Reactions of 2-(arylazo)aniline with iridium trichloride: Synthesis, characterization and structure of new cyclometallated complexes of iridium(III)

Article abstract of DOI:10.1016/j.ica.2010.12.025

Reactions of 2-(arylazo)aniline, HL (H represents the dissociable protons upon orthometallation and HL is p-RC₆H₄NNC ₆H₄-NH₂; RH for HL¹; CH₃ for HL² and Cl for HL³) with IrCl₃ in methanol afforded orthometallated complexes of composition (L)(HL)IrCl₂ (2) and (L)(MeOH)IrCl₂ (3), respectively. Complex (L)(MeOH)IrCl ₂ (3) converted into (L)(CH₃CN)IrCl₂ (4) upon refluxing in acetonitrile. The X-ray structure of the complexes (L ¹)(HL¹)IrCl₂ (2a) and (L³)(CH ₃CN)IrCl₂ (4c) have been determined and characterized unequivocally. The anionic L^- binds the metal in tridentate (C, N, N) manner for all the complexes.

Full text of DOI:10.1016/j.ica.2010.12.025

Inorganica Chimica Acta 367 (2011) 182–186
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Inorganica Chimica Acta
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Reactions of 2-(arylazo)aniline with iridium trichloride: Synthesis,
characterization and structure of new cyclometallated complexes of iridium(III)
Jahar Lal Pratihar a, Poulami Pattanayak a, Debprasad Patra a, Rajendra Rathore b, Surajit Chattopadhyay a,
⇑
a Department of Chemistry, University of Kalyani, Kalyani 741235, India
b Department of Chemistry, Marquette University, P.O. Box 1881, Milwaukee, WI 53201, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Reactions of 2-(arylazo)aniline, HL (H represents the dissociable protons upon orthometallation and HL is
p-RC6H4N@NC6H4–NH2; R@H for HL1; CH3 for HL2 and Cl for HL3) with IrCl3 in methanol afforded ortho-
metallated complexes of composition (L)(HL)IrCl2 (2) and (L)(MeOH)IrCl2 (3), respectively. Complex
(L)(MeOH)IrCl2 (3) converted into (L)(CH3CN)IrCl2 (4) upon refluxing in acetonitrile. The X-ray structure
of the complexes (L1)(HL1)IrCl2 (2a) and (L3)(CH3CN)IrCl2 (4c) have been determined and characterized
unequivocally. The anionic Lꢀ binds the metal in tridentate (C, N, N) manner for all the complexes.
Ó 2011 Elsevier B.V. All rights reserved.
Received 24 September 2010
Accepted 11 December 2010
Available online 23 December 2010
Keywords:
2-(Arylazo)aniline
Cyclometallation
Iridium(III)
1. Introduction
Herein, we report the reaction of 2-(arylazo)aniline, HL (1), with
IrCl3 yielding cyclometallated complexes of Ir(III) of composition
Facile coordination of azo (–N@N–) nitrogen of multidentate
ligands, to heavier transition metal ions, are well documented
[1–26]. Most of these ligands are bidentate or tridentate. A few
tetradentate ligands have been reported recently [8–12]. Reactions
of tridentate azo ligands with the appropriate substrates of heavier
transition metal ions afforded complexes with metal–carbon bond
[1–7,20–23]. These metal–carbon bonded complexes exhibited
interesting reactivities and redox properties [1–7,20–23]. Often it
was stated that the types of complexes formed are very much
dependent of metal substrates.
Among the heavier transition metal ions, reactions of iridium
substrates with azo ligands have been studied scarcely [20,24–26].
Reports on reactions of IrCl3ꢁ3H2O with azo ligands are limited
[24–26]. Further, the reaction of 2-(arylazo)aniline, HL, 1, with RhCl3
in methanol enabled us to recognize the reductive cleavage
of –N@N– bond [1,2]. These interesting results prompted us to study
the reaction of IrCl3ꢁ3H2O with 2-(arylazo)aniline.
(L)(HL)IrCl2, (L)(MeOH)IrCl2 and (L)(MeCN)IrCl2. All the complexes
were characterized unequivocally. The X-ray structures of the
complexes (L1)(HL1)IrCl2 (2a) and (L3)(CH3CN)IrCl2 (4c) have been
determined.
2. Results and discussion
2.1. Synthesis
Reaction of iridium(III) chloride with 2-(arylazo)aniline in 1:2
stoichiometric ratio afforded two products (L)(HL)IrCl2, (2) and
(L)(MeOH)IrCl2 (3) in ꢂ10% and ꢂ60% yields, respectively upon
boiling in methanol for 3 h (Eq. (1)). The ligands used and the prod-
ucts obtained are shown in Eq. (1). Complex (L)(MeOH)IrCl2 (3)
converted into (L)(CH3CN)IrCl2 (4) upon refluxing in acetonitrile
(Eq. (2)).
In contrast to the reaction of RhCl3 with HL, herein, the reduc-
tive cleavage of –N@N– could not be identified. The reduction of
azo (–N@N–) bond, in the case of RhCl3, was reported to occur by
Rh(I) species which formed in situ in boiling methanol [1,2].
Although, the mention regarding the formation of such Rh(I) spe-
cies in boiling methanol has been included in the text books
[1,2,27] but the formation of Ir(I) species upon boiling IrCl3 in
methanol has not been indicated. Conversion of RhCl3 and IrCl3
into Rh(I) and Ir(I) species, respectively were compared and
reported elsewhere [28]. It was described that IrCl3 afforded
IrIII(H)Cl2(PPh3)3 rather than IrI(PPh3)3Cl upon reaction with PPh3
in boiling ethanol or methanol [28]. Whereas Rh(PPh3)3Cl could
be prepared at ease upon reaction of RhCl3 with PPh3 in boiling
R
R = H (for 1a)
= Me (for 1b)
= Cl (for 1c)
N
N
NH2
HL (1)
⇑
Corresponding author. Tel.: +91 33 25828750; fax: +91 33 25828282.
E-mail address: scha8@rediffmail.com (S. Chattopadhyay).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.12.025

J.L. Pratihar et al. / Inorganica Chimica Acta 367 (2011) 182–186
183
prepared from the Ir(I) substrates IrCl(C8H4)2 [28]. This fundamen-
tal difference in the reactivities of IrCl3 and RhCl3 in boiling meth-
anol has never been addressed unambiguously due to complexity
in isolation and characterization of products directly. However,
the noncleaveage of –N@N– by IrCl3 upon reaction with HL is an
indirect evidence regarding the intricacy in the formation of Ir(I)
species in boiling methanol. As a result upon refluxing 2 with IrCl3
in methanol did not afford the azo (–N@N–) cleaved product as in
the case of RhCl3 [1,2].
R
R
N
R
N
Cl
Ir
N
N
NH2
MeOH
+
+
IrCl3
N
Cl
N
NH2
NH2
1
ð1Þ
2
Fig. 1. UV–Vis spectra of (L1)(HL1)IrCl2 (–), (L1)(MeOH)IrCl2 (—) and
(L1)(CH3CN)IrCl2 (ꢁꢁꢁ).
R
N
Cl
Ir
OMe
H
N
in ethanol or methanol [29]. Moreover, the Ir(I) compounds are
more air sensitive than the corresponding Rh(I) analogues [28]
indicating the difficulty of formation of appreciably stable Ir(I)
species upon boiling IrCl3 in methanol. Notably, Ir(PPh3)3Cl was
Cl
NH2
3
Fig. 2. Views of molecular structures of (L1)(HL1)IrCl2 and (L3)(CH3CN)IrCl2 with atom numbering scheme. The hydrogen atoms, excepting those of the amino groups and
acetonitrile solvent molecule, have been omitted for clarity.

184
J.L. Pratihar et al. / Inorganica Chimica Acta 367 (2011) 182–186
R
N
Table 2
R
Selected bond distances (Å) and angles (°) for compound (L3)(CH3CN)IrCl2.
Cl
Ir
Cl
Ir
NCCH3
OMe
H
Distances
CH3CN
Reflux
Ir(1)–Cl(1)
Ir(1)–Cl(2)
Ir(1)–N(3)
Ir(1)–N(1)
Ir(1)–N(1S)
Ir(1)–C(12)
2.3575(9)
2.3543(9)
2.189(3)
1.945(3)
2.029(3)
1.995(3)
N(3)–C(2)
N(1)–N(2)
N(2)–C(7)
N(1)–C(1)
N(1S)–C(1S)
1.461(5)
1.279(5)
1.401(5)
1.418(5)
1.134(5)
N
N
N
Cl
ð2Þ
Cl
NH2
NH2
4
3
Angles
Cl(1)–Ir(1)–Cl(2)
Cl(1)–Ir(1)–N(3)
Cl(1)–Ir(1)–N(1)
Cl(1)–Ir(1)–N(1S)
Cl(1)–Ir(1)–C(12)
Cl(2)–Ir(1)–N(1)
Cl(2)–Ir(1)–N(1S)
176.34(3)
88.42(8)
91.83(10)
87.13(9)
91.55(10)
89.74(9)
91.32(9)
Cl(2)–Ir(1)–C(12)
N(3)–Ir(1)–N(1)
N(1)–Ir(1)–N(1S)
N(3)–Ir(1)–C(12)
N(1)–Ir(1)–N(3)
N(1)–Ir(1)–C(12)
N(1S)–Ir(1)–C(12)
91.99(10)
82.03(13)
178.92(13)
161.57(15)
98.20(13)
79.54(16)
100.21(15)
2.2. Spectral characterization and solution structures
Solutions 2, 3 and 4 in common organic solvents are green,
greenish-brown and green, respectively. UV–Vis spectra of the
complexes were recorded in dichloromethane solutions character-
istic spectra for 2a, 3a and 4a are shown in Fig 1. Spectra of other
complexes are given in Supplementary material (Figs. S1–S9). The
UV–Vis spectral data are given in the Section 4. All the complexes
displayed several absorptions in the visible and ultraviolet regions.
A characteristic low energy absorption band appeared near 625 nm
for all the complexes.
The IR spectra of the complexes (Figs. S10–S18) in solid KBr
support exhibited several overlapping mN–H absorptions within
the ranges 3090–3064 cmꢀ1 for 2 indicating the presence of more
than one amino group. Complexes 3 and 4 exhibited mN–H near
3165–3254. The mN@N of all the complexes shifted to lower energy
(1368–1404) than the mN@N of the free ligands (1458–1474) indi-
cating the coordination of azo nitrogen [17–19]. The IR data are
collected in Section 4.
The composition of 2, 3 and 4 matched well with the C, H, N
analytical data and 1H NMR spectral data. The 1H NMR spectra
(Figs. S19–S24 and S25–S27) of the complexes were recorded in
CDCl3 for 2 and CDCl3-DMSO-d6 mixed solvent for 3. The amino
protons appeared as broad singlet near d 3.75 and d 4.75 for 2 indi-
cating two types of amino groups and consistent to the structure
(see below). Complex 3 exhibit only one resonance for amino pro-
ton near d 6.10. The resonances for NH2 protons of 4 shifted mar-
ginally and appeared near d 6.25. The total count of aromatic
protons (d 6.85–d 8.22) matched well with the composition of
the complexes (Section 4; Figs. S5–S8). The spectra of 2b displayed
two resonances for R = Me at d 2.35 and d 2.40. Whereas 3b exhib-
ited one methyl resonance for R = Me at d 2.45. The resonances for
–CH3 protons of coordinated MeOH and CH3CN appeared near d
2.50 and d 2.75 for 3 and 4, respectively.
evaporation of acetonitrile solutions, respectively. Both the crystals
of 2a and 4c are monoclinic with the space group P21/c. The molec-
ular structures of 2a and 4c are given in Fig. 2 with atom number-
ing scheme. The selected bond distances and angles are given in
Tables 1 and 2 for 2a and 4c, respectively. Since the geometry
and bond parameters are similar in the two molecules in the asym-
metric unit of 2a, therefore those are same molecules. In
(L1)(HL1)IrCl2 tridentate (L1)ꢀ is coordinated to Ir(III) forming
cyclometallated chelate. Another HL1 ligand binds the Ir(III) centre
in monodentate fashion through amino-N. Two chloride ligands
completed hexacoordination about Ir(III). A second molecule of
2-(phenylazo)aniline binds in a monodentate fashion through the
amino nitrogen at the sixth position of hexacoordinated Ir(III) in
2a while in 4c the nitrogen of acetonitrile solvents binds at the
sixth position of hexacoordinated Ir(III). The geometries about Ir(-
III), for both the complexes, are distorted octahedral where the
chloride ligands are mutually trans with Cl–Ir–Cl angle being equal
to 174.05(14) and 176.34(3) for 2a and 4c, respectively. The Ir–C,
Ir–N(azo), Ir–Cl bond distances are all quite normal [20,24–26].
The Ir–N(azo) distance (1.910(13) Å) of 2a is shorter than the Ir–
N(amine) lengths [Ir–N(3), 2.177(14); Ir–N(6), 2.167(11) Å] of the
same molecule consistent to stronger Ir?N(azo) back bonding
[1]. The Ir–N(3) [2.177(14) Å] bond is longer than the Ir–N(6) dis-
tance [2.167(11) Å] of 2a due to stronger trans effect of aryl carbon
[1]. Similar trends in Ir–N bond distances have been observed for
4c also: Ir–N(azo) [1.945(3) Å] < Ir–N(amine) [Ir–N(3), 2.189(3) Å;
Ir–N(1S), 2.029(3) Å]; Ir–N(3) [2.189(3) Å] > Ir–N(6) [2.167(11) Å]
as a result of dp–pp backbonding and trans influence of aryl car-
bon, respectively. In the structure of 2a C(aryl)–N(amine) bond is
longer [2a: N(3)-C(2),1.42(2) Å; N(6)–C(14), 1.43(2) Å.] than that
of in the azoimine (N, N) chelates of 1, where it is shorter
(av. ꢂ 1.34 Å) and similar to imine length due to dissociation of
an amino proton followed by delocalization [17–19].
2.3. X-ray structures
The complexes, 2a and 4c, were crystallized by slow diffusion of
petroleum ether (60–80 °C) into the dichloromethane and slow
Table 1
Selected bond distances (Å) and angles (°) for compound (L1)(HL1)IrCl2.
3. Conclusion
Distances
Ir(1)–Cl(1)
Ir(1)–Cl(2)
Ir(1)–N(1)
Ir(1)–N(3)
Ir(1)–N(6)
Ir(1)–C(12)
2.349(4)
2.343(5)
1.910(13)
2.177(14)
2.167(11)
2.030(12)
N(3)–C(2)
N(1)–N(2)
N(2)–C(7)
N(1)–C(1)
N(4)–C(13)
N(4)–N(5)
1.42(2)
1.271(19)
1.43(3)
1.46(2)
1.41(2)
1.23(2)
The reaction of 2-(arylazo)aniline with IrCl3 afforded cyclomet-
allated complexes of Ir(III), 2 and 3. Upon boiling 3 in CH3CN affor-
ded complex 4 where CH3CN is N-coordinated. It is proposed that
the reduction of IrCl3 in boiling methanol to form Ir(I) species, suit-
able for in situ reduction of –N@N– bond does not occur.
Angles
Cl(1)–Ir(1)–Cl(2)
Cl(1)–Ir(1)–N(3)
Cl(1)–Ir(1)–N(1)
Cl(1)–Ir(1)–N(6)
Cl(1)–Ir(1)–C(12)
Cl(2)–Ir(1)–N(1)
Cl(2)–Ir(1)–N(6)
174.05(14)
85.8(4)
92.3(4)
86.5(3)
93.1(4)
90.1(4)
90.7(3)
Cl(2)–Ir(1)–C(12)
N(3)–Ir(1)–N(1)
N(3)–Ir(1)–N(6)
N(3)–Ir(1)–C(12)
N(2)–Ir(1)–N(4)
N(1)–Ir(1)–C(12)
N(6)–Ir(1)–C(12)
92.7(4)
82.7(5)
93.5(4)
161.15(12)
160.2(5)
77.6(6)
4. Experimental
4.1. Materials
The solvents used in the reactions were of reagent grade (E.
Marck, Kolkata, India) and were purified and dried by reported
106.2(5)

J.L. Pratihar et al. / Inorganica Chimica Acta 367 (2011) 182–186
185
procedure [30]. IrCl3ꢁ3H2O was obtained from Arora-Mathey, India
and used as it was received. Silical gel G with binder was used for
thin layer chromatography. The ligands 2-(phenylazo)aniline
(HL1), 2-(p-tolylazo)aniline (HL2), and 2-(p-chlorophenylazo)ani-
line (HL3) were prepared following the reported procedures
[17–19].
(L2)(CH3OH)RhCl2 (3b): Yield: 60%. IrC14H16N3OCl2 (505): Anal.
Calc. C, 33.26; H, 3.16; N, 8.31. Found: C, 33.35; H, 3.19; N, 8.22.
UV–Vis spectrum (CH2Cl2) kmax
(1720), 365 (6770), 270 (4700), 230 (7660). IR (KBr pellets,
cmꢀ1): = 3191 (NH2), 1368(N@N). 1H NMR (CDCl3+ 1 drop
(e
, Mꢀ1 cmꢀ1) = 630 (520), 435
m
DMSO-d6, ppm): d 8.10–8.09 (m, 1H), 7.95–7.82 (m, 1H), 7.74 (s,
1H), 7.64–7.41 (m, 1H), 7.34–7.24 (m, 1H), 6.78 (d, 1H), 6.09 (s,
2H), 2.51 (s, 3H), 2.45 (s, 3H).
4.2. Physical measurements
4.3.4. (L3)(HL3)RhCl2 (2c) and (L3)(CH3OH)RhCl2 (3c)
Microanalysis (C, H, N) was performed using a Perkin–Elmer
2400 C, H, N, S/O series II elemental analyzer. Infrared spectra were
recorded on a Parkin-Elmer L120-00A FT-IR spectrometer with the
samples prepared as KBr pellets. Electronic spectra were recorded
on a Shimadzu UV-1800 PC spectrophotometer. 1H NMR spectra
were obtained on Brucker DPX 400 and Brucker 500 RPX NMR
spectrometers in CDCl3 or CDCl3-DMSO-d6 mixture using TMS as
the internal standard.
The complexes 2c and 3c were prepared following the same
procedure as in the cases of 2a and 3a using 2-(p-chloropheny-
lazo)aniline, 1c (160 mg, 0.76 mmol), in place of 1a. The solvent
used for thin layer chromatographic separation is toluene–metha-
nol (90:10 V/V) mixed solvent. Yield: 10% (for complex 2c) and 50%
(for complex 3c). IrC24H19N6Cl4 (725): Anal. Calc. C, 39.72; H, 2.61;
N, 11.57. Found: C, 39.83; H, 2.69; N, 11.67. UV–Vis spectrum
(CH2Cl2) kmax
(23,800), 275 (10,900), 235 (19,800). IR (KBr pellets, cmꢀ1):
= 3250, 3215, 3167 (NH2), 1373 (N@N). 1H NMR CDCl3: d 8.16–
(e,
Mꢀ1 cmꢀ1) = 620 (1100), 430 (3580), 350
4.3. Syntheses of complexes
m
4.3.1. (L)(HL)IrCl2 (2) and (L)(CH3OH)IrCl2 (3)
8.14 (m, 1H), 8.00 (d, 1H), 7.90–7.85 (m, 3H), 7.56–7.51 (m, 2H),
The (L)(HL)IrCl2 (2) and (L)(CH3OH)IrCl2 (3) complexes were ob-
tained by following a general procedure. Specific details are given
below for a particular complex.
7.47–7.24 (m, 7H), 7.01 (d, 1H), 4.78 (s, 2H), 3.56 (s, 2H).
(L3)(CH3OH)RhCl2 (3c): Yield: 60%. IrC13H13N3OCl3 (525.5):
Anal. Calc. C, 29.68; H, 2.47; N, 7.99. Found: C, 29.77; H, 2.53; N,
8.12. UV–Vis spectrum (CH2Cl2) kmax
435 (2480), 380 (8970), 360 (9960), 275 (7080), 230 (11,590). IR
(KBr pellets, cmꢀ1): = 3176 (NH2), 1373 (N@N). 1H NMR (CDCl3+
(e
, Mꢀ1 cmꢀ1) = 635 (770),
4.3.2. (L1)(HL1)IrCl2 (2a) and (L1)(CH3OH)IrCl2 (3a)
2-(Phenylazo)aniline, 1a, (60 mg, 0.30 mmol) was dissolved in
methanol (40 mL), and to it IrCl3 (100 mg, 0.15 mmol) was added.
The mixture was then heated to reflux for 4 h to afford green solu-
tion. Evaporation of the solvent gave a dark green residue, which
was introduced for purification by thin layer chromatography on
silica gel. Two green bands separated in toluene–methanol
(90:10, V/V) mixed solvent. From the first and second bands 2a
and 3a, respectively, were isolated in pure form upon extracting
with dichloromethane and methanol, respectively. Yield: 10% (for
complex 2a) and 60% (for complex 3a). IrC24H21N6Cl2 (656): Anal.
Calc. C, 43.90; H, 3.20; N, 12.80. Found: C, 43.45; H, 3.28; N,
m
1 drop DMSO-d6, ppm): d 8.14–8.09 (m, 1H), 7.90 (d, 1H), 7.83
(d, 1H), 7.67–7.59 (m, 1H), 7.36–7.25 (m, 2H), 6.95 (d, 1H), 6.22
(s, 2H), 2.52 (s, 3H).
4.3.5. Synthesis of (L1–3)(CH3OH)IrCl2 (4a–c)
(L)(CH3CN)IrCl2 (4) complexes were obtained from (L)(CH3O-
H)IrCl2 (3) upon refluxing in acetonitrile for 4 h to afford green
solution. Slow evaporation of the solvent gave crystals of
(L)(CH3CN)IrCl2 (4).
(L1)(CH3CN)IrCl2 (4a): Yield: 85%. IrC14H13N4Cl2 (500): Anal.
Calc. C, 33.60; H, 2.60; N, 11.20. Found: C, 33.74; H, 2.45; N,
12.65%. UV–Vis spectrum (CH2Cl2) kmax
(780), 430 (2730), 340 (19,660), 270 (9300), 235 (18,250). IR (KBr
pellets, cmꢀ1): = 3254, 3211, 3176 (NH2), 1372 (N@N). 1H NMR
(e,
Mꢀ1 cmꢀ1) = 620
11.02. UV–Vis spectrum (CH2Cl2) kmax
425 (3360), 360 (13,830), 265 (8550), 235 (11,250). IR (KBr pellets,
cmꢀ1): = 3254, 3209, 3191 (NH2), 1381 (N@N). 1H NMR (CDCl3+
(e
, Mꢀ1 cmꢀ1) = 620 (1240),
m
CDCl3: d 8.22–8.15 (m, 1H), 8.11 (d, 1H), 7.90–7.88 (m, 2H),
7.53–7.46 (m, 3H), 7.41–7.39 (m, 4H), 7.32–7.23 (m, 5H), 7.19 (t,
1H), 4.76 (s, 2H), 3.57 (s, 2H).
m
1
drop DMSO-d6, ppm): d 8.14 (d, 1H), 8.01 (d, 1H), 7.62–7.57 (m,
2H), 7.40 (t, 1H), 7.33 (t, 1H), 7.15 (t, 1H), 7.06 (t, 1H), 6.29 (s,
2H), 2.76 (s, 3H).
(L1)(CH3OH)IrCl2 (3a): Yield: 60 %. IrC13H14N3OCl2 (491): Anal.
Calc. C, 31.77; H, 2.85; N, 8.55. Found: C, 31.65; H, 2.73; N,
(L2)(CH3CN)IrCl2 (4b): Yield: 90%. IrC15H15N4Cl2 (514): Anal.
Calc. C, 35.01; H, 2.91; N, 10.89. Found: C, 35.22; H, 2.98; N,
8.74%. UV–Vis spectrum (CH2Cl2) kmax
440 (1790), 360 (7100), 230 (9580). IR (KBr pellets, cmꢀ1):
= 3216, 3185 (NH2), 1369 (N@N). 1H NMR (CDCl3+ 1 drop
(e
, Mꢀ1 cmꢀ1) = 640 (500),
10.75. UV–Vis spectrum (CH2Cl2) kmax
420 (3250), 380 (11,000), 270 (7100), 240 (10,500). IR (KBr pellets,
cmꢀ1): = 3252, 3203, 3099 (NH2), 1380 (N@N). 1H NMR (CDCl3+
(e
, Mꢀ1 cmꢀ1) = 615 (990),
m
DMSO-d6, ppm): d 8.15–8.13 (m, 1H), 8.01–7.91 (m, 2H), 7.59–
7.56 (m, 1H), 7.32–7.28 (m, 2H), 7.14–7.06 (m, 1H), 6.95 (t, 1H),
6.10 (s, 2H), 2.51 (s, 3H).
m
1
drop DMSO-d6, ppm): d 8.13 (d, 1H), 7.89 (d, 1H), 7.54 (d, 1H),
7.41–7.27 (m, 3H), 6.88 (d, 1H), 6.12 (s, 2H), 2.75 (s, 3H), 2.47 (s,
3H).
4.3.3. (L2)(HL2)RhCl2 (2b) and (L2)(CH3OH)RhCl2 (3b)
(L3)(CH3CN)RhCl2 (4c): Yield: 90%. IrC14H12N4Cl3 (534.5): Anal.
Calc. C, 31.43; H, 2.24; N, 10.47. Found: C, 31.56; H, 2.32; N,
The complexes 2b and 3b were prepared following the same
procedure as in the cases of 2a and 3a using 2-(p-tolylazo)aniline,
1b (160 mg, 0.76 mmol), in place of 1a. The solvent used for thin
layer chromatographic separation is toluene–methanol (90:10 V/
V) mixed solvent. Yield: 15% (for complex 2b) and 50% (for com-
plex 3b). IrC26H25N6Cl2 (684): Anal. Calc. C, 45.61; H, 3.65; N,
12.28. Found: C, 45.45; H, 3.60; N, 12.32. UV–Vis spectrum
10.50. UV–Vis spectrum (CH2Cl2) kmax
420 (3400), 380 (9900), 265 (7050), 235 (10,950). IR (KBr pellets,
cmꢀ1): = 3260, 3234 (NH2), 1404 (N@N). 1H NMR (CDCl3+ 1 drop
(e
, Mꢀ1 cmꢀ1) = 610 (1000),
m
DMSO-d6, ppm): d 8.21 (d, 1H), 8.02 (d, 1H); 7.63 (d, 1H), 7.58–7.54
(m, 1H), 7.51–7.48 (m, 1H), 7.40 (t, 1H), 7.14–7.12 (m, 1H), 6.27 (s,
2H), 2.84 (s, 3H).
(CH2Cl2) kmax
(37,000), 275 (16,000), 235 (29,400). IR (KBr pellets, cmꢀ1):
= 3250, 3215, 3167 (NH2), 1368 (N@N). 1H NMR CDCl3: d 8.16–
(e,
Mꢀ1 cmꢀ1) = 620 (1593), 430 (6080), 350
m
5. Crystallography
8.13 (m, 1H), 7.99 (d, 1H), 7.88–7.82 (m, 4H), 7.53–7.45 (m, 2H),
7.41–7.39 (m, 3H), 7.32–7. 20 (m, 6H), 6.94 (d, 1H), 4.75 (s, 2H),
3.56 (s, 2H), 2.53 (s, 3H), 2.40 (s, 3H).
Single crystals of (L)(HL)IrCl2 and (L)(MeCN)IrCl2 were grown by
slow diffusion of a dichloromethane solution into petroleum ether

186
J.L. Pratihar et al. / Inorganica Chimica Acta 367 (2011) 182–186
Table 3
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Figures
S1–S18 show the UV–Vis and IR spectra and Figures S19–S27 the
1H NMR spectra of all the complexes. Supplementary data associ-
ated with this article can be found, in the online version, at
doi:10.1016/j.ica.2010.12.025.
Crystallographic data for (L1)(HL1)IrCl2 and (L3)(CH3CN)IrCl2.
Complex
(L1)(HL1)IrCl2
(L3)(CH3CN)IrCl2
Formula
C24H21N6IrCl2
656.59
P21/c
C14H12N4IrCl3
534.85
P21/c
Formula weight
Space group
Crystal system
a (Å)
b (Å)
c (Å)
monoclinic
20.6735(15)
10.2520(7)
23.7851(17)
90.000(0)
104.867(4)
90.000(0)
0.71073
4872.4(6)
8
monoclinic
13.7822(8)
10.2484(6)
12.3338(8)
90.000(0)
114.186(3)
90.000(0)
0.71073
1589.17(17)
4
150
2.236
20.911
0.0175
0.0422
2412
1.24
References
a
(°)
b (°)
(°)
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data collection parameters and relevant crystal data are collected
in Table 3.
x
a
a
Acknowledgments
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We are thankful to the DST (New Delhi) for funding under DST-
SERC Project (SR/S1/IC-0026/2007). JP is thankful to the CSIR (New
Delhi) for his fellowship (No. 09/106(0097)2K8-EMR-I). The neces-
sary laboratory and infrastructural facility are provided by the
Department of Chemistry, University of Kalyani. The support of
DST under FIST Program to the Department of Chemistry, Univer-
sity of Kalyani is acknowledged. We acknowledge Prof. Jui-Hsien
Huang, Department of Chemistry, National Changhua University
of Education, Changhua, Taiwan for X-ray study of (L1)(HL1)IrCl2.
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Appendix A. Supplementary material
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CCDC 741096 and 741097 contain the supplementary crystallo-
graphic data for (L1)(HL1)IrCl2 and (L3)(MeCN)IrCl2. These data can