Arene ruthenium β-diketonato triazolato derivatives: Synthesis and spectral studies (β-diketones: 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one, acetylacetone derivatives)

Article abstract of DOI:10.1016/j.jorganchem.2009.08.006

Mononuclear neutral arene ruthenium(II) β-diketonato complexes of the general formula (η⁶-arene)Ru(LL)Cl [LL = 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one (L1), arene = C₆H₆ (1), p-ⁱPrC₆H₄Me

Full text of DOI:10.1016/j.jorganchem.2009.08.006

Journal of Organometallic Chemistry 694 (2009) 3881–3891
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Arene ruthenium b-diketonato triazolato derivatives: Synthesis
and spectral studies (b-diketones: 1-phenyl-3-methyl-4-benzoyl
pyrazol-5-one, acetylacetone derivatives)
Saphidabha L. Nongbri a, Babulal Das b, K. Mohan Rao a,
*
a Department of Chemistry, North Eastern Hill University, Shillong 793 022, India
b Department of Chemistry, Indian Institute of Technology, Guwahati, India
a r t i c l e i n f o
a b s t r a c t
Mononuclear neutral arene ruthenium(II) b-diketonato complexes of the general formula (g
6-arene)-
Article history:
Received 17 June 2009
Received in revised form 23 July 2009
Accepted 4 August 2009
Available online 8 August 2009
Ru(LL)Cl [LL = 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one (L1), arene = C6H6 (1), p-iPrC6H4Me (2),
C6Me6 (3); arene = p-iPrC6H4Me, LL = 1-benzoylacetone (L3) (8); arene = p-iPrC6H4Me, LL = dibenzoyl-
methane (L4) (9)] have been synthesized and their subsequent substitution reactions with NaN3 in
alcohol at room temperature yielded the corresponding neutral terminal azido complexes (
Ru(LL)N3 [LL = 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one (L1), arene = C6H6 (4), p-iPrC6H4Me (6),
C6Me6 (7); arene = p-iPrC6H4Me, LL = dibenzoylmethane (L4) (10)] as well as
cationic complex
[(
6-p-iPrC6H4Me)Ru(L4) (PPh3)]BF4 (12) with PPh3. The [3 + 2] cycloaddition reaction of selective azido
complexes with the activated alkynes dimethyl and diethyl acetylenedicarboxylates produced the arene
triazolato complexes [(
6-arene)Ru(LL){N3C2(CO2R)2}] [arene = p-iPrC6H4Me, LL = L1, R = Me (13); are-
g
6-arene)-
Keywords:
a
1-Phenyl-3-methyl-4-benzoyl
pyrazol-5-one
Ruthenium
Hexamethylbenzene
Sodium azide
g
g
ne = C6Me6, LL = L1, R = Me (14); arene = C6Me6, LL = acetyl acetone (L2), R = Me (15); arene = C6Me6,
LL = L3, R = Me (16); arene = p-iPrC6H4Me, LL = L1, R = Et (17); arene = C6Me6, LL = L1, R = Et (18); are-
ne = C6Me6, LL = L2, R = Et (19); arene = C6Me6, LL = L3, R = Et (20)]. With fumaronitrile the reaction
Triazoles
Cycloaddition
yielded the triazoles [(g
6-arene)Ru(LL)(N3C2HCN)] [arene = p-iPrC6H4Me, LL = L1 (21), arene = C6Me6,
LL = L1 (22), arene = C6Me6, LL = L2 (23), arene = C6Me6, LL = L3 (24)]. In the above triazolato complexes
only N(2) isomer was obtained. The complexes were characterized on the basis of spectroscopic data.
Crystal structure of representatives complexes were determined by single crystal X-ray diffraction.
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
These b-diketonate ligands have been used commonly as mono-
anionic O,O0-chelating agents. Besides this normal chelating mode,
The applications of half-sandwich
g
6-arene ruthenium com-
they exhibit various other bonding modes to metal ions as neutral,
di- and tri-anions [8–11]. All relevant complexes reported so far
are centered on the acetylacetone ligand and its derivatives
[3,12–14]. Challenges are thus still open for designing new com-
plexes based on other functionalized b-diketonato derivatives.
Organic azides have useful applications in organic synthesis
[15,16]. One of the most useful synthetic applications of azides is
the preparation of 1,2,3-triazoles via 1,3-dipolar cycloadditions of
azides with alkenes, alkynes, nitriles and isonitriles [15–18]. Such
reactions give favorable results in the presence of transition metal
catalysts [18–22]. The catalytic role of half-sandwich arene ruthe-
nium complexes is also noteworthy [23–25]. Analogously, metal-
coordinated azido ligands also undergo 1,3-dipolar cycloaddition
reactions [26,27]. Although such reactions have so far focused on
syntheses of organic triazoles, isolation of the metallacycle inter-
mediate azide derivatives has been relatively unexplored. Recent
studies reveal that dipolar cycloaddition reactions of neutral arene
ruthenium azido complexes are favorable. These azido complexes
plexes are extensive, particularly in synthetic organic chemistry.
These purely inorganic materials are extraordinarily robust and
therefore well suited as homogenous catalysts under mild
conditions [1] and also as anti-cancer drugs [2]. Only a few reports
of the chemistry of arene ruthenium(II) complexes containing
O,O0-donor ligands are available; mainly concerning acetylacetona-
to [3–5] and carboxylato [6,7] complexes. A new class of b-diketo-
nate ligands – the acylpyrazolones – have been developed which
possess a pyrazole ring fused to the O,O0- chelating fragment [8].
Marchetti et al. [R] reported extensive syntheses and studies of a
series of substituted acylpyrazolone and their complexes with
various transition metals. Metal derivatives of these ligands are
generally considered to be more stable than the analogous acetyl-
acetonates [9].
* Corresponding author. Tel.: +91 364 272 2620; fax: +91 364 272 1010.
E-mail address: mohanrao59@gmail.com (K.M. Rao).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.08.006

3882
S.L. Nongbri et al. / Journal of Organometallic Chemistry 694 (2009) 3881–3891
undergo [3 + 2] cycloadditions with a series of activated alkynes
and fumaronitrile to produce arene ruthenium triazolato com-
plexes [13–14,28–31]. Cu(I) catalysts have proved considerably
useful in azide–alkyne cycloadditions, but are efficient only with
terminal alkyne substrates [19,24]. However, ruthenium catalysts
act well with internal alkynes as well, expanding the scope of this
cycloaddition process [24].
Arene ruthenium acylpyrazolate complexes and their reactions
involving substitution of chloride ion by neutral and anionic li-
gands have already been reported [32]. However, 1,3-dipolar cyclo-
addition reactions of these complexes have not been reported so
far to the best of our knowledge. Though the analogous triazole
complexes of arene and indenyl ruthenium(II) b-diketonate have
been reported in our recent papers [12–14,29–31], triazole com-
plexes of hexamethylbenzene ruthenium(II) b-diketonate have
not been reported. In continuation of earlier work, we report here
the syntheses of some arene ruthenium(II) b-diketonato complexes
along with their subsequent substitution reactions with mono-
dentate ligands and the syntheses of triazolato complexes.
fumaronitrile (Acros Organics), acetylacetone (SD Fine-Chem) and
sodium azide were purchased and used as received. The
compounds [(
-Cl)Cl]2 [33,34], [(
Ru( -N3)Cl]2 [35,36], [(
Ru(L2)Cl], [(
[(
6-C6Me6)Ru(L3)N3] [12] and 1-phenyl-3-methyl-4-benzoyl
pyrazol-5-one (L1) [38] were prepared according to the literature
methods. [( -Cl)Cl]2 was prepared using
6ÙC6Me6)Ru(
g
6ÙC6H6)Ru(
l
-Cl)Cl]2 [33], [(
g
6-p-iPrC6H4Me)Ru
6-p-iPrC6H4Me)-
-N3)Cl]2 [37], [(
6-C6Me6)-
[(
6-C6Me6)Ru(L2)N3],
(
l
g
6ÙC6H6)Ru(
g
l-N3)Cl]2 [14], [(
g
l
6-C6Me6)Ru(
l
g
g
6-C6Me6)Ru
(L3)Cl],
g
g
g
l
a
Microwave Discover CEM. NMR spectra were recorded on an
AMX-400 MHz spectrometer. Infrared spectra were recorded as
KBr pellets on a Perkin–Elmer 983 spectrophotometer. The follow-
ing structures represent the ligands L1, L2, L3 and L4.
CH3
3
2
N
R1
R
1
N
4 C
5'
5
O
O
ONa
O
H
2. Experimental
1-phenyl-3-methyl-4-benzoyl pyrazol-5-one (L1)
R, R1 = Me, Me = L2
R, R1 = Me, Ph = L3
Caution: All the azide reactions should be performed with ex-
treme care.
R, R1 = Ph, Ph = L4
2.1. Physical methods and materials
2.2. Single crystal X-ray structure analyses
All solvents were dried and purified by standard procedure.
Ruthenium trichloride hydrate (Arora Matthey Ltd.), hexamethyl-
benzene, dibenzoylmethane and dimethyl acetylenedicarboxylate
(Aldrich), benzoylacetone, diethyl acetylenedicarboxylate and
Crystals suitable for X-ray diffraction study for compounds 6
and 10 were grown by slow diffusion of diethyl ether into dichlo-
romethane, while requisite size crystals of complexes 9 and 17
Table 1
Summary of crystal structure determination and refinement parameters for complexes 6, 9, 10 and 17.
Complex 6
Complex 9
Complex 10
Complex 17
Empirical formula
Formula weight
T (K)
C27H27N5O2Ru
554.61
293(2)
C25H25ClO2Ru
493.97
293(2)
C25H25N3O2Ru
500.55
293(2)
C35H37N5O6Ru
724.77
296(2)
k (Å)
0.71073
0.70930
0.70930
0.71073
Crystal system
Space group
Unit cell dimensions
a (Å)
b (Å)
c (Å)
Triclinic
P1
Monoclinic
P2ð1Þ=c
Monoclinic
P2ð1Þ=c
Monoclinic
P2(1)/n
ꢀ
ꢀ
ꢀ
9.0717(2)
10.4835(2)
14.0584(3)
88.7910(10)
87.9000(10)
73.3230(10)
1279.82(5)
2
1.439
0.645
568
0.50 ꢀ 0.35 ꢀ 0.24
1.45–27.51
ꢁ11 6 h 6 11
ꢁ13 6 k 6 13
ꢁ17 6 l 6 18
15 326
16.4040(9)
7.7290(10)
17.2040(7)
90
103.094(4)
90
2124.5(3)
4
1.544
10.6790(4)
11.9520(11)
17.7020(10)
90
90.554(4)
90
2259.3(3)
4
1.472
13.9402(18)
13.7348(16)
18.065(2)
90
94.708(7)
90
3447.2(8)
4
1.396
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (Mg/m3)
Absorption coefficient (mm-1
F(0 0 0)
)
0.882
1008
0.720
1024
0.506
1496
Crystal size (mm3)
0.25 ꢀ 0.175 ꢀ 0.20
1.27–24.93
0 6 h 6 19
0 6 k 6 9
ꢁ20 6 l 6 19
3470
0.35 ꢀ 0.15 ꢀ 0.10
1.90–24.93
0 6 h 6 12
0 6 k 6 14
ꢁ20 6 l 6 20
3526
0.38 ꢀ 0.25 ꢀ 0.16
1.78–28.43
ꢁ18 6 h 6 18
ꢁ18 6 k 6 17
ꢁ24 6 l 6 24
45 930
H
Range for data collection (°)
Index ranges
Reflections collected
Independent reflections (Rint
Completeness to h (%)
Absorption correction
Refinement method
)
5591 (0.0142)
27.51–96.9
None
Full-matrix
559/1/321
1.043
3470 (0.0000)
24.93–85.7
Psi-scan
Full-matrix
3470/0/363
1.074
3526 (0.0000)
24.93–84.3
Psi-scan
Full-matrix
3526/0/380
1.069
8533 (0.0330)
28.43–98.3
None
Full-matrix squares on F2
8533/0/418
1.010
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0574,
wR2 = 0.1736
R1 = 0.0598,
wR2 = 0.1773
0.675 and -0.732
R1 = 0.0262
wR2 = 0.0652
R1 = 0.0308
wR2 = 0.0684
0.750 and -0.609
R1 = 0.0266
wR2 = 0.0602
R1 = 0.0369
wR2 = 0.0658
0.325 and -0.413
R1 = 0.0434
wR2 = 0.1252
R1 = 0.0560
wR2 = 0.1357
0.890 and ꢁ0.894
Largest diff. peak and hole (e Åꢁ3
)

S.L. Nongbri et al. / Journal of Organometallic Chemistry 694 (2009) 3881–3891
3883
Table 2
Selected bond lengths (Å) for the complexes 6, 9, 10 and 17 with estimated standard deviations (esd’s) in parentheses.
Complex 6
Complex 9
Complex 10
Complex 17
Selected bonds
Bond lengths (Å)
Selected bonds
Bond lengths (Å)
Selected bonds
Bond lengths (Å)
Selected bonds
Bond lengths (Å)
Ru(1)–cent
Ru(1)–O(1)
Ru(1)–O(2)
Ru(1)–N(3)
O(1)–C(9)
O(2)–C(11)
C(9)–C(8)
C(11)–C(8)
N(2)–C(7)
N(1)–C(9)
N(4)–N(3)
N(4)–N(5)
1.645
Ru(1)–cent
Ru(1)–O–(1)
Ru(1)–O(2)
Ru(1)–Cl(1)
O(1)–C(14)
O(2)–C(12)
C(14)–C(13)
C(12)–C(13)
1.656
Ru(1)–cent
Ru(1)–O(1)
Ru(1)–O(2)
Ru(1)–N(1)
O(1)–C(11)
O(2)–C(19)
C(11)–C(18)
C(19)–C(18)
N(1)–N(2)
N(2)–N(3)
1.654
Ru(1)–cent
Ru(1)–O(1)
Ru(1)–O(2)
Ru(1)–N(1)
O(1)–C(20)
O(2)–C(11)
C(20)–C(18)
C(11)–C(18)
N(4)–C(20)
N(5)–C(19)
N(2)–C(29)
N(3)–C(28)
N(4)–N(5)
N(1)–N(3)
N(1)–N(2)
1.652
2.094(3)
2.092(3)
2.210(7)
1.262(5)
1.273(5)
1.422(6)
1.404(5)
1.320(6)
1.355(3)
0.843(11)
1.462(15)
2.0683(18)
2.0675(17)
2.4173(8)
1.272(3)
1.277(3)
1.391(4)
1.389(4)
2.0795(19)
2.0652(19)
2.155(3)
1.279(3)
1.279(3)
1.392(4)
1.392(4)
1.038
2.082(19)
2.093(19)
2.074(2)
1.267(4)
1.268(3)
1.427(4)
1.401(4)
1.369(4)
1.314(4)
1.334(4)
1.341(3)
1.391(4)
1.338(3)
1.340(3)
1.227
Table 3
Selected bond angles (°) for the complexes 6, 9, 10 and 17 with estimated standard deviations (esd’s) in parentheses.
Complex 6 Complex 9 Complex 10
Complex 17
Selected bond angles Bond angles (°) Selected bond angles Bond angles (°) Selected bond angles Bond angles (°) Selected bond angles Bond angles (°)
O(2)–Ru(1)–O(1)
O(2)–Ru(1)–N(3)
O(1)–Ru(1)–N(3)
Ru(1)–N(3)–N(4)
N(3)–N(4)–N(5)
88.20(12)
82.34(17)
82.68(19)
116.5(7)
O(2)–Ru(1)–O(1)
O(2)–Ru(1)–Cl(1)
O(1)–Ru(1)–Cl(1)
87.59(7)
84.87(6)
85.46(6)
O(2)–Ru(1)–O(1)
O(2)–Ru(1)–N(1)
O(1)–Ru(1)–N(1)
Ru(1)–N(1)–N(2)
N(1)–N(2)–N(3)
87.21(8)
80.26(10)
83.41(10)
127.7(3)
174.2(4)
O(2)–Ru(1)–O(1)
O(2)–Ru(1)–N(1)
O(1)–Ru(1)–N(1)
Ru(1)–N(1)–N(2)
Ru(1)–N(1)–N(3)
N(3)–N(1)–N(2)
88.80(8)
82.99(8)
85.81(9)
123.81(18)
122.73(17)
113.3(2)
169.6(11)
were obtained by diffusion of hexane into chloroform or dichloro-
methane. The red colored crystal of compound 6 and the bright or-
ange crystal of 17 were mounted on a Stoe-Image Plate Diffraction
ation at 293(2) K, with a 0.3° x scan mode and 10 s per frame.
However, the orange-red crystals of the complexes 9 and 10 were
mounted on the end of the glass fibre on a Nonius MACH3 diffrac-
system equipped with a / circle goniometer, using Mo K
a
graphite
tometer with graphite monochromatized Mo Ka (k = 0.70930 Å)
monochromated radiation (k = 0.71073 Å) with a / range of 0–200°
radiation at 293 K for cell determination and intensity data collec-
tion. The intensity data were corrected for Lorenz and polarization
effects. The structures were solved by direct methods using the
program SHELXS-97 [39]. Refinement and all further calculations
in increments of 1.2°, and Dmax ꢁ Dmin = 12.45–0.81 Å. X-ray inten-
sity data were collected with Mo Ka graphite monochromatic radi-
Fig. 1. Molecular structure of complex [(
g
6-p- iPrC6H4Me)Ru(L1)N3] (6) with atom
Fig. 2. Molecular structure of complex [(g
6-p-iPrC6H4Me)Ru(L4)Cl] (9) with atom
numbering scheme. Thermal ellipsoids are depicted with 35% probability level.
Hydrogen atoms are omitted for clarity.
numbering scheme. Thermal ellipsoids are depicted with 50% probability level.
Hydrogen atoms are omitted for clarity.

3884
S.L. Nongbri et al. / Journal of Organometallic Chemistry 694 (2009) 3881–3891
were carried out using SHELXL-97 [40]. The H-atoms were included
in calculated positions and treated as riding atoms using the SHELXL
default parameters. The non-H atoms were refined anisotropically,
using weighted full-matrix least-squares on F2. The data collection
parameters, selective bond lengths and bond angles are presented
in Tables 1–3, respectively. Figs. 1–4 are the ORTEP [41] representa-
tion of the molecules with 35% (Figs. 1, 3 and 4) and 50% (Fig. 2)
probability thermal ellipsoids displayed.
2.3. Synthesis of complexes
2.3.1. Preparation of [(
To the dimer [(
g
6-C6Me6)Ru(-Cl)Cl]2
g
6-p-iPrC6H4Me)Ru(
-Cl)Cl]2 (200 mg, 0.33 mmol)
l
taken in a sealed glass vial of 5 ml capacity, a threefold excess of
hexamethylbenzene (0.98 mmol) was added and mixed properly.
The reaction was carried out fixing the microwave at 170 °C and
a pressure of 5 bar. With the 200 W microwave system, this tem-
perature was reached within a few minutes, and the reaction com-
pleted in 10 min. Excess hexamethylbenzene was recovered by
washing with hexane through a silica gel column using hexane
as eluant. The orange-red band [(g l-Cl)Cl]2 was col-
6-C6Me6)Ru(
lected by passing a mixture of methanol–acetone in 1:1 ratio.
The solvent was removed on a rotary evaporator. The resulting
complex was washed with hexane and diethyl ether and dried in
vacuum.
Yield = 175 mg (96%); M.pt. = 270 °C; 1H NMR (CDCl3, d): 2.06 (s,
36H, C6Me6).
2.3.2. Preparation of [(
g
6-C6H6)Ru(L1)Cl] (1)
6ÙC6H6)Ru(
l-Cl)Cl]2 (450 mg,
To a solution of the complex [(
g
0.9 mmol) in acetonitrile, the ligand L1 (500 mg, 1.8 mmol) and
NaOMe (97 mg, 1.8 mmol) were added. The resulting solution
was stirred whereby compound 1 started precipitating after
5 min. Stirring was continued further to complete the reaction.
The precipitate was filtered and washed with diethyl ether. The fil-
trate was dried under vacuum, the residue dissolved in dichloro-
methane (10 ml) and the solution filtered to remove sodium
chloride. The solution was concentrated to 2 ml, whereupon addi-
tion of excess diethyl ether precipitated the additional complex
which was separated and dried under vacuum.
Yield = 550 mg (60.1%); IR (KBr, cmꢁ1): 1603
m(C@O), 1585, 1575
m(C@O
1H NMR (CDCl3, d): 2.27 (s, 3H, CH3), 5.8 (s, 6H, C6H6),
+ C@C)
7.38–7.5 (m, 8H, C6H5 and N1–C6H5), 7.92 (d, 2H, JH–H = 8,
N1–C6H5).
Fig. 3. Molecular structure of complex [(g
6-p-iPrC6H4Me)Ru(L4)(N3)] (10) with
atom numbering scheme. Thermal ellipsoids are depicted with 35% probability
level. Hydrogen atoms are omitted for clarity.
2.3.3. Preparation of [(
Complex 2 was prepared following a method similar to that de-
scribed for complex 1. Reaction of [( -Cl)Cl]2
6-p-iPrC6H4Me)Ru(
g
6-p-iPrC6H4Me)Ru(L1)Cl] (2)
g
l
(500 mg, 0.82 mmol) with ligand L1 (454 mg, 1.63 mmol) in 1:2 ra-
tio in the presence of NaOMe (88 mg, 1.63 mmol) in methanol
yielded complex 2.
Yield = 880 mg (78.8%); IR (KBr, cmꢁ1): 1601
m
(C@O), 1591, 1576
m(C@O+C@C)
.
1H NMR (CDCl3, d): 1.3 (d, 6H, JH–H = 2.8, CH(CH3)2), 1.6
(s, 3H, CH3cym), 2.2 (s, 3H, CH3), 2.9 (m, 1H, CH(CH3)2), 5.2 (d, 2H,
JH–H = 5.6, C6H4cym), 5.5 (d, 2H, JH–H = 4.8, C6H4cym), 7.2–7.4 (m,
8H, C6H5 and N1–C6H5), 7.8 (d, 2H, JH–H = 7.6, N1–C6H5).
2.3.4. Preparation of [(g
6-C6Me6)Ru(L1)Cl] (3)
Following a method similar to that described for the prepara-
tion of complex 1, complex 3 was prepared by the reaction of
[(g l-Cl)Cl]2 (500 mg, 0.75 mmol) with ligand L1
6-C6Me6)Ru(
(80 mg, 1.5 mmol) in 1:2 ratio in the presence of NaOMe (80 mg,
1.5 mmol), using methanol instead of acetonitrile.
Yield = 760 mg (88.37%); IR (KBr, cmꢁ1): 1600
m
(C@O), 1582, 1573
m(C@O+C@C)
.
1H NMR (CDCl3, d): 2.09 (s, 18H, C6Me6), 2.17 (s, 3H,
CH3), 7.35–7.5 (m, 8H, C6H5 and N1–C6H5), 7.95 (d, 2H, JH–H = 8,
N1–C6H5).
13C {1H} NMR (CDCl3, d): 15.27 (s, Me (C6Me6)), 16.38 (s, CH3
(C3–CH3)), 89.79 (s, C (C6Me6)), 106 (s, C4), 138.76 (s, C3),
120.73–148.89 (N1–C6H5), 127.56–139.49 (Ph (C50-Ph)), 163.23
(s, C5), 188.15(s, CO (C50-CO)).
2.3.5. Preparation of [(g
6-C6H6)Ru(L1)N3] (4)
Fig. 4. Molecular structure of complex [(g
6-p-iPrC6H4Me)Ru(L1){N3C2(CO2Et)2}]
(17) with atom numbering scheme. Thermal ellipsoids are depicted with 35%
Route (a): A suspension of complex 1 (250 mg, 0.5 mmol) and
probability level. Hydrogen atoms are omitted for clarity.
NaN3 (66 mg, 1.016 mmol) in ethanol (25 ml) was stirred at room

S.L. Nongbri et al. / Journal of Organometallic Chemistry 694 (2009) 3881–3891
3885
temperature for 6 h. The solvent was removed to dryness using ro-
5.51 (d, 2H, JH–H = 5.5, C6H4cym), 5.78 (s, 1H, L3-
c
H), 7.31–7.42
tary evaporator; the residue was extracted with dichloromethane,
filtered, and diffused with diethyl ether. On slow evaporation, the
compound was obtained as red crystals. [The remaining ether-
insoluble red-brown residue was extracted with acetone, filtered
and concentrated. On addition of excess hexane, an orange-red so-
lid precipitated out. It was ambiguously characterized to be
(m, 3H, p,m-Ph), 7.81 (d, 2H, JH–H = 7.2, o-Ph).
Complex 9 [(
IR (KBr, cmꢁ1): 1592
): 1.42 (d, 6H, JH–H = 6, CH(CH3)2), 2.34 (s, 3H, CH3cym), 3.02 (sept,
1H, CH(CH3)2), 5.32 (d, 2H, JH–H = 6, C6H4cym), 5.58 (d, 2H, JH–H = 6,
C6H4cym), 6.38 (s, 1H, L4– H), 7.38 (m, 6H, Ph), 7.90 (m, 4H, Ph).
g
6-p-iPrC6H4Me)Ru(L4)Cl]: Yield = 400 mg (87%);
m
(C@O), 1543, 1520 m(C@O+C@C).
1H NMR (CDCl3,
d
c
[(
g
6ÙC6H6)Ru(
Route (b): The benzene ruthenium azido bridge dimer
6ÙC6H6)Ru(
-N3)Cl]2 (250 mg, 0.49 mmol) was added to a
l-N3)Cl]2 (5)].
2.3.9. Preparation of [(g
6-p-iPrC6H4Me)Ru(L4)(N3)] (10)
[(
g
l
A suspension of complex 9 (100 mg, 0.2 mmol) and NaN3
(13 mg, 0.2 mmol) in ethanol (15 ml) was stirred at room temper-
ature for 1 h. Solvent was dried on a rotary evaporator and the res-
idue dissolved in dichloromethane, filtered, diffused with diethyl
ether and on slow evaporation, the compound 10 was obtained
as red crystals. [The remaining ether-insoluble red-brown residue
was extracted with acetone, filtered through silica gel and
concentrated. On addition of excess hexane, an orange-red solid
methanolic solution of L1 (270 mg, 0.97 mmol) and NaOMe
(50 mg, 0.96 mmol). The mixture was stirred at room temperature;
within 30 min, the color of solution changed from reddish-brown
to brown while stirring was continued for 6 h. The solvent was re-
moved in vacuum; the residue was dissolved in dichloromethane
and filtered. The filtrate was concentrated and the excess diethyl
ether was added for precipitation. The product was separated,
washed with diethyl ether and dried in vacuum.
precipitated out and was ambiguously characterized as [(g6
p-iPrC6H4Me)Ru(
-N3)Cl]2 (11)].
Complex 10 [(
6-p-iPrC6H4Me)Ru(L4)(N3)]: Yield = 65 mg
(64%); IR (KBr, cmꢁ1): 2030 m(N3terminal) 1593
(C@O), 1543, 1533
1H NMR (CDCl3, d): 1.32 (d, 6H, JH–H = 6, CH(CH3)2),
-
Yield = 115 mg (46.74%); IR (KBr, cmꢁ1): 2026
m(C@O), 1591, 1575 m(C@O+C@C)
1H NMR (CDCl3, d): 2.27 (s, 3H, CH3),
m(N3terminal), 1603
l
.
g
5.77 (s, 6H, C6H6), 7.2–7.35 (m, 8H, C6H5 and N1–C6H5) 7.96 (d, 2H,
JH–H = 8, N1–C6H5).
m
m(C@O+C@C).
2.32 (s, 3H, CH3cym), 3.02 (sept, 1H, CH(CH3)2), 5.32 (d, 2H,
JH–H = 6, C6H4cym), 5.58 (d, 2H, JH–H = 6, C6H4cym), 6.41 (s, 1H, L4–
2.3.6. Preparation of [(
The required starting complexes (2 and [(
-N3)Cl]2) were treated with sodium azide and L1, respectively,
g
-6p-iPrC6H4Me)Ru(L1)N3] (6)
6-p-iPrC6H4Me)R-
g
cH), 7.42–7.87 (m, 10H, Ph).
u(l
in appropriate ratio, yielding complex 6 by following the methods
(route a/route b) described above for the preparation of complex 4.
2.3.10. Preparation of [(g
6-p-iPrC6H4Me)Ru(L4)(PPh3)]BF4 (12)
A suspension of complex 9 (100 mg, 0.2 mmol), PPh3 (51 mg,
0.2 mmol) and NH4BF4 (40 mg, 0.39 mmol) in methanol (10 ml)
was refluxed for 2 h. Solvent was removed to dryness on vacuum;
the residue extracted with chloroform and filtered. Addition of ex-
cess hexane to the concentrated solution afforded compound 12 as
a yellow solid.
[No by-product [(
this case via either route.]
Yield = 245 mg (74.2%); IR (KBr, cmꢁ1): 2035
m(C@O), 1598, 1583 m(C@O+C@C)
1H NMR (CDCl3, d): 1.36 (d, 6H,
g l-N3)Cl]2 was obtained in
6-p-iPrC6H4Me)Ru(
m
(N3terminal), 1605
.
JH–H = 2.8 CH(CH3)2), 1.66 (s, 3H, CH3cym), 2.23 (s, 3H, CH3), 2.9
(m, 1H, CH(CH3)2), 5.28 (d, 2H, JH–H = 4.8, C6H4cym), 5.5 (d, 2H,
JH–H = 5.2, C6H4cym), 7.35–7.5 (m, 8H, C6H5 and N1–C6H5), 7.93 (d,
2H, JH–H = 7.8, N1–C6H5).
Yield = 75 mg (80%); IR (KBr, cmꢁ1): 1593 m(C@O), 1543, 1533
m
(C@O+C@C), 1081 m(B–F).
1H NMR (CDCl3, d): 1.32 (d, 6H, JH–H = 6,
CH(CH3)2), 2.32 (s, 3H, CH3cym), 3.02 (sept, 1H, CH(CH3)2), 5.32 (d,
2H, JH–H = 6, C6H4cym), 5.58 (d, 2H, JH–H = 6, C6H4cym), 6.41 (s, 1H,
L4–cH), 7.42–7.87 (m, 25H, Ph).
2.3.7. Preparation of [(
g
6-C6Me6)Ru(L1)N3] (7)
Complex 7 was prepared by either of the methods (route a/route
b) described for the preparation of complex 4 by reacting the re-
2.3.11. General procedure for preparation of [(
{N3C2(CO2R)2}]
g
6-arene)Ru(L)-
quired starting complexes (3 and [(
sodium azide and L1, respectively, in appropriate ratio. [No by-
product [( -N3)Cl]2 was obtained in this case via
6-C6Me6)Ru(
either route.]
Yield = 285 mg (81.42%); IR (KBr, cmꢁ1): 2027 m(N3terminal)
1593 (C@O), 1582, 1573 m(C@O+C@C)
1H NMR (CDCl3, d): 2.06
g l-N3)Cl]2) with
6-C6Me6)Ru(
(arene = p-iPrC6H4Me, LL = L1, R = Me (13); arene = C6Me6,
LL = L1, R = Me (14); arene = C6Me6, LL = L2, R = Me (15); are-
ne = C6Me6, LL = L3, R = Me (16); arene = p-iPrC6H4Me, LL = L1,
R = Et (17); arene = C6Me6, LL = L1, R = Et (18); arene = C6Me6,
LL = L2, R = Et (19); arene = C6Me6, LL = L3, R = Et (20)).
g
l
,
m
.
(s, 18H, C6Me6), 2.1 (s, 3H, CH3), 7.2–7.5 (m, 8H, C6H5 and
Into a round-bottomed flask charged with the azido complex 6
N1–C6H5), 7.96 (d, 2H, JH–H = 8, N1–C6H5).
(100 mg, 0.18 mmol) or 7 (100 mg, 0.17 mmol) or [(
g
6-C6Me6)R-
13C {1H} NMR (CDCl3, d): 15.18 (s, Me (C6Me6)), 16.3 (s, CH3 (C3–
CH3)), 90.34 (s, C (C6Me6)), 106.01(s, C4), 138.67 (s, C3), 120.71–
149.3 (N1–C6H5), 127.61–139.3 (Ph (C50-Ph)), 163.4 (s, C5),
188.75 (s, CO (C50-CO)).
u(L2)N3] (100 mg, 0.25 mmol) or [(
g
6-C6Me6)Ru (L3)N3] (100 mg,
0.17 mmol), a fivefold excess of dimethyl acetylenedicarboxylate/
diethyl acetylenedicarboxylate and dichloromethane (20 ml) was
added. The mixture was stirred at room temperature for 15 h.
The solution was reduced to ca. 2 ml on rotary evaporator. To this
solution, 30 ml of hexane was added whereupon the compound
precipitated out as a yellow solid. The solid was collected by cen-
trifuge, washed with hexane (2 ꢀ 20 ml) and dried under vacuum.
2.3.8. Preparation of [(
g
6-p-iPrC6H4Me)Ru(LL)Cl]; LL = L3 (8); LL = L4
(9)
A
suspension of [(
g
6-p-iPrC6H4Me)Ru(
l-Cl)Cl]2 (285 mg,
0.45 mmol) and sodium salt of L3/L4 (1.13 mmol) in methanol
(50 ml) was stirred at room temperature for 2 h. Solvent was re-
moved on a rotary evaporator; the residue was extracted with
chloroform and filtered to remove any insoluble materials. Addi-
tion of excess hexane resulted in precipitation of the desired com-
pound as an orange-red microcrystalline solid.
Complex 13 [(
71 mg (89.87%); IR (KBr, cmꢁ1): 1724 m(C@O of ester group), 1603
g
6-p-iPrC6H4Me)Ru(L1){N3C2(CO2Me)2}]: Yield =
m
(C@O), 1584, 1575 m(C@O+C@C), 1476 m(C–H def), 1440 m(C–N), 771 of tri-
azole ring. 1H NMR (CDCl3, d): 1.23 (d, 6H, JH–H = 6.92, CH(CH3)2),
2.075 (s, 3H, CH3cym), 2.76 (sept, 1H, CH(CH3)2), 3.04 (s, 3H, CH3),
3.76 (s, 6H, CO2CH3), 5.57 (d, 2H, JH–H = 8, C6H4cym), 5.68 (d, 2H,
JH–H = 6, C6H4cym), 7.2–7.5 (m, 8H, C6H5 and N1–C6H5), 7.79 (d,
2H, JH–H = 7.6, N1–C6H5).
Complex 8 [(
IR (KBr, cmꢁ1): 1589
): 1.36 (d, 6H, JH–H = 7, CH(CH3)2), 2.11 (s, 3H, L3-CH3), 2.28 (s, 3H,
CH3cym), 2.94 (sept, 1H, CH(CH3)2), 5.24 (d, 2H, JH–H = 5, C6H4cym),
g
6-p-iPrC6H4Me)Ru(L3)Cl]: Yield = 365 mg (90%);
(C@O), 1556, 1518 m(C@O+C@C)
1H NMR (CDCl3,
m
.
d
13C {1H} NMR (CDCl3, d): 15.9 (s, CH3 (C3–CH3)), 17.87 (s, Me
(CMe)), 22.21 (s, Me (CHMe2)), 30.7 (s, CH (CHMe2)), 51.64 (s,

3886
S.L. Nongbri et al. / Journal of Organometallic Chemistry 694 (2009) 3881–3891
CH3 (CO2CH3)), 80.31–100.73 (C6H4cym), 106.04 (s, C4), 138.38 (s,
C3), 120.47–149.17 (N1–C6H5), 127.52–138.34 (Ph (C50-Ph)),
139.77 (s, C (C–CO2CH3)), 162.6 (s, CO2 (CO2CH3)), 163.7 (s, C5),
190.062 (s, CO (C50-CO)).
13C {1H} NMR (CDCl3, d): 14.17 (s, CH3 (CO2CH2CH3)), 15.36 (s,
Me (C6Me6)), 28.1 (s, CH3 (L2-CH3)), 60.45 (s, CH2 (CO2CH2CH3)),
90.16 (s,
C (C6Me6)), 96.27 (s, cC (L2-cC)), 141.06 (s, C
(C–CO2CH2CH3)2), 163.6 (s, CO2 (CO2CH2CH3)), 190.1 (s, CO (L2-
Complex 14 [(
g
6-C6Me6)Ru(L1){N3C2(CO2Me)2}]: Yield = 62 mg
group), 1593 (C@O), 1575,
(C–N), 765 of triazole ring.
CO).
(77%); IR (KBr, cmꢁ1): 1734 m(C@O
m
Complex 20 [(
(93%); IR (KBr, cmꢁ1): 1736 m(C@O of ester group), 1601 m(C@O)
,
g
6-C6Me6)Ru(L3){N3C2(CO2Et)2}]: Yield = 68 mg
of ester
1568
m
(C@O+C@C), 1474 m(C–H def), 1441
m
1H NMR (CDCl3, d): 2.07 (s, 18H, C6Me6), 2.18 (s, 3H, CH3), 3.81
(s, 6H, CO2CH3), 7.31–7.45 (m, 8H, C6H5 and N1–C6H5), 7.8 (d,
2H, JH–H = 8, N1–C6H5).
1585, 1577 m(C@O+C@C), 1474 m(C–H def), 1446 m(C–N), 790 of triazole
ring. 1H NMR (CDCl3, d): 1.22 (t, 6H, OCH2CH3), 1.95 (s, 3H, L3-
CH3), 2.06 (s, 18H, C6Me6), 4.2 (q, 4H, OCH2CH3), 5.32 (s, 1H, L3-
13C {1H} NMR (CDCl3, d): 15.23 (s, Me (C6Me6)), 16.28 (s, CH3
(C3–CH3), 51.57 (s, CH3 (CO2CH3)), 92.04 (s, C (C6Me6)), 106.04 (s,
C4), 138.52 (s, C3), 120.35–148.95 (N1–C6H5), 127.59–139.5 (Ph
(C50-Ph)), 140.06 (s, C (C–CO2CH3)), 162.6 (s, CO2 (CO2CH3)),
163.17 (s, C5), 188.48 (s, CO (C50-CO)).
Complex 15 [(
(82%); IR (KBr, cmꢁ1): 1736 m(C@O of ester group), 1601 m(C@O)
1577, 1568 (C@O+C@C), 1474 (C–H def), 1440 (C–N), 786 of triazole
ring. 1H NMR (CDCl3, d): 1.95 (s, 6H, L2-CH3), 2.05 (s, 18H,
c
H), 7.4 (m, 3H, L3-Ph), 7.6 (m, 2H, L3-Ph).
13C {1H} NMR (CDCl3, d): 14.2 (s, CH3 (CO2CH2CH3)), 15.11 (s, Me
(C6Me6)), 27.58 (s, CH3 (L3-CH3)), 60.6 (s, CH2 (CO2CH2CH3)), 91 (s,
C (C6Me6)), 98.1 (s, C (L3- C)), 128.12-130.5 (Ph (L3-Ph)), 140.8 (s,
c
c
C (C–CO2CH3)), 162.86 (s, CO2 (CO2CH2CH3)), 181.6 (s, CO (L3-CO)),
189.03 (s, CO (L3-CO)).
g
6-C6Me6)Ru(L2){N3C2(CO2Me)2}]: Yield = 60 mg
,
m
m
m
2.3.12. Preparation of [(g
6-p-iPrC6H4Me)Ru(L1)(N3C2HCN)] (21)
A round-bottomed flask was charged with the azido complex 6
(100 mg, 0.18 mmol) and fumaronitrile (70 mg, 0.9 mmol) and
20 ml of methanol was added. The mixture was refluxed for 3 h.
The solvent was removed by rotary evaporation, the residue dis-
solved in dichloromethane and concentrated to 2 ml. Addition of
excess of hexane gave a chocolate brown precipitate. The chocolate
brown solid was collected by centrifuging, washed with hexane
(2 ꢀ 20 ml) and dried under vacuum.
C6Me6), 3.75 (s, 6H, CO2CH3), 5.08 (s, 1H, L2-cH).
13C {1H} NMR (CDCl3, d): 15.05 (s, Me (C6Me6)), 27.94 (s, CH3
(L2-CH3)), 51.32 (s, CH3 (CO2CH3)), 89.93 (s, C (C6Me6)), 98.27 (s,
c
C (L2-
182.92 (s, CO (L2-CO).
Complex 16 [(
6-C6Me6)Ru(L3){N3C2(CO2Me)2}]: IR (KBr,
cmꢁ1): 1726 m(C@O of ester group), 1600
(C@O), 1578, 1575, 1568
(C@O+C@C), 1464 m(C–H def), 1442
(C–N), 786 of triazole ring. 1H
NMR (CDCl3, d): 1.9 (s, 3H, L3-CH3), 2.06 (s, 18H, C6Me6), 3.5 (s,
cC)), 140.06 (s, C (C–CO2CH3)), 162.86 (s, CO2(CO2CH3)),
g
m
m
m
Yield = 82 mg (89.7%); IR (KBr, cmꢁ1): 2239 mCN, 1602 mC@O
,
1593, 1571 m(C@O+C@C), 1475 m(C–H def), 1446 m(C–N), 790 for the tria-
6H, CO2CH3), 5.5 (s, 1H, L3-
L3-Ph).
c
H), 7.1 (m, 3H, L3-Ph), 7.4 (m, 2H,
zole ring. 1H NMR (CDCl3, d): 1.3 (d, 6H, JH–H = 6, CH(CH3)2), 1.6 (s,
3H, CH3cym), 1.8 (m, 1H, CH(CH3)2), 2.18 (s, 3H, CH3), 5.2 (d, 2H,
JH–H = 4.8, C6H4cym), 5.4 (d, 2H, JH–H = 5, C6H4cym), 6.9 (s, 1H, CH),
7.3–7.4 (m, 8H, C6H5 and N1–C6H5), 7.9 (d, 2H, N1–C6H5).
13C {1H} NMR (CDCl3, d): 16.02 (s, CH3 (C3–CH3)), 17.9 (s, Me
(CMe)), 22.23 (s, Me (CHMe2)), 31.02 (s, CH (CHMe2)), 80.11–
101.28 (C6H4cym), 106.22 (s, C4), 114.81 (s, C„N) 134.91 (s, CH),
138.56 (s, C (C„N)), 138.7 (s, C3), 120.62–150.11 (N1–C6H5),
128.11–140.5 (Ph (C50-Ph)), 164.2 (s, C5), 190.05 (s, CO
(C50–CO)).
13C {1H} NMR (CDCl3, d): 15.27 (s, Me (C6Me6)), 27.58 (s, CH3
(L3-CH3)), 51.62 (s, CH3 (CO2CH3)), 92.19 (s, C (C6Me6)), 98.7 (s,
cC (L3-cC)), 127.12–130.18 (Ph), 140.22 (s, C (C–CO2CH3)),
162.98 (s, CO2 (CO2CH3)), 180.86 (s, CO (L3-CO)), 188.13 (s, CO
(L3-CO)).
Complex 17 [(
71 mg (88.4%); IR (KBr, cmꢁ1): 1724 m(C@O of ester group), 1605
g
6-p-iPrC6H4Me)Ru(L1){N3C2(CO2Et)2}]: Yield =
m
(C@O), 1594, 1583, 1575 m(C@O+C@C), 1474 m(C–H def), 1440 m(C–N),
786 of triazole ring. 1H NMR (CDCl3, d): 1.2 (d, 6H, JH–H = 7,
CH(CH3)2), 1.3 (t, 6H, OCH2CH3), 1.9 (s, 3H, CH3cym), 2.2 (s, 3H,
CH3), 2.8 (m, 1H, CH(CH3)2), 4.3 (q, 4H, OCH2CH3), 5.6 (d, 2H,
JH–H = 6, C6H4cym), 5.7 (d, 2H, JH–H = 5.6, C6H4cym), 7.2–7.4 (m, 8H,
C6H5 and N1–C6H5), 7.8 (d, 2H, JH–H = 8, N1–C6H5).
2.3.13. Preparation of [(g
6-C6Me6)Ru(L1)(N3C2HCN)] (22)
Employing a procedure similar to that described for complex 21,
complex 22 was prepared using complex 7 (100 mg, 0.171 mmol)
with a fivefold excess of fumaronitrile (66 mg, 0.855 mmol).
13C {1H} NMR (CDCl3, d): 14.15 (s, CH3 (CO2CH2CH3)), 16.32 (s,
CH3 (C3–CH3), 18.2 (s, Me (CMe)), 22.24 (s, Me (CHMe2)), 31.02 (s,
CH (CHMe2)), 80.09–101.31 (C6H4cym), 61.21 (s, CH2 (CO2CH2CH3)),
106.06 (s, C4), 138.54 (s, C3), 140.1 (s, C (C–CO2CH2CH3)), 120.36–
150.0 (N1–C6H5), 127.67–139.45 (Ph (C50-Ph)). 163.25 (s, C5),
162.12 (s, CO2 (C–CO2CH2CH3)), 189.56 (s, CO (C50–CO)).
Yield = 71 mg (78%); IR (KBr, cmꢁ1): 2226
(C@O+C@C), 1474 m(C–H def), 1440 m
m
CN, 1594, 1577, 1568
m
(C–N), 781 for the triazole ring. 1H
NMR (CDCl3, d): 2.072 (s, 18H, C6Me6), 2.17 (s, 3H, CH3), 6.97 (s, 1H,
CH), 7.2–7.5 (m, 8H, C6H5 and N1–C6H5), 7.94 (d, 2H, JH–H = 8, N1–
C6H5).
13C {1H} NMR (CDCl3, d): 15.178 (s, Me (C6Me6)), 17.02 (s, CH3
(C3–CH3), 89.82 (s, C (C6Me6)), 106.12 (s, C4), 114.79 (s, C„N),
135.13 (s, CH), 138.62 (s, C (C„N)), 138.72 (s, C3), 120.66–
150.07 (N1–C6H5), 127.621–140.01 (Ph (C50-Ph), 163.4 (s,C5),
188.83 (s, CO (C50–CO)).
Complex 18 [(
g
6-C6Me6)Ru(L1){N3C2(CO2Et)2}]: Yield = 69 mg
(89.6%); IR (KBr, cmꢁ1): 1736 m(C@O of ester group), 1601 m(C@O)
,
1594, 1577, 1568 m(C@O+C@C), 1474 m(C–H def), 1440 m(C–N), 786 of tri-
azole ring. 1H NMR (CDCl3, d): 1.23 (t, 6H, OCH2CH3), 2.07 (s, 18H,
C6Me6), 2.1 (s, 3H, CH3), 4.3 (q, 4H, OCH2CH3), 7.31–7.56 (m, 6H,
C6H5 and N1–C6H5), 7.8 (d, 2H, JH–H = 8, N1–C6H5).
2.3.14. Preparation of [(
A round-bottomed flask was charged with the azido complex
6-C6Me6)Ru(L2)N3] (100 mg, 0.247 mmol), fumaronitrile
g
6-C6Me6)Ru(L2)(N3C2HCN)] (23)
13C {1H} NMR (CDCl3, d): 14.15 (s, CH3 (CO2CH2CH3)), 15.23 (s,
Me (C6Me6)), 16.32 (s, CH3 (C3–CH3), 61.19 (s, CH2 (CO2CH2CH3)),
92.045 (s, C (C6Me6)), 106.03 (s, C4), 138.66 (s, C3), 140.05 (s, C
(C–CO2CH2CH3)), 120.4–148.9 (N1–C6H5), 127.56–139.45 (Ph
(C50-Ph)). 163.14 (s, C5), 162.8 (s, CO2 (C–CO2CH2CH3)), 188.61 (s,
CO (C50–CO)).
[(g
(96 mg, 1.235 mmol) and 20 ml of dichloromethane. The mixture
was stirred for 8 h. The solution was concentrated to 2 ml and ex-
cess of hexane was added to give a yellow microcrystalline precip-
itate. The precipitate was collected by centrifuging, washed with
hexane (2ꢀ20 ml) and dried under vacuum.
Complex 19 [(
(78.5%); IR (KBr, cmꢁ1): 1734
(C@O+C@C), 1477 m(C–H def), 1438
NMR (CDCl3, d): 1.26 (t, 6H, OCH2CH3), 1.96 (s, 6H, L2-CH3), 2.05
(s, 18H, C6Me6), 4.45 (q, 4H, OCH2CH3), 4.98 (s, 1H, L2- H).
g
6-C6Me6)Ru(L2){N3C2(CO2Et)2}]: Yield = 55 mg
(C@O of ester group), 1584, 1571, 1568
(C–N), 782 of triazole ring. 1H
m
Yield = 69 mg (78.4%); IR (KBr, cmꢁ1): 2229 m(C„N), 1577, 1518
m
m
m
(C@O+C@C), 1471 m(C–H def), 1438
1H NMR (CDCl3, d): 2.07 (s, 18H, C6Me6), 2.01 (s, 6H, CH3), 5.17
(s, 1H, L2- H), 7.1 (s, 1H, CH).
m(C–N), 781 for the triazole ring.
c
c

S.L. Nongbri et al. / Journal of Organometallic Chemistry 694 (2009) 3881–3891
3887
13C {1H} NMR (CDCl3, d): 15.025 (s, Me (C6Me6)), 27.85 (s, CH3
(L2-CH3)), 92.26 (s, C (C6Me6)), 98.862 (s, C (L2- C)), 114.91 (s,
C„N), 134.91 (s, CH), 138.56 (s, C (C„N)), 185.93 (s, CO (L2-CO)).
to the metal. The IR spectrum of L1 showed a broad band at
c
c
3000 cmꢁ1, a medium peak at 1758 cmꢁ1 due to mC@O and a
mC@O+m
C@C conjugated peak at 1508 cmꢁ1. The presence of a strong
broad band around 3000 cmꢁ1 arises from intra-molecular O–
Hꢂ ꢂ ꢂO bonding, indicating that L1 exist in the enol form. The disap-
pearance of this band upon complexation indicates presence of the
deprotonated L1 ligand in the complexes 1–3. The melting point
recorded at 120 °C is in agreement with the reported result, and
indicates intra-molecular O–Hꢂ ꢂ ꢂO bonding in this ligand [38].
The 1H NMR spectrum of the ligand exhibits a singlet at d 2.0 for
methyl protons, multiplets in the aromatic region at d 7.3–7.4
and a doublet at d 7.8 for the two phenyl groups. The increasing
number of signals in the multiplet aromatic region and the absence
of a singlet at the region ca. d 3–3.5 confirmed acylation at the C4
position. The calculated mass of L1 is 278.29 and the MS recorded
m/z is 279.0. The increase in m/z ratio from 174.9 of phenyl pyra-
zole moiety to 279.0 in the acyl pyrazolone ligand L1 also con-
firmed bonding of the acyl group to the pyrazole ring.
2.3.15. Preparation of [(
Employing a procedure similar to that described above for com-
plex 23, complex 24 was prepared using [(
6-C6Me6)Ru(L3)N3]
g
6-C6Me6)Ru(L3)(N3C2HCN)] (24)
g
(100 mg, 0.171 mmol) with a fivefold excess of fumaronitrile
(66 mg, 0.855 mmol).
Yield = 61 mg (68%); IR (KBr, cmꢁ1): 2239 m(C
„
1584, 1515
N),
m
(C@O+C@C), 1469 m(C–H def), 1442
1H NMR (CDCl3, d): 2.07 (s, 18H, C6Me6), 2.01 (s, 3H, CH3), 5.73
(s, 1H, L3- H), 7.11 (s, 1H, CH), 7.2–7.9 (m, 5H, L3-Ph).
13C {1H} NMR (CDCl3, d): 15.19 (s, Me (C6Me6)), 27.94 (s, CH3
(L3-CH3)), 91.3 (s, C (C6Me6)), 98.062 (s, C (L3- C)), 114.45 (s,
m(C–N), 779 for the triazole ring.
c
c
c
C„N), 126.92–132.34 (Ph (L3-Ph)), 139.23 (s, C (C„N)), 182.3 (s,
CO (L3-CO)), 187.32 (s, CO (L3-CO).
3. Results and discussion
3.3. Syntheses of ruthenium b-diketonato complexes
3.1. Synthesis of hexamethylbenzene ruthenium (II) chloro bridged
dimer
The precursor complexes [(g l-Cl)Cl]2 (arene = C6H6,
6-arene)Ru(
p-iPrC6H4Me, C6Me6) undergo a bridged cleavage reaction in 1:2
molar ratio with the ligand L1 in methanol and in the presence
of a base such as sodium methoxide, giving the mononuclear com-
plexes 1–3 (Scheme 1). In these reactions, the products 1–3 are
precipitated during the course of reaction. The compounds 1–3
are air stable and soluble in most organic solvents, but complexes
2 and 3 are more soluble in almost all polar solvents compared to
complex 1.
Although most of the early pioneering experiments were per-
formed by conventional methods, in this paper we report a more
convenient microwave synthetic method using optimized molar
ratios from 1:10 to 1:3 for the reactants and reduced the duration
of the preparation from 2 h to 10 min. Moreover, it produced better
yields of [(g l-Cl)Cl]2 in comparison to the conven-
6-C6Me6)Ru(
tional method [34]. 1H NMR spectrum of the complex shows a sin-
glet at d 2.06 for the methyl protons which is in agreement with
the reported result in the literature [34].
IR spectra show a typical low frequency shift of mC@O from
1683 cmꢁ1 in the ligand to 1600–1603 cmꢁ1 in these complexes
upon coordination of the chelating bidentate acyl pyrazolone to
the metal. The 1H NMR spectrum of 1 shows a singlet at d 5.8
assignable to the six arene protons of the monomer. The 1H NMR
spectrum of complex 2 exhibits two doublets at d 5.2 and d 5.5 cor-
responding to two protons each, a singlet at d 1.6 for the three
methyl group protons, a multiplet at d 2.9 and a doublet at d 1.3
for one methylene and six methyl protons, respectively. Similarly,
the 1H NMR spectrum of complex 3 shows a downfield shift of the
3.2. Synthesis of ligand L1
The ligand L1 was prepared as per the methods reported in the
literature [38] and its structure was confirmed by melting point,
infrared, mass and NMR spectroscopy. Acylation easily occurs at
the C4 position of the pyrazole ring. The neutral ligand L1 is
coordinated in O2-chelating bidentate keto-amino tautomeric form
N
N
R
Cl
R
Cl
Cl
N
Ru
Ru
Ru
Ru
Cl
N
N
N
NaN3
Cl
Cl
R
R
route a
route b
NaOMe
NaOMe
LL = L1
LL = L1
R
L
R
L
NaN3
Ru
N
L
Ru
L
Cl
N
N
7
6
1
=
4
2
=
3
,
,
,
,
R
R
Scheme 1.

3888
S.L. Nongbri et al. / Journal of Organometallic Chemistry 694 (2009) 3881–3891
N
N
N
L
Ru
L
LL=L3
Cl
Cl
L
Ru
+
8
Ru
Cl
Ru
Cl
L
N
N
Ru
N
Cl
Ru
NaN3
Cl
10
N
Cl
N
N
L
LL=L4
11
Ru
L
Cl
PPh3
L
9
Ru
PPh3
12
BF4
L
Scheme 2.
arene methyl protons from d 2.06 in the starting dimer to d 2.09.
The 13C {1H} NMR spectra also show singlets at d 15.27 and d
89.79 corresponding to the carbons of the hexamethylbenzene
ring, along with a singlet for the carbonyl group at d 188.15. Apart
from these, in the 1H NMR spectra of these complexes, the methyl
group of the pyrazolate ligand exhibit singlets at d 2.2–2.5 and a
range of multiplets from d 7.2–7.5 and a doublet at d 7.8–7.9 for
the aromatic protons. These spectroscopic data confirmed the for-
mation of these complexes.
Me)Ru(L4)Cl] (9) with azide ion have also been carried out. Treat-
ment of these complexes with mono-dentate ligands such as NaN3
in polar solvent resulted in substitution of the chloride ligand
(Schemes 1 and 2), affording the mononuclear neutral complexes
4, 6, 7 and 10 and the azido bridged binuclear complexes 5 and 11.
One interesting observation is the unexpected formation of the
ether-insoluble by-products 5 and 11 during the preparation of 4
and 10, respectively (Schemes 2 and 3). These complexes show
strong characteristic IR absorption bands assigned to the bridged
azido ligand, but no bands assignable to mC@O (as must be associ-
ated with the L1 or L4 ligands) was observed. The 1H NMR spectra
show peaks corresponding to resonance of the protons of the arene
ligand but none for the L1 or L4 ligand. We unambiguously propose
The reaction of [(g l-Cl)Cl]2 with 2 equiv. of
6-p-iPrC6H4Me)Ru(
the sodium salt of 1-benzoylacetone (L3) or dibenzoylmethane
(L4) at ambient temperature in methanol for 2 h afforded orange-
red colored compounds of the formula [(g
6-p-iPrC6H4Me)Ru(LL)Cl]
[LL = L3 (8); LL = L4 (9)] as shown in Scheme 2. The sodium salts
were prepared by reacting equimolar amounts of NaOH and the
free b-diketones in ethanol at ambient temperature. It was ob-
served that no reactions took place when the free ligands were
used. Moreover, attempts to prepare the analogous complexes
from the sodium salt of dimethyl or diethylmalonate were unsuc-
cessful, probably due to easy hydrolysis of these ligands.
The IR spectra of both complexes showed bands at ca. 1590,
1550, 1520 cmꢁ1 which were assigned to the m(C@O+C@C) modes of
the bidentate O,O0-donor ligands.
the formulae [(g l-N3)Cl]2 and [(g l-
6-C6H6) Ru( 6-p-iPrC6H4Me)Ru(
N3)Cl]2 for 5 and 11, respectively. It is somewhat difficult to explain
how complexes 5 and 11 were generated, which should essentially
proceed via displacement of the L1 and L4 ligands, respectively. It
is probably due to generation of hydrazoic acid (HN3) under the
reaction conditions which would lead to protonation of the b-dike-
tonate ligand and hence result in de-coordination. Repetition of the
preparation of 4 and 10 invariably give these by-products 5 and 11.
However, we made no extra efforts to improve the synthetic proce-
dures for the preparation of 5 and 11 as these compounds can be
These complexes are highly soluble in polar solvents. The 1H
prepared in high yield starting from [(
g l-Cl)Cl]2 or
6-C6H6)Ru(
NMR spectrum of the complex [(
CDCl3 shows (beside the characteristic peaks corresponding to
the p-cymene ligand) a singlet for the -hydrogen resonating at d
g
6-p-iPrC6H4Me)Ru(L3)Cl] (8) in
[( -Cl)Cl]2 and trimethylsilyl azide [35] or so-
g
6-p-iPrC6H4Me)Ru(
l
dium azide [36]. The IR spectra of complexes 4, 6, 7 and 10 show
characteristic bands at 2026–2035 cmꢁ1 due to the terminally
bound azido ligands.
c
5.78. This compound also shows two singlets corresponding to
the methyl protons at d 2.28 and d 2.11. In comparison with the
spectrum of the starting dimeric complex, the latter chemical shift
may be assigned to the methyl proton of the L3 ligand. The 1H NMR
In addition, the terminal azido complexes 4, 6 and 7 have also
been prepared from arene ruthenium azide dimers (Scheme 1:
route b). Treatment of [(g l-N3)Cl]2 (arene = C6H6,
6-arene)Ru(
spectrum of the complex [(
essentially similar, except that the
g
6-p-iPrC6H4Me)Ru(L4)Cl] (9) is also
-hydrogens resonate at a rela-
p-iPrC6H4Me, C6Me6) with ligand L1 in the presence of the proton
c
tively lower field (d 6.38) while 10 multiplets in the aromatic re-
gion are observed due to the phenyl groups of the L4 ligand.
Single crystal X-ray studies of complex 9 confirmed the spectro-
scopic formulation, and the geometry of the compound can be de-
scribed as a piano-stool distorted octahedron with the O,O0 and Cl
acting as the legs (Fig 2).
N
N
Cl
N
L
L
NaN3
Ru
+
Ru
Ru
Ru
LL=L1
N
N
L
L
Cl
N
Cl
4
1
N
3.4. Syntheses of ruthenium azido complexes
N
N
5
Some initial studies of the reactivity of [(
g
6-arene)Ru(L1)Cl]
6-p-iPrC6H4-
(arene = C6H6 (1), p-iPrC6H4Me (2), C6Me6(3)) or [(
g
Scheme 3.

S.L. Nongbri et al. / Journal of Organometallic Chemistry 694 (2009) 3881–3891
3889
scavenger sodium methoxide yielded complexes 4, 6 and 7. The IR
spectra of these complexes show absence of the bridging azido
band in the range 2045–2065 cmꢁ1 and the appearance of new
bands in the range 2026–2035 cmꢁ1. This leads us to infer the for-
mation of terminal azido complexes. Note that this synthetic route
does not give the by-product 5. This accounts for the higher yield of
the complexes 4 by this route as compared to that obtained by the
diethyl acetylenedicarboxylate (EtO2CC2CO2Et) (DED) in dichloro-
methane at room temperature afforded the yellow ruthenium tria-
zolato complexes in good yield (Scheme 4). The absence of a
terminal absorption band at 2026–2035 cmꢁ1 and the presence
of a strong C@O absorption band (for the ester group of the triazole
mN3
m
moiety at around 1724–1736 cmꢁ1) in the IR spectra of complexes
13–20 indicate the occurrence of 1,3-dipolar cycloaddition be-
tween Ru–N3 and the substituted alkyne (DMD or DED). In addition
to the C@O stretching frequencies, the IR spectra of these com-
plexes show a pair of strong bands at around 1568–1585 cmꢁ1
which are assignable to coupled (C@O) + (C@C) modes of b-diketo-
nate [42,43].
previous route (route a). Attempts to synthesize [(
Me)Ru( -N3)N3]2 from p-cymene ruthenium b-diketone com-
plexes by reacting with NaN3 have been carried out, but
invariably only the azido bridging dimer [(
6-p-iPrC6H4Me)Ru(
N3)Cl]2 (10) was reported, showing the characteristic bridging
N3 IR band at 2056 cmꢁ1 [35]. Structures of the complexes 6
g
6-p-iPrC6H4-
l
g
l-
m
The 1,3-dipolar cycloaddition of complex azides and non-termi-
nal alkynes, a direct route to 1,2,3-triazoles, is usually slow, not
regioselective and concerted [24,27]. The nature of the substitu-
ent/group(s) influences the regioselectivity of these reactions.
Depending on the nature of the alkyne employed here (dialkylacet-
ylenedicarboxylate), the regioselectivity seems to be governed pri-
marily by the electronic, and, possibly, the steric factor. Reactivity
of the dipolarophile increases with increased electron-withdraw-
ing power of its substituents and the reaction rate is also influ-
enced by the electron-releasing power of the terminal nitrogen
atom of the azide ligand [26]. It had been considered in the case
of cobalt chelate complexes that the scope of cycloaddition reac-
tions of azido complexes can be considerably widened by including
metal chelates that provide substantial electron delocalization in
the chelate ring and a suitable steric environment for uninhibited
approach of a dipolarophile toward the azide [26]. The same
and 10 are further confirmed by single crystal X-ray studies (Figs.
1 and 3).
3.5. Synthesis of cationic complex
Treatment of the complex [(g
6-p-iPrC6H4Me)Ru(L4)Cl] (9) with
phosphine generates the cationic complex 12 which was isolated
in good yield (80%) as the BF4 salt. Formation of the cationic com-
plex is confirmed by the appearance of the mC@O absorption band at
1593 cmꢁ1 and of the strong m(B–F) absorption band at 1081 cmꢁ1
.
3.6. Reaction of ruthenium azido complexes with DMD or DED
The reaction of terminal azido complexes with a fivefold excess
of dimethyl acetylenedicarboxylate (MeO2CC2CO2Me) (DMD) or
R
L
Ru
N
L
MeOOC
MeO2CC2CO2Me
N
N
R
MeOOC
, LL = L1 (13)
=
=
, LL = L1 (14)
, LL = L2 (15)
, LL = L3 (16)
R
R
N
R
L
L
Ru
Ru
N
L
L
EtOOC
EtO2CC2CO2Et
N
N
N
N
EtOOC
R
R
, LL = L1 (17)
=
=
R
=
6
7
, LL = L1 (18)
, LL = L2 (19)
, LL = L3 (20)
,
R
L
Ru
N
L
H
N
NC-CH=CH-CN
N
C
R
R
, LL = L1 (21)
=
=
N
, LL = L1 (22)
, LL = L2 (23)
, LL = L3 (24)
CH3
3
2
N
1
N
R
R1
4
C
5
5'
O
O
ONa
O
H
1-phenyl-3-methyl-4-benzoyl pyrazol-5-one
L-L = L1
R, R1, L-L = Me, Me = L2
R, R1, L-L = Me, Ph = L3
Scheme 4.

3890
S.L. Nongbri et al. / Journal of Organometallic Chemistry 694 (2009) 3881–3891
situation probably prevails here for these cases of ruthenium che-
late diketone complexes.
olone ligand, whereas complexes 23 and 24 exhibit a singlet in the
region d 5.1–5.7 attributed to the -proton of the b-diketonato
c
Previous results revealed that the triazole anion could be coor-
dinated by a metal through either its N(1) or N(2) nitrogen atoms
[27,44] which are essentially isoenergetic as indicated by molecu-
lar orbital calculations [28,44]. Evidence obtained to date indicated
that both the two isomers [corresponding to coordination at N(1)
and at N(2)] were formed simultaneously [26–28,44], or else only
the N(2) bound isomer was produced exclusively [27,26,45,46]. In
contrast to the result published earlier by our group [13], we here
obtain only the N(2) bound isomers for both alkoxy substituted
acetylenes. Ellis et al. have reported the initial formation of the
N(1) bonded complex via azide attack on the coordinated nitrile
carbon of pentamethylamine cobalt complexes which slowly isom-
erized to the N(2) bonded complex [47]. It is believed that the tria-
zolato complexes initially form the N(1) bonded complexes.
Published results have confirmed that the N(1) bound isomers
are definitely the kinetic product of these reactions; the isolated
thermodynamically stable product is the N(2) bound isomer. Isom-
erization from N(1) to N(2) bound triazole is most likely sterically
promoted, as has been found for the analogous tetrazolato com-
plexes [48], while electronic factors favor no isomerization at all.
It has been reported that electronic factors such as nucleophilic-
ity of the triazole anion would favor N(1) bound isomers. Accord-
ingly, formation of the N(1) bound isomers would be expected to
prevail in the ethoxy substituted triazolato complexes, as has been
observed in previous work reported from our laboratory [13].
However, supporting data in this present work confirms the forma-
tion of only the N(2) bonded complexes for both type of alkoxy
substituted triazole. As supported by previous discussions, the ste-
ric factor involved in the chelating b-diketone ligand would favor
formation of the N(2) bound triazolato complexes. On the basis
of spectroscopic data and X-ray analysis, both the methoxy and
the ethoxy substituted triazolato complexes are confirmed to be
N(2) bonded triazolato complexes.
group. In addition, the 1H NMR spectrum of complex 21 contains
doublet resonances in the region d 5.4 corresponding to the p-cym-
ene group and arising from the arene ring protons. A multiplet at
ca. d 1.8 is due to the CHMe group, a singlet at d 1.6 to the methyl
group and a doublet at d 1.3 to the methyl protons of the isopropyl
group. The 1H NMR spectra of complexes 22–24 also show singlets
in the region around d 2.06–2.07 pertaining to the methyl group
protons of the hexamethylbenzene ring. Apart from this, the 13C
{1H} NMR of these complexes exhibit single resonances at around
d 114–115 due to the C„N moiety, while the carbon of the b-dike-
tone group appears at d 185–187. The 1,3-dipolar cycloaddition of
coordinated azide to fumaronitrile may take place via the C@C or
C„N functionalities. In continuation of our work on other related
complexes [13–15,30], we herein report the formation of the tria-
zolato complexes 21–24 by [3 + 2] cyclization between the azido li-
gand and the C@C double bond following removal of an HCN
molecule.
3.8. Molecular structures
Molecular structures of the mononuclear neutral complexes 6,
9, 10 and 17 are drawn in ORTEP with atom-labeling schemes as de-
picted in Figs. 1–4, respectively. The data collection parameters are
listed in Table 1, and selected bond lengths and bond angles in Ta-
ꢀ
bles 2 and 3, respectively. Complex 6 crystallized in the P1 space
group while complexes 9, 10 and 17 crystallized in the P2(1)/c
space group. The p-cymene ligand is bonded to the ruthenium
atom in
g
6-fashion with a Ru(1)–centroid distance of 1.655 Å
[13,32]; these complexes adopt a typical three-legged piano-stool
conformation with N (or Cl in complex 9) and the two O-atoms
as the legs. Moreover, complexes 6 and 17 acquire quasi-octahe-
dral geometry [32]. The Ru(1)–O(1) and Ru(1)–O(2) bond distances
in these complexes range from 2.0652 to 2.093 Å, which is compa-
rable to other reported Ru–O bond lengths [49]. In complex 9, the
Ru(1)–Cl(1) bond length is 2.4173(8) Å, while the Ru(1)–O(1) and
Ru(1)–O(2) bond distances are almost the same, being 2.0683(18)
and 2.0675(17) Å, respectively. In comparison to 9, complex 10
possesses a Ru(1)–O(1) bond length of 2.0795(19) Å which is
slightly but significantly longer than the reported Ru(1)–O(2) dis-
tance of 2.0652(19) Å [13]. The Ru(1)–O(1) and Ru(1)–O(2) bond
distances in complex 6 are 2.094(3) Å and 2.092(3) Å, respectively,
while for complex 17 these respective bond lengths are
2.0819(19) Å and 2.0937(19) Å, which are comparable to those in
the starting azido complex 6. In comparison to the ruthenium–oxy-
gen bond distances of complexes 9 and 10, the complexes 6 and 17
possess longer ruthenium–oxygen bond length; this may be attrib-
uted to bonding by the pyrozolate ligand. The bond distance be-
tween the Ru atom and the ligating nitrogen of the azide group
in complex 10 is 2.155(3) Å. The N(1)–N(2)–N(3) bond angle is
174.2(4)° [35], showing a slight deviation from perfectly linear
geometry. In comparison to 10, complex 6 possesses a Ru(1)–
N(3) bond length of 2.210(7) Å and the N(3)–N(4)–N(5) bond angle
is 169.6(11)°. The bond distances N(1)–N(2) (1.038 Å) and N(2)–
N(3) (1.227 Å) in complex 10 differ by only ca. 0.2 Å, whereas in
complex 6 the bond distances N(4)–N(3) (0.843(11) Å) and N(4)–
N(5) (1.462(15) Å) exhibit a larger difference of ca. 1.4 Å. Similar
results are also observed when complex 6 is compared to other re-
ported complexes [12,13,32]. With respect to the starting azido
complex 6, the Ru(1)–N(1) length in the triazole complex 17 is
2.074(2) Å. It appears that, after undergoing reductive elimination
reaction during the course of the 1,3-dipolar cycloaddition reaction
[25], the Ru(1)–N(3) bond in the starting azido complex 6 gets con-
verted to a Ru(1)–N(1) bond in the ruthenacycle complex 17. The
N(3)–N(1)–N(2) bond angle in the triazole ring of complex 17 is
The 1H NMR spectra of complexes 13–16 exhibit a singlet at ca.
d 3.5–3.8, assigned to the methoxy carbonyl group protons of the
triazolato group. Likewise, the 1H NMR spectra of complexes 17–
20 exhibit a quartet at ca. d 4.5 and a triplet at ca. d 1.2–1.3 due
to methylene and methyl protons of the ethoxy carbonyl group.
In addition, the 1H NMR spectra of complexes 13, 14, 17 and 18 ex-
hibit characteristic peaks corresponding to the ligand L1. Similarly,
the singlets observed in the region d 4.9–5.1 for the
c protons indi-
cate coordination of the b-diketone ligand L2 in complexes 15 and
19, and of L3 in complexes 16 and 20, respectively. Apart from
these, complexes 13 and 17 show peaks for the p-cymene moiety,
whereas complexes 14–16 and 18–20 exhibit prominent singlet at
ca. d 2.07 corresponding to the protons of the methyl groups of the
hexamethylbenzene ring. The 13C {1H} NMR of complexes 14–16
and 18–20 exhibit a single resonance at ca. d 162 due to the carbon
of the CO2 group, while the carbons of the b-diketonate group ap-
pear at d 182–190.
3.7. Reaction of ruthenium azido complexes with fumaronitrile
The reaction of ruthenium(II) terminal azido complexes with
excess of fumaronitrile at room temperature for 10–15 h affords
the N(2) bound 4-cyano-1,2,3-triazole complexes 21–24. Forma-
tion of these triazolato complexes is readily confirmed by the ab-
sence of the starting azide stretching frequency and the
appearance of a strong band at around 2226–2239 cmꢁ1 corre-
sponding to the stretching frequency of the C„N group of the coor-
dinated triazolato group. The 1H NMR spectra of these complexes
show characteristic singlet resonances at around d 6.9–7.1, as-
signed to the CH group protons of the triazole ring. Complexes
21 and 22 show a characteristic signal corresponding to the pyraz-

S.L. Nongbri et al. / Journal of Organometallic Chemistry 694 (2009) 3881–3891
3891
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middle nitrogen with regard to the N(2) isomers in complex 17,
which is different from previously reported results [13], but is in
agreement with the results on benzene ruthenium triazolato com-
plexes [14].
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4. Conclusions
As a consequence of our quest for the synthesis of new com-
pounds, we have reported herein the synthesis of a few new com-
plexes, and confirmed their formation through various analyses.
Apart from acetylacetone derivatives, we have used functionalized
b-diketones and 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one in
this present work, thereby extending the scope for development
of new intermediate ruthenacycle triazole complexes having a pyr-
azole group fused to the O,O0-chelating moiety. In this work, only
N(2) bound isomers were formed with dimethyl and diethyl acet-
ylenedicarboxylate ligands, as is the case with benzene [14,30] and
indenyl systems [31]. The X-ray crystal structure of complex 17
supports formation of the N(2) bound isomer with diethyl acety-
lenedicarboxylate, which is not in agreement with previous work
on p-cymene ruthenium systems [13], where formation of N(1)
bound isomers was reported. We conclude here that, in addition
to the effects peculiar to each substituted acetylene ligand used;
the nature and type of the b-diketone ligand coordinated to the
ruthenium center also plays a significantly important role in the
formation of isomerized triazoles in the 1,3-dipolar cycloaddition
reactions studied here.
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