New series of platinum group metal complexes bearing η5- and η6-cyclichydrocarbons and Schiff base derived from 2-acetylthiazole: Syntheses and structural studies

Article abstract of DOI:10.1016/j.poly.2009.05.059

The mononuclear complexes [(η⁶-arene)Ru(ata)Cl]PF₆{ata = 2-acetylthiazole azine; arene = C₆H₆[(1)PF₆]; p-ⁱPrC₆H₄Me [(2)PF₆]; C₆Me₆[(3)

Full text of DOI:10.1016/j.poly.2009.05.059

Polyhedron 28 (2009) 2649–2654
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
New series of platinum group metal complexes bearing
g -
5- and g6
cyclichydrocarbons and Schiff base derived from 2-acetylthiazole:
Syntheses and structural studies
Kota Thirumala Prasad a, Gajendra Gupta a, Anna Venkateswara Rao 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
Article history:
The mononuclear complexes [(
g
6-arene)Ru(ata)Cl]PF6 {ata = 2-acetylthiazole azine; arene = C6H6
[(1)PF6]; p-iPrC6H4Me [(2)PF6]; C6Me6 [(3)PF6]}, [( 5-C5Me5)M(ata)]PF6 {M = Rh [(4)PF6]; Ir [(5)PF6]}
g
Received 20 April 2009
Accepted 26 May 2009
Available online 2 June 2009
and [(
[(8)PF6]} have been synthesised from the reaction of 2-acetylthiazole azine (ata) and the corresponding
dimers [( -Cl)Cl]2, [( -Cl)Cl]2, and [(
6-arene)Ru( 5-C5Me5)M( 5-Cp)Ru(PPh3)2Cl], respectively. In addi-
g {g g g g
5-Cp)Ru(PPh3)2Cl] 5-Cp = 5-C5H5 [(6)PF6]; 5-C5Me5 (Cp*) [(7)PF6]; 5-C9H7 (indenyl);
g
l
g
l
g
Keywords:
Arene
Cyclopentadienyl
2-Acetylthiazole azine
Ruthenium
Rhodium
tion to these complexes a hydrolysed product (9)PF6, was isolated from complex (4)PF6 in the process of
crystallization. All these complexes are isolated as hexafluorophosphate salts and characterized by IR,
NMR, mass spectrometry and UV–Vis spectroscopy. The molecular structures of [2]PF6 and [9]PF6 have
been established by single-crystal X-ray structure analyses.
Ó 2009 Elsevier Ltd. All rights reserved.
Iridium
1. Introduction
chemical properties of the complexes [26,27]. The arene and cyclo-
pentadienyl platinum group metal complexes containing thiazole
Recent interest in half- sandwich platinum group metal com-
plexes with symmetrical Schiff bases come from the fact they
can serve as synthetic models related to biological systems [1–7],
as homogeneous catalysts in systems like [8–17], and supported
chemical processes [18,19], and very recently as non-linear optical
(NLO) materials [20,21]. Their attractiveness does also come from
their preparative accessibility, their structural variability in addi-
tion to many of these novel ruthenium complexes combine an
appropriate balance between the electronic and steric environ-
ment around the metal core.
Moreover, some of the nitrogen-donor ligands impart to the cat-
alyst for good tolerance towards various organic functionalities,
air, and moisture, thus widening the scope and limit’s of their
application. Of the above mentioned ligands, Schiff bases are of a
great interest for creating new active and selective ruthenium cat-
alytic systems [22,23]. There are few reports of half-sandwich
Ru(II), Rh(III) and Ir (III) complexes with N,N-donor polypyridyl
azine Schiff base ligands [24,25], but there are no reports with thi-
azole azine ligand in the literature. Complexes imparting other
than pyridyl azine ligands are yet to be explored, in view of the fact
that ring size and the substituents in the heterocyclic ring system
significantly modifies the acidity and regulate the physical and
azine ligand is being reported for the first time.
In the present communication we focus on the synthetic meth-
odology applied for the development of homogeneous and immo-
bilized half- sandwich ruthenium, rhodium and iridium complexes
bearing Schiff base (ata) as a specific N,N-bidentate bridging ligand
has shown below.
S
N
N
N
N
S
2-acetylthiazole azine (ata)
Ligand used in this study
2. Experimental
2.1. General remarks
All solvents were dried and distilled prior to use. Ruthenium tri-
chloride trihydrate (Arora Matthey Ltd.), 2-acetylthiazole (Aldrich)
* Corresponding author. Tel.: +91 9436166937; fax: +91 364 2550486.
E-mail addresses: mohanrao59@gmail.com, kmrao@nehu.ac.in (K.M. Rao).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.05.059

2650
K.T. Prasad et al. / Polyhedron 28 (2009) 2649–2654
were purchased and used as received. [(
g
6-C6H6)Ru(
-Cl)Cl]2 [28–30],
5-C5H5)Ru(PPh3)2
g
5-C9H7)Ru(PPh3)2Cl] [33,35,36]
l-Cl)Cl]2,
Table 2
[(
[(
g
g
6-p-iPrC6H4Me)Ru(
l
-Cl)Cl]2, [(
-Cl)Cl]2 (M = Rh, Ir) [31–33], [(
5-C5Me5)Ru(PPh3)2Cl], [(
g l
6-C6Me6)Ru(
Selected bond lengths (Å) and angles (°) for complexes [1]PF6.and [9]PF6.
5-C5Me5)M(
l
g
[1]PF6
Interatomoic distances
[9]PF6
Cl] [34], [(
g
Ru–N1
Ru–N2
Ru–Cl1
Ru–centroid (arene)
N2–N3
N1–C13
N2–C14
C13–C14
2.087(3)
2.104(2)
2.406(8)
1.692
1.398(3)
1.326(4)
1.299(4)
1.439(4)
Rh–N1
Rh–N2
Rh–Cl1
Rh–centroid (C5 ring)
N2–N3
N1–C13
N2–C11
C11–C13
2.097(4)
2.136(5)
2.396(15)
1.782
1.369(6)
1.318(7)
1.292(7)
1.458(8)
and ligand ata [37,38] were prepared according to literature meth-
ods. NMR spectra were recorded on AMX-400 MHz spectrometer.
Infrared spectra were recorded as KBr pellets on a Perkin–Elmer
983 spectrophotometer; elemental analyses of the complexes
were performed on a Perkin–Elmer-2400 CHN/S analyzer. Mass
spectra were obtained from ZQ mass spectrometer by ESI method.
Absorption spectra were obtained at room temperature using a
Perkin–Elmer Lambda 25 UV–Vis spectrophotometer.
Angles
N1–Ru–N2
N1–Ru–Cl1
N2–Ru–Cl1
Ru1–N2–C14
Ru1–N1–C13
75.58(10)
83.80(7)
88.24(7)
119.10(2)
114.39(2)
N2–Rh–N3
N4–Rh–Cl1
N3–Rh–Cl1
Rh1–N1–C13
Rh1–N2–C11
75.88 (17)
84.25(13)
87.88(13)
114.13(4)
117.59(4)
2.2. Single crystal X-ray structure analyses
Crystals suitable for X-ray diffraction study for compound
[2]PF6 and [4]PF6 were grown by slow diffusion of diethylether into
dichloromethane solution of complexes [2]PF6 and [4]PF6, respec-
tively. The bright orange crystals of compound [2]PF6, the red color
crystal of [4]PF6 were mounted on a Stoe-Image Plate Diffraction
system equipped with a / circle goniometer, using Mo Ka graphite
monochromated radiation (k = 0.71073 Å) with / range 0–200°,
increment of 1.2°, Dmax–Dmin = 12.45–0.81 Å. X-ray intensity data
Calculated centroid of the C6 or C5 coordinated aromatic ring.
2.5 equivalents of NH4PF6 in dry methanol (15 ml) was stirred at
room temperature for 6 h. The precipitate was separated by filtra-
tion, washed with cold methanol and diethyl ether to remove ex-
cess ligand and dried under vacuum.
were collected with Mo K
a
graphite monochromatic radiation at
2.3.1. [(g
6-C6H6)Ru(ata)Cl]PF6 ([1]PF6)
296 (2) K, with 0.3° scan mode and 10 second per frame. The
x
Orange–yellow solid, yield 70 mg (79%): Anal. Calc. for
C16H21ClN4S2RuPF6 (609.5): C, 34.89; H, 3.84; N, 10.17. Found: C,
34.68; H, 3.98; N, 10.28%.
intensity data were corrected for Lorentz and polarization effects.
The structures were solved by direct methods using the program
SHELXS-97 [39]. Refinement and all further calculations 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 and bond lengths and angles are presented in Tables
1 and 2, respectively. Figs. 1 and 2 were drawn with ORTEP [41].
1H NMR (CD3CN, d): 8.75 (d, 1H, JH–H = 2.98 Hz), 8.52 (d, 1H,
JH–H = 3.20 Hz), 7.98 (d, 1H, JH–H = 3.20 Hz), 7.62 (d, 1H, JH–H
=
3.2 Hz), 6. 50 (s, 6H), 2.56 (s, 3H, tz-Me), 2.47 (s, 3H, tz-Me); ESI-
MS (m/z): 525.1 (100%) [MÀPF6]+; IR (KBr, cmÀ1): m(P–F) 844s;
1604, 1408, 558.
2.3.2. [(g
6-p-iPrC6H4Me)Ru(ata)Cl]PF6 ([2]PF6)
Dark orange solid, yield 86 mg (89%): Anal. Calc. for
C20H24ClS2N4RuPF6 (651.5): C, 36.07; H, 3.63; N, 8.41. Found: C,
36.18; H, 3.68; N, 8.35%.
2.3. General procedure for the preparation of the mononuclear
complexes [1]PF6–[3]PF6
1H NMR (CDCl3, d): 8.55 (d, 1H, JH–H = 2.88 Hz), 8.06 (d, 1H,
A
mixture
of
[(
g
6-arene)Ru(
l
-Cl)Cl]2
(arene = C6H6,
JH–H = 3.20 Hz), 7.98 (d, 1H, JH–H = 3.2 Hz), 7.71 (d, 1H, JH–H
2.80 Hz), 5.90 (d, 1H, JH–H = 2.8 Hz, Arp-cy), 5.87 (d, H, JH–H
=
=
p-iPrC6H4Me and C6Me6) (0.07 mmol), ligand ata (0.18 mmol) and
2.4 Hz, Arp-cy), 5.72 (d, 1H, JH–H = 4 Hz, Arp-cy), 5.68 (d, 1H,
JH–H = 2.8 Hz, Arp–cy), 2.93 (sept, 1H, JH–H = 4.4 Hz, CH(CH3)2), 2.56
(s, 3H, tz-Me), 2.47 (s, 3H, tz-Me), 2.28 (s, 3H, Arp-cy–Me), 1.26 (d,
3H, CH(CH3)2), 1.18 (d, 3H, CH(CH3)2); ESI-MS (m/z): 525.1
Table 1
Crystallographic and structure refinement parameters for complexes.
(100%) [MÀPF6]+; IR (KBr, cmÀ1):
m(P–F) 844s; 1629, 1406, 763, 558.
Complex
[2]PF6
[9]PF6
Chemical formula
Crystal system
Space group
Crystal color and shape
Crystal size
a (Å)
C20H24ClF6N4PRuS2
triclinic
P1
C15H22ClF6N3PRhS
triclinic
P1
2.3.3. [(g
6-C6Me6)Ru(ata)Cl]PF6 ([3]PF6)
Orange–yellow solid, yield 85 mg (88%): Anal. Calc. for
C22H28ClN4S2RuPF6 (694.1): C, 38.07; H, 4.07; N, 8.07. Found: C,
38.11; H, 4.18; N, 8.02%.
ꢀ
ꢀ
plates, yellow
0.45 Â 0.30 Â 0.18
7.8486 (4)
12.9523 (7)
13.4155 (8)
99.008 (3)
90.073 (3)
98.780 (3)
1330.74 (13)
2
plates, redish yellow
0.36 Â 0.28 Â 0.18
8.2601 (9)
11.6219 (12)
12.1958 (14)
76.593 (7)°
77.719 (7)°
78.838 (7)°
1099.9 (2)
2
1H NMR (CDCl3, d): 8.75 (d, 1H, JH–H = 2.98 Hz), 8.52 (d, 1H,
b (Å)
c (Å)
JH–H = 3.20 Hz), 7.98 (d, 1H, JH–H = 3.20 Hz), 7.62 (d, 1H, JH–H
=
3.2 Hz), 2.56 (s, 3H, tz-Me), 2.47 (s, 3H, tz-Me), 2.28 (s, 18H), ESI-
MS (m/z): 549.14 (100%) [MÀPF6]+; IR (KBr, cmÀ1): m(P–F) 844s;
1624, 1437, 1409, 769, 558.
a
(°)
b (°)
c
(°)
V (Å3)
Z
2.4. General Procedure for the preparation of the mononuclear
complexes [4]PF6 and [5]PF6
T (K)
296 (2)
1.662
0.97
296 (2)
1.690
1.12
Dx (g /cm3)
l
(mmÀ1
)
A mixture of [(g l-Cl)Cl]2 (M = Rh, Ir) (0.07 mmol),
5-C5Me5)M(
Scan range (°)
Unique reflections
Reflections used [I > 2
Rint
1.54 < h < 28.38
6542
5109
1.74 < h < 28.08
4390
3402
ligand ata (0.15 mmol) and 2.5 equivalents of NH4PF6 in dry meth-
anol (15 ml) was refluxed for 4 h. The reaction mixture was cooled
over night at room temperature during this time dark yellow color
crystalline compound formed. It was separated by filtration,
washed with cold methanol and diethyl ether to remove excess li-
gand and dried under vacuum.
r
(I)]
0.037
0.043
Final R indices [I > 2
R indices (all data)
r(I)]
0.0406, wR2 0.0943
0.0563, wR2 0.1013
1.022
0.62, À0.62
0.0556, wR2 0.1439
0.0742, wR2 0.1556
1.098
0.76, À0.72
Goodness-of-fit (GOF)
Max., Min. d
q
(e ÅÀ3
)

K.T. Prasad et al. / Polyhedron 28 (2009) 2649–2654
2651
Fig. 1. Molecular structure of [2]PF6 at 50% probability level. Hydrogen atoms, and hexafluorophosphate anion have been omitted for clarity.
3.24 Hz), 2.57 (s, 3H, tz-Me), 2.40 (s, 3H, tz-Me), 1.99 (s, 15H,
C5Me5); ESI-MS (m/z): 613.18 (100%) [MÀPF6]+; IR (KBr, cmÀ1):
m(P–F) 845s; 1631, 1495, 760, 558.
2.5. General Procedure for the preparation of the mononuclear
complexes [6]PF6- [8]PF6
A mixture of [(
5-C9H7) (0.1 mmol), ligand ata (0.12 mmol) and 1.5 equivalents of
g g g g
5-Cp)Ru(PPh3)2Cl] ( 5-Cp = 5-C5H5, 5-C5Me5,
g
NH4PF6 in dry ethanol (15 ml) was refluxed for 10 h. It was chan-
ged to dark red color from dark yellow color. The solvent was evap-
orated on rotary evaporator and residue was dissolved in
dichloromethane and filtered to remove ammonium chloride and
filtrate was evaporated to 2 ml and excess hexane was added to in-
duce dark color precipitate.
2.5.1. [(g
5-C5H5)Ru(ata)(PPh3)]PF6 ([6]PF6)
Orange color, yield 60 mg (73%): Anal. Calc. for
C33H30N4S2RuP2F6 (823.75): C, 48.12; H, 3.67; N, 6.80. Found: C,
48.11; H, 3.73; N, 6.75%.
1H NMR (CDCl3, d) 8.52 (d, 1H, JH–H = 2.80 Hz), 8.12 (d, 1H, JH–H
=
3.2 Hz), 7.77 (d, 1H, JH–H = 3.2 Hz), 7.68 (d, 1H, JH–H = 3.2 Hz), 7.46–
7.23 (m, 15H), 4.57 (s, 5H, C5H5), 2.57 (s, 3H, tz-Me), 2.50 (s, 3H,
tz-Me); ESI-MS (m/z): 678.78 (100%) [MÀPF6]+; IR (KBr, cmÀ1):
m(P–F) 845s; 1626, 1458, 766, 558. 31P {1H} (CDCl3): 49.34 ppm.
Fig. 2. Molecular structure of [9]PF6 at 50% probability level. Hydrogen atoms and
hexafluorophosphate anion have been omitted for clarity.
2.5.2. [(g
5-C5Me5)Ru(ata)(PPh3)]PF6 ([7]PF6)
Orange color, yield 68 mg (76%): Anal. Calc. for
C38H40N4S2RuP2F6 (893.88): C, 51.06; H, 4.51; N, 6.27. Found: C,
51.10; H, 4.62; N, 6.24%.
2.4.1. [(g
5-C5Me5)Rh(ata)Cl]PF6 ([4]PF6)
Dark yellow color, yield 86 mg (85%): Anal. Calc. for
C20H25ClN4S2RhPF6 (668.89): C, 35.91; H, 3.77; N, 8.38. Found: C,
36.00; H, 3.89; N, 8.29%.
1H NMR (CDCl3, d) 8.87 (d, 1H, JH–H = 2.80 Hz), 8.52 (d, 1H,
JH–H = 3.2 Hz), 7.87 (d, 1H, JH–H = 3.2 Hz), 7.79 (d, 1H, JH–H
=
1H NMR (CD3CN, d): 8.33 (d, 1H, JH–H = 5.58 Hz), 8.05 (d, 1H,
3.2 Hz), 7.46–7.23 (m, 15H), 2.57 (s, 3H, tz-Me), 2.50 (s, 3H, tz-
Me), 2.19 (s, 15H, C5Me5); ESI-MS (m/z): 748.88 (100%) [MÀPF6]+;
IR (KBr, cmÀ1): m(P–F) 845s; 1621, 1479, 749, 558. 31P {1H} (CDCl3):
48.54 ppm.
JH–H = 3.2 Hz), 7.82 (d, 1H, JH–H = 2.8 Hz), 7.68 (d, 1H, JH–H
=
3.2 Hz), 2.57 (s, 3H, tz-Me), 2.50 (s, 3H, tz-Me), 1.77 (s, 15H,
C5Me5); ESI-MS (m/z): 523.1 (100%) [MÀPF6]+; IR (KBr, cmÀ1):
m(P–F) 845s; 1626, 1458, 759, 558.
2.5.3. [(g
5-C9H7)Ru(ata)(PPh3)]PF6 ([8]PF6)
2.4.2. [(
g
5-C5Me5)Ir(ata)Cl]PF6 ([5]PF6)
Yellowish brown color, yield 66 mg (76%): Anal. Calc. for
C37H35N4S2RuP2F6 (876.83): C, 50.68; H, 4.02; N, 6.39. Found: C,
50.61; H, 4.19; N, 6.34%.
Dark yellow color, yield 95 mg (84%): Anal. Calc. for
C20H25ClN4S2IrPF6 (818.21): C, 31.68; H, 3.32; N, 7.39. Found: C,
31.70; H, 3.48; N, 7.48%.
1H NMR (CDCl3, d) 8.52 (d, 1H, JH–H = 2.80 Hz), 8.12 (d, 1H, JH–H
=
1H NMR (CD3CN, d): 8.58 (d, 1H, JH–H = 3.28 Hz), 8.26 (d, 1H,
3.2 Hz), 7.77 (d, 1H, JH–H = 3.2 Hz), 7.68 (d, 1H, JH–H = 3.2 Hz), 7.46–
JH–H = 3.26 Hz), 7.88 (d, 1H, JH–H = 2.88 Hz), 7.68 (d, 1H, JH–H
=
7.23 (m, 20H), 4.87(t, 1H), 4.71 (d, 2H); 2.57 (s, 3H, tz-Me), 2.50 (s,

2652
K.T. Prasad et al. / Polyhedron 28 (2009) 2649–2654
3H, tz-Me); ESI-MS (m/z): 731.87 (100%) [MÀPF6]+; IR (KBr, cmÀ1):
m(P–F) 845s; 1629, 1468, 763, 558. 31P {1H} (CDCl3): 54.42 ppm.
[(g
5-C5Me5)Ir(ata)Cl]PF6 [5]PF6 (Scheme 1) which are isolated as
their hexafluorophosphate salts.
The cyclopentadienyl ruthenium triphenylphosphine com-
2.5.4. [(
g
5-C5Me5)Rh(ata*)Cl]PF6 ([9]PF6)
plexes [(
[(
5-C9H7)Ru(PPh3)2Cl] with the 2-acetylthiazole azine (ata) ligand
in methanol at 70 °C leads to the formation of the mononuclear
cationic complexes [(
5-C5H5)Ru(ata)PPh3]PF6 [6]PF6, [(g5
C5Me5)Ru(ata)PPh3]PF6 [7]PF6 and [(
5-C9H7)Ru(ata)PPh3]PF6
g g
5-C5H5)Ru(PPh3)2Cl], [( 5-C5Me5)Ru(PPh3)2Cl] and
The complex [4]PF6 (50 mg, 0.074 mmol) was dissolved in 20 ml
of dichloromethane in a small diameter test tube and layered with
diethylether and it was sealed and kept at room temperature. Dark
orange crystalline compound was observed after three days. The
crystalline compound was separated by filtration and washed with
diethylether and dried at room temperature.
g
g
-
g
[8]PF6 (Scheme 1) by replacement of one triphenylphosphine and
chloride which are isolated as their hexafluorophosphate salts.
In order to prepare the dinuclear complexes we have used two
fold metal-to-ligand or one fold metal to mononuclear complexes
concentration, but we were not successful in either of the cases.
This could be due to the steric strain from arene or pentamethylcy-
clopentadienyl ligands already present on metal atoms.
Anal. Calc. for C15H22ClF6N3PRhS (559.73): C, 32.19; H, 3.96; N,
7.51. Found: C, 32.00; H, 3.99; N 7.29%.
1H NMR (CD3CN, d): 8.23 (d, 1H, JH–H = 5.58 Hz), 7.89(d, 1H,
JH–H = 2.8 Hz), 4.78 (s, 2H, NH2), 2.61 (s, 3H, tz-Me), (s, 15H,
C5Me5); ESI-MS (m/z): 415.72 (100%) [MÀPF6]+; IR (KBr, cmÀ1):
m(P–F) 845s; 759, 558, 1626, 1458, 2891.
3.1. Characterization
3. Results and discussion
The mononuclear complexes were fully characterized by IR,
NMR (1H and 31P), and electronic spectroscopy. Analytical data of
the complexes conformed well to their respective formulations.
Further information about composition of the complexes has also
been obtained from Mass spectrometry.
Mononuclear cationic arene ruthenium complexes having ata li-
gand viz., [(
ta)Cl]PF6 [2]PF6, and [(
have been expediently prepared by the reaction of arene ruthe-
nium dimers [(
6-arene)Ru( -Cl)Cl]2 (arene = C6H6, p-iPrC6H4Me,
g g
6-C6H6)Ru(ata)Cl]PF6 [1]PF6, [( 6-p-iPrC6H4Me)Ru(a-
g
6-C6Me6)Ru(ata)Cl]PF6 [3]PF6 (Scheme 1)
Infrared spectra of the ligand display an absorption band at
1606 cmÀ1 (ata) assignable to the C@N Bond, consistent with the
fact that C@N stretching frequencies of Schiff bases appear in the
range 1680–1603 cmÀ1 [42–44] and complexes display the same
g
l
C6Me6) and two equivalents of 2-acetylthiazole azine (ata) in
methanol at room temperature in the presence of NH4PF6. These
complexes are isolated as hexafluorophosphate salts.
band at higher wave numbers and appeared around 1626 cmÀ1
.
Similarly, the pentamethylcyclopentadienyl Rh and Ir dimers
[(g l-Cl)Cl]2 (M = Rh, Ir) with the 2-acetylthiazole
5-C5Me5)M(
The bands associated with thiazole ring such as C@N and C@S ap-
peared at about 1430 and 1406 cmÀ1, these values are showing less
wave numbers as compared to free ligand (1490 and 1417 cmÀ1),
azine (ata) ligand at 50 °C leads to the formation of the mononu-
clear cationic complexes [(
g
5-C5Me5)Rh(ata)Cl]PF6 [4]PF6 and
R
N
R
S
1
Ru
S
N
N
Cl
N
2
3
+0.5[(
η
6-arene)Ru(
μ-Cl)Cl]2
S
N
N
N
N
S
-Cl)Cl]2
+[(
η
5-Cp)Ru(PPh3)2Cl]
R
R
+0.5[(
η
5-C5Me5)M(
μ
N
N
6
7
S
S
Ru PPh3
N
M
N
N
N
Cl
N
N
S
8
S
M = Rh 4; Ir 5
Scheme 1.

K.T. Prasad et al. / Polyhedron 28 (2009) 2649–2654
2653
respectively. The shift in the position of
mC=N of both azine and thi-
cant differences in both the cations and other reported values
azole suggested that the coordination of the metal ion is through
thiazole and azine of nitrogen and not through the thiazole sulfur.
Strong band in the region 844 cmÀ1 have been assigned to counter
ion PF6.
[50]. The N–M–N bond angles [75.58(10)° in 2 and 75.88(17)° in
9] are similar to those in other reported complexes [(
g
5-C5Me5)R-
5-C9H7)Ru–
u(PPh3)(C5H4N–CH@N–N@CH–C5H4N)]BF4 and [(
g
(PPh3)(C5H4N-2-CH@N@C6H4-p-NO2)]PF6 [75.90(2) and 75.53(8)°]
[51].
The 1H NMR spectrum of free ligand (ata) exhibit a characteris-
tic set of three resonances for the thiazole ring protons and methyl
protons of N@C–CH3 group. Upon coordination with the metal
atom, the mononuclear cationic complexes [1]PF6 to [5]PF6 exhib-
ited six distinct resonances assignable to thiazolyl ring and N@C–
CH3 protons of the ata ligand indicating formation of mononuclear
complexes. Besides these signals complexes [1]PF6 and [3]PF6 exhi-
bit a singlet for the protons of the benzene ring and protons of the
hexamethylbenzene at d 6.50 and 2.28, respectively. Complex 2 ex-
hibit a singlet at d = 2.28 for methyl protons, a septet at d = 2.82 for
the CH proton of the isopropyl group. Interestingly we observe an
unusual pattern for the diastereotopic methyl protons of the iso-
propyl group and diastereotopic CH protons of the p-cymene li-
gand showing two doublets at d = 1.26–1.18, and four doublets in
the range d = 5.90–5.68 instead of one doublet and two doublets,
respectively with reference to the starting precursor. This unusual
pattern is due to the diastereotopic methyl protons of the isopropyl
group and aromatic protons of the p-cymene ligand, since the
ruthenium atom is stereogenic due to the coordination of four dif-
ferent ligand atoms and chiral nature of metal atom [45,46,52].
Complexes [4]PF6 and [5]PF6 exhibit a singlet for the methyl
protons of the pentamethylcyclopentadienyl ligand at d 1.77 and
1.99 ppm. Complexes [6]PF6 and [7]PF6 exhibit a singlet at d 4.57
and 2.19 for the protons of cyclopentadienyl ligand and methyl
protons of pentamethylcyclopentadienyl ligands respectively.
Complex [8]PF6 exhibits a characteristic three sets of signals such
as multiplet, triplet and doublet, for the protons of the indenyl li-
gand in the range of 7.46, 4.81 and 4.71, respectively. The protons
of the triphenylphosphine ligand exhibit a multiplet at d = 7.22 to
7.55.
The distances between the ruthenium atom and centroid of
g
6-p-iPrC6H4Me ring is 1.692 Å in complex [2]PF6, whereas the
distance betwen the rhodium atom and the centroid of the g5
C5Me5 ring is 1.782 Å in complex [9]PF6. These bond distances
are comparable to those in the related complex cations [(g6
p-iPrC6H4Me)Ru(pyNp)Cl]PF6 5-C5Me5)Ir(pyNp)Cl]PF6
and [(
(PyNp=2-(2-pyridyl)-1,8-naphthyridine) (1.68 and 1.79 Å) [52].
-
-
g
The solid state molecular structures of representative com-
plexes have been presented in Figs. 1 and 2, respectively.
4. UV–Vis spectroscopy
Electronic absorption spectra of complexes [1]PF6 to [4]PF6 and
[6]PF6 and [7]PF6 were acquired in acetonitrile, at 10À5 M concen-
tration in the range 250–550 nm and spectral data are summarized
in Table 3. The spectra of these complexes are characterized by two
main features, viz., an intense ligand–localized or intra-ligand
p
? p* transition in the ultraviolet region and metal-to-ligand
charge transfer (MLCT) dp(M) ? p* (ata-ligand) bands in the visi-
ble region [53]. Since the low spin d6 configuration of the mononu-
clear complexes provides filled orbitals of proper symmetry at the
Ru(II), Rh(III) and Ir(III) centres, these can interact with low lying
p
* orbitals of the ligands. All these complexes show an intense
band in the region 310–320 nm and a low energy absorption band
in the visible region 407–425 nm. The high intensity band in UV re-
gion is assigned to inter and intra-ligand p–p* transitions [54,55],
The 31P NMR spectra of complexes [6]PF6, [7]PF6, and [8]PF6
showing down field shift compared to starting precursors viz. d
49.34, 48.54, and 54.42 ppm, respectively. This down field chemi-
cal shift of phosphorus nucleus indicates the formation of cationic
complexes.
3.2. Molecular structure presentation
The molecular structures of [(
and [(
5-C5Me5)Rh(ata*)Cl]+ (9) (ata* = hydrolysed product of
g
6-p-iPrC6H4Me)Ru(ata)Cl]+ (2)
g
ata) (N(CH2CH2SCC(CH3))N–NH2) have been established by sin-
gle-crystal X-ray analysis of their hexafluorophosphate salts. All
the cationic complexes show a typical piano-stool geometry with
the metal centre being coordinated by the arene/pentamethylcy-
clopentadienyl ligand, a terminal chloride and the chelating ata/
ata* ligand. The metal atom is in octahedral arrangement with
two cis-nitrogen atoms of the ata/ata* ligand acting as a bidentate
chelating ligand through two neighbouring thiazole and azine
nitrogen atoms. The molecular structures of complexes [2]PF6
and [9]PF6 are shown in Figs. 1 and 2, respectively, and bond
lengths and angles are presented in Table 2.
Fig. 3. UV–Vis electronic spectra of complexes in acetonitrile at 298 K.
In the mononuclear complexes [2]PF6 and [9]PF6 the metal to
nitrogen bond distance (2.087(3), and 2.097(4) Å) of the thiazole
is shorter than the corresponding azine N-metal distance
(2.104(2) and 2.136(5) Å) which are comparable to those in
Table 3
UV–Vis spectral data for selected complexes in acetonitrile at 298 K.
Sl. No.
Complex
kmax (nm)/
e
 10À5 MÀ1 cmÀ1
[(
(mes)Cl-{C5H4N-2-C(Me)@N(CHMePh)}]BF4 [48], [(
g
6-C6Me6)RuCl–(C5H4N-2-CH@N@C6H4-p-NO2)]PF6 [47], [Ru
1
2
3
4
6
7
[(g
[(g
[(g
[(g
[(g
[(g
6-p-iPrC6H4Me)Ru(ata)Cl]+
6-C6H6)Ru(ata)Cl]+
320 (0.93) 412
319(0.95) 415
319 (0.90) 420
310 (0.80) 413
320 (0.61) 407
310 (0.29) 425
g
5-C5Me5)RhCl
6-C6Me6)Ru(ata)Cl]+
5-C5Me5)Rh(ata)Cl]+
5-C5H5)Ru(ata)PPh3]+
5-C5Me5)Ru(ata)PPh3]+
(C5H4N-2-CH@N@C6H4-p-NO2)]BF4 [49]. The Rh–N bond distance
(2.097(4) and 2.136(5) Å) in [9]PF6 is slightly longer than the cor-
responding distances of ruthenium complex 2 (2.104(3) Å), while
the M–Cl [2.406(8) and 2.396(15)] bond lengths show no signifi-

2654
K.T. Prasad et al. / Polyhedron 28 (2009) 2649–2654
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Appendix A. Supplementary data
CCDC 727807 and 727808 contain the supplementary crystallo-
graphic data for [2]PF6 and [9]PF6. 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,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: de-
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