Reactivity studies of cyclopentadienyl ruthenium(II), osmium(II) and pentamethylcyclopentadienyl iridium(III) complexes towards 2-(2′-pyridyl)imidazole derivatives

Article abstract of DOI:10.1016/j.poly.2007.03.055

The reaction of [CpRu(PPh₃)₂Cl] and [CpOs(PPh₃)₂Br] with chelating 2-(2′-pyridyl)imidazole (N ∩ N) ligands and NH₄PF₆ yields cationic complexes of the type [CpM(N ∩ N)(PPh₃)]

Full text of DOI:10.1016/j.poly.2007.03.055

Polyhedron 26 (2007) 3638–3644
www.elsevier.com/locate/poly
Reactivity studies of cyclopentadienyl ruthenium(II), osmium(II)
and pentamethylcyclopentadienyl iridium(III) complexes towards
2-(20-pyridyl)imidazole derivatives
a
b
c
c
Khenglawt Pachhunga , Bruno Therrien , Kevin A. Kreisel , Glenn P.A. Yap ,
a,
*
Mohan Rao Kollipara
a
Department of Chemistry, North-Eastern Hill University, Shillong 793022, India
b
ˆ
Institut de Chimie, Universite´ de Neuchatel, Switzerland
Brown Laboratory, Department of Chemistry and Biochemistry, University of Delaware, USA
c
Received 1 March 2007; accepted 29 March 2007
Available online 12 April 2007
Abstract
The reaction of [CpRu(PPh3)2Cl] and [CpOs(PPh3)2Br] with chelating 2-(20-pyridyl)imidazole (N \ N) ligands and NH4PF6 yields
cationic complexes of the type [CpM(N \ N)(PPh3)]+ (1: M = Ru, N \ N = 2-(20-pyridyl)imidazole; 2: M = Ru, N \ N = 2-(20-pyr-
idyl)benzimidazole; 3: M = Ru, N \ N = 2-(20-pyridyl)-4,5-dimethylimidazole; 4: M = Ru, N \ N = 2-(20-pyridyl)-4,5-diphenylimidaz-
ole; 5: M = Os, N \ N = 2-(20-pyridyl)imidazole; 6: M = Os, N \ N = 2-(20-pyridyl)benzimidazole). They have been isolated and
characterized as their hexafluorophosphate salts. Similarly, in the presence of NH4PF6, [Cp Ir(l-Cl)Cl]2 reacts in dry methanol with
*
N \ N chelating ligands to afford in excellent yield [Cp Ir(N \ N)Cl]PF6 (7: N \ N = 2-(20-pyridyl)imidazole; 8: N \ N = 2-(20-pyr-
*
idyl)benzimidazole). All the compounds have been characterized by infrared and NMR spectroscopy and the molecular structure of
[1]PF6, [2]PF6 and [7]PF6 by single-crystal X-ray structure analysis.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Cyclopentadienyl; Pentamethylcyclopentadienyl; Ruthenium; Osmium; Iridium; 2-(20-Pyridyl)imidazole
1. Introduction
complex [CpOs(PPh3)2Br] chemistry have not been studied
extensively due to lower kinetic liability of the triphenyl-
phosphines compared to its ruthenium analogue [5]. Until
recently far fewer studies had been carried out on penta-
methylcyclopentadienyl rhodium(III) and iridium(III)
complexes with chelating N \ N-donor bases [6]. The
chemistry of [CpRu(PPh3)2Cl] is characterized by facile dis-
placement of either chloride or one or both triphenylphos-
phine ligands, affording cationic or neutral compounds,
respectively, depending on the solvent and reaction condi-
tions [7]. The electron rich metal center contributes to the
stabilization of unusual ligands such as vinyllidines
and allenylidines [8]. We had reported that the reactions
The chemistry of cyclopentadienyl bisphosphine ruthe-
nium complexes [CpRu(PPh3)2X] is the family of an area
of active research [1] due to their high reactivity and cata-
lytic activities [2,3]. These properties have prompted wide-
spread interest regarding both the synthetic applications
and the mechanistic features of cyclopentadienyl complexes
for a large number of transition metals. Similarly, there is
an increasing interest in the organometallic chemistry of
osmium as the nature of the differences from its lighter con-
gener ruthenium becomes more apparent [4]. However, the
of cyclopentadienyl ruthenium(II), [Cp Ru(PPh ) -
*
*
3 2
Corresponding author. Tel.: +91 364 272 2620; fax: +91 364 255 0076.
E-mail addresses: mohanrao59@hotmail.com, mohanraokollipara@
(CH3CN)]+ and [(g5-C9H7)Ru(PPh3)2(CH3CN)]+ [9] with
a variety of nitrogen based ligands.
yahoo.co.in (M.R. Kollipara).
0277-5387/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.03.055

K. Pachhunga et al. / Polyhedron 26 (2007) 3638–3644
3639
In this paper, as a part of our continuing study, we
would like to report the synthesis and characterization of
new cationic cyclopentadienyl (Cp) ruthenium(II),
evaporated at reduced pressure. Then the residue is dis-
solved in dichloromethane (5 ml), and the solution filtered
to remove ammonium chloride. The yellow solution is con-
centrated (2 ml) and by addition of an excess of hexane the
orange yellow product precipitates. The compound is
filtered and dried under vacuum to give [1]PF6.
osmium(II) and pentamethylcyclopentadienyl (Cp ) irid-
*
ium(III) complexes with chelating N \ N-donor ligands
[L1 = 2-(20-pyridyl)imidazole, L2 = 2-(20-pyridyl)benzimid-
azole, L3 = 2-(20-pyridyl)-4,5-dimethylimidazole, L4 = 2-
(20-pyridyl)-4,5-diphenylimidazole (Scheme 1). In order to
confirm the nature of bonding, the molecular structures
of [CpRu{2-(20-pyridyl)imidazole}(PPh3)]PF6 ([1]PF6),
Complex
[CpRu{2-(20-pyridyl)imidazole}(PPh3)]PF6
[1]PF6 (Yield: 63 mg, 64%). Elemental Anal. Calc. for
C31H27N3F6P2Ru: C, 51.81; H, 3.76; N, 5.85. Found: C,
51.54; H, 4.17; N, 5.44%. IR (KBr pellets, cmꢀ1): 1606
1
[CpRu{2-(20-pyridyl)benzimidazole}(PPh3)]PF6
and [Cp Ir{2-(20-pyridyl)imidazole}Cl] PF ([7]PF ) have
([2]PF6)
(mC@C), 1480, 1440 (mC@N), 857 (mPF6), H NMR (CDCl3,
d): 12.01 (s, 1H, NH); 9.04 (d, JH–H = 5.74 Hz, 1H, H6);
8. 75 (d, JH–H = 6.08 Hz, H7); 8.50 (d, JH–H = 6.02 Hz,
H8); 8.00 (d, JH–H = 5.12 Hz, 1H, H3); 7.78 (m, 15H, Ph);
7.70 (t, 1H, H4); 7.32 (t, 1H, H5); 4.68 (s, 5H, C5H5).
Complex [CpRu{2-(20-pyridyl)benzimidazole}(PPh3)]-
PF6 [2]PF6 (Yield: 65 mg, 62%). Elemental Anal. Calc.
for C35H29F6P2N3Ru: C, 54.69; H, 3.78; N, 5.47. Found:
C, 54.87; H, 4.12; N, 5.67%. IR (KBr pellets, cmꢀ1): 1613
(mC@C), 1447 (mC@N), 850 (mPF6), 1H NMR (CDCl3, d):
12.01 (s, 1H, NH); 8.94 (d, JHH = 5.42 Hz, 1H, H6); 8.07
(d, JHH = 5.80 Hz, 1H, H3); 7.98 (t, 1H, H4); 7.90 (t, 1H,
H5); 7.48 (m, 15H, Ph); 7.32 (m, 4H H7–10); 4.64 (s, 5H,
C5H5).
Complex [CpRu{2-(20-pyridyl)-4,5-dimethylimidazole}-
(PPh3)]PF6 [3]PF6 (Yield: 64 mg, 62%). Elemental Anal.
Calc. for C33H31F6P2N3Ru: C, 53.08; H, 4.16; N, 5.63.
Found: C, 53.28; H, 4.66; N, 5.77%. IR (KBr pellets,
cmꢀ1): 1604 (mC@C), 1480, 1447 (mC@N); 855 (mP–F), 1H
*
6
6
been solved by X-ray crystallography.
2. Experimental
Elemental analyses were performed on a Perkin–Elmer-
2400 CHN/O analyzer. Infrared spectra were recorded on a
Perkin–Elmer Model 983 spectrophotometer with the sam-
1
ple prepared as KBr pellets. The H NMR spectra were
recorded on a Bruker ACF-300 (300 MHz) spectrometer
in CDCl3 solvents with TMS as internal reference. All
chemicals used were of reagent grade. All reactions were
carried out in distilled and dried solvents. Ruthenium tri-
chloride, iridium trichloride and osmium tetraoxide were
purchased from Arora Matthey Ltd. and Aldrich. The 2-
(20-pyridyl)imidazole and its derivatives were prepared by
following a literature procedure [10]. 2-(20-Pyridyl)benz-
imidazole (Aldrich), pyridine-2-aldehyde (Fluka), glyoxal
(Aldrich), 2,3-butanedione (Aldrich) and benzyl (Sd Fine)
were used as received. The precursor’s complexes
NMR (CDCl3, d): 12.10 (s, 1H, NH); 8.50 (d, JH–H
=
5.74 Hz, 1H, H6); 8.18 (d, JH–H = 5.00 Hz, 1H, H3); 7.53
(m, 15H, Ph); 7.39 (t, 1H, H4); 7.28 (t, 1H, H5); 4.67 (s,
5H, C5H5); 3.21 (s, 6H, CH3).
[CpRu(PPh ) Cl], [CpOs(PPh ) Br] [11] and [Cp Ir(l-
*
3 2
3 2
Complex [CpRu{2-(20-pyridyl)-4,5-diphenylimidazole}-
(PPh3)]PF6 [4]PF6 (Yield: 70 mg, 60%). Elemental Anal.
Calc. for C43H35N3P2F6Ru: C, 59.31; H, 4.02; N, 4.83.
Found: C, 60.23; H, 4.23; N, 5.13%. IR (KBr pellets,
cmꢀ1): 1600 (mC@C), 1480, 1440 (mC@N), 850 (mP–F), 1H
NMR (CDCl3, d): 8.50 (d, JH–H = 5.0 Hz, 1H, H6); 8.27
(d, JH–H = 5.73 Hz, 1H, H3), 7.92 (m, 25H, Ph); 7.60 (t,
1H, H4); 7.37 (t, 1H, H5); 4.62 (s, 5H, C5H5).
Cl)Cl]2 [12] were prepared by following the reported litera-
ture methods.
2.1. Synthesis of [CpRu(N \ N)(PPh3)]PF6
The following general procedure was used for the prep-
aration of complexes [1]PF6 to [4]PF6.
2.1.1. Preparation of [1]PF6
2.2. Synthesis of [CpM(N \ N)(PPh3)]PF6
A mixture of [CpRu(PPh3)2Cl] (0.1 g, 0.14 mmols), 2-
(20-pyridyl)imidazole (0.04 g, 0.28 mmols) and NH4PF6
(0.046 g, 0.28 mmols) was refluxed in dry methanol
(20 ml) under a nitrogen atmosphere for 6 h. The yellow
suspension turns to a light yellow color. The solvent is
These complexes were prepared by the same method
given in Section 2.1 using of [CpOs(PPh3)2(CH3CN)]PF6
instead of [CpRu(PPh3)2Cl].
6
3
6
6
6
3
5
4
5
4
5
4
5
4
N
N
N
N
N
N
N
N
3
3
7
9
Ph
7
HN
HN
HN
HN
8
8
Ph
10
L1
L2
L3
L4
Scheme 1. Ligands and numbering scheme used in this study.

3640
K. Pachhunga et al. / Polyhedron 26 (2007) 3638–3644
Complex
[CpOs{2-(20-pyridyl)imidazole}(PPh3)]PF6
The intensity data were corrected for Lorenz and polariza-
tion effects. The structures were solved by direct methods
using the program SHELXS-97 [13]. Refinement and all fur-
ther calculations were carried out using SHELXL-97 [14].
The H-atoms were included in calculated positions and
treated as riding atoms using the SHELXL default parame-
ters. The non-H-atoms were refined anisotropically, using
weighted full-matrix least-square on F2. In [2]PF6 Æ H2O,
the –C5H4NC3N2H– fragment of the 2-(20-pyridyl)benz-
imidazole was found to be disordered over two positions
and the partial occupancy factor was refined at 76:24.
Crystallographic details are summarized in Table 1. Figs.
1, 2 and 4 are drawn with ORTEP32 [15] while Figs. 3 and
5 are drawn with MERCURY [16].
[5]PF6 (Yield: 48 mg, 57%). Elemental Anal. Calc. for
C31H27N3P2F6Os: C, 46.09; H, 3.35; N, 5.21. Found: C,
46.36; H, 4.03; N, 5.65%. IR (KBr pellets, cmꢀ1): 1600
1
(mC@C), 1480, 1440 (s, mC@N), 885 (s, br, mPF6) H NMR
(CDCl3, d): 8.95 (d, JH–H = 5.7 Hz, 1H, H6); 8.78 (d,
JH–H = 6.05 Hz, 1H, H3); 8.63 (d, JH–H = 6.12 Hz, 1H,
H7); 8.59 (d, JH–H = 5.52 Hz, 1H, H8); 7.89 (m, 15H, Ph);
7.75 (t, 1H, H4); 7.48 (t, 1H, H5); 4.59 (s, 5H, C5H5).
Complex [CpOs{2-(20-pyridyl)benzimidazole}(PPh3)]-
PF6 [6]PF6 (Yield: 46 mg, 52%). Elemental Anal. Calc.
for C35H29N3P2F6Os: C, 49.01; H, 3.38; N, 4.90. Found:
C, 49.15; H, 3.56; N, 5.15%. IR (KBr pellets, cmꢀ1): 1613
1
(mC@C), 1447 (mC@N), 885 (s, br, mPF6). H (NMR, CDCl3,
d): 8.50 (d, JH–H = 5.2 Hz, 1H, H6); 8.10 (d, JH–H
=
5.2 Hz, 1H, H3); 7.93 (m, 15H, Ph); 7.78 (t, 1H, H4); 7.56
(t, 1H, H5); 7.37 (m, 4H H7–10); 4.65 (s, 5H, C5H5).
3. Results and discussion
The reactions in dry methanol of [CpRu(PPh3)2Cl] and
[CpOs(PPh3)2Br] (Cp = g5-C5H5) with an excess of chelat-
ing N \ N-ligands and NH4PF6 result, under refluxing con-
ditions, in the dissociation of one triphenylphosphine and
the halide ligands to yield the monocationic complexes
[CpM(N \ N)(PPh3)]+ (1: M = Ru, N \ N = 2-(20-pyridyl)
imidazole; 2: M = Ru, N \ N = 2-(20-pyridyl)benzimid-
azole; 3: M = Ru, N \ N = 2-(20-pyridyl)-4,5-dimethylimi-
dazole; 4: M = Ru, N \ N = 2-(20-pyridyl)-4,5-diphenyl-
imidazole; 5: M = Os, N \ N = 2-(20-pyridyl)imidazole; 6:
2.3. Synthesis of [Cp Ir(N \ N)Cl]PF
*
6
These complexes were prepared by the same method
given in Section 2.1 using 0.5 equiv. of [Cp Ir(l-Cl)Cl]
*
2
instead of 1 equiv. of [CpM(PPh3)2Cl].
Complex [Cp Ir{2-(20-pyridyl)imidazole}Cl]PF [7]PF
*
6
6
(Yield: 52 mg, 64%). Elemental Anal. Calc. for
C18H22ClN3F6PIr: C, 33.13; H, 3.37; N, 6.44. Found: C,
32.87; H, 3.88; N, 6.23%. IR (KBr pellets, cmꢀ1): 1600
(mC@C), 1460–1327 (mC@N), 850 (mP–F), H NMR (CDCl3,
d): 8.94 (d, JH–H = 6.4 Hz, 1H, H6); 8.50 (d, JH–H
1
M = Os,
N \ N = 2-(20-pyridyl)benzimidazole),
see
=
Scheme 2. The compounds are isolated and characterized
as hexafluorophosphate salts.
6.12 Hz, 1H, H3); 8.00 (d, JH–H = 6.03 Hz, 1H, H7); 7.90
(d, JH–H = 5.23 Hz, 1H, H8); 7.73 (t, 1H, H4); 7.43 (t,
1H, H5); 1.86 (s, 15H, C5Me5).
In the case of the reaction of the dinuclear iridium(III)
complex [Cp Ir(l-Cl)Cl] (Cp = g5-C Me ) with 2 equiv.
*
2
5
5
Complex
[Cp Ir{2-(20-pyridyl)benzimidazole}Cl]PF
of chelating N \ N-ligands in the presence of NH4PF6,
*
6
[8]PF6 (Yield: 54 mg, 62%). Elemental Anal. Calc. for
C22H24ClN3F6PIr: C, 37.61; H, 3.42; N, 5.98. Found: C,
37.52; H, 3.87; N, 6.15%. IR (KBr pellets, cmꢀ1): 1600
cleavage of the chloro-bridge followed by dissociation of
one chloride ligand, affords the complexes [Cp Ir{2-(20-
*
pyridyl)imidazole}Cl]PF6([7]PF6) and [Cp Ir{2-(20-pyr-
*
1
(mC@C), 1474–1407 (mC@N), 850 (mP–F), H NMR (CDCl3,
idyl)benzimidazole}Cl]PF6 ([8]PF6), see Scheme 3.
d): 8.97 (d, JH–H = 5.63 Hz, 1H, H6); 8.90 (d, JH–H
5.29 Hz, 1H, H3); 7.85 (t, 1H, H4); 7.43 (t, 1H, H5); 7.24
(m, 4H, H7–10); 1.82 (s, 15H, C5Me5).
=
The complexes 1–8 are pale yellow to orange reddish
colored. They are highly soluble in polar solvents such as
chloroform, acetone, methanol, dichloromethane etc., but
insoluble in non-polar solvents such as hexane, pentane
1
2.4. Single-crystal X-ray structures analyses
etc., C, H, N analyses, IR, H NMR spectroscopic data
were given in the experimental section, which supported
the formation of these complexes. The X-ray structures
of representative complexes 1, 2 and 7 were determined
to confirm the structure of the complexes (1–8). The infra-
red spectra of complexes 1–6 exhibited very strong bands at
1613–1600 cmꢀ1 and 1480–1440 cmꢀ1corresponding to
phenyl groups of triphenylphosphine and N-bases, while
in complexes 7 and 8 prominent peaks were observed at
1600 cmꢀ1 and 1474–1327 cmꢀ1. The counter ion (PF6)
exhibit a strong band around 845 cmꢀ1 for mPF6 group.
The protons’ corresponding to the cyclopentadienyl
ligands appear in the region of 4.6–4.7 ppm while the tri-
phenylphosphine peaks are observed as a multiplet in the
aromatic region between 7 and 8 ppm. The chemical shifts
of cyclopentadienyl groups appear downfield as compared
Crystal suitable for X-ray diffraction study for
compound [1]PF6, [2]PF6 and [7]PF6 were grown by slow
diffusion of diethylether into dichloromethane solution of
complexes [1]PF6, [2]PF6 and [7]PF6, respectively. The
orange reddish crystals of compound [1]PF6 and [7]PF6
were mounted on a Stoe Image Plate Diffraction system
equipped with a / circle goniometer, using Mo Ka graphite
˚
monochromated radiation (k = 0.71073 A) with / range
˚
0–200ꢁ, increment of 1.2ꢁ, Dmax–Dmin = 12.45–0.81 A.
Whereas crystal of [2]PF6 was mounted on a Bruker Apex
CCD diffractometer in a full reciprocal sphere equipped
with a CCD detector, X-ray intensity data were collected
with Mo Ka graphite monochromated radiation at
120(2) K, with 0.3ꢁx scan mode and 10 second per frame.

K. Pachhunga et al. / Polyhedron 26 (2007) 3638–3644
3641
Table 1
Crystallographic and structure refinement parameters for complexes [1]PF6, [2]PF6 Æ H2O and [7]PF6
[1]PF6
[2]PF6 Æ H2O
[7]PF6
Chemical formula
Formula weight
Crystal system
C31H27F6N3P2Ru
718.57
C35H31F6N3OP2Ru
786.64
triclinic
C18H22ClF6N3PIr
653.01
triclinic
monoclinic
P21/c (no. 14)
orange block
0.32 · 0.20 · 0.20
13.552(3)
14.582(3)
17.920(6)
90
126.31(2)
90
2853.6(13)
4
ꢀ
ꢀ
Space group
P1 (no. 2)
P1 (no. 2)
Crystal colour and shape
Crystal size
red block
0.28 · 0.23 · 0.18
10.379(4)
11.285(4)
15.601(6)
108.602(5)
91.211(5)
104.887(5)
1663.0(10)
2
red block
0.35 · 0.26 · 0.21
8.0428(9)
11.4031(14)
11.7074(13)
93.585(14)
96.862(14)
98.154(14)
1051.8(2)
2
˚
a (A)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
T (K)
173(2)
1.673
0.729
120(2)
1.571
0.635
173(2)
2.062
6.613
Dc (g cmꢀ3
)
l (mmꢀ1
)
Scan range (ꢁ)
1.86 < h < 29.24
6277
4388
1.98 < h < 28.23
7437
6379
2.58 < h < 26.03
3821
3518
Unique reflections
Reflections used [I > 2r(I)]
Rint
Final R indices [I > 2r(I)]a
R indices (all data)
Goodness-of-fit
0.0588
0.0261
0.0501
0.0387, wR2 0.0860
0.0605, wR2 0.0926
0.910
0.0457, wR2 0.1073
0.0543, wR2 0.1131
1.016
0.754, ꢀ0.530
0.0323, wR2 0.0782
0.0373, wR2 0.0884
1.112
1.775, ꢀ1.850
ꢀ3
˚
Maximum and minimum Dq (e A
)
0.763, ꢀ1.038
P
P
P
a
2
Structures were refined on Fo2: wR2 = [ [w(Fo ꢀ Fc2)2]/ w(Fo2)2]1/2, where wꢀ1 = [ (Fo2) + (aP)2 + b] and P = [max(Fo2, 0) + 2Fc2]/3.
Fig. 2. ORTEP diagram with labelling scheme for [CpRu{2-(20-pyr-
idyl)benzimidazole}(PPh3)]+ ([2]PF6 Æ H2O) at 50% probability level, H-
atoms, PF6 anion and water molecule omitted for clarity.
Fig. 1. ORTEP diagram with labelling scheme for [CpRu{2-(20-pyr-
idyl)imidazole}(PPh3)]+ ([1]PF6), at 50% probability level, H-atoms and
PF6 anion omitted for clarity.
and H5) of the N \ N-donor ligands, a singlet at
to the precursor complexes (4.43–4.31 ppm). The downfield
shift position of the cyclopentadienyl protons in complexes
1–6, which might results from the change in electron den-
sity on the metal center due to chelation of the nitrogen
base ligands through the nitrogen atoms of the 2-(20-pyr-
idyl)imidazole derivatives ligands. The H NMR spectra
of complexes 1–6 also showed two pseudo-triplets in the
range of 7.85–6.32 ppm due to the pyridine protons (H4
12.01 ppm corresponds to the NH protons of the ligands.
The spectra of the Cp complexes 7 and 8 showed reso-
*
nance for the methyl protons of the Cp ligand as singlets
*
at 1.86 ppm and 1.82 ppm, respectively.
Molecular structure of the representative hexafluoro-
phosphates salts [1]PF6, [2]PF6 and [7]PF6 are presented
in Figs. 1, 2 and 4, respectively. Selected bond lengths
and angles are recorded in Table 2. The molecular
1

3642
K. Pachhunga et al. / Polyhedron 26 (2007) 3638–3644
Fig. 3. Hydrogen-bonded system observed in [2]PF6 Æ H2O.
Fig. 4. ORTEP diagram with labelling scheme for [Cp Ir{2-(20-pyr-
*
idyl)imidazole}Cl]+ ([7]PF6) at 50% probability level, H-atoms and PF6
+
(PF6)
anion omitted for clarity.
R
N N
M
M
N
X
Ph3P
PPh3
NH4PF6
R
Table 2
N
Ph3P
N
Selected bond lengths and angles for complexes [1]PF6, [2]PF6 Æ H2O and
[7]PF6
H
M = Ru, X = Cl
M = Os, X = Br
1
2
7
˚
Distances (A)
1-6
Ru–P
Ir–Cl
2.316(1)
2.325(1)
2.4183(14)
2.106(5)
2.080(5)
2.178(6)
2.149(5)
2.158(6)
2.144(6)
2.164(6)
Scheme 2.
M–N1
M–N3
M–C1
M–C2
M–C3
M–C4
M–C5
2.113(3)
2.093(3)
2.208(4)
2.177(4)
2.150(4)
2.180(4)
2.215(4)
2.1169(17)
2.0939(15)
2.109(4)
2.157(3)
2.226(3)
2.219(3)
2.146(4)
+
(PF6)
R
Ir
Ir
Cl
N
N
N
Cl
Cl
0.5
R
Angles (ꢁ)
N1–M–N3
N1–M–P1
N3–M–P1
N1–Ir–Cl1
N3–Ir–Cl1
Cl
NH4PF6
N
Cl
75.98(10)
90.12(8)
87.66(8)
76.08(17)
92.15(6)
89.02(6)
76.48(19)
N
H
Ir
84.60(14)
86.95(14)
7-8
Scheme 3.
˚
2 [2.325(1) A] with reported values [9d,19]. The N(1)–
Ru–N(3) bond angle in complexes 1 [76.0(1)ꢁ] and 2
[76.1(2)ꢁ] are similar to those of compounds [(g6-p-PriC6H4-
Me)RuCl(2,3-bis(2-pyridyl)pyrazine)]+ [N–Ru–N = 76.5
(2)ꢁ] [17] and [(g6-p-PriC6H4Me)RuCl(2,3-bis(a-pyr-
idyl)quinoxaline)]+ [N–Ru–N = 76.2(2)ꢁ] [18b]. The angles
between the least-square planes of g5-C5H5 and that of
the N \ N-ligand are 57.8(2)ꢁ in 1 and 55.3(2)ꢁ in 2.
structures of [CpRu{2-(20-pyridyl)imidazole}(PPh3)]+ (1)
and [CpRu{2-(20-pyridyl)benzimidazole}(PPh3)]+ (2) have
been established by single-crystal X-ray structure analysis
of [1]PF6 and [2]PF6ꢁ ꢁ ꢁH2O, respectively. Both complexes
show typical piano-stool geometry with the metal center
coordinated by a cyclopentadienyl ligand, a PPh3 ligand
and a chelating N \ N-ligand, see Figs. 1 and 2.
˚
The Ru–N bond distances [2.113(3) and 2.093(3) A in
Complex [2]PF6 crystallizes with one molecule of water
per asymmetric unit, which forms a hydrogen-bonded net-
work with two hexafluorophosphate anions and the N–H
group of the N \ N ligand, see Fig. 3. The N–O and O–
F distances of the hydrogen bonds are, respectively,
1; 2.117(2) and 2.094(2) in 2] are comparable to those
in
BF4[17] and [(g
[(g6-p-PriC6H4Me)RuCl(2,3-bis(2-pyridyl)pyrazine)]-
6
-C6H6)RuCl(2-(1-imidazole-2-yl)pyri-
dine)]PF6 [18a]. Accordingly, there is no significant
0
˚
2.820(3) A for the N–H of the 2-(2 -pyridyl)benzimidazole
˚
difference in the Ru–P bond length in 1 [2.316(1) A] or

K. Pachhunga et al. / Polyhedron 26 (2007) 3638–3644
3643
Fig. 5. Dimeric structure of [7]PF6 showing the intermolecular NHꢁ ꢁ ꢁCl hydrogen contacts and p–p interacting system.
˚
ligand and H2O, and 2.941(4) and 2.907(4) A between the
hexafluorophosphate anions and the water molecule. The
N–Hꢁ ꢁ ꢁO angle is 167.1ꢁ while the O–Hꢁ ꢁ ꢁF angles are
178ꢁ and 153ꢁ, respectively.
Acknowledgements
Mohan Rao Kollipara greatly acknowledges the Depart-
ment of Science and Technology, New Delhi (Sanction Or-
der No. SR/S1/IC-11/2004) for financial support. We
The molecular structure of [Cp Ir{2-(20-pyridyl)imidaz-
*
ole}Cl]+ (7) has been established by single-crystal X-ray
structure analysis of [7]PF6 (see Fig. 4). The complex shows
a typical piano-stool geometry with the metal center
coordinated by the pentamethylcyclopentadienyl ligand, a
terminal chloride and the 2-(20-pyridyl)imidazole ligand.
also thank Mıriam Perez, Servei RMN Universitat Auto-
noma de Barcelona 08193 Bellaterra, Barcelona for provid-
ing the NMR facility.
´
´
`
Appendix A. Supplementary material
˚
The Ir–N bond distances [2.106(5) and 2.080(5) A] are
slightly shorter to those in [1]PF6 and [2]PF6. The average
distance between the metal atom and the carbon atoms of
CCDC 637370, 637371 and 637372 contain the supple-
mentary crystallographic data for [1]PF6, [2]PF6 Æ H2O
and [7]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: deposit@ccdc.cam.ac.uk. Supplementary
data associated with this article can be found, in the online
version, at doi:10.1016/j.poly.2007.03.055.
5
˚
the g -C5Me5 ring is 2.16 A. This average bond length is
comparable to that in the related g5-C5Me5 iridium
complex
mine)] [2.17 A] [20]. The Ir–Cl bond length is 2.4183(14)
A in 7, which is slightly longer to the reported iridium com-
[(g5-C5Me5)IrCl((S)-1-phenylethylsalicylaldii-
˚
˚
plex
[(g5-C5Me5)IrCl((S)-1-phenylethylsalicylaldiimine)]
˚
[2.4017(16) A] [20].
In the crystal packing of [7]PF6, two molecules of 7 form
a dimer through N–Hꢁ ꢁ ꢁCl contacts and p-stacking interac-
References
˚
tions, see Fig. 5. The N–Cl separation is 3.254(5) A with an
[1] (a) W. Baratta, E. Herdtweck, W.A. Hermann, P. Rigo, J. Schwarz,
Organometallics 21 (2002) 2101;
N–Hꢁ ꢁ ꢁCl angle of 162.1ꢁ. The distance observed between
the p-stacking interacting systems (centroidꢁ ꢁ ꢁcentroid
(b) M.A. Bennett, K. Khan, E. Wenger, in: G. Wilkinson, F.G.A.
Stone, E.W. Abel (Eds.), Comprehensive Organometallic Chemistry
II, second ed., vol. 7, Elsevier, Oxford, 1995, Chapter 8 and references
cited therein.
˚
3.76 A) is in good agreement with the theoretical value
calculated for this stacking mode [21]. The distance
observed between the two iridium centers of the dimer
˚
[2] (a) S.G. Davies, J.P. McNally, J. Smallridge, Adv. Organomet. Chem.
30 (1991) 1;
is 7.841(1) A and excludes any possible metal–metal
interactions.
(b) B.M. Trost, J.A. Marting, R.J. Kulawiec, A.F. Indolese, J. Am.
Chem. Soc. 115 (1993) 10402;
(c) P. Pertici, V. Ballantini, P. Salvadori, M.A. Bennett, Organomet-
allics 14 (1995) 2565;
4. Conclusions
(d) D.L. Davies, J. Fawcett, R. Krafczyk, D.R. Russell, J. Organo-
met. Chem. 545–546 (1997) 581.
The present study describes the synthesis of eight
[3] (a) B.M. Trost, M.U. Frederiksen, M.T. Rudd, Angew. Chem., Int.
Ed. Eng. 44 (2005) 6630, and references cited therein;
(b) W. Baratta, A.D. Zotto, P. Rigo, Chem. Commun. (1997) 2163;
(c) A.D. Zotto, W. Baratta, G. Verardo, P. Rigo, Eur. J. Org. Chem.
(2000) 2795.
new CpRu, CpOs and Cp Ir complexes containing 2-
*
(20-pyridyl)imidazole ligands. Representative complexes
have been characterized by single X-ray study. In the
crystal packing of [7]PF6, two molecules of 7 form a
dimer through N–Hꢁ ꢁ ꢁCl contacts and p-stacking
interactions.
´
´
[4] M.A. Esteruelas, E.G. Puebla, A.M. Lopez, E. Onate, J.I. Tolosa,
Organometallics 19 (2000) 275.

3644
K. Pachhunga et al. / Polyhedron 26 (2007) 3638–3644
[5] (a) R. Lalrempuia, H. Yennawar, Y.A. Mozharivskyj, K. Mohan
Rao, J. Organomet. Chem. 689 (2004) 539;
(c) K. Sarjit Singh, P.J. Carroll, K. Mohan Rao, Polyhedron 24
(2005) 391;
(b) T. Wilczewski, J. Organomet. Chem. 317 (1986) 307;
(c) T. Wilczewski, J. Organomet. Chem. 297 (1985) 331;
(d) M.I. Bruce, G.A. Koutsantonis, M.J. Liddel, B.K. Nicholson, J.
Organomet. Chem. 320 (1987) 217, and references cited therein.
[6] (a) P. Govindaswamy, K. Mohan Rao, J. Coord. Chem. 59 (2006)
663;
(d) K. Sarjit Singh, Y.A. Mozharivskyj, C. Thone, K. Mohan Rao, J.
Organomet. Chem. 690 (2005) 3720.
[10] B. Chiswell, F. Lions, B.S. Morris, Inorg. Chem. 31 (1964) 110.
[11] (a) M.I. Bruce, N.J. Windsor, Aust. J. Chem. 30 (1977) 1601;
(b) M.I. Bruce, P.J. Low, B.W. Skelton, E.R.T. Tiekink, A. Werth,
A.H. White, Aust. J. Chem. 48 (1995) 1887.
(b) P. Govindaswamy, Y.A. Mozharivskyj, K. Mohan Rao, Polyhe-
dron 24 (2005) 1710;
[12] (a) J.W. Kang, K. Moseley, P.M. Maitlis, J. Am. Chem. Soc. 91
(1969) 5970;
(c) H. Aneetha, P.S. Zacharias, B. Srinivas, G.H. Lee, Y. Wang,
Polyhedron 18 (1999) 299.
[7] (a) T. Blackmore, M.I. Bruce, F.G.A. Stone, J. Chem. Soc. A (1971)
2376;
(b) C. White, A. Yates, P.M. Maitlis, Inorg. Synth. 29 (1992) 228.
[13] M. Sheldrick, Acta Crystallogr., Sect. A 46 (1990) 467.
[14] M. Sheldrick, SHELXL-97, University of Go¨ttingen, Go¨ttingen, Ger-
many, 1999.
(b) G.S. Ashby, M.I. Bruce, I.B. Tomkins, R.C. Wallis, Aust. J.
Chem. 32 (1979) 1003;
(c) S.G. Davies, S.J. Simpson, H. Felkin, T. Fillebeen-Khan,
Organometallics 2 (1983) 539;
(d) S.G. Davies, S.J. Simpson, H. Felkin, T. Fillebeen-Khan, F.
Tadjand, O. Watts, J. Chem. Soc., Chem. Commun. (1981) 341;
(e) M.I. Bruce, S.F. Wong, B.W. Skelton, A.H. White, J. Chem. Soc.,
Dalton Trans. (1981) 1398.
[15] L.J. Farrugia, J. Appl. Cryst. 30 (1997) 565.
[16] I.J. Bruno, J.C. Cole, P.R. Edgington, M. Kessler, C.F. Macrae, P. Mc
Cabe, J. Pearson, R. Taylor, Acta Crystallogr., Sect. B 58 (2002) 389.
[17] A. Singh, N. Singh, D.S. Pandey, J. Organomet. Chem. 642 (2002) 48.
[18] (a) H. Mishra, R. Mukherjee, J. Organomet. Chem 691 (2006)
3545;
(b) R. Lalrempuia, K. Mohan Rao, Polyhedron 22 (2003) 3155.
[19] P. Govindaswamy, C. Sinha, K. Mohan Rao, J. Organomet. Chem.
690 (2005) 3465.
[20] H. Brunner, A. Ko¨llnberger, T. Burgemeister, M. Zabel, Polyhedron
19 (2000) 1519.
[21] S. Tsuzuki, K. Honda, T. Uchimura, M. Mikami, K. Tanabe, J. Am.
Chem. Soc. 124 (2002) 104.
[8] (a) J.P. Selegue, Organometallics 1 (1982) 217;
(b) J.P. Selegue, J. Am. Chem. Soc. 105 (1983) 5921.
[9] (a) R. Lalrempuia, P. Govindaswamy, Y.A. Mozharivskyj, K. Mohan
Rao, Polyhedron 23 (2004) 1069;
(b) K. Mohan Rao, E.K. Rymmai, Polyhedron 22 (2003) 307;