3)(apg)]
[Ru(CO)(AsPh3)(apb)]
[Ru(CO)(AsPh3)(atg)]
[Ru(CO)(Py)(apg)]
[Ru(CO)(Py)(apb)]
[Ru(CO)(Py)(atg)]
5. Kureshy, R. I.; Khan, N. H.; Abdi, S. H.R. Enantioselective cata-
lytic epoxidation of styrenes by iodosylbenzene using chiral
ruthenium(II) Schiff base complexes. J. Mol. Cat. 1995, 96,
117–122.
6. Bhowon Minu, G.; Li Kam Wah, H.; Narain, R. Schiff base com-
plexes of ruthenium(II) and their use as catalytic oxidants. Poly-
hedron 1999, 18, 341–345.
7. Vogel, A. I. Textbook of Practical Organic Chemistry, 5th Ed.;
ELBS: London, 1989.
8. Ahmed, N.; Levison, J. J.; Robinson, S. D.; Uttley, M. F. Com-
plexes of ruthenium, osmium, rhodium and iridium containing
hydride, carbonyl or nitrosyl ligands. Inorg Synth. 1974, 15,
45–54.
aYield based on substrate.
bMoles of product per mole of calalyst.
9. Sanchez-Delgado, R. A.; Lee, W. Y.; Choi, S. R.; Cho, Y.;
Jun, M. J. The chemistry and catalytic properties of ruthenium
and osmium complexes. Part 5. Synthesis of new compounds con-
taining arsine ligands and catalytic activity in the homogeneous
hydrogenation of aldehydes. Trans. Metal. Chem. 1991, 16,
241–244.
10. Gopinathan, S.; Unny, I. R.; Deshpande, S. S.; Gopinathan, C.
Ruthenium(II) complexes containing nitrogen heterocyclics.
Indian J. Chem. 1986, 25A, 1015–1017.
11. Jadamus, H.; Fernando, Q.; Freiser, H. Metal ion induced
rearrangements of bisbenzthiazolines to Schiff-base chelates.
J. Amer. Chem. Soc. 1964, 86, 3056–3059.
12. Jayabalakrishnan, C.; Natarajan, K. Synthesis, characterisation
and biological activities of ruthenium(II) carbonyl complexes
containing bifunctional tridentate Schiff bases. Synth. React.
Inorg. Met.-Org. Chem. 2001, 31, 983–995.
FIG. 2. Structure of the Ru(II) complexes.
13. Samuel, B.; Smith, R.; Sommerfield, C.; Wade, K. Azomethine
derivatives. Part XIII. Azomethine stretching frequencies of
some di- and tri- substituted methyleneamines, their hydrochlo-
rides, and their boron trifluride adducts. J. Chem. Soc(A) 1970,
2019–2022.
confirmed by IR and NMR spectral data. Electronic spectra
show the charge transfer transitions in the complexes and
support an octahedral geometry around ruthenium(II). The
new complexes exhibit catalytic activity for the oxidation of
benzyl alcohol in the presence of N-methylmorpholine-N-
oxidant.
14. Stiefel, E. I.; Waters, J. H.; Billig, E.; Gray, H. B. The myth of
nickel(III) and nickel(IV) in planar complexes. J. Amer. Chem.
Soc. 1965, 3016–3017.
15. Sato, S.; Hori, A.; Shiotani, H.; Mizutta, M. Infrared and
Raman spectra of (Thioacetoxythio) triorgano derivatives of
silicon, germanium, tin and lead. J. Org. Metal. Chem. 1974,
82, 223–230.
REFERENCES
1. Singh, P.; Goel, R. L.; Singh, B. P. 8-Acetyl-7-Hydroxy-4-Methyl
coumarin as a gravimetric reagent for Cu2þ and Fe3þ. J. Ind.
Chem. Soc. 1975, 52, 958–959.
16. Muthusamy, G.; Ramesh, R.; Natarajan, K. b-diketonate and a,
b-unsaturated-b-ketoaminate complexes of ruthenium(II) con-
taining carbonyl, thiocarbonyl and pyridine ligands. Synth.
React. Inorg. Met.-Org. Chem. 1994, 24, 545–548.
17. Lever, A. B.P. Electronic spectra of dn ions. In Inorganic Elec-
tronic Spectroscopy, 2nd Ed.; Elsevier: New York, 1984.
18. Dharmaraj, N.; Natarajan, K. Synthesis and characterisation of
new mixed ligand complexes of ruthenium(II) containing triphe-
nylphosphine and 20-hydroxychalcones. Indian J. Chem. 1994,
33A, 785–787.
2. Palet, P. R.; Thaker, B. T.; Zele, S. Preparation and characteriz-
ation of some lanthanide complexes involving a heterocyclic
b-diketone. Ind. J Chem. 1999, 38A, 563–567.
3. Ashmawy, F. M.; Issa, R. M.; Amer, S. A.; McAuliffe, C. A.;
(Dick) Parish, R. V. Synthesis and characterisation of some
cobalt(II) complexes of Schiff-base ligands and their reactions
with molecular oxygen. Effects of chelate ring size. J. Chem.
Soc. Dalton trans. 1986, 421–426.
4. McAuliffe, C. A.; (Dick)Parish, R. V.; Ashmawy, F. M.;
Issa, R. M.; Amer, S. A. Synthesis and characterisation of some