Synthesis, characterization and photophysical study of a series of neutral isocyano rhodium(I) complexes with pyridylindolide ligands

Article abstract of DOI:10.1016/j.jorganchem.2011.06.032

Pyridylindole ligand and its chloro substituted derivatives have been synthesized and incorporated into the square planar bis(phenylisocyano) rhodium(I) complexes to give a series of neutral rhodium(I) complexes with general formula of [Rh(X-pyind)(CNR)

Full text of DOI:10.1016/j.jorganchem.2011.06.032

Journal of Organometallic Chemistry 696 (2011) 3223e3230
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis, characterization and photophysical study of a series of neutral isocyano
rhodium(I) complexes with pyridylindolide ligands
*
Wing-Kin Chu, Larry Tso-Lun Lo, Shek-Man Yiu, Chi-Chiu Ko
Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Pyridylindole ligand and its chloro substituted derivatives have been synthesized and incorporated into
the square planar bis(phenylisocyano) rhodium(I) complexes to give a series of neutral rhodium(I)
complexes with general formula of [Rh(X-pyind)(CNR)2] (R ¼ 2,6-(CH3)2-4-BrC6H2, 2,4-Cl2-6-(CH3O)
C6H2, 2,4,6-Br3C6H2, 2,4,6-Cl3C6H2; L ¼ 2-(20-pyridyl)indole, 5-chloro-2-(20-pyridyl)indole, 4,6-dichloro-
Received 30 March 2011
Received in revised form
22 June 2011
Accepted 28 June 2011
2-(20-pyridyl)indole). The structures of two complex precursors [Rh(cod)(Cl-pyind)] and [Rh(cod)(Cl2
-
pyind)], and the target complex [Rh(pyind)(CNC6H2-2,4-Cl2-6-(OCH3))2] were determined by X-ray
crystallography. The UVevis absorption properties of these complexes and their responses towards the
change of temperature were also investigated.
Keywords:
Rhodium
Isocyanide
Pyridylindole
Aggregation
Thermochromism
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
such as substituted pyridylindolides (X-pyind) as the alternative to
the cyclometalating NeC ligands. As an extension of our previous
Cyclometalated transition metal complexes, such as those of
phenylpyridine complexes, have attracted much attention in recent
years as they are potentially useful in the development of the
optical sensors and electroluminescent devices such as organic
light-emitting diode (OLED) and light-emitting electrochemical
cells (LEC) [1e5]. The enhanced luminescent behavior of these
cyclometalated complexes is attributed to the strong ligand-field
work in the development of tunable thermochromic bis(phenyli-
socyano) rhodium(I) diimine complexes with interesting thermally
mediated aggregation [22], herein we report the synthesis and
UVevis absorption properties of a new series of neutral square
planar bis(phenylisocyano) rhodium(I) complexes with different
anionic cyclometalated pyridylindolide ligands. The thermo-
chromism of these complexes have also been described.
(LF) splitting resulting from the strong anionic
s-donating
ligating atom, which raises common deactivating d-d LF state. On
the other hand, the occurrence of close-lying, ligand-centered
2. Result and discussion
pep* electronic transitions can allow facile tuning of emission
2.1. Synthesis and characterization
wavelength across the whole visible spectrum. However, the study
of these transition metal complex systems with cyclometalating
ligands [6e8] have been mainly confined to metal centers, such as
Ru(II) [9e11], Os(II) [12e14], Ir(III) [15e18] and Pt(II) [19e21], that
are capable of undergoing cyclometalation as it requires the
deprotonation of a CeH group. To retain the advantages of the
cyclometalating ligands and to develop new classes of metal
complexes with metal centers that are difficult to undergo cyclo-
Using the method developed by Ugi et al. [23e26], all 2,4,6-
trisubstituted phenylisocyanide ligands were synthesized by the
dehydration of the corresponding N-phenyl formamide using
phosphoryl chloride in the presence of triethylamine. All
substituted pyridylindole ligands (X-pyind: pyind, Cl-pyind,
Cl2pyind) were prepared by the polyphosphoric acid (PPA) cata-
lyzed Fischer indole synthesis from the corresponding substituted
phenylhydrazones of the 2-acetylpyridine, which were freshly
prepared from the condensation reactions between the substituted
phenylhydrazium hydrochlorides and 2-acetylpyridine [27e30].
Reactions of [Rh(cod)Cl]2 with the corresponding pyridylindole
ligands in the presence of triethylamine in CH2Cl2 at room
temperature gave the rhodium(I) complex precursors [Rh(cod)
metalation, we propose to use other strong
s-donating and p-
accepting bidentate anionic ligands with more acidic N-H proton
* Corresponding author. Tel.: þ852 3442 6958; fax: þ852 3442 0522.
E-mail address: vinccko@cityu.edu.hk (C.-C. Ko).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.06.032

3224
W.-K. Chu et al. / Journal of Organometallic Chemistry 696 (2011) 3223e3230
(X-pyind)]. With the complex precursors, the bidentate 1,5-
cyclooctadiene (cod) ligand could be readily replaced by
substituted phenylisocyanide via the ligand substitution reactions
with two mole equivalents of isocyanide ligands in THF solution at
room temperature to afford the target complexes 1e10 [22,31,35].
After recrystallization from the slow diffusion of diethylether vapor
into the concentrated dichloromethane or acetone solution of the
complexes, analytically pure complexes isolated as yellow to
yellowish green crystalline solids were obtained. The synthetic
routes for the substituted pyridylindole ligands and the target
complexes are summarized in Scheme 1.
unit. Perspective drawings of complexes [Rh(cod)(Cl-pyind)],
[Rh(cod)(Cl2pyind)] and 1 are depicted in Fig. 1. The structure
determination data are collected in Table 1 and selected bond
lengths and angles are summarized in Table 2. In these structures,
the rhodium metal centers adopted distorted square planar
geometry. The bite angles of the pyridylindolide ligands in these
complexes are in the range of 78e80ꢁ, which are much smaller than
the ideal angle 90ꢁ in a regular square planar geometry. The devi-
ation from the ideal angle of 90ꢁ is a result of steric requirement of
the chelating pyridylindolide ligand, which is typically observed in
related cyclometalated transition metal complexes [1e5]. The
noticeable shorter RheN(indole) bond distance than the
RheN(pyridine) bond (averaged distance of 2.060 Å vs. 2.104 Å) is
attributed to the stronger Coulombic interaction between the
rhodium(I) cationic metal center and the anionic N-donor atoms
and is commonly observed in other metal complexes with related
ligands [32e36]. The shortest intermolecular RheRh distances in
these complexes are in the range of 6.02e8.10 Å, which are much
longer than typical RheRh distances (3.2e3.9 Å) in stacked Rh(I)
complexes [22]. In the crystal structure of 1, the rhodium metal
center adopted a square planar geometry with the phenyl ring of
the non-coplanar isocyanide ligand, which is cis- to the indolide
moiety, tilted by 75ꢁ relative to the plane of the complexes. The
highly tilted phenyl ring is attributed to the steric hindrance of
phenyl moiety of the indole ring and the adjacent phenylisocyanide
ligand. The RheC and ChN bond lengths in complex 1 are in the
range of 1.858e1.881 Å and 1.158e1.164 Å, respectively, similar to
those reported in other related rhodium isocyanide complexes [37].
The deviations of the linearity of the isocyanide ligands in 1, as
reflected from the ChNeC(phenyl) bond angles of 167.4ꢁ and
All substituted pyridylindole ligands and their rhodium
complexes 1e10 were characterized by elemental analyses, IR
spectroscopy, 1H NMR spectroscopy and positive FAB mass spec-
trometry. The crystal structures of two complex precursors,
[Rh(cod)(Cl-pyind)] and [Rh(cod)(Cl2pyind)], and 1 were also
determined by X-ray crystallography. Upon coordination of the
substituted pyridylindole ligands into rhodium complexes, most of
the 1H NMR signals of the ligands are upfield shifted compared to
those of the free ligands and the corresponding indole NH NMR
signal is not observed. This observation is in line with the increased
electron density in the deprotonated anionic indolide moiety. The
target complexes 1e10 show two strong ChN stretches in the
range of 2000e2130 cmꢀ1
, consistent with cis- isocyanide
arrangement in a square planar geometry. The lower stretching
frequency of the ChN stretches in these complexes compare to that
of the free ligands can be attributed to a
p back-bonding interaction
between rhodium(I) metal center and isocyanide ligands through
which ChN bond of the isocyanide ligand is weaken due to the
back-donation of electron density from the metal center to the anti-
bonding
p* orbital of the isocyanide ligands. The observation of the
174.3ꢁ for two different isocyanide ligands, are the results of the
p-
well-separated ChN stretches with considerable different
stretching frequencies is consistent with the significant difference
in the electronic natures of the trans- neutral pyridine and anionic
indolide moieties. This is in accordance with the longer ChN
distance and more bending of ChNeC in the isocyanide ligand
trans- to the indolide moiety in the crystal structure of 1.
back bonding interaction between the isocyanide ligands and the
rhodium metal center [37e41]. The more bending observed for the
isocyanide ligand trans- to the indolide moiety is suggestive of
a better
stronger
p
s
-back bonding interaction. This is consistent with the
-donating and weaker -accepting abilities of the
p
anionic indolide moiety compared to those of the pyridine moiety.
2.2. X-ray crystal structure determination
2.3. Electronic absorption spectroscopy
Single crystals of complexes [Rh(cod)(Cl-pyind)], [Rh(cod)(Cl2
pyind)] and 1 were obtained by slow diffusion of diethylether
The electronic absorption spectra of 1e10 in acetone show very
intense absorption bands, with molar extinction coefficients in the
order of 105 dm3 molꢀ1 cmꢀ1 in the UV region of 330e350 nm and
moderately intense absorptions in the visible region of
380e480 nm (Table 3). With reference to the previous
-
vapor into
a concentrated dichloromethane solution of the
complexes. For the structure of [Rh(cod)(Cl-pyind)], there are two
independent formula units in one crystallographic asymmetric
Scheme 1. Synthetic routes for substituted pyridylindole ligands and their isocyano rhodium(I) complexes

W.-K. Chu et al. / Journal of Organometallic Chemistry 696 (2011) 3223e3230
3225
spectroscopic studies of the free isocyanide ligands and their
transition metal complexes, these absorptions were tentatively
electron withdrawing substituents (Cl2pyind > Cl-pyind > pyind)
as reflected by the order of labs: 9 (403, 460 nm) < 5 (417,
464 nm) < 2 (428, 478 nm) and 10 (398, 456 nm) < 6 (409,
461 nm) < 3 (415, 465 nm) (Fig. 2b). This energy trend can be
assigned as spin allowed intraligand (IL)
p / p* transition of the
isocyanide and pyridylindolide moieties. The two lowest energy
absorptions at 380e430 nm and 440e480 nm are ascribed to the
spin allowed and spin forbidden metal-to-ligand charge transfer
attributed to the better stabilization of the d
of the more electron withdrawing substituents in the pyr-
idylindolide ligand, leading to a higher energy of MLCT [d (Rh) /
*(CNR)] transition.
As demonstrated in our previous communication [22], all the
p(Rh) orbital as a result
(MLCT) [d
p(Rh) /
p*(CNR)] transitions, similar to those observed
p
in other related tetra(phenylisocyano) Rh(I) complexes [42e45].
The peaks of these two absorptions are sensitive to the electronic
nature of the isocyanide ligands. With the same pyridylindolide
ligand, the absorption maxima of these bands are in line with the
p
square planar bis(phenylisocyano) rhodium(I) diimine complexes
with general formula of [Rh(NeN)(CNR)2]BF4 (NeN ¼ bpy, Me2bpy,
Br2phen; CNR ¼ CNC6H3(CH3)-2,6, CNC6H2Br3-2,4,6, CNC6H4Cl-4)
were found to show thermochromic behavior due to the thermally
mediated aggregation properties. The thermal responses of
complexes 1 e 10 in THF solutions were also studied by the UVevis
absorption spectroscopy. However, unlike the bis(phenylisocyano)
rhodium(I) diimine complexes, in which the thermochromic
behavior for all the solutions of the complexes with different
substituents of diverse electronic and steric natures could be readily
observed at low concentration, only the solutions of 3, 6 and 10 all
with the 2,4,6-trichlorophenylisocyanide ligand at concentration
p-accepting ability of the isocyanide ligands (Fig. 2a):2 (428,
478 nm) > 3 (415, 465 nm) > 1 (412, 462 nm) for complexes with
pyind; 5 (417, 464 nm) > 6 (409, 461 nm) > 4 (384, 450 nm) for
complexes with Cl-pyind; 9 (403, 460 nm) > 10 (398, 456 nm) > 8
(401, 454 nm) > 7 (384, 444 nm) for complexes with Cl2pyind.
These trends are in agreement with MLCT assignment. Besides,
these absorption bands also show dependence on the electronic
nature of the pyridylindolide ligand. For complexes with the same
isocyanide ligands, the absorption energies of these bands are
higher for the complex with pyridylindolide ligand bearing more
Fig. 1. Perspective drawings of (a) two independent molecules of [Rh(cod)(Cl-pyind)], (b) [Rh(cod)(Cl2pyind)] and (c) 1 with atom numbering. Hydrogen atoms have been omitted
for clarity. Thermal ellipsoids are shown at the 50% probability level.

3226
W.-K. Chu et al. / Journal of Organometallic Chemistry 696 (2011) 3223e3230
Table 1
Crystal and structure determination data for [Rh(cod)(Cl-pyind)], [Rh(cod)(Cl2pyind)] and 1.
[Rh(cod)(Cl-pyind)]
[Rh(cod)(Cl2pyind)]
1
Formula
Mr
C
21H20ClN2Rh
C21H19Cl2N2Rh
473.19
C29H19Cl4N4O2Rh
700.19
438.75
T (K)
a (Å)
b (Å)
c (Å)
293(2)
293(2)
293(2)
11.05083(13)
13.15739(18)
13.28968(19)
110.0538(13)
93.8999(11)
105.9273(11)
1717.14(4)
Orange
7.74390(10)
10.44030(10)
11.82230(10)
77.2380(10)
80.1270(10)
75.6790(10)
896.308(16)
Yellow
34.1908(8)
8.09680(10)
24.0801(6)
90
121.211(3)
90
5071.4(2)
Red
Monoclinic
C2/c
a
b
g
(ꢁ)
(ꢁ)
(ꢁ)
V (Å3)
Crystal color
Crystal system
Space group
Z
Triclinic
ꢀ
Pı
4
Triclinic
ꢀ
Pı
2
8
F(000)
888
1.697
476
1.753
2800
1.631
Dc (g cmꢀ3
)
Crystal dimensions, (mm)
0.7 ꢂ 0.3 ꢂ 0.3
0.71073
1.16
0.5 ꢂ 0.3 ꢂ 0.1
0.71073
1.26
0.5 ꢂ 0.3 ꢂ 0.2
0.71073
1.01
l
(Å) (graphite-monochromated, Mo-Ka)
m
(mmꢀ1
)
Collection range
3.5ꢁ
ꢃ
q
ꢃ 25.0ꢁ (h: ꢀ13 to 13;
3.4ꢁ
ꢃ
q
ꢃ 25.0ꢁ (h: ꢀ9 to 9;
3.5ꢁ
ꢃ
q
ꢃ 25.0ꢁ (h: ꢀ40 to 40;
k: ꢀ15 to 15; l: ꢀ15 to 15)
k: ꢀ12 to 12; l: ꢀ14 to 14)
k: ꢀ9 to 9; l: ꢀ28 to 28)
Completeness to theta
No. of data collected
No. of unique data
No. of data used in refinement, m
No. of parameters refined, p
Ra
99.6%
31092
6018
99.7%
19727
3158
99.7%
23747
5009
5498
478
0.020
0.053
1.10
3096
235
0.018
0.050
1.15
4304
380
0.024
0.060
1.03
wRa
Goodness-of-fit, S
Maximum shift (
D
/
s
)
0.004
þ0.31, ꢀ0.54
0.001
þ0.34, ꢀ0.59
0.003
þ0.35, ꢀ0.33
max
Residual extrema in final
difference map, eÅꢀ3
a
w ¼ 1/[
s
2(Fo2) þ (aP)2 þ bP], where P is [2Fc2 þ Max(F2o,0)]/3.
> 0.35 mM exhibit observable thermochromism (Fig. 3). This
suggests that the aggregation affinity of these complexes is much
lower than that of the diimine analogous complexes. The lower
aggregation affinity of these complexes may be explained by the
increased steric repulsion as the phenyl ring of the non-coplanar
isocyanide ligand is considerably more deviated from the planarity
of complexes due to the more sterically demanding indole ring in the
pyridylindolide ligand. While the absence of the thermochromic
behavior of other complexes (1e2, 4e5 and 7e9) may be attributed
to the more sterically demanding nature of their isocyanide ligands
compared to the 2,4,6-trichlorophenylisocyanide ligand.
d ps[pz(Rh)] of the dimeric complex [Rh(X-
s*[d2z*(Rh)] to
pyind)(CNC6H2Cl3-2,4,6)2]2 (Scheme 2). The slight red shift of the
new absorption (Fig. 3a) may be ascribed to the shortening of the
Rh-Rh distance in the dimeric units as the temperature decreases.
As stronger Rh-Rh interaction would raise the ds*[dz2*(Rh)] orbital
and stabilize p
s
[pz(Rh)], both factors would also lead to narrowing
[pz(Rh)] transition. On
down of the energy gap of ds*[dz2*(Rh)] to p
s
warming to the room temperature, the new absorption decreases in
intensity and the absorption spectra reverts back into its original
spectra before cooling.
Upon cooling, the solutions of 3, 6 and 10 gradually change their
color from yellow to green with the evolution of a new absorption
band at ca. 563e607 nm. This new absorption band grows in
intensity and shows a slight red shift as temperature decreases. In
light of previous spectroscopic and aggregation studies on rho-
dium(I) complexes with isocyanide ligands [22,41,44,46,47], this
absorption is tentatively assigned to the transition from
3. Conclusion
A
new class of square planar bis(phenylisocyano) pyr-
idylindolido rhodium(I) complexes, [Rh(X-pyind)(CNR)2], with
Table 3
Photophysical data for complexes 1e10.
Complex
T/K
Absorptiona labs/nm ( /dm3molꢀ1cmꢀ1
3 )
Table 2
Selected bond lengths [Å] and angles [ꢁ] with estimated standard deviations in
parenthese for [Rh(cod)(Cl-pyind)], [Rh(cod)(Cl2pyind)] and 1.
1
2
3
298
298
298
173
298
298
298
173
298
298
298
298
173
348 (38755), 412 (13945), 462 sh (6390)
344 (24010), 428 (10585), 478 sh (2910)
344 (27880), 415 (11645), 465 sh (3710)
579b
345 (28055), 384 (13385), 450 sh (3820)
344 (33775), 417 (15005), 464 sh (5025)
340 (30515), 409 (8755), 461 sh (2910)
607b
330 (29140), 384 (15680), 444 sh (3700)
344 (24210), 401 (10110), 454 sh (2295)
341 (33325), 403 (17590), 460 sh (3060)
344 (10570), 398 (6625), 456 sh (1080)
563b
[Rh(cod)
(Cl-pyind)] Rh(2)eN(3)
Rh(1)eN(1)
2.108(16) Rh(1)eN(2)
2.114(17) Rh(2)eN(4)
2.063(16)
2.072(16)
79.39(6)
4
5
6
N(1)eRh(1)eN(2) 79.69(6) N(3)eRh(2)eN(4)
[Rh(cod) Rh(1)eN(1) 2.104(15) Rh(1)eN(2)
(Cl2pyind)] N(1)eRh(1)eN(2) 79.46(6)
2.060(15)
7
8
9
10
1
Rh(1)eN(1)
Rh(1)eC(14)
N(3)eC(14)
2.095(17) Rh(1)eN(2)
1.881(3) Rh(1)eC(15)
1.158(3) N(4)eC(15)
2.052(18)
1.858(2)
1.164(3)
N(1)eRh(1)eN(2) 78.99(7) C(14)eRh(1)eC(15) 87.00(9)
N(1)eRh(1)eC(14) 94.57(8) N(2)eRh(1)eC(15) 99.47(8)
C(14)eN(3)eC(16) 174.3(2) C(15)eN(4)eC(23) 167.4(3)
a
In acetone.
b
Absorption of the dimeric unit of the complexes in THF.

W.-K. Chu et al. / Journal of Organometallic Chemistry 696 (2011) 3223e3230
3227
procedure [22,35]. Substituted phenylisocyanide ligands, CNC6H2
(CH3)2-2,6-Br-4, CNC6H2Cl2-2,4-OCH3-6, CNC6H2Br3-2,4,6, CNC6H2
Cl3-2,4,6 were prepared from the corresponding substituted
formamides according to the synthetic methodology reported by
Ugi et al. [23e26]. All other reagents and solvents were of analytical
grade and were used as received.
a
b
1
2
3
2
5
9
40
30
20
10
0
4.2. Physical measurements and instrumentation
1H NMR spectra were recorded on a Bruker AV400 (400 MHz)
FT-NMR spectrometer at 293 K. Chemical shifts (d, ppm) were
400
λ / nm
500
400
λ / nm
500
reported relative to tetramethylsilane (Me4Si). Infrared spectra of
the solid samples as KBr discs were obtained in the range of
4000e400 cmꢀ1 using an AVATAR 360 FTIR spectrometer. All
positive-ion FAB mass spectra were recorded on a Finnigan MAT95
mass spectrometer. The elemental analyses were performed on an
Elementar Vario EL III Analyser. Electronic absorption spectra were
recorded on a Hewlett-Packard 8453 or Hewlett-Packard 8452A
diode array spectrophotometer with the temperature control using
an Oxford Instruments cryostat (Optistat DN).
Fig. 2. Overlaid UVevis spectra of (a) 1, 2, 3 and (b) 2, 5, 9 in acetone solutions at
298 K.
isocyanide and pyridylindolide ligands of different electronic and
steric features has been successfully synthesized. These complexes
have been characterized by 1H NMR and IR spectroscopy, mass
spectrometry and elemental analyses. The X-ray crystal structures
of two of the complex precursors [Rh(cod)(Cl-pyind)] and
[Rh(cod)(Cl2pyind)], and the target complex [Rh(pyind)(CNC6H2
Cl2-2,4-OCH3-6)2] have also been determined. The UVevis
absorption properties of these complexes and responses towards
the change of the temperature have been investigated. Of all
complexes investigated, only the solutions of 3, 6 and 10 all with
the 2,4,6-trichlorophenylisocyanide ligand exhibit observable
thermochromism.
4.3. X-ray crystal structure determination
The crystal structures were determined on an Oxford Diffraction
Gemini S Ultra X-ray single crystal diffractometer using graphite
monochromatised Mo-Ka radiation (
l
¼ 0.71073 Å). The structures
were solved by direct methods employing SHELXL-97 program [48]
on PC. Rh and many non-H atoms were located according to the
direct methods. The positions of other non-hydrogen atoms were
found after successful refinement by full-matrix least-squares
using SHELXL-97 program [48] on a PC. In the final stage of least-
squares refinement, all non-hydrogen atoms were refined aniso-
tropically. H atoms were generated by program SHELXL-97 [48].
The positions of H atoms were calculated based on riding mode
with thermal parameters equal to 1.2 times that of the associated C
atoms, and participated in the calculation of final R-indices. A
4. Experimental
4.1. Materials and reagents
Phenylhydrazine hydrochloride and ortho-phosphoric acid
were purchased from Merck Chemical Company. 4-Chloropheny
lhydrazinum hydrochloride and 3,5-chlorophenylhydrazinum
hydrochloride were obtained from Meryer Chemical Company. 2-
Acetylpyridine, 2,4,6-tribromoaniline, 2,4,6-trichloroaniline, 4-
bromo-2,6-dimethylaniline, 1,5-cyclooctadiene (cod), formic acid,
phosphoryl chloride, phosphorus pentoxide and triethylamine
were obtained from Aldrich Chemical Company and used as
received. Rhodium(III) chloride hydrate was obtained from Strem
Chemical Inc. [Rh(cod)Cl]2 was synthesized from the reaction
between rhodium(III) chloride and cod according to a literature
conventional index R1 based on observed F values larger than 4s(Fo)
is given (corresponding to Intensity ꢄ2
s
(I)). wR2 ¼ {S[w(Fo2 ꢀ Fc2)2]/
S[w(Fo2)2]}1/2, R1 ¼ SkFoj ꢀ jFck/SjFoj, The Goodness of Fit is always
based on F2: GooF ¼ S ¼ {S[w(Fo2 ꢀ Fc2)2]/(n ꢀ p)}1/2, where n is the
number of reflections and p is the total number of parameters
refined. The weighting scheme is: w ¼ 1/[
s
2(Fo2) þ (
a
P)2 þ bP],
where P is [2F2c þ Max(Fo2,0)]/3.
4.4. Synthesis
0.2
3
293K
a
b
Unless otherwise specified, all the syntheses were performed
under strictly anaerobic and anhydrous conditions in an inert
atmosphere of argon using standard Schlenk techniques.
6
273K
253K
233K
223K
213K
203K
193K
183K
173K
10
4.4.1. Synthesis of substituted 2-acetylpyridine phenylhydrazones
4.4.1.1. General synthetic procedure: These compounds were
synthesized according to a modified literature procedure [27e30].
A solution of 2-acetylpyridine (1 g, 8.0 mmol) and the corre-
sponding substituted phenylhydrazium hydrochloride (1 mol
equiv.) in EtOH (20 mL) were heated to reflux for 30 min. After that,
the mixture was cooled to room temperature to commence
precipitation. The precipitate was collected by suction filtration and
washed with cold ethanol. After vacuum drying, the substituted 2-
acetylpyridine phenylhydrazones were obtained as orange powder,
which were sufficiently pure for the use in the syntheses of the
corresponding substituted 2-(20-pyridyl)indoles. Yield: 75e80%.
0.1
0.0
600
700
600
700
λ / nm
λ / nm
Fig. 3. (a) The absorption spectral changes of 6 (0.39 mM) in THF solution upon
cooling from 293 K to 173 K. (b) The overlaid absorption spectra of 3, 6 and 10 at the
concentration of 0.39 mM in THF solution at 173 K.

3228
W.-K. Chu et al. / Journal of Organometallic Chemistry 696 (2011) 3223e3230
4.4.2. 2-(20-Pyridyl)indole (pyind)
0.9 Hz, 7-indolinyl H’s), 7.75 (td, 1H, J ¼7.9, 1.7 Hz, 40-pyridyl H’s),
7.83 (ddd,1H, J ¼ 7.9,1.2,1.0 Hz, 30-pyridyl H’s), 8.58 (ddd,1H, J ¼ 4.9,
1.7, 1.0 Hz, 60-pyridyl H’s), 9.87 (s, 1H, 1-indolinyl H’s); Positive-ion
FAB-MS: m/z 263.0 [M]þ; Elemental analyses calcd (%) for
Cl2pyind: C 59.34, H 3.06, N 10.65; found: C 59.09, H 3.13, N 10.67.
The ligand was synthesized according a literature procedure
commonly employed for Fischer indole synthesis [27e30]. To
a mixture of 2-acetylpyridine phenylhydrazone (2 g, 9.4 mmol) and
polyphosphoric acid (10 g) was heated to reflux for 1.5 h. After
cooling to room temperature, the resulting mixture was neutralized
by 10% NaOH aqueous solution and then extracted with CH2Cl2
(3 ꢂ 50 mL). The combined organic extracts was washed with
deionized water and dried over MgSO4. After removal of the solvent
under reduced pressure, the crude product was further purified by
column chromatography on silica gel using CH2Cl2 as eluent.
Subsequent recrystallization by slow diffusion of diethylether vapor
into a concentrated acetone solution of the compound gave the
analytically pure pyind as off-white powder. Yield: 19.6% (0.36 g,
4.4.5. Synthesis of precursor complexes [Rh(cod)(X-pyind)]
General synthetic procedure: To a solution of [Rh(cod)Cl]2
(100 mg, 0.203 mmol) and pyridylindole ligand (2 mol equiv.) in
CH2Cl2 (50 mL) was added, triethylamine (3 mol equiv.). The
resulting solution was then stirred at room temperature for 24 h.
Thereafter, the resulting solution was washed with deionized
water. Recrystallization by the slow diffusion of diethylether vapor
into a concentrated dichloromethane solution of the complexes
gave desired precursor complexes [Rh(cod)(X-pyind)] as analyti-
cally pure products.
1.8 mmol); 1H NMR (400 MHz, CDCl3, 298 K):
d
7.02 (dd, 1H, J ¼ 2.0,
0.9 Hz, 3-indolinyl H’s), 7.12 (td, 1H, J ¼ 8.0, 0.9 Hz, 5-indolinyl H’s),
7.18 (ddd, 1H, J ¼ 8.0, 4.9, 1.2 Hz, 50-pyridyl H’s), 7.21 (td, 1H, J ¼ 8.0,
1.2 Hz, 6-indolinyl H’s), 7.41 (dd, 1H, J ¼ 8.0, 0.9 Hz, 7-indolinyl H’s),
7.67 (dd, 1H, J ¼ 8.0, 0.9 Hz, 4-indolinyl H’s), 7.72 (td, 1H, J ¼ 8.0,
1.7 Hz, 40-pyridyl H’s), 7.80 (ddd, 1H, J ¼ 8.0, 1.2, 1.0 Hz, 30-pyridyl
H’s), 8.58 (ddd, 1H, J ¼ 4.9, 1.7, 1.0 Hz, 60-pyridyl H’s), 9.59 (s, 1H, 1-
indolinyl H’s); positive-ion FAB-MS: m/z 195.1 [M]þ.
4.4.5.1. [Rh(cod)(pyind)] Yield: 97.1% (160 mg, 0.39 mmol); 1H
NMR (400 MHz, CDCl3, 298 K):
d
¼ 1.93e2.12 (m, 4H, CH2 of cod),
2.47e2.61 (m, 4H, CH2 of cod), 4.01 (s, 2H, CH of cod), 5.53 (s, 2H, CH
of cod), 6.87e7.02 (m, 5H, 3,5,6,7-indolinyl H’s, 50-pyridyl H’s), 7.46
(d, 1H, J ¼ 5.6 Hz, 4-indolinyl H’s), 7.53 (d, 1H, J ¼ 7.7 Hz, 40-pyridyl
H’s), 7.64 (td,1H, J ¼ 7.7,1.4 Hz, 30-pyridyl H’s), 7.73 (d,1H, J ¼ 7.7 Hz,
60-pyridyl H’s).
4.4.3. 5-Chloro-2-(20-pyridyl)indole (Cl-pyind)
The ligand was synthesized according to a procedure similar to
that of pyind except 2-acetylpyridine-40-chlorophenylhydrazone
(3 g, 12 mmol) was used in place of 2-acetylpyridine phenyl-
hydrazone. After recrystallization by slow diffusion of diethylether
vapor into a concentrated acetone solution of the ligand, Cl-pyind
was obtained as colorless needle-shaped crystals. Yield: 11.6%
4.4.5.2. [Rh(cod)(Cl-pyind)] Yield: 55.8% (100 mg, 0.23 mmol); 1H
NMR (400 MHz, CDCl3, 298 K):
d 1.94e2.11 (m, 4H, CH2 of cod),
2.48e2.61 (m, 4H, CH2 of cod), 4.04 (d, 2H, J ¼ 2.5 Hz, CH of cod),
5.45 (d, 2H, J ¼ 2.5 Hz, CH of cod), 6.83 (s, 1H, 3-indolinyl H’s), 6.86
(d, 1H, J ¼ 8.9 Hz, 6-indolinyl H’s), 6.90 (dd, 1H, J ¼ 8.9, 2.0 Hz, 7-
indolinyl H’s), 7.00 (td, 1H, J ¼ 7.1, 1.4 Hz, 50-pyridyl H’s), 7.47e7.52
(m, 2H, 4-indolinyl H’s, 40-pyridyl H’s), 7.66 (td, 1H, J ¼ 7.1, 1.4 Hz, 30-
pyridyl H’s), 7.71 (d, 1H, J ¼ 7.1 Hz, 60-pyridyl H’s); Elemental anal-
yses Calcd (%) for [Rh(cod)(Cl-pyind)]: C 58.92, H 5.59, N 5.98;
found: C 58.64, H 5.29, N 6.21.
(0.32 g, 1.4 mmol); 1H NMR (400 MHz, CDCl3, 298 K):
d 6.95 (d, 1H,
J ¼ 2.1 Hz, 3-indolinyl H’s), 7.15e7.21 (m, 2H, 6-indolinyl H’s, 50-
pyridyl H’s), 7.32 (d, 1H, J ¼ 8.7 Hz, 7-indolinyl H’s), 7.61 (d, 1H,
1.2 Hz, 4-indolinyl H’s), 7.73 (td, 1H, J ¼ 8.7, 1.7 Hz, 40-pyridyl H’s),
7.80 (ddd,1H, J ¼ 8.0,1.2,1.0 Hz, 30-pyridyl H’s), 8.58 (ddd,1H, J ¼ 4.9,
1.7, 1.0 Hz, 60-pyridyl H’s), 9.60 (s, 1H, 1-indolinyl H’s); Positive-ion
FAB-MS: m/z 229.0 [M]þ; Elemental analyses calcd (%) for Cl-
pyind: C 68.28, H 3.97, N 12.25; found: C 68.05, H 4.01, N 12.26.
4.4.5.3. [Rh(cod)(Cl2pyind)] Yield: 76.4% (148 mg, 0.31 mmol); 1H
NMR (400 MHz, CDCl3, 298 K):
d 1.97e2.11 (m, 4H, CH2 of cod),
2.52e2.57 (m, 4H, CH2 of cod), 4.07 (s, 2H, CH of cod), 5.41 (s, 2H, CH
of cod), 6.83 (s, 1H, 3-indolinyl H’s), 6.91 (s, 1H, 5-indolinyl H’s),
6.96 (s, 1H, 7-indolinyl H’s), 7.03 (t, 1H, J ¼ 6.8 Hz, 50-pyridyl H’s),
7.49 (d, 1H, J ¼ 6.8 Hz, 40-pyridyl H’s), 7.70 (d, 1H, J ¼ 6.8 Hz, 30-
pyridyl H’s), 7.76 (d, 1H, J ¼ 6.8 Hz, 60-pyridyl H’s). Elemental anal-
yses Calcd (%) for [Rh(cod)(Cl2pyind)]$½CH2Cl2: C 51.74, H 4.80, N
5.13; found (%): C 51.54, H 4.54, N 5.39.
4.4.4. 4,6-Dichloro-2-(20-pyridyl)indole (Cl2pyind)
The ligand was synthesized by a procedure similar to that of
pyind except 2-acetylpyridine-30,50-dichlorophenylhydrazone (3 g,
10.6 mmol) was used in place of 2-acetylpyridine phenylhydrazone.
After recrystallization by slow diffusion of diethylether vapor into
a concentrated acetone solution of the ligand, Cl2pyind was
obtained as colorless needle-shaped crystals. Yield: 19.4% (0.54 g,
2.0 mmol); 1H NMR (400 MHz, CDCl3, 298 K):
d
7.06 (dd, 1H, J ¼ 2.1,
4.4.6. Synthesis of [Rh(X-pyind)(CNR)2]
General synthetic procedure: To a solution of [Rh(cod)(X-pyind)]
(0.12 mmol) in THF (40 mL) was added in a dropwise manner,
0.9 Hz, 3-indolinyl H’s), 7.13 (d, 1H, J ¼ 1.6 Hz, 5-indolinyl H’s), 7.24
(ddd, 1H, J ¼ 7.9, 4.9, 1.2 Hz, 50-pyridyl H’s), 7.27 (dd, 1H, J ¼ 1.6,
Cl
N
N
Cl
N
X2
X2
Rh
Rh
Cl
Cl
X1
X1
Cl
N
N
N
X2
Cl
Cl
Cl
N
X2
Rh
2
Cl
Cl
Cooling
X1
N
Cl
Cl
N
N
X2
Cl
N
Cl
Cl
Cl
N
X2
Cl
Cl
3: X1 = X2 = H
6: X1 = Cl; X2 = H
10
:
X1 = H; X2 = Cl
Scheme 2. Thermally mediated dimerization of 3, 6 and 10

W.-K. Chu et al. / Journal of Organometallic Chemistry 696 (2011) 3223e3230
3229
a solution of substituted phenylisocyanide ligand (2 mol equiv.) in
THF (10 mL). The resulting mixture was stirred at room tempera-
ture for 24 h. Thereafter, the solvent was removed under reduced
pressure and the crude product was washed with n-pentane
(3 ꢂ 10 mL). The crude product was further purified by recrystalli-
zation to give the analytically pure complex.
MHz, DMSO, 298 K):
d
6.88e6.90 (dd, 1H, J ¼ 8.8, 2.1 Hz, 6-indolinyl
H’s), 7.06 (s, 1H, 3-indolinyl H’s), 7.33e7.38 (m, 1H, 50-pyridyl H’s),
7.46 (d, 1H, J ¼ 2.1 Hz, 4-indolinyl H’s), 7.63e7.69 (m,1H, 7-indolinyl
H’s), 8.00 (t, 1H, J ¼ 7.4 Hz, 40-pyridyl H’s), 8.06 (d, 1H, J ¼ 7.4 Hz, 30-
pyridyl H’s), 8.17 (s, 2H, phenyl H’s), 8.22 (s, 2H, phenyl H’s), 8.89 (d,
1H, J ¼ 5.4 Hz, 60-pyridyl H’s). Positive-ion FAB-MS: m/z 1010.0
[M]þ; IR (KBr disc, /cmꢀ1): 2119, 2019
n n(N^C); Elemental analyses
4.4.6.1. [Rh(pyind)(CNC6H2Cl2-2,4-OCH3-6)2] (1) After recrystalli-
zation by the slow diffusion of diethylether vapor into a concen-
trated dichloromethane solution of 1, analytically pure complex
was obtained as yellow crystalline solids. Yield: 34.7%; 1H NMR
Calcd (%) for 5: C 32.10, H 1.20, N 5.55; found: C 32.30, H 1.34, N
5.58.
4.4.6.6. [Rh(Cl-pyind)(CNC6H2Cl3-2,4,6)2] (6) After recrystallization
by the slow diffusion of diethylether vapor into a concentrated
dichloromethane solution of 6, analytically pure complex was
obtained as yellowish green crystalline solids. Yield: 34.3%; 1H NMR
(400 MHz, CDCl3, 298 K): d 3.91 (s, 3H, eOCH3), 3.94 (s, 3H, eOCH3),
6.86 (d, 1H, 2.0 Hz, 3-indolinyl H’s), 6.87e6.92 (m, 2H, phenyl H’s),
6.93e7.02 (m, 3H, 50-pyridyl H’s, 5,6-indolinyl H’s), 7.06e7.10 (m,
2H, phenyl H’s), 7.55 (d, 1H, J ¼ 7.8 Hz, 7-indolinyl H’s), 7.68 (td, 1H,
J ¼ 8.0,1.5 Hz, 4-indolinyl H’s), 7.76 (d,1H, J ¼ 8.0 Hz, 40-pyridyl H’s),
7.96 (d, 1H, J ¼ 8.0 Hz, 30-pyridyl H’s), 8.82 (d, 1H, J ¼ 5.8 Hz, 60-
(400 MHz, CDCl3, 298 K): d 6.90 (s, 1H, 3-indolinyl H’s), 6.94 (dd, 1H,
J ¼ 8.8, 1.7 Hz, 6-indolinyl H’s), 7.02 (dd, 1H, J ¼ 8.8, 5.6 Hz, 50-pyr-
idyl H’s), 7.43 (s, 2H, phenyl H’s), 7.46 (s, 2H, phenyl H’s), 7.50 (d, 1H,
J ¼ 1.7 Hz, 4-indolinyl H’s), 7.74e7.78 (m, 3H, 30,40-pyridyl H’s, 7-
indolinyl H’s), 8.78 (d, 1H, J ¼ 5.7 Hz, 60-pyridyl H’s); Positive-ion
pyridyl H’s); Positive-ion FAB-MS: m/z 699.9 [M]þ; IR (KBr disc,
n/
cmꢀ1): 2122, 2049
49.74, H 2.74, N 8.00; found (%): C 49.64, H 2.89, N 8.02.
n(N^C); Elemental analyses Calcd (%) for 1: C
FAB-MS: m/z 743.7 [M]þ; IR (KBr disc,
n
/cmꢀ1): 2119, 2027
n
(N^C); Elemental analyses, Calcd (%) for 6$0.5CH2Cl2: C 40.60, H
4.4.6.2. [Rh(pyind)(CNC6H2Br3-2,4,6)2] (2) After recrystallization
by the slow diffusion of diethylether vapor into a concentrated
acetone solution of 2, analytically pure complex was obtained as
yellow crystalline solids. Yield: 35.8%; 1H NMR (400 MHz, CDCl3,
1.70, N 6.76; found: C 40.51, H 1.53, N 6.87.
4.4.6.7. [Rh(Cl2pyind)(CNC6H2Br-4-(CH3)2-2,6)2] (7) After recrys-
tallization by the slow diffusion of diethylether vapor into
a concentrated dichloromethane solution of 7, analytically pure
complex was obtained as yellow crystalline solids. Yield: 39.9%; 1H
298 K):
d
6.90 (s, 1H, 3-indolinyl H’s), 6.97e7.04 (m, 3H, 50-pyridyl
H’s, 5,6-indolinyl H’s), 7.55 (d, 1H, J ¼ 7.0 Hz, 7-indolinyl H’s), 7.70 (t,
1H, J ¼ 8.0 Hz, 4-indolinyl H’s), 7.75e7.78 (m, 3H, 40-pyridyl H’s,
phenyl H’s), 7.80 (m, 2H, phenyl H’s), 7.85 (d, 1H, 8.0 Hz, 30-pyridyl
H’s), 8.84 (d, 1H, J ¼ 5.5 Hz, 60-pyridyl H’s). Positive-ion FAB-MS: m/
NMR (400 MHz, CDCl3, 298 K):
d 2.45 (s, 6H, eCH3), 2.51 (s, 6H,
eCH3), 6.89 (d, 1H, J ¼ 1.6 Hz, 3-indolinyl H’s), 7.02 (m, 2H, 50-pyr-
idyl H’s, 5-indolinyl H’s), 7.29 (d, 4H, J ¼ 5.5 Hz, phenyl H’s), 7.54 (s,
1H, 7-indolinyl H’s), 7.74 (td, 1H, J ¼ 7.8, 1.4 Hz, 40-pyridyl H’s), 7.81
(d, 1H, J ¼ 7.8 Hz, 30-pyridyl H’s), 8.60 (d, 1H, J ¼ 5.4 Hz, 60-pyridyl
z 975.5 [M]þ; IR (KBr disc, /cmꢀ1): 2104, 2008
n n(N^C); Elemental
analyses Calcd (%) for 2$CH3CH2OCH2CH3: C 35.46, H 2.11, N 5.34;
found: C 35.77, H 2.11, N 5.26.
H’s); Positive-ion FAB-MS: m/z 784.8 [M]þ; IR (KBr disc, /cmꢀ1):
n
2122, 2067
n(N^C); Elemental analyses Calcd (%) for 7: C 47.42, H
4.4.6.3. [Rh(pyind)(CNC6H2Cl3-2,4,6)2] (3) After recrystallization by
the slow diffusion of diethylether vapor into a concentrated
dichloromethane solution of 3, analytically pure complex was
obtained as yellow crystalline solids. Yield: 37.7%; 1H NMR
2.95, N 7.14; found (%): C 47.38, H 3.19, N 7.10.
4.4.6.8. [Rh(Cl2pyind)(CNC6H2Cl2-2,4-OCH3-6)2] (8) After recrys-
tallization by the slow diffusion of diethylether vapor into
a concentrated acetone solution of 8, analytically pure complex was
obtained as yellow crystalline solids. Yield: 35.9%; 1H NMR
(400 MHz, CDCl3, 298 K): d 6.90 (s, 1H, 3-indolinyl H’s), 6.94 (dd,1H,
J ¼ 8.8, 2.1 Hz, 5-indolinyl H’s), 7.0e7.04 (m, 2H, 50-pyridyl H’s, 6-
indolinyl H’s), 7.42 (s, 2H, phenyl H’s), 7.46 (s, 2H, phenyl H’s),
7.50 (d, 1H, 2.1 Hz, 7-indolinyl H’s), 7.71e7.78 (m, 3H, 30,40-pyridyl
H’s, 4-indolinyl H’s), 8.77 (dd, 1H, 5.6, 1.0 Hz, 60-pyridyl H’s);
(400 MHz, DMSO, 298 K):
d 3.92 (s, 3H, eOCH3), 3.97 (s, 3H,
eOCH3), 6.92 (d, 1H, J ¼ 1.6 Hz, 3-indolinyl H’s), 7.18 (d, 1H,
J ¼ 0.9 Hz, 5-indolinyl H’s), 7.38e7.43 (m, 3H, 50-pyridyl H’s, phenyl
H’s), 7.45e7.49 (m, 2H, phenyl H’s), 7.62 (dd, 1H, J ¼ 1.6, 0.9 Hz, 7-
indolinyl H’s), 8.03 (td, 1H, J ¼ 8.0, 1.6 Hz, 40-pyridyl H’s), 8.19 (d,
1H, J ¼ 8.0 Hz, 30-pyridyl H’s), 8.82 (d, 1H, 6.1 Hz, 60-pyridyl H’s);
Positive-ion FAB-MS: m/z 709.1 [M]þ; IR (KBr disc, /cmꢀ1): 2115,
n
2027
n(N^C); Elemental analyses Calcd (%) for 3$0.5CH2Cl2: C
43.95, H 1.88, N 7.46; found: C 43.84, H 1.86, N 7.51.
Positive-ion FAB-MS: m/z 767.8 [M]þ; IR (KBr disc, /cmꢀ1): 2137,
n
4.4.6.4. [Rh(Cl-pyind)(CNC6H2Br-4-(CH3)2-2,6)2] (4) After recrys-
tallization by the slow diffusion of diethylether vapor into
a concentrated dichloromethane solution of 4, analytically pure
complex was obtained as yellow crystalline solids. Yield: 46.9%; 1H
2052
n(N^C); Elemental analyses Calcd (%) for 8$0.5H2O: C 44.76, H
2.33, N 7.20; found: C 44.62, H 2.47, N 6.95.
4.4.6.9. [Rh(Cl2pyind)(CNC6H2Br3-2,4,6)2] (9) After recrystalliza-
tion by the slow diffusion of diethylether vapor into a concentrated
acetone solution of 9, analytically pure complex was obtained as
yellow crystalline solids. Yield: 36.4%; 1H NMR (400 MHz, CDCl3,
NMR (400 MHz, CDCl3, 298 K):
d 2.44 (s, 6H, eCH3), 2.49 (s, 6H,
-CH3), 6.87 (dd, 1H, J ¼ 7.8, 2.1 Hz, 6-indolinyl H’s), 6.91 (s, 1H, 3-
indolinyl H’s), 6.99 (ddd, 1H, J ¼ 7.2, 5.6, 1.5 Hz, 50-pyridyl H’s),
7.28 (s, 2H, phenyl H’s), 7.30 (s, 2H, phenyl H’s), 7.51e7.55 (m, 2H,
4,7-indolinyl H’s), 7.73 (dd,1H, J ¼ 7.2,1.5 Hz, 40-pyridyl H’s), 7.77 (d,
1H, J ¼ 7.2, 1.5 Hz, 30-pyridyl H’s), 8.61 (d, 1H, 5.6 Hz, 60-pyridyl H’s);
298 K):
d
6.91 (d, 1H, J ¼ 1.7 Hz, 3-indolinyl H’s), 7.01e7.06 (m, 2H,
5-indolinyl H’s, 50-pyridyl H’s), 7.71e7.77 (m, 4H, 7-indolinyl H’s, 40-
pyridyl and phenyl H’s), 7.79e7.80 (m, 3H, 30-pyridyl and phenyl
H’s), 8.83 (d, 1H, J ¼ 5.4 Hz, 60-pyridyl H’s); Positive-ion FAB-MS: m/
Positive-ion FAB-MS: m/z 749.9 [M]þ; IR (KBr disc, /cmꢀ1): 2111,
n
2056
n
(N^C); Elemental analyses Calcd (%) for 4: C 49.60, H 3.22, N
z 1045.0 [M]þ; IR (KBr disc, /cmꢀ1): 2111, 2016
n n(N^C); Elemental
7.46; found: C 49.58, H 3.39, N 7.43.
analyses Calcd (%) for 9$0.5CH3CH2OCH2CH3: C 32.20, H 1.49, N
5.18; found: C 32.18, H 1.37, N 5.37.
4.4.6.5. [Rh(Cl-pyind)(CNC6H2Br3-2,4,6)2] (5) After recrystalliza-
tion by the slow diffusion of diethylether vapor into a concentrated
dichloromethane solution of 5, analytically pure complex was
obtained as yellow crystalline solids. Yield: 37.5%; 1H NMR (400
4.4.6.10. [Rh(Cl2pyind)(CNC6H2Cl3-2,4,6)2] (10) After recrystalliza-
tion by the slow diffusion of diethylether vapor into a concentrated
acetone solution of 10, analytically pure complex was obtained as

3230
W.-K. Chu et al. / Journal of Organometallic Chemistry 696 (2011) 3223e3230
yellowish green crystalline solids. Yield: 42.7%; 1H NMR (400 MHz,
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Y.-L. Tung, S.-W. Lee, Y. Chi, C.-S. Liu, Chem. Eur. J. 10 (2004) 6255.
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[15] M.G. Colombo, T.C. Brunold, T. Riedener, H.U. Güdel, M. Förtsch, H.-B. Bürgi,
Inorg. Chem. 33 (1994) 545.
[16] V.V. Grushin, N. Herron, D.D. LeCloux, W.J. Marshall, V.A. Petrov, Y. Wang,
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CDCl3, 298 K):
d
6.93 (d, 1H, J ¼ 1.5 Hz, 3-indolinyl H’s), 7.01 (d, 1H,
J ¼ 6.3 Hz, 5-indolinyl H’s), 7.06 (t,1H, J ¼ 6.7 Hz, 50-pyridyl H’s), 7.45
(s, 2H, phenyl H’s), 7.47 (s, 2H, phenyl H’s), 7.72 (s, 1H, 7-indolinyl
H’s), 7.75e7.78 (m, 2H, 30,40-pyridyl H’s), 8.76 (d, 1H, J ¼ 4.9 Hz, 60-
pyridyl H’s); Positive-ion FAB-MS: m/z 778.0 [M]þ; IR (KBr disc,
n/
cmꢀ1): 2111, 2001
n
(C^N). Elemental analyses Calcd (%) for
10$0.5CH3COCH3: C 42.42, H 1.75, N 6.94; found: C 42.14, H 2.05, N
6.96.
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The work described in this paper was supported by grants from
City University of Hong Kong (project nos. 7002435 and 7002594).
W.-K. Chu and L.T.-L. Lo acknowledge the receipt of a Postgraduate
Studentship from the City University of Hong Kong.
Appendix. Supplementary data
CCDC 819246e819248 contain the supplementary crystallo-
graphic data for 1, [Rh(cod)(Cl-pyind)] and [Rh(cod)(Cl2pyind)].
These data can be obtained free of charge via http://www.ccdc.cam.
ac.uk/conts/retreving.html, or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: þ44 1223
336 033; or e-mail: deposit@ccdc.cam.ac.uk.
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