Ru(II)-halide-carbonyl complexes of naphthylazoimidazoles: Synthesis, spectra, electrochemistry, catalytic activity and electronic structure

Article abstract of DOI:10.1016/j.jorganchem.2012.06.009

[Ru(CO)₂Cl₂(α/β-NaiR)] (1, 2) and [Ru(CO)₂I₂(α/β-NaiR)] (3, 4) are synthesized by the reaction of [Ru(CO)₂Cl₂]_n or [Ru(CO) ₄I₂] with α/β-NaiR (1-alkyl-2-(na

Full text of DOI:10.1016/j.jorganchem.2012.06.009

Journal of Organometallic Chemistry 716 (2012) 129e137
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Ru(II)ehalideecarbonyl complexes of naphthylazoimidazoles: Synthesis,
spectra, electrochemistry, catalytic activity and electronic structure
1
*
Shyamal Kumar Sarkar , Mahendra Sekhar Jana, Tapan Kumar Mondal, Chittaranjan Sinha
Department of Chemistry, Inorganic Chemistry Section, Jadavpur University, Kolkata 700032, India
a r t i c l e i n f o
a b s t r a c t
Article history:
[Ru(CO)2Cl2(
[Ru(CO)2Cl2]n or [Ru(CO)4I2] with
where, R ¼ Me, CH2CH3 and CH2Ph)) and have been characterized by spectroscopic data. The geometry of
the representative complexes [Ru(CO)2Cl2( -NaiMe)] (2a) and [Ru(CO)2I2( -NaiEt)] (4b) have been
structurally confirmed by X-ray diffraction study. The redox property is examined by electrochemistry.
Catalytic activity of these compounds is investigated to the oxidation of PhCH2OH to PhCHO, 2-butanol
(C4H9OH) to 2-butanone, 1-phenylethanol (PhC2H4OH) to acetophenone, cyclopentanol (C5H9OH) to
cyclopentanone and cyclohexanol to cyclohexanone by N-methylmorpholine-N-oxide (NMO), H2O2 or
ButOOH in CH2Cl2 and NMO shows highest yield. The catalytic efficiency is again dependent on RueX
a
/
b
-NaiR)] (1, 2) and [Ru(CO)2I2(
a
/
b
-NaiR)] (3, 4) are synthesized by the reaction of
Received 16 April 2012
Received in revised form
31 May 2012
a
/b
-NaiR (1-alkyl-2-(naphthyl-
a/
b
-azo)imidazole -NaiR/ -NaiR,
(
a
b
b
b
Accepted 13 June 2012
Keywords:
Naphthylazoimidazole
Rutheniumecarbonylehalide
X-ray structure
Catalytic oxidation
Electrochemistry
DFT calculation
(X ¼ Cl or I) bond and higher yield is observed for [Ru(CO)2Cl2(
a/b-NaiR)] (1, 2). Electronic structure,
spectral and redox properties are explained based on DFT and TD-DFT calculations on the representative
complexes.
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
using oxidants such as air, molecular oxygen, hydrogen peroxide,
tert-butyl hydroperoxide and N-methylmorpholine-N-oxide (NMO)
The transition metalepolypyridine complexes are attracting
much for their spectroscopic, electrochemical, photophysical,
photochemical properties and their therapeutic and catalytic appli-
cations [1e7]. The structures, spectra and electrochemical properties
of ruthenium complexes of azoimine function (eN]NeC]Ne) and
the correlation with calculated electronic structure and composition
of MOs have been described extensively [8e12]. They have been used
as catalysts and photo-catalysts for water oxidation [13] or oxidation
of organic compounds [14,15]. The oxidation of alcohols plays an
important role in organic synthesis and the efforts are continuing for
the development of new oxidative processes [16e18]. The traditional
methods for oxidation using stoichiometric amount of inorganic
oxidants in high temperature and pressure cause serious environ-
mental problems and have lower selectivity [19]. It would be of great
economical and ecological importance to develop processes, which
take place at milder conditions and causes less environmental
pollution. With this view, in the past few decades there has been
a growing interestin transition metal-catalyzed oxidationof alcohols
[20e29]. Among the second row transition metal ions, ruthenium
mediated oxidations are finding application because its oxidation
state can vary from þII to þVIII [30e33].
We have been engaged in the last few years to develop
rutheniumecarbonyl chemistry of diimine and azoimine func-
tionalized heterocyclic ligands [34e38]. We report herein, the
synthesis, crystal and electronic structures, spectroscopic proper-
ties of hitherto new ruthenium(II)ecarbonyl complexes (1e4) of
1-alkyl-2-(naphthyl-
a
/b-azo)imidazoles
(a-NaiR/b-NaiR, where
R ¼ Me, CH2CH3 and CH2Ph) (Scheme 1). The catalytic activity of the
complexes for the oxidation of primary and secondary alcohols to
the respective aldehyde and ketones are studied using N-methyl-
morpholine-N-oxide (NMO) and peroxides (H2O2, ButOOH) as
oxidizing agents.
2. Results and discussion
2.1. Synthesis and formulation
The reaction of 1-alkyl-2-(naphthyl-a/b-azo)imidazoles (a/b-
* Corresponding author. Fax: þ91 033 2413 7121.
E-mail address: c_r_sinha@yahoo.com (C. Sinha).
Present address: Department of Chemistry, Uluberia College, Uluberia, Howrah
NaiR, where R ¼ CH3, CH2CH3 and CH2Ph) with [Ru(CO)2Cl2]n in
1
dry MeCN in inert (N2) environment under refluxing condition for 6
711315, India.
h has resulted dark red solution and the complexes [Ru(CO)2Cl2(a/b-
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.06.009

130
S.K. Sarkar et al. / Journal of Organometallic Chemistry 716 (2012) 129e137
Scheme 1.
NaiR)] (1, 2) are isolated by evaporation of the solvent (Scheme 1).
The purification of the complexes has been carried out by chro-
have been downfield shifted (Dd ¼ 0.60e0.80 ppm). The singlet
nature of imidazole protons may be due to rapid proton exchange at
the NMR time scale with solvent proton (may be coming from
matographic process. [Ru(CO)2I2(a/b-NaiR)] (3, 4) have been
synthesized by reacting [Ru(CO)4I2] with
a/b
-NaiR following the
moisture during measurement). The 1-R signals of a/b-NaiR appear
similar reaction conditions. All the complexes, 1e4 are diamagnetic
and the microanalytical and spectral data support the composition.
at their usual position [39,40]. 1-Me appears as a singlet at
4.25e4.30 ppm; 1-CH2eCH3 gives a quartet (4.51e4.67 ppm,
(J ¼ 8.0 Hz)) and a triplet (1.67e1.71 ppm (J ¼ 7.0 Hz)) respec-
tively; 1-CH2e(Ph) gives a singlet at 5.69e5.85 ppm. The RueX
bonds have significant control over proton signal position; in
The structural confirmation in case of [Ru(CO)2Cl2(b-NaiMe)] (2a)
and [Ru(CO)2I2( -NaiEt)] (4b) have been established bysingle crystal
b
X-ray diffraction studies.
general [Ru(CO)2Cl2(
show higher chemical shift than [Ru(CO)2I2(
[Ru(CO)2I2( -NaiR)] (4).
a
-NaiR)] (1) and [Ru(CO)2Cl2(
b-NaiR)] (2)
a-NaiR)] (3) and
2.2. Infrared and 1H NMR spectra
b
The complexes show two equally intense
n(CO) bands at
1995e2006 and 2048e2065 cmꢀ1 which supports the cis-Ru(CO)2
configuration [36e38]. Infrared spectra of the complexes also
2.3. Molecular structures
exhibit
n
(C]N) at 1542e1563 cmꢀ1 and
n
(N]N) at
The molecular structures of [Ru(CO)2Cl2(b-NaiMe)] (2a) and
[Ru(CO)2I2(b-NaiEt)] (4b) are shown in Figs. 1 and 2, respectively;
1355e1365 cmꢀ1 (see Experimental section). The azo (eN]Ne)
stretching is significantly shifted to lower frequency region
compared to free ligand value (1400e1410 cmꢀ1), which supports
selected bond parameters are listed in Table 1. The structure is
similar to [Ru(CO)2Cl2(1-ethyl-2-(phenylazo)imidazole)] [38]. Ru
atom is in a distorted octahedral geometry with RuC2X2(N,N/)
coordination sphere (N,N/ refer to N(imidazole) and N(azo) donor
dp(Ru) / p*(N]N) back donation in the complexes [39,40].
The 1H NMR spectra of all the complexes are recorded in CDCl3
solution. The 1H NMR signals of the complexes are shifted to
downfield side compare to free ligand value (see Experimental
section) [39] which may be due to strong retrobonding effect of
centers respectively of
b
-NaiMe in 2a and
b
-NaiEt in 4b) (X ¼ Cl in
2a and I in 4b). The atomic arrangements in the coordination
sphere involve two trans-X (Cl or I), a chelated 1-methyl or ethyl-2-
CO (dp
(Ru) /
p*(CO)). Imidazole protons, 4- and 5-H appear as
(naphthyl-b-azo)imidazole (b-NaiMe in 2a and b-NaiEt in 4b) and
a broad singlet at 7.75e7.85 and 7.45e7.55 ppm, respectively and
two cis-CO within the coordination sphere. The trans-X,X angles,

S.K. Sarkar et al. / Journal of Organometallic Chemistry 716 (2012) 129e137
131
about Ru define the distorted octahedral geometry in the
complexes.
The RueN(azo) distance (Ru(1)eN(1), 2.145(4) Å in 2a) and
(Ru(1)eN(4), 2.130(3)
Å in 4b) is significantly longer than
RueN(imidazole) distance Ru(1)eN(2), 2.072(5) Å in 2a and
(Ru(1)eN(1), 2.093(3) Å in 4b). In general the RueN(azo) bond
distance is shorter than RueN(imidazole) bond length which may
due to better d
Because of stronger
dinated trans to each other may reduce d
p
(Ru) /
-acidity of CO than eN]Ne function coor-
(Ru) / *(N]N) back
p*(N]N) back donation than imidazole-N.
p
p
p
donation process and may be responsible for elongation of
RueN(azo) lengths compared to reported bond lengths [34]. The
azo bond lengths in the complexes are 1.265(7) Å in 2a and
1.278(4) Å in 4b respectively and are closer to free ligand azo
distance, 1.267(3) Å [41]. The azo distance for non-carbonyl
ruthenium complexes with this ligand system was found to be
longer than present complexes [39,42].
Fig. 1. ORTEP plot of [Ru(CO)2Cl2(b-NaiMe)] (2a) (35% ellipsoidal probability).
2.4. DFT calculation: electronic structure and spectra
The full geometry optimizations were carried out for the
representative complexes 2a and 4b using DFT method. The
calculated bond distances and angles are well reproduced the X-ray
data (Table 1). Selected molecular orbitals along with energy and
composition for 2a and 4b are summarized in Supplementary
Tables S1 and S2 respectively. Contour plots of some selected
molecular orbitals are given in Figs. 3 and 4 for 2a and 4b respec-
tively. The higher energy occupied orbitals (HOMO and HOMO ꢀ 1)
for 2a have 32e37% ruthenium character along with 55e62%
contribution from Cl. In 4b the corresponding orbitals have less
ruthenium contribution (15e19%) and increased iodide character
(79e83%). The high energy occupied orbitals, HOMO ꢀ 2 to
Fig. 2. ORTEP plot of [Ru(CO)2I2(b-NaiEt)] (4b) (35% ellipsoidal probability).
X(1)eRueX(2) are of 174.83(6)ꢁ and 176.95(1)ꢁ in 2a and 4b
respectively. The deviation of the coordination sphere from the
ideal octahedron is due to the small bite angle of the five membered
chelate ring (Ru(1)eN(1)eN(3)eC(3)eN(2), 74.85(18)ꢁ in 2a and
Ru(1)eN(1)eC(7)eN(3)eN(4), 75.37(11)ꢁ in 4b). Other angles
HOMO ꢀ 6 have mixed ligand and halide p
p character. In both 2a
and 4b the LUMO has ligand character (90e93%) with a HOMO-
eLUMO energy gap 2.62 eV and 2.33 eV in 2a and 4b
Table 1
Bond distances (Å) and angles (ꢁ) of [Ru(CO)2Cl2(
b
-NaiMe)] (2a) and [Ru(CO)2I2(b-NaiEt)] (4b).
Bond distances (Å)
2a
Bond distances (Å)
4b
X-ray
Calc.
X-ray
Calc.
2.093
Ru(1)eN(1)
Ru(1)eN(2)
Ru(1)eCl(1)
Ru(1)eCl(2)
Ru(1)eC(15)
Ru(1)eC(16)
C(15)eO(1)
C(16)eO(2)
2.145(4)
2.072(5)
2.3723(15)
2.3804(15)
1.135(10)
1.090(9)
1.135(10)
1.090(9)
1.265(7)
2.193
2.129
Ru(1)eN(1)
Ru(1)eN(4)
Ru(1)eI(1)
Ru(1)eI(2)
Ru(1)eC(1)
Ru(1)eC(2)
C(1)eO(1)
C(2)eO(2)
N(3)eN(4)
2.093(3)
2.130(3)
2.6966(9)
2.7059(9)
1.881(4)
1.885(4)
1.127(5)
1.131(5)
1.278(4)
2.129
2.696
2.705
1.884
1.881
1.131
1.127
1.278
2.454
2.457
1.889
1.883
1.150
1.149
1.277
N(1)eN(3)
Bond angles (ꢁ)
N(1)eRu(1)eN(2)
N(1)eRu(1)eCl(1)
N(1)eRu(1)eCl(2)
N(1)eRu(1)eC(15)
N(1)eRu(1)eC(16)
N(2)eRu(1)eCl(1)
N(2)eRu(1)eCl(2)
N(2)eRu(1)eC(15)
N(2)eRu(1)eC(16)
Cl(1)eRu(1)eCl(2)
Cl(1)eRu(1)eC(15)
Cl(1)eRu(1)eC(16)
Cl(2)eRu(1)eC(15)
Cl(2)eRu(1)eC(16)
C(15)eRu(1)eC(16)
Ru(1)eC(15)eO(1)
Ru(1)eC(16)eO(2)
74.85(18)
88.82(11)
86.06(11)
101.4(2)
169.1(2)
88.27(12)
89.67(12)
176.1(2)
94.6(2)
174.83(6)
90.65(17)
93.56(17)
91.09(17)
91.33(17)
89.3(3)
74.52
89.37
86.21
99.41
170.0
90.05
86.29
173.3
95.58
174.8
92.71
92.00
90.53
90.90
90.40
178.7
177.5
N(1)eRu(1)eN(4)
N(1)eRu(1)eI(1)
N(1)eRu(1)eI(2)
N(1)eRu(1)eC(1)
N(1)eRu(1)eC(2)
N(4)eRu(1)eI(1)
N(4)eRu(1)eI(2)
N(4)eRu(1)eC(1)
N(4)eRu(1)eC(2)
I(1)eRu(1)eI(2)
I(1)eRu(1)eC(1)
I(1)eRu(1)eC(2)
I(2)eRu(1)eC(1)
I(2)eRu(1)eC(2)
C(1)eRu(1)eC(2)
Ru(1)eC(1)eO(1)
Ru(1)eC(2)eO(2)
75.37(11)
88.48(9)
90.22(9)
95.88(15)
174.63(15)
85.53(7)
75.37
88.48
90.22
174.6
95.88
85.53
91.47
99.30
171.1
176.9
90.43
92.57
90.61
90.30
89.42
177.9
177.9
91.47(7)
171.08(14)
99.30(15)
176.95(1)
92.57(12)
90.43(12)
90.31(12)
90.61(12)
89.42(18)
177.9(3)
177.5(5)
177.0(6)
178.0(4)

132
S.K. Sarkar et al. / Journal of Organometallic Chemistry 716 (2012) 129e137
Fig. 3. Contour plots of some selected molecular orbitals of [Ru(CO)2Cl2(b-NaiMe)] (4a).
respectively. LUMO þ 3 to LUMO þ 5 show high degree of mixing
between Ru(d ) and *(CO).
indicate the higher extent of back donation from d
This in fact influences stretching frequency of CO (n
p
(Ru) /
(CO in the
complexes) 1995e2006 and 2048e2065 cmꢀ1
< n(CO in free state),
p*(CO).
p
p
To further study the electronic structures of the complexes NBO
calculations on the optimized geometry of 2a and 4b were per-
formed. The polarity of the bonds is accounted on Natural bond
orbital (NBO) analysis. The RueC has one natural bond orbital while
each CeO has three natural bond orbitals. The RueC bond orbitals are
usually polarized the carbon atom, and subsequently the CeO bond
orbitals are polarized the oxygen. The occupancies and hybridization
of the CO and RueC bonds are summarized in Supplementary
Table S3. The NBO charge of Ru atom is 0.038 and 0.021 in 2a and
4b, respectively, which are much lower than þ2 formal charge. The
charge on carbon atom of carbonyl groups is þ0.693 (C15), þ0.708
(C16) in 2a and þ0.665 (C1), þ0.642 (C2) in 4b, oxygen atom is
negative ꢀ0.434 (O1), ꢀ0.434 (O2) in 2a and ꢀ0.421 (O1), ꢀ0.422
(O2) in 4b (Supplementary Table S4). The highly populated anti-
bonding NBOs (0.3021e0.3048 in 2a and 0.3314e0.3416 in 4b)
2143 cmꢀ1).
The absorption spectra of the complexes are measured at room
temperature in dry acetonitrile (Fig. 5), and the experimental
absorption bands are assigned based on singletesinglet vertical
excitations calculated by TD-DFT/CPCM method in acetonitrile on
the optimized geometry of 2a and 4b. Some of the calculated
excitation wavelength and their assignment are given in Table 2 and
Table 3 for 2a and 4b, respectively. The complexes 2a and 4b show
moderately intense band at 473 nm and 485 nm respectively
corresponds to HOMO ꢀ 1 / LUMO, mixed MLCT and XLCT tran-
sitions. The band at 411 nm and 367 nm for 2a and 4b respectively
has ILCT/XLCT character. In addition the intense bands at
390e310 nm for the complexes are purely intra-ligand charge
transfer transitions (ILCT).
Fig. 4. Contour plots of some selected molecular orbitals of [Ru(CO)2I2(b-NaiEt)] (4b).

S.K. Sarkar et al. / Journal of Organometallic Chemistry 716 (2012) 129e137
133
2.6. Catalytic oxidation
Catalytic oxidation of benzyl alcohol (PhCH2OH), 2-butanol
(C4H9OH), 1-phenylethanol (PhC2H4OH), cyclopentanol (C5H9OH)
and cyclohexanol (CyCHeOH) was carried out using [Ru(CO)2X2(
a/
b-NaiR)] (X ¼ Cl or I and R ¼ Me or Et) as catalyst and N-methyl-
morpholine-N-oxide (NMO)/H2O2 (30%)/ButOOH as oxidant in
CH2Cl2 in refluxing condition for an appropriate period of time. The
complexes catalyze the oxidation of PhCH2OH to PhCHO, C4H9OH to
C4H7O (2-butanone), PhC2H4OH to PhCOCH3 (acetophenone),
C5H9OH to C5H8O (cyclopentanone) and CyCHeOH to CyC]O
(cyclohexanone) with high yields and the results are given in
Table 5, Supplementary Tables S5 and S6. The aldehyde or ketone
formed after 1 h of reflux was determined by GC and there was no
detectable oxidation in the absence of ruthenium complex. Results
of the investigations suggest that the complexes are able to react
efficiently with NMO or peroxides (H2O2/ButOOH) to yield a high
valent ruthenium-oxo species [43,44], which is capable of oxygen
atom transfer to alcohols. The residue has been dried by evapora-
tion. The volatile organic matter may be evaporated during drying
of oxidation product; however, the existence of Ru(IV)]O species
Fig. 5. UVevis spectra of [Ru(CO)2Cl2(
(3a) (d) in acetonitrile.
a-NaiMe)] (1a) (d) and [Ru(CO)2I2(a-NaiMe)]
([Ru(
a
/
b
-NaiR) ¼ O]*) has been proved by FT-IR spectra [44,45]
(w860 cmꢀ1). The catalyst is also susceptible to generate oxida-
tion products like CO2 and XOꢀ3 /XOꢀ4 . We do not have any technical
support to collect CO2 and its measurement but presence of halate
(ClOꢀ3 and IOꢀ3 ) is identified qualitatively by manganous sulfate-
phosphoric acid test [46]. A plausible oxidation loop is given in
Fig. 7. The oxidation activity follows NMO > ButOOH > H2O2 which
may be due to their inbuilt oxygen transfer efficiency to the catalyst.
2.5. Electrochemistry
The complexes, 1 and 2, show one quasi-reversible oxidation at
1.19e1.33 E, 125e135 mV) and one reductive response,
ꢀ(0.44e0.55 V) ( E, 77e86 mV) along with one irreversible,
ꢀ(1.13e1.27 V) reduction. The compounds, 3 and 4 show one quasi-
reversible, 1.39e1.48 V ( E, 115e125 mV) and one irreversible,
V
(D
D
D
0.62e0.67 V oxidative response positive to reference Ag/AgCl elec-
trode along with one reversible reductive responses, ꢀ(0.53e0.57 V)
The catalytic efficiency of [Ru(CO)2Cl2(
than [Ru(CO)2I2( -NaiR)] (3, 4) which may be due to the
consumption of oxidant for some unidentified reaction (oxidation
of iodide!). Besides, Ru( -NaiR)-compounds (1, 3) show better
catalytic activity than Ru( -NaiR)-compounds (2, 4). Out of these
five alcohols cyclohexanol and 1-phenylethanol show higher
product conversion ratio than others and least activity is observed
for 2-butanol. The compounds reported in this article show
comparable catalytic efficiency with reported catalysts for sup-
porting oxidation of alcohols by NMO or peroxides such as Ru-
azophelato compounds [47] or Ru-Schiff bases [48].
a/b-NaiR)] (1, 2) is higher
a/b
(D
E, 80e87 mV) and one irreversible, ꢀ(1.27e1.33 V) reductive
response (Fig. 6, Table 4).
a
b
The redox couples have been assigned on the basis of DFT
results. The HOMO and HOMO ꢀ 1 of 4b have 17e19% Ru character
and 79e83% iodine contribution. So, the first irreversible oxidation
in complexes 3 and 4 has been assigned as Iꢀ/½I2 oxidation and the
quasi-reversible second oxidation at higher potential range is RuII/
RuIII couple. Although Cl contributes 55% character to HOMO of 2a
but its energy is about 0.30 eV stabilized more than that of 4b and
thus Clꢀ/½Cl2 oxidation is not feasible. In 2a the ruthenium
contribution to HOMO and HOMO ꢀ 1 has been increased to
32e37% than that of 4b and the oxidation has been assigned as RuII/
RuIII couple in complexes 1, 2. LUMOs of the complexes exclusively
have ligand character with 44e48% azo contribution, so the
reductions are taking place on azo bond in all the complexes
leading to the formation of Lꢂꢀ on first and L2ꢀ after second
reductions respectively.
3. Experimental section
3.1. Materials and instrumentation
The 1-alkyl-2-(naphthyl-a/b-azo)imidazoles were synthesized
following a previously published procedure [39]. [Ru(CO2)Cl2]n and
Table 2
Calculated singletesinglet vertical electronic transitions for [Ru(CO)2Cl2(b-NaiMe)] (2a) in acetonitrile.
Eexcitation (eV)
lexcitation (nm)
Osc. strength (f)
Key transition
Character
Ru(d )/Cl(p
(MLCT, XLCT)
Ru(d )/Cl(p
(MLCT, XLCT)
-NaiMe( )/Cl(p
(ILCT/XLCT)
-NaiMe( )/Cl(p
(ILCT/XLCT)
2.3336
531.3
0.0101
0.0674
0.1165
0.0753
0.0353
0.0411
0.1219
(72%)HOMO / LUMO
p
p
) /
b
-NaiMe(
p
p
*)
*)
2.5447
2.7758
3.5987
4.1229
4.2259
4.4620
487.2
446.7
344.5
300.7
293.4
277.9
(84%)HOMO ꢀ 1 / LUMO
(72%)HOMO ꢀ 6 / LUMO
p
p) /
b-NaiMe(
b
p
p
p
) /
) /
b
b
-NaiMe(
p
*)
*)
(32%)HOMO ꢀ 7 / LUMO
(20%)HOMO ꢀ 6 / LUMO
(61%)HOMO ꢀ 10 / LUMO
b
p
-NaiMe(
p
b
-NaiMe(
(ILCT)
-NaiMe(
(ILCT)
-NaiMe(
(ILCT)
p
p
p
) /
) /
) /
b
b
b
-NaiMe(
-NaiMe(
-NaiMe(
p
p
p
*)
*)
*)
(43%)HOMO ꢀ 2 / LUMO þ 4
(23%)HOMO ꢀ 10 / LUMO
(59%)HOMO ꢀ 12 / LUMO
b
b

134
S.K. Sarkar et al. / Journal of Organometallic Chemistry 716 (2012) 129e137
Table 3
Calculated singletesinglet vertical electronic transitions for [Ru(CO)2I2(b-NaiEt)] (4b) in acetonitrile.
Eexcitation (eV)
lexcitation (nm)
Osc. strength (f)
0.0075
Key transition
Character
Ru(d )/I(p
(MLCT, XLCT)
Ru(d )/I(p ) /
(MLCT, XLCT)
-NaiEt( )/I(p
(ILCT, XLCT)
-NaiEt( )/I(p
(ILCT, XLCT)
2.2587
548.9
(96%)HOMO / LUMO
p
p
) /
b
b
-NaiEt (
p
p
*)
*)
2.5012
3.0094
3.2345
3.9896
4.2394
4.4070
4.5786
495.7
412.0
383.3
310.8
292.4
281.3
270.8
0.1035
0.1723
0.1268
0.0793
0.0485
0.0714
0.1396
(77%)HOMO ꢀ 1 / LUMO
(77%)HOMO ꢀ 5 / LUMO
(83%)HOMO ꢀ 6 / LUMO
(65%)HOMO ꢀ 11 / LUMO
(69%)HOMO ꢀ 2 / LUMO þ 2
(67%)HOMO ꢀ 12 / LUMO þ 2
p
p
-NaiEt (
b
p
p
) /
) /
b
-NaiEt(
-NaiEt(
p
*)
*)
b
p
p
b
p
b
-NaiEt(
(ILCT)
-NaiEt(
p
) /
b
-NaiEt(
) / -NaiEt (
-NaiEt( *)
) / -NaiEt(
p*)
b
p
)/I(p
p
b
b
p*)
(ILCT, XLCT)
b
-NaiEt(
(ILCT)
-NaiEt(
p
) /
p
(39%)HOMO ꢀ 4 / LUMO þ 2
(30%)HOMO ꢀ 2 / LUMO þ 4
b
p
)/I(p
p
b
p*)
(ILCT, XLCT)
[Ru(CO)4I2] were prepared by a reported method [36,49]. Imidazole
and all other organic chemicals and inorganic salts were available
from Sisco Research Lab, Mumbai, India. All other chemicals and
solvents were of reagent grade and were used without further
purification. Commercially available SRL silica gel (60e120 mesh)
was used for column chromatography.
0.44 mmol) was added and the reaction mixture was refluxed for
6 h under N2 atmosphere. The color of the solution changed from
orange to dark red. The solvent was removed under reduced
pressure. The dark red dry mass was then dissolved in minimum
volume of CH2Cl2 and subjected to chromatography separation on
a silica gel column (60e120 mesh). The desired red band of 1a was
eluted by 1:10 CH2Cl2eMeCN mixture. Slow evaporation of the
solvent the red crystalline complex 1a was obtained. The yield was
141.92 mg (72%). The other compounds 1b, 1c, 2a, 2b and 2c were
synthesized following the same procedure by the reaction of
Microanalytical data (C, H, N) were collected on PerkineElmer
2400 CHNS/O elemental analyzer. Infrared spectra were taken on
a RX-1 Perkin Elmer spectrophotometer with samples prepared as
KBr pellets. UVevis spectral studies were performed on a Perkin
Elmer Lambda 25 spectrophotometer. 1H NMR spectra were
recorded using a Bruker (AC) 300 MHz FTNMR spectrometer in
CDCl3. Cyclic voltammetric measurements were carried out using
a CH1 Electrochemical workstation. A platinum wire working
electrode, a platinum wire auxiliary electrode and Ag/AgCl refer-
ence electrode were used in a standard three-electrode configu-
ration. [nBu4N][ClO4] was used as the supporting electrolyte and
the scan rate used was 50 mV sꢀ1 in dry acetonitrile under N2
atmosphere. The reported potentials are uncorrected for junction
potential. The catalytic yields were determined using Agilent 7890
series Gas chromatography instrument equipped with a flame
ionization detector (FID) using a HP-5 column of 30 m length,
[Ru(CO)2Cl2]n with a/b-NaiR ligands in the same molar ratio (1:1).
The yields were about (65e74)%.
Microanalytical data: Calc. (found). For C16H12N4OCl2Ru (1a): C,
41.40 (41.28); H, 2.61 (2.64); N, 12.07 (12.03). IR data (KBr disc)
(cmꢀ1): 2005, 2065 (N]N). 1H NMR
n(CO), 1563 n(C]N), 1362 n
data in CDCl3 (ppm): 7.82 (4-H, s), 7.47 (5-H, s), 4.28 (NeCH3, s),
8.75 (7-H, d, J ¼ 7.60 Hz), 8.34 (13-H, d, J ¼ 9.74 Hz), 7.63 (8,9-H,
m), 8.05 (10,13-H, m). UVevis (CH3CN): lmax
(
, Mꢀ1 cmꢀ1): 482
3
(13,481), 350 (19,834), 283 (33,532). For C17H14N4OCl2Ru (1b): C,
42.69 (42.79); H, 2.95 (2.90); N, 10.04 (10.07). IR data (KBr disc)
(cmꢀ1): 2006, 2062 (N]N). 1H NMR
n(CO), 1548 n(C]N), 1365 n
data in CDCl3 (ppm): 7.80 (4-H, s), 7.51 (5-H, s), 4.51 (NeCH2eCH3,
q, J ¼ 7.50 Hz), 1.67 (NeCH2eCH3, t, J ¼ 7.00 Hz), 8.74 (7-H, d,
J ¼ 7.50 Hz), 8.31 (13-H, d, J ¼ 8.75 Hz), 7.60 (8,9-H, m), 8.09
0.53 mm diameter and 5.00 mm film thickness.
(10,13-H, m). UVevis (CH3CN): lmax
(
, Mꢀ1 cmꢀ1): 470 (12,350),
3
3.2. Synthesis of complexes
3.2.1. Synthesis of [Ru(CO)2Cl2(
To a 20 mL acetonitrile suspension of [Ru(CO2)Cl2]n (100 mg,
0.43 mmol) 15 mL acetonitrile solution of -NaiMe (1a) (103.63 mg,
a-NaiMe)] (1a)
Table 4
Cyclic voltammetric dataa of 1e4.
a
Complexes E (Iꢀ/½I2)b (V) E1/2 (RuII/RuIII
)
E1/2 (L/Lꢂꢀ
(V) ( Ep, mV)
)
E (Lꢂꢀ/L2-
)
(V)
d
c,d
(V) (
DEp, mV)
D
1a
1b
1c
2a
2b
2c
3a
3b
3c
4a
4b
4c
1.27(127)
1.20(133)
1.19(125)
1.33(130)
1.25(135)
1.23(133)
1.47(115)
1.48(120)
1.43(117)
1.39(122)
1.42(125)
1.43(120)
ꢀ0.44(77)
ꢀ0.50(83)
ꢀ0.47(82)
ꢀ0.55(85)
ꢀ0.53(77)
ꢀ0.52(86)
ꢀ0.55(85)
ꢀ0.53(87)
ꢀ0.54(80)
ꢀ0.53(85)
ꢀ0.57(80)
ꢀ0.56(87)
ꢀ1.13
ꢀ1.21
ꢀ1.16
ꢀ1.22
ꢀ1.27
ꢀ1.21
ꢀ1.27
ꢀ1.29
ꢀ1.30
ꢀ1.30
ꢀ1.33
ꢀ1.27
0.63
0.65
0.62
0.65
0.67
0.62
a
In acetonitrile solution, supporting electrolyte Bu4NClO4 (0.1 M), reference
electrode Ag/AgCl, scan rate ¼ 50 mV sꢀ1. E ¼ 0.5 (Epa þ Epc) where Epa and Epc are
½
anodic and cathodic peak potentials, respectively;
D
Ep ¼ Epa ꢀ Epc
.
b
Fig. 6. Cyclic voltammogram of [Ru(CO)2Cl2(
NaiEt)] (4b) (——) in acetonitrile solution, supporting electrolyte Bu4NClO4 (0.1 M),
reference electrode Ag/AgCl at scan rate of 50 mV sꢀ1
b-NaiMe)] (2a) (d) and [Ru(CO)2I2(
b
-
Anodic potential.
Cathodic potential.
c
d
.
L ¼ Chelated
a/b-NaiR.

S.K. Sarkar et al. / Journal of Organometallic Chemistry 716 (2012) 129e137
135
Table 5
Catalytic oxidation of alcohols by Ru(II) complexes (1e4) using NMO as co-oxidant.
Complex
Substrate
Product
Yielda(%)
Turnoverb(%)
1a
Benzyl alcohol
2-Butanol
Benzaldehyde
2-Butanone
78
76
84
82
84
85
79
89
86
90
79
75
84
80
83
74
71
77
75
78
86
79
90
86
90
77
75
80
79
81
66
64
68
67
70
72
66
78
74
78
64
62
72
67
73
70
67
74
71
74
73
69
81
77
80
71
67
73
72
73
78
76
84
82
84
85
79
89
86
90
79
75
84
80
83
74
71
77
75
78
86
79
90
86
90
77
75
80
79
81
66
64
68
67
70
72
66
78
74
78
64
62
72
67
73
70
67
74
71
74
73
69
81
77
80
71
67
73
72
73
1-Phenylethanol
Cyclopentanol
Cyclohexanol
Benzyl alcohol
2-Butanol
1-Phenylethanol
Cyclopentanol
Cyclohexanol
Benzyl alcohol
2-Butanol
1-Phenylethanol
Cyclopentanol
Cyclohexanol
Benzyl alcohol
2-Butanol
1-Phenylethanol
Cyclopentanol
Cyclohexanol
Benzyl alcohol
2-Butanol
1-Phenylethanol
Cyclopentanol
Cyclohexanol
Benzyl alcohol
2-Butanol
1-Phenylethanol
Cyclopentanol
Cyclohexanol
Benzyl alcohol
2-Butanol
1-Phenylethanol
Cyclopentanol
Cyclohexanol
Benzyl alcohol
2-Butanol
1-Phenylethanol
Cyclopentanol
Cyclohexanol
Benzyl alcohol
2-Butanol
1-Phenylethanol
Cyclopentanol
Cyclohexanol
Benzyl alcohol
2-Butanol
1-Phenylethanol
Cyclopentanol
Cyclohexanol
Benzyl alcohol
2-Butanol
1-Phenylethanol
Cyclopentanol
Cyclohexanol
Benzyl alcohol
2-Butanol
1-Phenylethanol
Cyclopentanol
Cyclohexanol
Acetophenone
Cyclopentanone
Cyclohexanone
Benzaldehyde
2-Butanone
Acetophenone
Cyclopentanone
Cyclohexanone
Benzaldehyde
2-Butanone
Acetophenone
Cyclopentanone
Cyclohexanone
Benzaldehyde
2-Butanone
Acetophenone
Cyclopentanone
Cyclohexanone
Benzaldehyde
2-Butanone
Acetophenone
Cyclopentanone
Cyclohexanone
Benzaldehyde
2-Butanone
Acetophenone
Cyclopentanone
Cyclohexanone
Benzaldehyde
2-Butanone
Acetophenone
Cyclopentanone
Cyclohexanone
Benzaldehyde
2-Butanone
Acetophenone
Cyclopentanone
Cyclohexanone
Benzaldehyde
2-Butanone
Acetophenone
Cyclopentanone
Cyclohexanone
Benzaldehyde
2-Butanone
Acetophenone
Cyclopentanone
Cyclohexanone
Benzaldehyde
2-Butanone
Acetophenone
Cyclopentanone
Cyclohexanone
Benzaldehyde
2-Butanone
Acetophenone
Cyclopentanone
Cyclohexanone
1b
1c
2a
2b
2c
3a
3b
3c
4a
4b
4c
Fig. 7. Cyclohexanol (C, ,) and benzyl alcohol (B, -) oxidation product conversion
ratio in presence of [Ru(CO)2Cl2(
catalytic loop.
a-NaiMe)] (3a) in CH2Cl2 under reflux and plausible
8.10 (10,13-H, m). UVevis (CH3CN): lmax
(
, Mꢀ1 cmꢀ1): 487
3
(10,117), 355 (15,822), 282 (39,350). For C16H12N4O2Cl2Ru (2a): C,
41.39 (41.37); H, 2.61 (2.56); N, 12.07 (12.00). IR data (KBr disc)
(cmꢀ1): 2000, 2053 (N]N). 1H NMR
n(CO), 1546 n(C]N), 1357 n
data in CDCl3 (ppm): 7.83 (4-H, s), 7.45 (5-H, s), 4.29 (NeCH3, s),
8.76 (6-H, s), 8.13 (8-H, d, J ¼ 6.64 Hz), 8.12 (9-H, d, J ¼ 7.38 Hz),
7.66 (10,13-H, m), 7.96 (11,12-H, m). UVevis (CH3CN): lmax
( ,
3
Mꢀ1 cmꢀ1): 473 (7854), 367 (11,532), 289 (31,453). For
C17H14N4O2Cl2Ru (2b): C, 42.69 (42.74); H, 2.95 (2.90); N, 10.04
(10.09). IR data (KBr disc) (cmꢀ1): 1998, 2052
n
(CO), 1551
n(C]N),
1361
n
(N]N). 1H NMR data in CDCl3 (ppm): 7.78 (4-H, s), 7.55 (5-
H, s), 8.73 (6-H, s), 4.57 (NeCH2eCH3, q, J ¼ 7.60 Hz), 1.70
(NeCH2eCH3, t, J ¼ 7.00), 8.17 (8-H, d, J ¼ 6.60 Hz), 8.15 (9-H, d,
J ¼ 7.50 Hz), 7.63 (10,13-H, m), 7.97 (11,12-H, m). UVevis (CH3CN):
lmax
(
, Mꢀ1 cmꢀ1): 465 (6915), 371 (10,781), 291 (35,626). For
3
C22H17N4O2Cl2Ru (2c): C, 48.90 (48.93); H, 2.98 (2.93); N, 10.37
(10.30). IR data (KBr disc) (cmꢀ1): 1996, 2055
(CO), 1556 (C]N),
1360
(N]N). 1H NMR data in CDCl3 (ppm): 7.75 (4-H, s), 7.50 (5-
n
n
n
H, s), 5.77 (NeCH2ePh, s), 8.15 (8-H, d, J ¼ 6.65 Hz), 8.15 (9-H, d,
J ¼ 9.80 Hz), 7.68 (10,13-H, m), 7.95 (11,12-H, m). UVevis (CH3CN):
lmax
(
, Mꢀ1 cmꢀ1): 483 (5637), 361 (9852), 285 (29571).
3
3.2.2. Synthesis of [Ru(CO)2I2(
The complex 3a was prepared by the reaction of [Ru(CO)4I2]
(100 mg, 0.21 mmol) with -NaiMe (1a) (51.82 mg, 0.22 mmol)
a-NaiMe)] (3a)
a
following the same procedure as of 1a. The purification was carried
out by column chromatography. Yield was 73.79 mg (69%).
Compounds 3b, 3c, 4a, 4b and 4c were prepared following the same
procedure by the reaction of Ru(CO)4I2 with a/b-NaiR ligands in the
same molar ratio (1:1). The yields were about (67e72)%.
Microanalytical data: Calc. (found) For C16H12N4O2I2Ru (3a): C,
29.69 (29.59); H, 1.87 (1.83); N, 8.66 (8.60). IR data (KBr disc)
(cmꢀ1): 1996, 2049 (N]N). 1H NMR data
n(CO), 1543 n(C]N), 1360 n
Substrate (1 mmol); NMO (3 mmol); complex (0.01 mmol); solvent
dichloromethane.
Yield of product was determined using Agilent 7890 series Gas chromatography
instrument equipped with a flame ionization detector (FID) using a HP-5 column of
in CDCl3 (ppm): 7.85 (4-H, s), 7.49 (5-H, s), 4.25 (NeCH3, s), 8.61 (7-
H, d, J ¼ 7.56 Hz), 8.23 (13-H, d, J ¼ 9.76 Hz), 7.66 (8,9-H, m), 7.89
a
30 m length, 0.53 mm diameter and 5.00
m
m film thickness.
(10,13-H, m). UVevis (CH3CN): lmax
(
, Mꢀ1 cmꢀ1): 499 (8092), 431
3
b
Moles of product per mole of catalyst.
(7440), 359 (10,734), 309 (19,945). For C17H14N4O2I2Ru (3b): C,
30.88 (30.81); H, 2.13 (2.10); N, 8.47 (8.53). IR data (KBr disc)
(cmꢀ1): 2004, 2051 (N]N). 1H NMR data
n(CO),1547 n(C]N), 1358 n
360 (17,742), 275 (35,423). For C22H17N4O2Cl2Ru (1c): C, 48.90
in CDCl3 (ppm): 7.51 (4-H, s), 7.52 (5-H, s), 4.60 (NeCH2eCH3, q,
J ¼ 7.70 Hz), 1.67 (NeCH2eCH3, t, J ¼ 7.20 Hz), 8.63 (7-H, d,
J ¼ 8.00 Hz), 8.29 (13-H, d, J ¼ 8.90 Hz), 7.64 (8,9-H, m), 7.90 (10,13-
(48.83); H, 2.98 (2.94); N, 10.37 (10.34). IR data (KBr disc) (cmꢀ1):
2005, 2059 n(CO), 1549 n(C]N), 1363 n
(N]N). 1H NMR data in
CDCl3 (ppm): 7.85 (4-H, s), 7.53 (5-H, s), 5.85 (NeCH2ePh, s), 8.77
(7-H, d, J ¼ 7.62 Hz), 8.33 (13-H, d, J ¼ 8.72 Hz), 7.65 (8,9-H, m),
H, m). UVevis (CH3CN): lmax (
, Mꢀ1 cmꢀ1): 497 (6091), 430 (5954),
3
308 (14,592), 359 (8225). For C22H17N4O2I2Ru (3c): C, 36.54 (36.47);

136
S.K. Sarkar et al. / Journal of Organometallic Chemistry 716 (2012) 129e137
H, 2.23 (2.27); N, 7.75 (7.67). IR data (KBr disc) (cmꢀ1): 2001, 2061
(CO), 1544 (C]N), 1353
(N]N). 1H NMR data in CDCl3 (ppm):
F2 using the SHELX-97 program [50,51]. The absorption corrections
were done by the multi-scan technique. All data were corrected for
Lorentz and polarization effects, and the non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were included in the
refinement process as per the riding model. All non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were con-
strained to ride on the respective carbon atoms with isotropic
displacement parameters equal to 1.2 times the equivalent
isotropic displacement of their parent carbon atoms in all cases.
n
n
n
7.85 (4-H, s), 7.46 (5-H, s), 5.69 (NeCH2ePh, s), 8.67 (7-H, d,
J ¼ 7.49 Hz), 8.13 (13-H, d, J ¼ 8.09 Hz), 7.54 (8,9-H, m), 7.66 (10,13-
H, m). UVevis (CH3CN): lmax
(
, Mꢀ1 cmꢀ1): 504 (6774), 437 (5771),
3
308 (15,904), 361 (8282). For C16H12N4O2I2Ru (4a): C, 29.70 (29.74);
H, 1.87 (1.83); N, 8.66 (8.71). IR data (KBr disc) (cmꢀ1): 2001, 2064
n
(CO), 1542 n(C]N), 1358 n
(N]N). 1H NMR data in CDCl3 (ppm):
7.80 (4-H, s), 7.45 (5-H, s), 8.69 (6-H, s), 4.30 (NeCH3, s), 8.10 (8-H, d,
J ¼ 6.70 Hz), 8.18 (9-H, d, J ¼ 8.73 Hz), 7.96 (10,13-H, m), 7.65 (11,12-
H, m). UVevis (CH3CN): lmax
(
, Mꢀ1 cmꢀ1): 486 (6781), 410
3
3.4. Procedure for catalytic oxidation of alcohols
(11,793), 312 (10,914). For C17H14N4O2I2Ru (4b): C, 30.88 (30.84); H,
2.13 (2.10); N, 8.47 (8.42). IR data (KBr disc) (cmꢀ1): 2000, 2053
Catalytic oxidation of primary alcohol to corresponding alde-
hyde and secondary alcohol to ketone by ruthenium(II) complexes
were studied in the presence of NMO, H2O2 or ButOOH as co-
oxidant. A typical reaction using the complex as a catalyst and
primary or secondary alcohol, as substrate at 1:100 molar ratio was
n
(CO), 1561 n(C]N), 1360 n
(N]N). 1H NMR data in CDCl3 (ppm):
7.81 (4-H, s), 7.48 (5-H, s), 8.70 (6-H, s), 4.67 (NeCH2eCH3, q,
J ¼ 7.32 Hz), 1.71 (NeCH2eCH3, t, J ¼ 7.31 Hz), 8.09 (8-H, d,
J ¼ 6.58 Hz), 8.15 (9-H, d, J ¼ 8.22 Hz), 7.64 (10,13-H, m), 7.96 (11,12-
H, m). UVevis (CH3CN): lmax
(
, Mꢀ1 cmꢀ1): 485 (9112), 411
3
described as follows. A solution of [Ru(CO)2Cl2(a-NaiEt)] (1b)
(15,545), 309 (12,864). For C22H17N4O2I2Ru (4c): C, 36.54 (36.49); H,
(0.01 mmol) in CH2Cl2 (20 ml) was added to the mixture containing
PhCH2OH (1 mmol), NMO (3 mmol) and molecular sieves. The
reaction mixture was refluxed for 1 h, and the solvent was then
evaporated under reduced pressure. The residue was then extrac-
ted with diethyl ether (20 ml), concentrated to z1 ml and was
analyzed by GC. The oxidation products were identified by GC co-
injection with authentic samples. All other alcohols were oxidized
following identical reaction protocol.
2.23 (2.27); N, 7.75 (7.78). IR data (KBr disc) (cmꢀ1): 2002, 2056
n
(CO), 1563 n(C]N), 1359 n
(N]N). 1H NMR data in CDCl3 (ppm):
7.79 (4-H, s), 7.46 (5-H, s), 8.69 (6-H, s), 5.77 (NeCH2ePh, s), 8.09 (8-
H, d, J ¼ 6.75 Hz), 8.17 (9-H, d, J ¼ 8.96 Hz), 7.64 (10,13-H, m), 7.96
(11,12-H, m). UVevis (CH3CN): lmax
(
, Mꢀ1 cmꢀ1): 491 (8315), 411
3
(15,164), 312 (14,219).
3.3. X-ray crystal structure analysis
3.5. Computational methods
Details of crystal analyses, data collection and structure
refinement data are given in Table 6. Crystal mounting was done
on glass fibers with epoxy cement. Single crystal data collections
were performed with an automated Bruker SMART APEX CCD
diffractometer. Unit cell parameters were determined from least-
All computations were performed using the Gaussian03 (G03)
[52] software. The Becke’s three-parameter hybrid exchange func-
tional and the Lee-Yang-Parr nonlocal correlation functional
[53e55] (B3LYP) was used throughout. The 6-31G(d) basis set for C,
H, N and O atoms, while MIDI! basis functions for Cl and I atoms
were used [56]. Lanl2TZ(f) basis set with effective core potential
was employed for Ru atom [57]. The vibrational frequency calcu-
lations were performed to ensure that the optimized geometries
represent the local minima and there are only positive Eigen values.
Natural bond orbital analyses were performed using the NBO 3.1
module of Gaussian03 [58]. Vertical electronic excitations based on
B3LYP optimized geometries were computed for the time-
dependent density functional theory (TD-DFT) formalism [59e61]
in acetonitrile using conductor-like polarizable continuum model
(CPCM) [62e64]. Gauss Sum [65] was used to calculate the frac-
tional contributions of various groups to each molecular orbital.
squares refinement of setting angles with
q
in the range 2.70 ꢃ
q
ꢃ 26.00ꢁ (2a) and 2.50 ꢃ
q
ꢃ 25.00ꢁ (4b). Out of 13,064 collected
data 3558 for 2a and 19,238 collected data 3670 for 4b with I > 2
s
(I) were used for structure solution. The hkl ranges
are ꢀ18 ꢃ h ꢃ 14, ꢀ10 ꢃ k ꢃ 11, ꢀ17 ꢃ l ꢃ 17 for 2a
and ꢀ19 ꢃ h ꢃ 19, ꢀ10 ꢃ k ꢃ 10, ꢀ17 ꢃ l ꢃ 17 for 4b. Reflection
data were recorded using the
u scan technique. The structures
were solved and refined by full-matrix least-squares techniques on
Table 6
Crystal data and details of the structure determination of 2a and 4b.
Compound
[Ru(CO)2Cl2(
b-NaiMe)]
[Ru(CO)2I2(b-NaiEt)]
(2a)
(4b)
4. Conclusion
Formula
Mr
C16H12N4O2Cl2Ru
464.27
C17H14N4O2I2Ru
661.19
Ruthenium/Osmium(II)eCO complexes of azoimine functions
Crystal system
Space group
a[Å]
Monoclinic
P 21/c
Monoclinic
P 21/c
from 1-alkyl-2-(naphthyl-
a
/b
-azo)imidazoles
(a/b-NaiR) are
14.904(3)
9.1824(17)
13.988(3)
109.475(3)
1804.8(6)
4
1.182
293
1.709
3558/0/226
0.0523, 0.0962
0.1007, 0.1117
1.00
16.612(5)
8.551(2)
14.723(4)
94.321(4)
2085.5(10)
4
3.730
298
2.106
3670/0/236
0.0280, 0.0706
0.0302, 0.0721
1.10
structurally and spectroscopically characterized. The redox prop-
erties of the compounds are studied by cyclic voltammetry exper-
iment. The catalytic activity of the complexes has been examined to
the oxidation of benzyl alcohol to aldehyde and cyclohexanol to
cyclohexanone by NMO, H2O2 or ButOOH as oxidant. Thus scope of
catalytic reaction has unveiled new defining area and we are
studying the oxidation and reduction reactions using platinum
metals complexes of arylazoimidazoles.
b[Å]
c[Å]
b
[ꢁ]
Cell volume [Å3]
Z
m
[mmꢀ1
]
T [K]
rcalcd [g cmꢀ3
Data/restraints/parameters
R1a, wR2b [I > 2
(I)]
]
s
R1, wR2(all data)
GOF
Acknowledgments
a
R ¼ S rF0 ꢀ Fcr/S F0.
P
P
Financial support from the Department of Science & Technology
and University Grants Commission, New Delhi is gratefully
acknowledged.
wR ¼ ½ wðF02 ꢀ Fc2Þ = wðF04Þꢄ1=2 are general but w are different, w ¼ 1/
b
[
s
2(F2) þ (0.0556P)2 þ 2.1396P] for (2a); w ¼ 1/[
s
2(F2) þ (0.1085P)2 þ 0.6247P] for
(4b) where P ¼ (F20 þ 2Fc2)/3.

S.K. Sarkar et al. / Journal of Organometallic Chemistry 716 (2012) 129e137
137
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Appendix A. Supplementary material
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Crystallographic data for the structures 2a and 4b have been
deposited with the Cambridge Crystallographic Data center, CCDC
No. 855664 (2a) and 855665 (4b) respectively. Copies of this
information may be obtained free of charge from the Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (e-mail: deposit@
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