Water soluble (η6-arene) ruthenium(II) complexes incorporating marine derived bioligand: Synthesis, spectral and structural studies

Article abstract of DOI:10.1016/j.ica.2009.09.006

A series of water soluble compounds of general formula [{(η⁶-arene)Ru(HMP)Cl}], [η⁶-arene = η⁶-cymene (1), η⁶-HMB (2), η⁶-C₆H₆ (3); HMP = 5-hydroxy-2-(hydroxymethyl)-4-pyrone] ha

Full text of DOI:10.1016/j.ica.2009.09.006

Inorganica Chimica Acta 362 (2009) 5252–5258
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Inorganica Chimica Acta
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Water soluble (
g
6-arene) ruthenium(II) complexes incorporating marine derived
bioligand: Synthesis, spectral and structural studies
b
a
b
Keisham Sarjit Singh a, , Volodymyr Svitlyk , Prabha Devi , Yurij Mozharivskyj
*
a Bioorganic Chemistry Laboratory, National Institute of Oceanography (CSIR), Goa 403 004, India
b Department of Chemistry, McMaster University, West Hamilton, ON, Canada L8S4M1
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 May 2009
Received in revised form 31 August 2009
Accepted 1 September 2009
Available online 6 September 2009
A series of water soluble compounds of general formula [{(
g
6-arene)Ru(HMP)Cl}], [ 6-arene = 6-cym-
g g
ene (1),
by the reaction of [{(
excellent yield tetra-azido complexes [{(
reaction of complex 3 with NaN3 yielded di-azdo complex [{(
arene)Ru( N3)Cl}2] with HMP in the presence of NaOMe resulted in the formation of azido complex
[{(
6-arene)Ru(HMP)N3}]. Mono and dinuclear complexes [{( 6-arene)Ru(HMP)(L1)}]+ and [{( 6-are-
ne)Ru(HMP)}2(
g g
6-HMB (2), 6-C6H6 (3); HMP = 5-hydroxy-2-(hydroxymethyl)-4-pyrone] have been prepared
g
6-arene) RuCl2}2] with HMP. The complexes 1 and 2 react with NaN3 to give in
6-arene)Ru(
N3)N3}2] (arene = cymene 4, HMB = 5) but similar
6-C6H6)Ru( N3)Cl}2] (6). Reaction of [{(g6
g
l
g
l
-
l
Keywords:
Arene
Azide
Kojic acid
Bioorganometallic
Crystallography
g
g
g
l
L2)]2+ were also prepared by the reaction of complexes 1 and 2 with the appropriate
ligand, L1 or L2 in the presence of AgBF4 (L1 = PyCN, DMAP; L2 = 4,40-bipy, pyrazine). The complexes are
characterized on the basis of spectroscopic data and molecular structures of three representative com-
pounds have been determined by single crystal X-ray diffraction study.
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
by various fungal or bacteria strains of genus Aspergillus and Peni-
cillium. It has been used in many countries as skin whitening agent
Arene ruthenium (II) complexes have been subject of current
interest owing to their biological and catalytic properties [1–6].
Catalytic activities of these complexes ranges from hydrogen trans-
fer [7] to ring closer metathesis [8]. Moreover, anti tumor [5,6,9],
antiviral [10] and catalytic activities [11,12] exhibited by some of
because of its tyrosinase inhibitory activity on melanin synthesis
[21,22]. Our current interest in
6-arene ruthenium(II) complexes
bearing oxygen ligands [20] has prompted us to study the synthe-
sis of
6-arene ruthenium complexes containing kojic acid ligand
keeping in mind their possible biological activities. In this paper,
we would like to report synthesis of water soluble (
6-arene)
ruthenium (II) complexes incorporating kojic acid ligand (HMP)
of the type [(
6-arene)Ru(HMP)X] (X = Cl, N3) and cationic com-
plexes [(
6-arene)Ru(HMP)L1]+ or [{( 6-arene)Ru(HMP)}2 L2]2+
(where, L1, L2 = neutral ligands). We also disclosed the reaction of
[(
6-arene)Ru(HMP)Cl] with sodium azide to yield azido dimeric
complexes [{( N3)N3}2] and [{( N3)Cl}2].
6-arene)Ru( 6-arene)Ru(
g
g
the water soluble (
g
6-arene) ruthenium(II) complexes has evoked
g
interest in recent years. Recently, much attention has focussed on
the development of bioorganometallic complexes. Some of these
complexes have been reported to exhibit side-on intercalative into
g
g
g
DNA [13,14]. There have been extensive studied on
ruthenium complexes bearing nitrogen ligands [15–19]. However,
6-arene ruthenium complexes bearing oxygen ligands are rela-
tively less explore. In our previous communication, we have re-
ported synthesis of (
6-arene) ruthenium(II) triazole compounds
g
6-arene
g
g
g
l
g
l
The complexes are fully characterized on the basis of FTIR and
NMR spectroscopic data.
g
containing b-diketonate group by the reaction of 1,3-dipolar addi-
The molecular structures of three representative compounds
tion of terminal azido group with activated alkynes [20]. Our cur-
viz. [( N3)N3}2]
g
6-p-cymene) Ru(HMP)Cl] (1), [{(
g
6-p-cymene)Ru(
l
rent interest on
(g
6-arene) ruthenium complexes containing
(4) and [(g
6-HMB)Ru(HMP)N3] (8) were established by single crys-
oxygen ligand arises due to labile nature of oxygen ligand and pos-
sibility of forming water soluble compounds.
tal X-ray diffraction.
During the course of our study on bioactive compounds from
marine organisms we isolated kojic acid from a marine fungus
Aspergillus species. Kojic acid is one of the metabolite produced
2. Experimental
2.1. General remarks
Solvents were dried using appropriate drying agents and dis-
tilled prior to use. RuCl3ꢀ3H2O (Arrora Matthey), pyridine cyanide
* Corresponding author. Tel.: +91 0832 2450392; fax: +91 0832 2450607.
E-mail addresses: keisham@nio.org, keisham.sarjit@gmail.com (K.S. Singh).
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.09.006

K.S. Singh et al. / Inorganica Chimica Acta 362 (2009) 5252–5258
5253
(PyCN), 4-(dimethyl amino) pyridine (DMAP), pyrazine (pz), so-
dium azide (Sigma Aldrich), 4,4-bipyridine (Merk) were used as re-
ceived. NMR spectra were recorded on a Bruker Avance 300 MHz
spectrometer at 300.13 (1H), 75.47 MHz (13C) with SiMe4 as inter-
nal references and coupling constants are given in Hertz. Infra red
spectra were recorded in a diffused reflection spectroscopy (DRS)
assembly on a Shimadzu-8201PC spectrometer with sample pre-
2.2.4. Synthesis of [{(g lN3)N3}2] (4)
6-p-cymene)Ru(
A mixture of complex 1 (0.1 g, 0.229 mmol), NaN3 (0.031 g,
0.480 mmol) and EtOH (20 ml) was stirred for 3 h at room temper-
ature. After which the solvent was rotary evaporated and the res-
idue was extracted with dichloromethane then filtered. The
filtrate on concentration to ca 3 ml and addition of excess diethyl
ether afforded red crystals of complex 4 after leaving overnight
at room temperature.
pared in KBr. The precursor complexes [{(
[23,24], [(
6-C6Me6)RuCl2]2 [25,26], [{( 6-C6H6)RuCl2}2] [23,24],
[{( N3)Cl}2] [27] and [{( N3)Cl}2]
6-p-cymene)Ru( 6-HMB)Ru(
g
6-p-cymene)RuCl2}2]
g
g
Yield: 0.056 g (54%).
g
l
g
l
IR (KBr, cmꢁ1): 2057 (
mN3), 2034, (mN3).
[28] were prepared according to literature procedures. Kojic acid
(HMP) was obtained from a marine derived fungus Aspergillus sp.
isolated from sea weeds.
1H NMR (CDCl3, d): 1.33 (d, 12H, JH–H = 6.9), 2.29 (s, 6H), 2.87
(qt, 2H), 5.24 (d, 4H, JH–H = 5.1), 5.49 (d, 4H, JH–H = 6.8).
2.2.5. Synthesis of [{(g lN3)N3}2] (5)
6-C6Me6)Ru(
2.2. Synthesis of compounds
This complex was synthesized by following a similar method as
described for complex 4 using complex 2 (0.04 g, 0.09 mmol) and
NaN3 (0.012 g, 0.18 mmol).
2.2.1. Synthesis of [(g
6-p-cymene)Ru(HMP)Cl] (1)
A mixture of kojic acid (0.05 g, 0.35 mmol) and NaOMe (0.019 g,
Yield: 0.025 g (81%).
0.35 mmol) in dry methanol (40 ml) was stirred for 10 min. After
IR (KBr, cmꢁ1): 2061 (
m
N3), 2025, (
mN3).
which the complex [(g
6-p-cymene)RuCl2]2 (0.1 g, 0.163 mmol)
1H NMR (CDCl3, d): 2.07 (s, 36H, HMB).
was added to the mixture and stirring continued for additional
5 h. Solution was rotary evaporated to dryness and taken in dichlo-
romethane to precipitate out sodium chloride. The solution was fil-
tered and concentrated to ca 3 ml then excess diethyl ether was
added. The yellow needle crystalline solid formed on leaving the
solution for 2 h at room temperature was collected, washed with
diethyl ether and dried in vacuum to afford 0.125 g (93% yield) of
the compound.
2.2.6. Synthesis of [{(
g
6-C6H6)Ru(
6-C6H6)Ru(HMP)Cl] (0.04 g, 0.084 mmol) and
lN3)Cl}2] (6)
A mixture of [(
g
NaN3 (0.016 g, 0.17 mmol) were stirred in 30 ml of ethanol for
5 h. The color of the solution tuned into dark red as the reaction
progress. After stirring for 5 h, the solvent was rotary evaporated
and the brown solid was washed with methanol then hexane
(2 ꢂ 10 ml) and dried under vacuum.
IR (KBr, cmꢁ1): 3300, 3043, 1602, 1562, 1502, 1469, 1288, 1247.
IR (KBr, cmꢁ1): 2056 cmꢁ1
.
1H NMR (CDCl3, d): 1.22 (dd, 6H, Me, CHMe2, JH–H = 2.1, JH–H
=
1H NMR (DMSO-d6, d): 5.78 (s, 12H, C6H6).
4.8), 2.30 (s, 3H, Me), 2.87 (sept, 1H, CHMe2), 4.44 (s, 2H, CH2–
C5H2O3), 5.30 (d, 2H, cymene ring, JH–H = 5.4), 5.51 (d, 2H, cymene
ring, JH–H = 5.1), 6.63 (s, 1H), 7.66 (s, 1H). 13C{1H} NMR (CDCl3, d):
15.25 (s, Me), 18.59 (s, Me, CMe), 22.31 (d, Me, JC–H = 5.28, CHMe2),
31.08 (s, CH, CHMe2), 60.73 (s, CH2, CH2OH), 77.43 (d, cymene
ring), 78.61 (t, JH–H = 46.7, cymene ring), 95.56 (s, C, CMe), 100.08
(s, C, CPri), 107.57 (s, CH, HMP), 141.07 (s, CH–O, HMP) 159.49 (s,
C, C@CH, HMP), 167.44 (s, C–O), 185.80 (s, C@O).
2.2.7. Synthesis of [(
g
6-p-cymene)Ru(HMP)N3] (7)
A mixture of HMP (0.024 g, 0.169 mmol), NaOMe (0.01 g,
0.185 mmol) and methanol (20 ml) were stirred at room tempera-
ture for 10 min. To this solution complex [(g lN3)Cl]2
6-cymene)Ru(
(0.052 g, 0.083 mmol) was added then the reaction mixture was
stirred at room temperature for 6 h. Initially orange suspension
turned bright red in color as the reaction progress. The solution
was rotary evaporated and the residue was dissolved in CH2Cl2
then filtered through a silica gel bed. The filtrate was concentrated
to ca 3 ml and excess diethyl ether was added. The red crystal of
complex 7 was separated when the solution allowed to kept over-
night under fridge. The crystal was collected, washed with hexane
(2 ꢂ 10 ml) and dried under vacuum.
2.2.2. Synthesis of [{(g
6-C6Me6)Ru(HMP)}Cl] (2)
This complex was prepared by following a similar procedure as
described in the preparation of 1 using kojic acid (0.046 g,
0.32 mmol), NaOMe (0.018 g, 0.33 mmol) and complex [(g6
C6Me6)RuCl2]2 (0.1 g, 0.149 mmol).
-
Yield: 0.095 g (72%).
Yield: 0.0512 g (74%).
FTIR (KBr, cmꢁ1): 3201, 1612, 1560, 1500, 1278, 1247.
IR (KBr, cmꢁ1): 3292, 2032, (
mN3); 1602 (C–O), 1560, 1500
1H NMR (CDCl3, d): 2.15 (s, 18H, HMB), 4.41 (s, 2H, HMP), 6.55
(s, 1H, HMP), 7.62 (s, 1H, HMP).
(C@O).
1H NMR (CDCl3, d): 1.33 (d, 6H, CHMe2, JH–H = 6.9), 2.29 (s, 3H,
Me), 2.87 (qt, 1H, CH, CHMe2), 4.46 (s, 2H, –CH2OH), 5.52 (d, 2H,
cymene ring), 5.49 (d, 2H, cymene ring), 6.62 (s, 1H), 7.68 (s, 1H).
13C{1H} NMR: 17.92 (s, Me), 22.30 (s, Me, CHMe2) 30.95 (d, CH,
CHMe2), 60.86 (s, CH2, HMP), 78.58 (s, C, cymene ring), 80.11 (d, C,
cymene ring), 95.07 (s, C, CMe), 99.46 (s, C, CPri), 107.66 (s, CH,
HMP), 141.32 (s, CH-O, HMP), 159.36 (s, C@CH, HMP), 167.32 (s,
C–O, HMP), 185.71 (s, C@O, HMP).
13C (CDCl3, d): 15.59 (s, Me, HMB), 60.90 (s, CH2, CH2OH) 89.75
(s, C, HMB ring), 107.75 (s, CH, HMP) 140.72 (s, CH–O, HMP),
159.73 (s, C@CH, HMP), 166.08 (s, C–O), 185.69 (s, C@O).
2.2.3. Synthesis of [{(g
6-C6H6)Ru(HMP)}Cl] (3)
A mixture of HMP (0.06 g, 0.42 mmol) and NaOMe (0.023 g,
0.43 mmol) was stirred at room temperature for 30 min. To this
stirring solution, complex [{(g
6-C6H6)RuCl2}2] (0.1 g, 0.19 mmol)
was added and reaction further stirred for another 4 h. During this
time the brown suspension became clear and bright orange solid
precipitated out. The orange solid was collected washed with cold
methanol (2 ꢂ 10 ml) and diethyl ether (2 ꢂ 10 ml) then dried un-
der vacuum. Additional compound was recovered by concentrating
the mother solution.
2.2.8. Synthesis of [(
To a suspension of HMP (0.048 g, 0.34 mmol) and NaOMe
(0.02 g, 0.34 mmol) was added complex [( N3)Cl]2
6-C6Me6)Ru(
g
6-C6Me6)Ru(HMP)N3] (8)
g
l
(0.1 g, 0.15 mmol). The mixture was stirred at room temperature
for 6 h. As the reaction proceed the yellow orange solution turned
into a red and suspension became clear. The solution was evapo-
rated to dryness and residue dissolved in dichloromethane and fil-
tered. The filtrate on subsequent concentration to ca 3 ml and
addition of diethyl ether gave red crystals of complex.
Yield: 0.09 g (66%).
Overall yield: 0.083 g (98%).
FTIR (KBr, cmꢁ1): 3058, 1602, 1550, 1504.
1H NMR (MeOD-d4, d): 4.42 (s, 2H, HMP) 5.77 (s, 6H, C6H6), 6.70
(s, 1H, HMP), 7.81 (s, 1H, HMP).

5254
K.S. Singh et al. / Inorganica Chimica Acta 362 (2009) 5252–5258
IR (KBr, cmꢁ1): 2036, 1604, 1556, 1508, 1471, 1272.
the mixture was stirred for 10 h after adding the appropriate li-
gand, L2 (0.025 mmol). The solvent was rotary evaporated and
the residue was dissolved in dichloromethane then filtered
through a short silica gel bed. Addition of excess diethyl ether to
this filtrate afforded a yellow solid that was washed with hexane
(2 ꢂ 10 ml) and dried under vacuum.
1H NMR (CDCl3, d): 2.09 (m, 18H, Me), 4.39 (s, 2H), 6.27 (m, 1H),
6.61 (m, 1H).
2.2.9. Synthesis of [(
A mixture of kojic acid (0.023 g, 0.2 mmol), NaOMe (0.011 g,
0.2 mmol) and [( N3)Cl}2] (0.05 g, 0.097 mmol) were
6-C6H6)Ru(
g
6-C6H6)Ru(HMP)N3] (9)
g
l
Compound 12a: Yield (0.022 g, 68%).
stirred in MeOH (40 ml) for 10 h at room temperature. During
the course of reaction the brown solid dissolved completely and
solution turned into yellow orange color. The solution was filtered
to remove insoluble materials and volume was reduced to ca 3 ml
under reduce pressure. Addition of excess diethyl ether to this
solution causes precipitation of yellow solid. The yellow solid
was centrifuged, washed with diethyl ether (2 ꢂ 10 ml) and dried
in vacuum.
1H NMR (DMSO-d6, d): 1.24 (t, 12H, JH–H = 4.2, Me), 2.03 (s, 6H,
Me), 2.83 (m, 2H), 4.24 (s, 4H), 5.7 (br, 2H, OH), 5.93 (d, 4H, JH–
H = 5.7), 5.98 (d, 4H, JH–H = 5.7), 6.65 (s, 2H), 8.00 (s, 2H), 8.10 (s,
4H), 8.61 (d, 4H, JH–H = 6).
Compound 12b: Yield (16 mg, 53%).
1H NMR (CDCl3, d): 1.27 (m, 12H, Me), 2.12 (s, 6H, Me), 2.84 (m,
2H), 4.39 (s, 4H), 5.53 (m, 4H), 5.64 (m, 4H), 6.76 (s, 2H), 6.84 (s,
2H), 7.65 (s, 2H), 8.50 (s, 2H).
Yield: 0.036 g (51%).
FTIR (KBr, cmꢁ1): 2038, 1645, 1556, 1523, 1485.
2.2.13. Synthesis of [{(
(13a), pyrazine (13b)}
These complexes were prepared by following a similar method
described above using complex 2 (0.057 g, 0.13 mmol) and AgBF4
(0.026 g, 0.13 mmol).
g l
6-HMB)Ru(HMP)}2( -L2)]2+ {L2 = 4,4-bipy
1H NMR (DMSO-d6, d): 4.38 (s, 2H), 5.73 (s, 6H, C6H6), 6.85 (s,
1H, OH), 7.35 (s, 1H), 7.82 (s, 1H).
2.2.10. Synthesis of [{(g
6-p-cymene)Ru(HMP)L1}]+ {L1 = PyCN (10a),
DMAP (10b)}
Compound 13a: Yield (0.041 g, 56%).
IR (KBr, cmꢁ1): 1602, 1550, 1492,1473, 1080.
1H NMR (MeOD-d4, d): 2.13 (d, 36H, HMB, JH–H = 11), 4.32 (s,
4H), 6.66 (s, 2H), 7.83 (s, 2H), 7.92 (s, 4H), 8.51 (d, 4H, JH–H = 4.2).
Compound 13b: Yield (0.035 g, 51%).
A mixture of complex 1 (0.05 g, 0.12 mmol) and AgBF4 (0.030 g,
0.15 mmol) suspended in acetone (30 ml) was stirred for 20 min
and then filtered to remove the white precipitate of silver chloride.
To this filtrate, ligand L1 (0.24 mmol) was added and the mixture
was stirred for 3 h then insoluble material was filtered off. The sol-
vent was evaporated to dryness under reduce pressure and residue
was dissolved in dichloromethane then filtered through a short
alumina bed. The filtrate on concentration to ca 3 ml and addition
of excess hexane afforded a yellow solid. The yellow solid was
washed with hexane (2 ꢂ 10 ml) and dried under vacuum.
Compound 10a: Yield (0.036 g, 52%).
1H NMR (CDCl3, d): 2.07 (s, 36H, HMB), 4.35 (s, 4H, HMP), 6.75
(s, 2H, HMP), 7.69 (s, 2H, HMP), 8.25 (d, 2H, pz, JHH = 4.6), 8.50 (br,
2H, pz).
Caution: (g
6-benzene)ruthenium azide dimer is highly explo-
sive in dried condition. Preparation of this complex on large scale
should be avoided.
IR (KBr, cmꢁ1): 2239, 1685, 1602, 1548, 1060.
3. Structure analysis and refinement
1H NMR (DMSO-d6, d): 1.32 (d, 6H, JH–H = 4.2), 2.12 (s, 3H), 2.85
(sept., 1H), 4.36 (s, 2H), 5.64 (d, 2H, JH–H = 6.6), 5.85 (d, 2H,
JH–H = 5.8), 6.72 (s, 1H), 7.87 (d, 2H, JH–H = 5.9), 7.93 (s, 1H), 8.80
(d, 2H, JH–H = 6.6).
The X-ray intensity data were measured at 293(2)° K on a Bru-
ker Apex II CCD area detector employing graphite monochromater
using Mo-K
correction was made by modeling a transmission surface by spher-
ical harmonics employing equivalent reflections with I > 2 (I)
a radiation (k = 0.71073 Å). An empirical absorption
Compound 10b: Yield (0.042 g, 59%).
1.26 (s, 6H, CHMe2, cymene), 2.09 (s, 3H, CHMe, cymene), 2.83
(m, 1H), 3.03 (s, 6H, NMe2, DMAP), 4.47 (s, 2H, CH2OH, HMP),
5.37 (s, 1H, OH), 5.52 (d, 2H, JH–H = 5.4), 5.57 (d, 2H, JH–H = 5.7),
5.79 (d, 1H, JH–H = 5.7, DMAP), 6.50 (s, 1H, HMP), 6.74 (s, 1H,
HMP), 7.63 (s, 1H, HMP), 7.81 (d, 1H, JH–H = 6.6, DMAP), 8.39 (d,
1H, JH–H = 6.9, DMAP).
r
(program SADBAS) [29]. The structures were solved by direct meth-
ods (SHELXS 97) [30] and refined by full matrix least-squares base
on F2 using (SHELXL-97) [31] softwares. The weighting scheme used
was W = 1/[
r
2(F02) + 0.0311 P2 + 3.5016 P] where P = ðF02 þ 2F2c )/3.
Non-hydrogen atoms were refined anisotropically and hydrogen
atoms were refined using a ‘‘riding” model. Refinement converged
at a final R = 0.0385, 0.0315 and 0.0583 (for complexes 1, 4 and 8,
respectively, for observed data F2), and wR2 = 0.0427, 0.0430 and
0.1267 (for complexes 1, 4 and 8, respectively, for unique data
F2). Molecular structures of the compounds are shown in Figs. 1–
3. Selected bond lengths and angles are tabulated in Tables 1–3.
Details of crystallographic data collection parameters and refine-
ment are summarized in Table 4.
2.2.11. Synthesis of [{(g
6-HMB)Ru(HMP)L1}]+ {L1 = PyCN (11a), DAMP
(11b)}
These complexes were prepared by following a similar method
described above using complex 2 (0.05 g, 0.11 mmol), AgBF4
(0.022 g, 0.11 mmol) and ligand L (0.22 mmol).
Complex 11a: Yield (0.048 g, 71%).
1H NMR (CDCl3, d): 2.09 (s, 18H, HMB), 4.39 (s, 2H, HMP), 6.73
(s, 1H, HMP), 7.63 (s, 1H, HMP), 7.75 (d, 2H, PyCN, JH–H = 6.3), 8.53
(d, 2H, PyCN, JH–H = 5.4).
Complex 11b: Yield (0.063 g, 91%).
4. Results and discussion
1H NMR (CDCl3, d): 2.07 (s, 18H, HMB), 3.04 (s, 6H, NMe2), 4.41
(s, 2H, HMP), 6.49 (d, 2H, JH–H = 6.9, DMAP), 6.69 (s, 1H, HMP), 7.57
(s, 1H, HMP), 7.60 (d, 1H, JH–H = 6.9, DMAP), 8.33 (d, 1H, JH–H = 7.2,
DMAP).
4.1. Neutral complexes
The reaction of [{(
HMP in the presence of NaOMe yielded a series of water soluble
complexes of formulation [{(
6-arene)Ru(HMP)Cl}] 6-are-
g
6-arene)RuCl2}2] with two equivalents of
2.2.12. Synthesis of [{(
g
6-p-cymene)Ru(HMP)}2(
l
-L2)]2+ {L2 = 4,4-bipy
g
(g
(12a), pyrazine (12b)}
ne = p-cymene, 1; HMB, 2; C6H6, 3) in good yield (Scheme 1). The
complexes were characterized on the basis of FTIR, 1H and partly
by 13C NMR spectroscopic data. 1H NMR spectrum of complex 1
exhibited resonance for isopropyl proton as two doublets at d
A mixture of complex 1 (0.025 g, 0.057 mmol) and AgBF4
(0.022 g, 0.114 mmol) in acetone (20 ml) was stirred for 30 min.
The white precipitate of AgCl formed was filtered off and then

K.S. Singh et al. / Inorganica Chimica Acta 362 (2009) 5252–5258
5255
Fig. 3. Molecular structure of complex 8. All hydrogen atoms have been omitted for
clarity.
Table 1
Selected bond lengths (Å) and bond angles (°) for complex 1 with estimated standard
deviations (esd’s) in parenthesis.
Fig. 1. Molecular structure of complex 1 showing two independent molecule A and
molecule B. All hydrogen atoms have been omitted for clarity.
Molecule A
Molecule B
Bond lengths (Å)
Ru–Cent
Ru–Cl
Ru–O1
Ru–O2
C17–O3
C14–O13
C16–O2
C11–O1
1.641
1.648
2.412 (3)
2.118 (7)
2.124 (8)
1.363 (12)
1.3900
2.418 (3)
2.173 (7)
2.129 (7)
1.435 (11)
1.3900
1.261 (8)
1.324 (8)
1.277 (8)
1.339 (8)
Bond angles (°)
O1–Ru–O2
O1–Ru–Cl
Ru–O2–C16
Ru–O1–C11
79.1 (3)
85.8 (2)
111.6 (5)
107.6 (5)
78.7 (3)
85.5 (2)
110.9 (5)
108.7 (5)
Table 2
Selected bond lengths (Å) and bond angles (°) for complex 4 with estimated standard
deviations (esd’s) in parenthesis.
Bond lengths (Å)
Ru1–Cent
N11–N12
N11B–N12B
Ru1A–N21
Ru1A–N11
1.562
Ru2–Cent
N12–N13
N12B–N13B
Ru1B–N21
Ru1B–N11
1.729
1.244 (8)
1.144 (10)
2.214 (6)
2.123 (5)
1.159 (10)
1.260 (11)
2.164 (6)
2.113 (5)
Fig. 2. Molecular structure of complex 4. All hydrogen atoms have been omitted for
clarity.
Bond angles (°)
Ru1A–N21–Ru1B
N21–Ru1A–N11
102.4 (3)
83.9 (3)
Ru1B–N11–Ru1A
N11–Ru1B–N21
107.3 (2)
75.8 (2)
1.31 which could be due to loss of planarity. In addition to the
p-cymene ring protons observed at d 5.30 and 5.51, the spectrum
also displayed two singlets at d 6.63 and 7.66 due to alkene protons
of HMP ligand. The methylene proton (–CH2OH) of HMP appeared
as a single resonance at d 4.41. In the case of complexes 2 and 3 a
singlet resonance were observed at d 2.15 and 5.77 assignable to
the protons of HMB and C6H6 groups, respectively. The 13C {1H}
NMR spectrum of 1 displayed fourteen distinct signals with olefinic
quaternary carbon appeared at d 159.4 while oxy-quaternary

5256
K.S. Singh et al. / Inorganica Chimica Acta 362 (2009) 5252–5258
Table 3
present work, treatment of [{(
did not yield complex [{(
6-arene)Ru(HMP)N3}] instead, an unex-
pected azido ruthenium complexes [{(
6-arene)Ru( N3)N3}2] (g6
g
6-arene)Ru(HMP)Cl}] with NaN3
Selected bond lengths (Å) and bond angles (°) for complex 8 with estimated standard
deviations (esd’s) in parenthesis.
g
g
l
-
Bond lengths (Å)
arene = p-cymene (4), HMB (5)) were obtained while the analogous
Ru1–Cent
Ru1–N1
N2–N3
1.644
benzene complex invariably yielded only disubstituted azido com-
2.113 (5)
1.163 (7)
2.105 (5)
N1–N2
C18–O4
Ru1–O2
1.176 (7)
1.300 (14)
2.108 (4)
plex [{(
It is noteworthy that the reaction of [{(
with NaN3 or SiMeN3 afforded compound of the type [{(
ene)Ru( N3)(Cl)}2] irrespective of the stoicheometric ratio of the
azide ligand used [27,28] but did not yield the complex [{(p-cym-
ene)Ru( N3)(N3)}2] (4). However, under similar reaction condition
analogous complex [{(
6-HMB)RuCl2}2] yielded both [{(g6
HMB)Ru( N3)Cl}2] and [{( N3)N3}2] (5) depending
6-HMB)Ru(
g
6-C6H6)Ru(
l
N3)Cl}2] (6) [34] (Scheme 1).
6-p-cymene)RuCl2}2]
6-p-cym-
g
Ru1–O1
g
Bond angles (°)
O1–Ru1–O2
N1–Ru1–O2
l
79.5 (2)
85.70 (18)
O1–Ru1–N1
C17–C18–O4
85.9 (2)
113.2 (8)
l
g
-
l
g
l
carbon (C–O) and C@O appeared at d 167.4 and 185.8, respectively.
The IR spectrum of these complexes showed absorption band due
to C@O stretching frequency at around 1602 cmꢁ1. In addition to
C@O stretching frequencies, the IR spectra also showed a pair of
strong bands in the region 1502–1562 cmꢁ1 assignable to coupled
C@O + C@C mode of vibrations [32,33]. Complex 1 was finally char-
acterized by X-ray crystallography, it crystallises in P21/c space
group in monoclinic unit cell and consists of 8 molecules per unit
cell of which two independent molecules are shown in Fig. 1. The
distance between centroid of the ring and ruthenium for molecule
A is 1.641 Å while for molecule B is 1.648 Å. The structure showed
shorter bond distance of C16–O2 (1.261 Å) as compared to C11–O1
(1.324 Å) suggesting significant localization of double bond elec-
tron at C16–O2. This indicates that double bond is localized at
C16–O2 and there is no extent of delocalisation of double bond
to C11–O1.
on the stoichiometric ratio of the sodium azide used [28]. We be-
lieved that, complexes 4 and 5 were resulted by displacement of
HMP with azide and HMP regenerated as its sodium salt. The for-
mation of complexes 4 and 5 were supported by the appearance
of absorption bands at 2034 cmꢁ1 and 2057 cmꢁ1 for complex 4
and 2025 cmꢁ1 and 2061 cmꢁ1 for complex 5 in their IR spectrum
corresponding to absorption band for terminal and bridged azide
groups, respectively. This leads to confirmation of molecular com-
position [{(g lN3)N3}2] (4) and [{(g lN3)
6-cymene)Ru( 6-HMB)Ru(
N3}2] (5) having both terminal and bridged azide ligands. The IR
spectrum of complex 6 showed a strong absorption band at
2056 cmꢁ1 due to bridge
m
N3 group but no absorption band corre-
sponding to terminal azide group, consistent with molecular com-
position [{( N3)Cl}2]. To the best of our knowledge
6-C6H6)Ru(
g
l
complex 4 represent the first example of tetra-azido p-cymene
ruthenium (II) complex. Solid state structure of complex 4 has been
determined by single X-ray analysis (Fig. 2). The complex crystal-
lizes in P1 space group in a triclinic crystal system. The distance
We have recently synthesized azide complex such as [[{(
g
6-p-
cymene)Ru(O,O0-diketonate)N3}] by reacting the complex [{(g6
-
p-cymene)Ru(O,O-diketonate)Cl}] with NaN3 [20]. However, in this
Table 4
Summary of crystal structure determination and refinement parameters for complexes 1, 4 and 8.
1
4
8
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C16H19ClO4Ru
411.83
293(2)
0.71073
Monoclinic
P21/c
C20H28N12Ru2
638.68
293(2)
C18H23N3O4Ru
446.46
293(2)
0.71073
0.71073
Triclinic
Triclinic
ꢀ
ꢀ
P1
P1
10.872(2)
14.255(3)
23.107(5)
90
113.08(3)
8.2082(9)
8.2204(8)
10.0122(11)
83.216(9)
82.420(9)
77.217(8)
650.30(12)
1
9.0285(10)
9.5758(11)
12.0705(15)
76.176(9)
76.975(9)
67.634(9)
926.53(19)
2
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
90
Volume (Å3)
3294.2(12)
8
1.661
1.128
1664
Z
Dcalc (Mg/m3)
Absorption coefficient (mmꢁ1
F(0 0 0)
1.631
1.194
320
1.600
0.874
456
)
Crystal size (mm)
h Range for data collection (°)
Index ranges
0.08 ꢂ 0.10 ꢂ 0.22
1.72–24.64
ꢁ12 6 h 6 12
ꢁ16 6 k 6 16
ꢁ27 6 ‘ 6 27
32,007
0.20 ꢂ 0.28 ꢂ 0.39
2.06–29.11
ꢁ11 6 h 6 11
ꢁ11 6 k 6 11
ꢁ13 6 ‘ 6 13
12,035
0.30 ꢂ 0.24 ꢂ 0.15
1.76–29.19
ꢁ12 6 h 6 12
ꢁ13 6 k 6 13
ꢁ16 6 ‘ 6 16
16,451
Reflections collected
Independent reflections [Rint
Completeness to h (%)
Absorption correction
Refinement method
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
Final R indices
]
5530 [0.1895]
24.64–99.5
Numerical
Full-matrix least-squares on F2
5530/0/363
0.534
R1 = 0.0385
wR2 = 0.0427
R1 = 0.1907
wR2 = 0.0631
0.717 and ꢁ0.479
6519 [0.0363]
29.11–99.6
4937 [0.0748]
29.19–98.2
6519/3/289
0.769
4937/0/230
0.887
0.0583
wR2 = 0.1267
R1 = 0.1152
wR2 = 0.1438
1.470 and ꢁ1.187
R1 = 0.0315
wR2 = 0.0430
R1 = 0.0669
wR2 = 0.0469
0.779 and ꢁ0.718
[I > 2
r(I)]
R indices (all data)
Largest difference in peak and hole (e Åꢁ3
)

K.S. Singh et al. / Inorganica Chimica Acta 362 (2009) 5252–5258
5257
N
N
N
R
R
R
Cl
X
Ru
Ru
Cl
Ru
R
NaOMe
Ru
Ru
NaN3
Kojic Acid
+
Cl
Cl
O
O
X
Cl
N
O
N
N
OH
R
R
R
4
= p-cymene, X = N3 ( )
1
2
3
= p-cymene ( ), HMB ( ), C6H6 ( )
NaN3
5
= HMB, X = N3 ( )
6
= C6H6, X = Cl ( )
N
N
N
R
R
R
Cl
7
= p-cymene ( )
N=N=N
HMP
Ru
8
HMB ( )
Ru
Ru
NaOMe
O
O
Cl
9
C6H6 ( )
N
N
N
OH
R
O
Scheme 1.
between centroid of p-cymene ring and ruthenium atom are
1.562 Å and 1.759 Å, respectively. The molecule adopt the well
known piano stool structure where the bond angle N11–RuA1–
N11A around the ruthenium atom is 85.4(3)°, which is a little high-
er than the analogous HMB compound [28]. The Ru–N bond dis-
tances of 2.128 (7) Å for RuA1–N11A and 2.214 (6) Å for RuA1–
N21 are comparable with the reported Ru–N bond distances [35].
The N–N bond distances in terminal azide are N11A–N12A
(1.219(10) Å) and N12A–N13A (1.062(11) Å), respectively which
is slightly shorter than the bridging N–N azide bond distances,
N11–N12 (1.244(8) Å) and N12–N13 (1.159(10) Å).
mined by X-ray crystallography (Fig. 3). Complex 8 crystallizes in
P1 space group in a triclinic crystal system. The geometry around
ꢀ
the ruthenium atom can be regarded as octahedral, in which three
coordination sites were occupied by
g
6-HMB, two by the HMP li-
gand and one by azide ligand (Fig. 3). The complex adopted the
well known piano stool structure where the bond angle O1–Ru–
O2 around the Ru is 79.5(2)°. The Ru1–N1 bond distance (2.113
(4) Å) is comparable to that of Ru–N bond length of complex 4
and the values fall within the usual range of Ru–N bond length
[35].
We have been interested on the synthesis of terminal azide
4.2. Cationic complexes
complex of formulation [{(
these complexes were achieved by azide bridged cleavage reaction
of [{( N3)Cl}2] with HMP ligand. Thus, reaction of
6-arene)Ru(
[{( N3)Cl}2] with two folds excess of HMP in the pres-
6-arene)Ru(
ence of NaOMe afforded the desire complexes [(
6-arene)R-
u(HMP)N3] {
6-arene = cymene (7), HMB (8), C6H6 (9)} in high
g
6-arene)Ru(HMP)N3}]. Preparation of
The reaction of complexes 1 and 2 with monodentate neutral li-
gand in the presence of halide scavengers such as AgBF4 afforded
mono-nuclear complexes 10–11 (Scheme 2). Similarly, dinuclear
compounds 12–13 were prepared by treating complexes 1 and 2
with the corresponding ligand (Scheme 2). The complexes were
soluble in water and isolated as their tetrafluoroborate salts in
moderate to high yield. The spectroscopic data are in agreement
with the formulation of these complexes. 1H NMR spectrum of
complexes (10a–10b) displayed two singlets at d 7.57 and 6.69
attributed to the olefinic methine (CH) of HMP while methyene
group of HMP ligand appeared as singlet at d 4.41. In the case of
complex (10a), a resonance was observed in the aromatic region
in the range of d 8.33–7.81 attributed to the DMAP ligand while
methyl protons of DMAP attached to the nitrogen atom was ap-
peared as singlet at d 3.04. The p-cymene signals are well resolved
and exhibit only H–H coupling. The p-cymene ring protons ap-
peared as two sets of doublet at around d 5.6 and 5.8 while a septet
is observed for HCMe2 at d 2.83 as observed in other p-cymene
complexes.
g
l
g
l
g
g
yield (Scheme 1). However, in the absence of NaOMe the reaction
did not undergo even by allowing a longer reaction time. The com-
plexes were isolated as red crystalline solid, soluble in water and
stable at room temperature. Formation of these complexes follows
from the lack of absorption bands at 2057, 2068 and 2056 cmꢁ1
corresponding to bridging azide group for the starting
ene,
6-HMB or 6-C6H6 azide complexes, respectively and
appearance of bands at 2032, 2036 and 2038 cmꢁ1 for complexes
7, 8 and 9, respectively, corresponding to terminal
N3. The 1H
g
6-p-cym-
g
g
m
NMR spectrum of complexes 7–9 showed two singlets in the region
of d 6.62–7.68 due to methine proton of HMP ligand, whereas
methylene proton of HMP ligand appeared at around d 4.46. Nota-
bly, the presence of HMP ligand provides versatile water soluble
properties to these complexes. We observed that coordination of
HMP ligand to (g
6-arene) ruthenium complexes makes the com-
1H NMR spectrum of 12a and 13a showed single resonances at d
4.24, 6.65 and 8.00 due to the HMP ligand. In the case of complex
12a a singlet is also observed at d 5.70 assignable to the OH group
of HMP ligand.
pound water soluble irrespective of the arene moiety present.
The azide complexes 7–9 were characterized with spectroscopic
data and the solid state structure of complex 8 has been deter-

5258
K.S. Singh et al. / Inorganica Chimica Acta 362 (2009) 5252–5258
OH
O
R
2+
+
R
R
O
L1
O
AgBF4
Acetone
Cl
AgBF4
Ru
Ru
Ru
L2
Ru
O
O
Acetone
O
O
O
O
OH
OH
O
O
OH
O
R
R
=
p-cymene, L2 = 4,4-bipy (12a), pz (12b)
=
10a
10b
)
p-cymene, L = PyCN (
), DMAP (
1
13a
13b
)
HMB, L2 = 4,4-bipy (
), pz (
11a
11b
)
HMB, L1 = PyCN (
) DMAP (
Scheme 2.
[4] R.E. Moris, R.E. Airid, P.D.S. Murdoch, H. Chen, J. Cummings, N.D. Hughes, S.
Parsons, A. Parkin, G. Boyd, D.I. Jordell, P.J. Sadler, J. Med. Chem. 44 (2001)
3616.
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566 (1998) 165.
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Weissenteiner, Dalton Trans. (2001) 2989.
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5. Concluding remarks
This paper described, synthesis of a series of water soluble (g6
-
arene) ruthenium (II) complexes containing marine derived bioli-
gand. Reaction of [{(
6-arene)RuCl}2] with HMP gave complexes
1–3 while reaction of HMP with [{( N3)Cl}2] afforded
6-arene)Ru(
azido complexes 7–9. We also described, reaction of [(
6-arene)R-
u(HMP)Cl] (
6-arene = 6-cymene, 1; 6-HMB, 2; 6-C6H6, 3) with
g
g
l
g
g
g
g
g
sodium azide. The former two yielded tetra-azido dimeric com-
plexes 4 and 5 while the later gives only di-azido dimeric complex
6. The complexes 1 and 2 undergo substitution reaction with
mono- or bidentate ligands to yield monomeric (10a–11b) and di-
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[13] D. Herebian, W.S. Sheldrick, J. Chem. Soc., Dalton Trans. (2002) 966.
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[15] D.L. Davies, J. Fawcett, S.A. Garratt, D.R. Russell, Organometallics 20 (2001)
3029.
[16] H.B. Ammar, J.L. Notre, M. Salem, M.T. Kaddachi, P.H. Dixneuf, J. Organomet.
Chem. 662 (2002) 63.
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meric complexes (12a–13b). Whereas the azido complex [(
ne)Ru(HMP)(N3)] undergo 1,3-dipolar cycloaddition reaction with
acetylenes to yield
6-arene ruthenium triazole complexes. This
g
6-are-
g
work is currently under progress in our laboratory.
Supplementary material
CCDC 702211, 702212 and 716745 contain the supplementary
Crystallographic data for complexes 1, 4 and 8. These data can be
obtained free of charge from the Cambridge Crystallographic Data
Centre via http://www.ccdc.cam.ac.uk or email: deposit@
ccdc.cam.ac.uk.
[21] Y. Higa, Fragrance J. 63 (1983) 40.
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Acknowledgements
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Chem. 10 (1980) 1014.
K.S.S. thanks the Council of Scientific and Industrial Research
(CSIR) and the Ministry of Earth Sciences (MoES), India for support
of this research.
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