Study of half-sandwich platinum group metal complexes bearing dpt-NH2 ligand

Article abstract of DOI:10.1016/j.poly.2009.10.016

A quite general approach for the preparation of η⁵-and η⁶-cyclichydrocarbon platinum group metal complexes is reported. The dinuclear arene ruthenium complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = C₆H₆, C₁₀H₁₄ and C₆Me₆) and η⁵-pentamethylcyclopentadienyl rhodium and iridium complexes [(η⁶-C₅Me₅)M(μ-Cl)Cl]₂ (M = Rh, Ir) react with 2 equiv. of 4-amino-3,5-di-pyridyltriazole (dpt-NH₂) in presence of NH₄PF₆ to afford the corresponding mononuclear complexes of the type [(η⁶-arene)Ru(dpt-NH₂)Cl]PF₆ {arene = C₁₀H₁₄ (1), C₆H₆ (2) and C₆Me₆ (3)} and [(η⁶-C₅Me₅)M(dpt-NH₂)Cl]PF₆ {M = Rh (4), Ir (5)}. However, the mononuclear η⁵-cyclopentadienyl analogues such as [(η⁵-C₅H₅)Ru(PPh₃)₂Cl], [(η⁵-C₅H₅)Os(PPh₃)₂Br], [(η⁵-C₅Me₅)Ru(PPh₃)₂Cl] and [(η⁵-C₉H₇)Ru(PPh₃)₂Cl] complexes react in presence of 1 equiv. of dpt-NH₂ and 1 equiv. of NH₄PF₆ in methanol yielded mononuclear complexes [(η⁵-C₅H₅)Ru(PPh₃)(dpt-NH₂)]PF₆ (6), [(η⁵-C₅H₅)Os(PPh₃)(dpt-NH₂)]PF₆ (7), [(η⁵-C₅Me₅)Ru(PPh₃)(dpt-NH₂)]PF₆ (8) and [(η⁵-C₉H₇)Ru(PPh₃)(dpt-NH₂)]PF₆ (9), respectively. These compounds have been totally characterized by IR, NMR and mass spectrometry. The molecular structures of 4 and 6 have been established by single crystal X-ray diffraction and some of the representative complexes have also been studied by UV-Vis spectroscopy.

Full text of DOI:10.1016/j.poly.2009.10.016

Polyhedron 29 (2010) 904–910
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Study of half-sandwich platinum group metal complexes bearing dpt-NH2 ligand
Gajendra Gupta a, Kota Thirumala Prasad a, Babulal Das b, Kollipara 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
g g
5-and
6-cyclichydrocarbon platinum group metal com-
6-arene)Ru(
-Cl)Cl]2 (arene = C6H6,
5-pentamethylcyclopentadienyl rhodium and iridium complexes [(g6
-Cl)Cl]2 (M = Rh, Ir) react with 2 equiv. of 4-amino-3,5-di-pyridyltriazole (dpt-NH2) in
presence of NH4PF6 to afford the corresponding mononuclear complexes of the type [(
6-arene)R-
u(dpt-NH2)Cl]PF6 {arene = C10H14 (1), C6H6 (2) and C6Me6 (3)} and [(
6-C5Me5)M(dpt-NH2)Cl]PF6
{M = Rh (4), Ir (5)}. However, the mononuclear
5-cyclopentadienyl analogues such as [(g5
C5H5)Ru(PPh3)2Cl], [(
5-C5H5)Os(PPh3)2Br], [( 5-C5Me5)Ru(PPh3)2Cl] and [( 5-C9H7)Ru(PPh3)2Cl] com-
plexes react in presence of 1 equiv. of dpt-NH2 and 1 equiv. of NH4PF6 in methanol yielded mononuclear
complexes [(
5-C5H5)Ru(PPh3)(dpt-NH2)]PF6 (6), [( 5-C5H5)Os(PPh3)(dpt-NH2)]PF6 (7), [( 5-C5Me5)R-
u(PPh3)(dpt-NH2)]PF6 (8) and [(
5-C9H7)Ru(PPh3)(dpt-NH2)]PF6 (9), respectively. These compounds have
Article history:
A quite general approach for the preparation of
Received 25 September 2009
Accepted 21 October 2009
Available online 28 October 2009
plexes is reported. The dinuclear arene ruthenium complexes [(
C10H14 and C6Me6) and
C5Me5)M(
g
l
g
-
l
g
Keywords:
Arene
Cyclopentadienyl
dpt-NH2
g
g
-
g
g
g
Ruthenium
g
g
g
g
been totally characterized by IR, NMR and mass spectrometry. The molecular structures of 4 and 6 have
been established by single crystal X-ray diffraction and some of the representative complexes have also
been studied by UV–Vis spectroscopy.
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
[16,17]. Although comprehensive studies have been made on g5
and
6-transition metal complexes, complexes containing NH2
substituted poly-pyridyl ligand of this type shown below have
-
g
Within the large family of
g
5- and
g
6-cyclichydrocarbon metal
complexes, piano-stool complexes of ruthenium are undeniably
the most studied class of complexes. Arene metal complexes have
been extensively investigated by organometallic and organic
not yet been reported.
N
chemists for over 50 years. In particular,
g
6-arene metal com-
N
plexes have emerged as versatile intermediates in organic synthe-
sis as a consequence of the ease with which the arene ligand can be
functionalized [1,2]. They have found applications in catalysis,
supramolecular assemblies, molecular devices, and have shown
antiviral, antibiotic, and anticancer activities. Half-sandwich com-
plexes have proved to be extremely useful in stoichiometric and
catalytic asymmetric syntheses and therefore attracted more
attention [3–6]. In addition, the four coordinated, pseudo-tetrahe-
dral geometry makes them particularly suitable for investigation of
the stereochemistry of reactions at the metal center [7]. In recent
N
N
NH2
N
dpt-NH2
Ligand used in this study
years we have been carrying out reactions of
g g
5- and 6-cyclichy-
g
5- and
drocarbon metal complexes with a variety of nitrogen-based li-
gands [8–15] including various poly-pyridyl ligands. Ruthenium
complexes of these types of nitrogen-based ligands have a capacity
to function as catalysts for the oxidation of water to dioxygen
Herein we describe the syntheses of nine mononuclear
6-cyclichydrocarbon platinum group metal complexes bearing
g
dpt-NH2 ligand. Attempts to prepare dimetallic derivatives by
addition of a second organometallic anion were unsuccessful. All
these complexes have been fully characterized by IR, NMR, mass
spectrometry and UV–Vis spectroscopy. Molecular structures of
the two representative complexes are also presented in this paper.
* Corresponding author. Tel.: +91 943 6166937; fax: +91 364 2550486.
E-mail address: mohanrao59@gmail.com (K.M. Rao).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.10.016

G. Gupta et al. / Polyhedron 29 (2010) 904–910
905
2. Experimental
All solvents were dried and distilled prior to use. 4-amino-3,5-
di-pyridyltriazole (dpt-NH2) was prepared using literature method
[18]. The precursor complexes [(
ne = C6H6, C10H14 and C6Me6), [(
6-C5Me5)M(
[19–22], [(
5-C5H5)Ru(PPh3)2Cl], [( 5-C5H5)Os(PPh3)2Br], [(g5
C5Me5)Ru(PPh3)2Cl] and [(
5-C9H7)Ru(PPh3)2Cl] were prepared
g
6-arene)Ru(
l-Cl)Cl]2 (are-
g
l-Cl)Cl]2 (M = Rh, Ir)
g
g
-
g
by following the literature methods [23,22b,24–27]. NMR spectra
were recorded on a Bruker AMX 400 MHz spectrometer. Infrared
spectra were recorded as KBr pellets on a Perkin–Elmer 983 spec-
trophotometer. Elemental analyses of the complexes were per-
formed on a Perkin–Elmer 2400 CHN/S analyzer. Mass spectra
were obtained from a ZQ mass spectrometer by the ESI method.
Absorption spectra were obtained at room temperature using a
Perkin–Elmer Lambda 25 UV–Vis spectrophotometer. All the new
complexes gave satisfactory CHN results.
2.1. Single-crystal X-ray structures analyses
Fig. 2. Molecular structure of complex 6 with 35% probability thermal ellipsoids.
Hydrogen atoms and PF6 are omitted for clarity.
Crystals of 4 were grown from acetone/petroleum ether as
small red plates. Crystals of 6 were grown by slow diffusion of
petroleum ether into a mixture of acetonitrile and dichlorometh-
ane solution of the respective complex as deep red blocks. The
crystallizations were done at room temperature. The intensity data
of 4 and 6 were collected using a Bruker SMART APEX-II CCD dif-
fractometer, equipped with a fine focus 1.75 kW sealed tube Mo
ꢀ
parameters and bond lengths and angles are presented in Tables 2
and 3.
2.2. Preparation of [(
g
6-p-PriC6H4Me)Ru(dpt-NH2)Cl]PF6 (1)
Ka radiation (a = 0.71073 Å) at 273(3) K, with increasing x (width
of 0.3° per frame) at a scan speed of 3 s/frame. The SMART [28] soft-
ware was used for data acquisition. Data integration and reduction
were undertaken with the SAINT [28] and XPREP [29] softwares. Struc-
tures were solved by direct methods using SHELXS-97 [30] and re-
fined with full-matrix least squares on F2 using SHELXL-97 [31]. All
non-hydrogen atoms were refined anisotropically. The hydrogen
atoms were located from the difference Fourier maps and refined.
Structural illustrations have been drawn with ORTEP-3 [32] for
Windows. The ORTEP presentations of the representative com-
plexes are shown in Figs. 1 and 2, respectively. The data collection
A mixture of [(
g
6-C10H14)Ru(
l-Cl)Cl]2 (100 mg, 0.16 mmol), 4-
amino-3,5-di-pyridyltriazole (dpt-NH2) (78 mg, 0.33 mmol) and
2 equiv. of NH4PF6 was stirred in dry methanol (30 ml) for 4 h at
room temperature. The yellow compound which formed was fil-
tered, washed with ethanol, diethyl ether and dried under vacuum.
Yield: 193 mg, 90%. Elemental Anal. Calc. for C22H24ClN6PF6Ru:
C, 40.43; H, 3.71; N, 12.81. Found: C, 40.51; H, 3.80; N, 12.73%. IR
(KBr pellets, cmꢀ1): 3430 (
mN–H); 1615 (mC@C); 1457 (mC@N); 846
(m
P–F); 1H NMR (400 MHz, CDCl3): d = 9.39 (d, J = 8 Hz, 1H), 8.81
(d, J = 7.2 Hz, 1H), 8.76 (d, J = 4.4 Hz, 1H), 8.41 (d, J = 8 Hz, 1H),
8.21 (t, J = 7.6 Hz, 1H), 8.06 (t, J = 7.6 Hz, 1H), 7.74 (t, J = 7.2 Hz,
1H), 7.61 (t, J = 5.2 Hz, 1H), 7.42 (s, 2H, –NH2), 5.98 (d, J = 4 Hz,
1H, Arp-cy), 5.90 (d, J = 6 Hz, 1H, Arp-cy), 5.79 (d, J = 6 Hz, 1H, Arp-
cy), 5.67 (d, J = 6 Hz, 1H, Arp-cy), 2.90 (sep, 1H), 2.24 (s, 3H), 1.24
(d, J = 6.8 Hz, 3H), 1.19 (d, J = 6.8 Hz, 3H); ESI-MS (m/z): 496.7
[MꢀPF6], 461.7 [MꢀPF6ꢀCl].
2.3. Preparation of [(
g
6-C6H6)Ru(dpt-NH2)Cl]PF6 (2)
A mixture of [(
g
6-C6H6)Ru(
l-Cl)Cl]2 (100 mg, 0.2 mmol), 4-
amino-3,5-di-pyridyltriazole (dpt-NH2) (96 mg, 0.4 mmol) and
2 equiv. of NH4PF6 was stirred in dry methanol (30 ml) for 4 h at
room temperature. The brown compound which formed was fil-
tered, washed with ethanol, diethyl ether and dried under vacuum.
Yield: 180 mg, 75%. Elemental Anal. Calc. for C18H16ClN6PF6Ru:
C, 36.19; H, 2.71; N, 14.03. Found: C, 36.28; H, 2.82; N, 13.95%. IR
(KBr pellets, cmꢀ1): 3432 (
mN–H); 1627 (mC@C); 1451 (mC@N); 838
(m
P–F); 1H NMR (400 MHz, CD3CN): d = 9.33 (d, J = 8 Hz, 1H), 8.92
(d, J = 7.2 Hz, 1H), 8.62 (d, J = 7.6 Hz, 1H), 8.31 (d, J = 8 Hz, 1H),
8.22 (t, J = 5.2 Hz, 1H), 8.09 (t, J = 7.2 Hz, 1H), 7.69 (t, J = 6.4 Hz,
1H), 7.54 (t, J = 5.6 Hz, 1H), 7.43 (s, 2H, –NH2), 6.29 (s, 6H, C6H6);
ESI-MS (m/z): 452.8 [MꢀPF6].
2.4. Preparation of [(
g
6-C6Me6)Ru(dpt-NH2)Cl]PF6 (3)
A mixture of [(
g
6-C6Me6)Ru(
l-Cl)Cl]2 (100 mg, 0.14 mmol), 4-
Fig. 1. Molecular structure of a complex 4 with 35% probability thermal ellipsoids.
Hydrogen atoms and PF6 are omitted for clarity.
ꢀ
amino-3,5-di-pyridyltriazole (dpt-NH2) (72 mg, 0.29 mmol) and

906
G. Gupta et al. / Polyhedron 29 (2010) 904–910
2 equiv. of NH4PF6 was stirred in dry methanol (30 ml) for 4 h at
room temperature. The solvent was removed by using rotary evap-
orator. The solid was dissolved in dichloromethane and then fil-
tered to remove ammonium chloride. The solution was
concentrated to 2 ml and excess of diethylether was added for pre-
cipitation. The light brown color product was separated out,
washed with diethylether and dried in vacuum.
7.38–7.21 (m, 15H, PPh3), 4.91 (s, 5H, C5H5); 31P {1H} NMR (CDCl3,
d): 50.82 (s, PPh3); ESI-MS (m/z): 696 [MꢀPF6].
Complex [7]: Yield: 71 mg, 67.6%. Anal. Calc. for C35H30N6P2F6Os:
C, 46.69; H, 3.32; N, 9.36. Found: C, 46.78; H, 3.39; N, 9.28%. IR (KBr
pellets, cmꢀ1): 3431 (
mN—H); 1616 (mC@C); 1451 (mC@N); 843 (mP–F);
1H NMR (400 MHz, CDCl3): d = 9.32 (d, J = 8 Hz, 1H), 8.88 (d,
J = 7.6 Hz, 1H), 8.71 (d, J = 6.4 Hz, 1H), 8.49 (d, J = 8 Hz, 1H), 8.21
(t, J = 5.6 Hz, 1H), 8.14 (t, J = 7.2 Hz, 1H), 7.73 (t, J = 7.6 Hz, 1H),
7.61 (t, J = 8 Hz, 1H), 7.48 (s, 2H, –NH2), 7.38–6.80 (m, 15H,
PPh3), 4.59 (s, 5H, C5H5); 31P {1H} NMR (CDCl3, d): ꢀ0.26 (s,
PPh3); ESI-MS (m/z): 758.5 [MꢀPF6].
Yield: 132 mg, 64.7%. Elemental Anal. Calc. for C24H28
ClN6PF6Ru: C, 42.31; H, 4.11; N, 12.29. Found: C, 42.43; H, 4.19;
N, 12.16%. IR (KBr pellets, cmꢀ1): 3433 (
(mC@N); 846 (m
m
N–H); 1618 (
mC@C); 1474
P–F); 1H NMR (400 MHz, CDCl3): d = 9.41 (d,
J = 7.2 Hz, 1H), 8.96 (d, J = 8 Hz, 1H), 8.73 (d, J = 8 Hz, 1H), 8.42 (d,
J = 7.6 Hz, 1H), 8.33 (t, J = 6.4 Hz, 1H), 8.16 (t, J = 7.6 Hz, 1H), 7.72
(t, J = 6.4 Hz, 1H), 7.63 (t, J = 5.6 Hz, 1H), 7.51 (s, 2H, –NH2), 2.10
(s, 18H, C6Me6); ESI-MS (m/z): 537.2 [MꢀPF6], 502.1 [MꢀPF6ꢀCl].
2.7. Preparation of [(
g
5-C5Me5)Ru(dpt-NH2)(PPh3)]PF6 (8)
A mixture of [(
g
5-C5Me5)Ru(PPh3)2Cl] (100 mg, 0.125 mmol), 4-
amino-3,5-di-pyridyltriazole (dpt-NH2) (30 mg, 0.125 mmol) and
1 equiv. of NH4PF6 in dry methanol (30 ml) were refluxed under
dry nitrogen for 12 h until the color of the solution changed from
pale yellow to orange. The solvent was removed using rotary evap-
orator under reduced pressure, the residue was dissolved in dichlo-
romethane (10 ml), and the solution filtered to remove ammonium
chloride. The orange solution was concentrated to 5 ml, when
addition of excess hexane gave the orange–yellow complex, which
was separated and dried under vacuum.
2.5. Preparation of [(
g
5-C5Me5)M(dpt-NH2)Cl]PF6 {M = Rh (4), Ir (5)}
A mixture of [(
g
5-C5Me5)M(
l-Cl)Cl]2 (M = Rh, Ir) (0.16 mmol),
4-amino-3,5-di-pyridyltriazole (dpt-NH2) (77 mg, 0.32 mmol) and
2 equiv. of NH4PF6 in dry methanol (30 ml) were stirred at room
temperature for 6 h until the color of the solution changed to dark
yellow. The solvent was removed using rotary evaporator under re-
duced pressure, the residue was dissolved in dichloromethane
(5 ml), and the solution was filtered to remove ammonium chlo-
ride. The light red solution was concentrated to 2 ml, when addi-
tion of excess hexane gave the orange–yellow complex, which
was separated and dried under vacuum.
Yield: 73 mg, 65.7%. Anal. Calc. for C40H40N6P2F6Ru: C, 54.47; H,
4.56; N, 9.55. Found: C, 54.51; H, 4.61; N, 9.45%. IR (KBr pellets,
cmꢀ1): 3435 ( P–F); 1H
mN–H); 1599 (mC@C); 1437 (mC@N); 844 (m
NMR (400 MHz, CDCl3): d = 8.65 (d, J = 7.6 Hz, 1H), 8.34 (d,
J = 8 Hz, 1H), 8.27 (d, J = 7.2 Hz, 1H), 8.09 (d, J = 8 Hz, 1H), 7.84 (t,
J = 6.4 Hz, 1H), 7.64 (t, J = 7.6 Hz, 1H), 7.38 (t, J = 8 Hz, 1H), 7.30
(t, J = 7.6 Hz, 1H), 7.25 (s, 2H, –NH2), 7.21–7.09 (m, 15H, PPh3),
2.03 (s, 15H, C5Me5); 31P {1H} NMR (CDCl3, d): 49.6 (s, PPh3); ESI-
MS (m/z): 739.8 [MꢀPF6].
Complex [4]: Yield: 150 mg, 75%. Elemental Anal. Calc. for
C22H25ClN6PF6Rh: C, 40.21; H, 3.81; N, 12.81. Found: C, 40.29; H,
3.90; N, 12.73%. IR (KBr pellets, cmꢀ1): 3446 (
m
N–H); 1632 (mC@C);
1457 (mC@N); 844 (m
P–F); 1H NMR (400 MHz, CDCl3): d = 8.95 (d,
J = 8 Hz, 1H), 8.77 (d, J = 5.6 Hz, 1H), 8.70 (d, J = 4.8 Hz, 1H), 8.35
(d, J = 4 Hz, 1H), 8.14 (t, J = 8 Hz, 1H), 7.97 (t, J = 6.4 Hz, 1H), 7.67
(t, J = 6.4 Hz, 1H), 7.51 (t, J = 5.6 Hz, 1H), 7.26 (s, 2H, –NH2), 1.59
(s, 15H, C5Me5); ESI-MS (m/z): 511.3 [MꢀPF6], 476.6 [MꢀPF6ꢀCl].
Complex [5]: Yield: 130 mg, 68%. Elemental Anal. Calc. for
C22H25ClN6PF6Ir: C, 35.44; H, 3.39; N, 11.24. Found: C, 35.53; H,
2.8. Preparation of [(
g
5-C9H7)Ru(dpt-NH2)(PPh3)]PF6 (9)
A mixture of [(
g
5-C9H7)Ru(PPh3)2Cl] (100 mg, 0.128 mmol), 4-
amino-3,5-di-pyridyltriazole (dpt-NH2) (31 mg, 0.128 mmol) and
1 equiv. of NH4PF6 in dry methanol (30 ml) were refluxed under
dry nitrogen for 8 h until the color of the solution changed from
pale yellow to dark red. The solvent was removed under vacuum,
the residue was dissolved in dichloromethane (10 ml), and the
solution filtered to remove ammonium chloride. The red solution
was concentrated to 5 ml, upon addition of diethylether the or-
ange–red complex precipitate, which was separated and dried un-
der vacuum. Yield: 69 mg, 61.9%. Anal. Calc. for C39H32N6P2F6Ru: C,
54.34; H, 3.72; N, 9.78. Found: C, 54.40; H, 3.81; N, 9.66%. IR (KBr
3.47; N, 11.18%. IR (KBr pellets, cmꢀ1): 3434 (
1457 ( C@N); 843 (
P–F); 1H NMR (400 MHz, CDCl3): d = 9.65 (d,
mN–H); 1630 (mC@C);
m
m
J = 7.6 Hz, 1H), 9.31 (d, J = 8 Hz, 1H), 9.00 (d, J = 5.6 Hz, 1H), 8.93
(d, J = 8 Hz, 1H), 8.41 (t, J = 7.6 Hz, 1H), 8.27 (t, J = 8 Hz, 1H), 7.89
(t, J = 9.2 Hz, 1H), 7.83 (t, J = 6.4 Hz, 1H), 7.47 (s, 2H, –NH2), 2.29
(s, 15H, C5Me5); ESI-MS (m/z): 600.8 [MꢀPF6], 565.8 [MꢀPF6ꢀCl].
2.6. Preparation of [(g
5-C5H5)M(dpt-NH2)(PPh3)]PF6 {M = Ru (6), Os
(7)}
pellets, cmꢀ1): 3446 (
mN–H); 1630 (mC@C); 1439 (mC@N); 843 (mP–F);
1H NMR (400 MHz, CDCl3): d = 9.22 (d, J = 5.6 Hz, 1H), 8.75 (d,
J = 8 Hz, 1H), 8.67 (d, J = 4.4 Hz, 1H), 8.41 (d, J = 8 Hz, 1H), 8.25
(s, 2H, –NH2), 8.23 (t, J = 7.6 Hz, 1H), 8.01 (t, J = 6.4 Hz, 1H), 7.96 (t,
J = 8 Hz, 1H), 7.94 (t, J = 9.2 Hz, 1H), 7.55–7.10 (m, 22H), 4.97 (d,
J = 8 Hz, 1H), 4.85 (d, J = 7.6 Hz, 1H), 4.43 (t, J = 2.4 Hz, 1H); 31P
{1H} NMR (CDCl3, d): 57.10 (s, PPh3); ESI-MS (m/z): 719.1 [MꢀPF6].
A mixture of [(g
5-C5H5)M(PPh3)2X] {M = Ru, X = Cl and M = Os,
X = Br} (0.137 mmol), 4-amino-3,5-di-pyridyltriazole (dpt-NH2)
(0.137 mmol) and 1 equiv. of NH4PF6 in dry methanol (30 ml) were
refluxed under dry nitrogen for 12 h until the color of the solution
changed from pale yellow to orange. The solvent was removed un-
der vacuum, the residue was dissolved in dichloromethane (10 ml),
and the solution filtered to remove ammonium halide. The orange
solution was concentrated to 5 ml, upon addition of diethylether
the orange–yellow complex was precipitated, which was separated
and dried under vacuum.
3. Results and discussion
3.1. Arene ruthenium complexes 1, 2 and 3
Complex [6]: Yield: 76 mg, 68%. Elemental Anal. Calc. for
C35H30N6P2F6Ru: C, 51.78; H, 3.72; N, 10.37. Found: C, 51.89; H,
The dinuclear arene ruthenium complexes [(g l-
6-arene)Ru(
3.79; N, 10.28%. IR (KBr pellets, cmꢀ1): 3436 (
m
N–H); 1615 (
m
C@C);
Cl)Cl]2 (arene = C6H6, C10H14 and C6Me6) reacts with the N,N0-based
ligand (dpt-NH2) in methanol to afford the mononuclear cationic
complexes 1, 2 and 3 (Scheme 1). The complexes 1 and 3 are yellow
in color while complex 2 is brown in color. These complexes are
non-hygroscopic and stable in air as well as in solution. They are
1440 (mC@N); 844 (m
P–F); 1H NMR (400 MHz, CDCl3): d = 9.37 (d,
J = 8 Hz, 1H), 8.73 (d, J = 7.6 Hz, 1H), 8.69 (d, J = 7.2 Hz, 1H), 8.43
(d, J = 8 Hz, 1H), 8.20 (t, J = 6.4 Hz, 1H), 8.12 (t, J = 7.2 Hz, 1H),
7.81 (t, J = 7.6 Hz, 1H), 7.70 (t, J = 6.4 Hz, 1H), 7.50 (s, 2H, –NH2),

G. Gupta et al. / Polyhedron 29 (2010) 904–910
907
R
R
+
+
Ru
Cl
M
Ru
dpt-NH2
NH4PF6
M
N
Cl
Cl
N
N
Cl
Cl
½
N
N
dpt-NH2
NH4PF6
N
Cl
N
Cl
Cl
½
Cl
N
N
Ru
Cl
N
M
NH2
NH2
M = Rh, 4; Ir, 5
R
R
1:
=
=
R
R
2:
3:
Scheme 2.
=
These complexes were also isolated as their hexafluorophos-
Scheme 1.
phate salts. Here also we are able to isolate only the mononuclear
complexes. Change in concentration and longer reaction time do
not change the reaction pathways. The orange–yellow complexes
are air stable, soluble in polar solvents but insoluble in hexane,
petroleum ether and diethylether. The infrared spectra of both
the complexes exhibit a chelated N,N0-bidentate ligand as broad
sparingly soluble in polar solvents like dichloromethane, chloro-
form, acetone and acetonitrile but are insoluble in non-polar sol-
vents like hexane, diethylether and petroleum ether.
The analytical data of these compounds are consistent with the
formulations. These complexes give only mononuclear complexes
irrespective of the metal–ligand ratio. The complexes are isolated
as their hexafluorophosphate salts. The infrared spectra of all these
complexes exhibit a chelated N,N0-bidentate ligand as broad bands
, , ,
bands at 3446 cmꢀ1 3434 cmꢀ1 1632 cmꢀ1 1630 cmꢀ1 and
1457 cmꢀ1 corresponding to the stretching frequencies of N–H
bond of NH2 group of triazole ring, C@C and C@N bond of the pyr-
idine ring of the ligand, respectively. The infrared spectra of these
complexes also exhibit a strong band at around 844 cmꢀ1 due to
around 3430 cmꢀ1, 3432 cmꢀ1, 3433 cmꢀ1, 1615 cmꢀ1, 1627 cmꢀ1
,
1618 cmꢀ1, 1457 cmꢀ1, 1451 cmꢀ1 and 1474 cmꢀ1 corresponding
to the stretching frequencies of N–H bond of NH2 group of triazole
ring, C@C and C@N bond of the pyridine ring of the ligand, respec-
tively. In addition, the infrared spectra contained a strong band at
846 cmꢀ1 due to the stretching frequency of P–F bond of PF6 for
these complexes.
the mP–F stretching frequency of the counter ion of these complexes.
In proton NMR spectra of these complexes, the ligand peaks spread
over a quite wide range as compared to that of the free ligand. The
free ligand exhibits two doublets at around 8.37–8.66 ppm in pro-
ton NMR. However, after metallation, these doublets shifted to
down field in the range of 9.31–9.65 ppm. Besides the ligand peaks
as mentioned in Section 2, the proton NMR spectra of these com-
pounds also exhibit a singlet at 1.59 ppm for complex 4 and
2.29 ppm for complex 5, respectively, corresponding to the protons
of the pentamethylcyclopentadienyl group. The molecular struc-
ture of complex 4 was solved by single crystal X-ray crystallogra-
phy and the structure is presented in Fig. 1.
The proton NMR spectra of all these complexes show downfield
shift as compared to that of the free ligand. In the free ligand, five
sets of signals viz. two doublets, singlet and two doublet of triplets
in the aromatic region at around 7.34–8.66 ppm corresponding to
the pyridyl and triazole protons are observed. Whereas in the com-
plexes, it displays a total of nine sets of signals, namely four dou-
blets, four triplets and a singlet as mentioned in Section 2. Beside
these signals complex 2 shows a singlet at 6.20 ppm corresponding
to the benzene protons of the complex and complex 3 displays a
singlet at 2.1 ppm which corresponds to the hexamethylbenzene
protons. Complex 1 exhibits an unusual pattern of resonances for
the p-cymene ligand. For instance, the methyl protons of the iso-
propyl group display two doublets at ca. 1.24–1.19 ppm, instead
of one doublet as in the starting precursor. The aromatic protons
of the p-cymene ligand for these complexes also display four dou-
blets at ca. 5.98–5.67 ppm, instead of two doublets as in the start-
ing precursor. This pattern is due to the diastereotopic nature of
the methyl protons of the isopropyl group and the aromatic pro-
tons of the p-cymene ligand. It may also be attributed to the behav-
iour of the ruthenium atom which is stereogenic when coordinated
with four different ligand atoms [33]. In other words we can say
that the different signals are entirely due to the chiral nature of
the metal [34,35].
3.3. Cyclopentadienyl ruthenium and osmium complexes 6–9
The mononuclear cyclopentadienyl complexes [(
(PPh3)2Cl] and [(
5-C5H5)Os(PPh3)2Br], [( 5-C9H7)Ru(PPh3)2Cl]
and pentamethylcyclopentadienyl complex [(
5-C5Me5)Ru(PPh3)2
g
5-C5H5)Ru
g
g
g
Cl] react with dpt-NH2 in refluxing methanol to give the corre-
sponding mononuclear complexes 6–9 (Chart 1). Compounds 6–9
are soluble in halogenated solvents and polar organic solvents such
as tetrahydrofuran, methanol or dimethylsulfoxide but are insolu-
ble in non-polar solvents. All these complexes are stable in solid
state as well as in solution. All complexes were characterized by
IR, 1H NMR and mass spectrometry as well as by elemental analysis
(see Section 2).
The infra red spectra of these complexes exhibit a broad band
between 3431 and 3446 cmꢀ1 due to the stretching frequency of
N–H bond NH2 group of triazole ring and band between
1599 cmꢀ1 and 1630 cmꢀ1 and between 1437 and 1451 cmꢀ1 cor-
responding to the stretching frequency of the C@C and C–N bond of
the pyridine ring of the ligand. In addition to these all the com-
plexes display a sharp peak at around 843 cmꢀ1 due to the stretch-
ing frequency of the P–F bond of PF6 for all the complexes. The
protons of complexes 6–9 also show downfield shift with respect
to the protons of the free ligand. Beside the aromatic protons of
the ligand as mentioned in Section 2, complexes 6 and 7 show a
singlet at 4.91 and 4.59 ppm which correspond to the protons of
3.2. Pentamethylcyclopentadienyl rhodium and iridium complexes 4
and 5
The dinuclear complexes [(
g l-Cl)Cl]2 (M = Rh or Ir)
5-C5Me5)M(
undergo a bridge cleavage reaction with N,N0-bidentate nitrogen
base (dpt-NH2) ligand in methanol at room temperature leading
to the formation of chloride displaced complexes 4 and 5, respec-
tively (Scheme 2).

908
G. Gupta et al. / Polyhedron 29 (2010) 904–910
+
+
+
+
Os
N
Ru
N
Ru
Ru
N
N
N
N
N
N
N
N
Ph3P
N
N
N
N
Ph3P
Ph3P
N
Ph3P
N
N
N
N
N
NH2
NH2
NH2
NH2
6
8
7
9
Chart 1.
the cyclopentadienyl ligand, while in the case of complex 8 it dis-
plays a singlet at 2.03 ppm corresponding to the methyl protons of
the pentamethylcyclopentadienyl ligand. These complexes also
show a multiplet in the range of 6.80–7.38 ppm due to the protons
of the triphenylphosphine group of these complexes. Complex 9
exhibits a characteristic three sets of signals such as multiplet, trip-
let and doublet, for the protons of the indenyl group. The protons of
the triphenylphosphine ligand exhibit
a multiplet at 7.10–
7.55 ppm. The 31P {1H} NMR spectra of the complexes 6, 7 and 9
exhibit a single sharp resonance for triphenylphosphine around
57.10–49.6 ppm, respectively, whereas in the starting precursors
the signal appear in the upfield region. In the case of complex 8
the 31P {1H} NMR spectra displays a sharp singlet at ꢀ0.26 ppm
as compared to the starting complex which shows at ꢀ6.29 ppm.
The structure of a representative complex 6 was solved by single
crystal X-ray diffraction study and is presented in Fig. 2.
The m/z values of all these complexes and their stable ion peaks
obtained from the ZQ mass spectra, as listed in Section 2, are in
good agreement with the theoretically expected values. ESI mass
spectra of the complexes also displayed prominent peaks corre-
sponding to the molecular ion fragment. All the halogenated com-
plexes displayed the prominent peak corresponding to the loss of
chloride ion from the molecular ion peak, but the loss of arene or
Cp or Cp* group is not observed indicating the stronger bond of me-
tal to these groups and remains intact.
Fig. 3. UV–Vis absorption spectra of mononuclear complexes 1, 2, 4, 5, 7, 8 and 9 in
acetonitrile at 298 K.
provides filled orbitals of proper symmetry at the Ru, Rh, Ir and Os
centers, these can interact with low lying p
* orbitals of the ligands.
The lowest energy absorption bands in the electronic spectra of
these complexes in the visible region ꢁ429–422 and ꢁ387–
341 nm have been tentatively assigned on the basis of their inten-
4. UV–Vis spectroscopy
UV–Vis spectra of some representative complexes were ac-
quired in acetonitrile and spectral data are summarized in Table
1. Electronic spectra of these complexes are depicted in Fig. 3.
The spectra of these complexes are characterized by two main fea-
sity and position to
higher energy side at ꢁ302–220 nm have been assigned to li-
gand-centered
*/ n ? * transitions [36,37]. In general, these
p ?
p* MLCT transitions. The bands on the
p
?
p
p
complexes follow the normal trends observed in the electronic
tures, viz., an intense ligand-localized or intra-ligand
tion in the ultraviolet region and metal-to-ligand charge transfer
p ? p
* transi-
spectra of the nitrogen-bonded metal complexes, which display a
ligand-based
p ?
p* transition for pyrazolylpyridazine ligands in
(MLCT) dp
(M) ? p* (dpt-NH2 ligand) bands in the visible region.
the UV region and metal-to-ligand charge transfer transitions in
the visible region.
Since the low spin d6 configuration of the mononuclear complexes
Table 1
UV–Vis absorption data of the representative complexes in acetonitrile at 298 K.
5. Molecular structures
Complex
kmax/nm (e )
/10ꢀ4 Mꢀ1 cmꢀ1
Molecular structures of 4 and 6 have been determined crystal-
lographically. The complexes crystallize in P1 and P21/n space
1
2
4
5
7
8
9
235 (0.60)
220 (0.27)
250 (0.20)
288 (0.46)
291 (0.21)
302 (0.12)
294 (0.27)
298 (0.19)
294 (0.16)
290 (0.20)
387 (0.05)
352 (0.06)
420 (0.03)
429 (0.05)
341 (0.11)
ꢀ
groups. Details about data collection, refinement and structure
solution are recorded in Table 2, and selected bond lengths and an-
gles are presented in Table 3. Crystal structures of 4 and 6 with
atom-numbering schemes are shown in Figs. 1 and 2. In complex
4 the metal is bonded with the major coordinated sites N1 and
244 (0.15)
229 (0.27)
228 (0.30)
422 (0.09)

G. Gupta et al. / Polyhedron 29 (2010) 904–910
909
Table 2
lengths are in the range of 2.069(2)–2.125(3) Å. The N–Ru–N angle
in these complexes are in the range of 75.49(9)° and 133.52(17)°,
which are comparatively less than other ruthenium polypyridyl-
triazole complexes [42]. The distance between the ruthenium atom
and the centroid of the Cp ring is 1.833 Å and is comparable to
those in other reported complexes. The Ru–P distance is around
2.318 Å and N–M–P angle are normal and are in the range of
90.84(7)–88.41(6)°. The P–F lengths are consistant with the values
reported previously [10].
Crystallographic and structure refinement parameters for complexes 4 and 6.
Compound
4
6
Empirical formula
Formula weight
T (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C22H25ClF6N6PRh
656.81
296(2)
0.71073
triclinic
C35H30F6N6P2Ru
811.66
296(2)
0.71073
monoclinic
P2(1)/n
ꢀ
P1
8.0012(15)
11.487(2)
14.975(3)
73.695(12)
88.467(14)
87.830(14)
1319.9(4)
2, 1.653
13.7582(5)
14.2396(5)
17.6420(6)
90
102.522(2)
90
b (Å)
c (Å)
6. Conclusion
a
(°)
In summary, a series of new
g g
5- and 6-cyclichydrocarbon plat-
b (°)
inum metal complexes bearing dpt-NH2 ligand, which are remark-
ably stable in the solid state and in solution have been successfully
synthesized in good yield. Our attempts to synthesize a dimetallic
derivative by addition of a second organometallic anion were
unsuccessful. As a continuation of our studies, we have been able
to condense the ligand dpt-NH2 with an aldehyde to form a corre-
sponding hexadentate ligand and this work is still in progress.
c
(°)
V (A3)
3374.1(2)
4, 1.598
Z, calculated density
(Mg/m3)
Absorption coefficient
0.875
0.629
(mmꢀ1
)
F(0 0 0)
Crystal size (mm)
660
1640
0.35 ꢂ 0.24 ꢂ 0.14
0.40 ꢂ 0.25 ꢂ 0.15
H
Range for data
1.42–28.17
1.71–28.33
collection (°)
Index ranges
7. Supplementary data
ꢀ8 ꢃ h ꢃ 9,
ꢀ12 ꢃ k ꢃ 15,
11 ꢃ l ꢃ 19
7835/4827
ꢀ18 ꢃ h ꢃ 18,
ꢀ18 ꢃ k ꢃ 19,
ꢀ23 ꢃ l ꢃ 23
35 680/8395
CCDC 742500 and 742501 contain the supplementary crystallo-
graphic data for 4 and 6. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
Reflections collected/
unique
[R(int)
]
0.1570
0.0261
Final R indices [I > 2
R indices (all data)
r
(I)]
0.0616, wR2 = 0.1797
0.0965, wR2 = 0.2483
0.913 and ꢀ0.721
0.0418, wR2 = 0.1373
0.0546, wR2 = 0.1486
0.875 and ꢀ0.626
Largest difference in
peak and hole (e Åꢀ3
)
Goodness-of-fit (GOF) on 0.994
1.088
F2
Acknowledgements
K.M. Rao gratefully acknowledges financial support from the
Department of Science and Technology, New Delhi, through the Re-
search Grant No. SR/S1/IC-11/2004. G.G. is also thankful for finan-
cial support from University Grant Commissions, New Delhi.
Table 3
Selected bond lengths and angles for complexes 4 and 6.
4
6
Bond distances (Å)
References
N(1)–M(1)
N(2)–M(1)
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2.090(9)
1.378(14)
1.416(13)
2.401(4)
1.769
2.125(3)
2.069(2)
1.373(3)
1.402(3)
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