A strategy of Pd(II) assisted C-H activation in 2-alkylamino azobenzene ligands: Syntheses, characterisation and structure of a new family of orthopalladated complexes

Article abstract of DOI:10.1016/j.poly.2005.05.022

Several 2-(arylazo)-N-alkyl aniline ligands, 1a-11a, have been prepared by the reaction between 2-(arylazo) aniline and the appropriate alkyl halide in the presence of K₂CO₃. Treatment of sodium tetrachloropalladate with 1a-11a in methanol afforded the orthopalladated complexes 1b-11b, where the ligand is tridentate (C,N,N). The ligands and complexes were characterised from spectroscopic data and confirmed by X-ray studies. The X-ray structure of 9b displayed an unsupported Pd(II)?Pd(II) interaction (3.301 ?).

Full text of DOI:10.1016/j.poly.2005.05.022

Polyhedron 24 (2005) 1953–1960
www.elsevier.com/locate/poly
A strategy of Pd(II) assisted C–H activation in 2-alkylamino
azobenzene ligands: Syntheses, characterisation and structure of
a new family of orthopalladated complexes
*
Jahar lal Pratihar, Nilkamal Maiti, Poulami Pattanayak, Surajit Chattopadhyay
Department of Chemistry, University of Kalyani, Kalyani 741235, India
Received 9 April 2005; accepted 2 May 2005
Available online 3 August 2005
Abstract
Several 2-(arylazo)-N-alkyl aniline ligands, 1a–11a, have been prepared by the reaction between 2-(arylazo) aniline and the
appropriate alkyl halide in the presence of K2CO3. Treatment of sodium tetrachloropalladate with 1a–11a in methanol afforded
the orthopalladated complexes 1b–11b, where the ligand is tridentate (C,N,N). The ligands and complexes were characterised from
spectroscopic data and confirmed by X-ray studies. The X-ray structure of 9b displayed an unsupported Pd(II)ꢀ ꢀ ꢀPd(II) interaction
˚
(3.301 A).
Ó 2005 Elsevier Ltd. All rights reserved.
Keywords: 2-Alkylamino azobenzene; Sodiumtetrachloropalladate; Orthopalladation; C–H activation
1. Introduction
functional group can be relevant for electro-optical
devices [5]. Therefore, specific functionalisation of new
azo systems via C–H activation would increase the scope
of research in this area.
Currently there is considerable interest in the exploi-
tation of transition metal mediated C–H activation for
bringing about interesting organic transformations [1].
These reactions involve the formation of reactive orga-
nometallic complexes, from which the desired products
are yielded. This work reports the results of palladation
reactions of several new azoamine substrates. The rea-
sons for choosing the azoamine target molecule are
manifold. Due to the basic interest and potential appli-
cations of aromatic azo compounds, it is an active area
of chemical research. The notable features of their inter-
ests include photochromism [2] redox activity [3] and
liquid crystal properties [4]. Syntheses of organometallic
or coordination compounds of azo ligands with
enhanced performance are still required. On the other
hand, thermotropic mesogens bearing an appropriate
With this background in mind, we are concerned with
synthesising new azoamine molecules since there are
only a few examples where these were utilized [6] as
ligands. The reaction of 2-(arylazo) aniline, A (Chart
1), one of the simplest azoamine ligands, with platinum
metals has been described only recently [6]. Neverthe-
less, the C–H activation in 2-(arylazo) aniline did not
occur as a result of unsuitable electronic criteria and
mismatch in appropriate geometry due to the formation
of a six membered azoimine chelate B (Chart 1) upon
dissociation of the amino proton. These results drew
our interest in synthesising modified 2-(arylazo) aniline
ligands and examining their reactions with Na2PdCl4.
Herein, we describe the syntheses of several such ligands
and the corresponding orthopalladated complexes of
type C (Chart 1). The ligands and complexes have been
characterized from the spectroscopic data. The crystal
*
Corresponding author. Tel.: +919830194190; fax: +913325828282.
E-mail address: scha8@rediffmail.com (S. Chattopadhyay).
0277-5387/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2005.05.022

1954
J. lal Pratihar et al. / Polyhedron 24 (2005) 1953–1960
R0 and R as given in Chart 2. The R0 substituents were
chosen on the basis of increasing chain length (H3C–,
H5C2–, H17C8–,) and varying the probable binding sites
R
R
R
Cl
Pd
N
N
N N
N
N
(CH2@CH–CH2–,
2-MeOC6H4CH2–,
C6H5CH2–,
M
N
NH2
EtO2CCH2–). Reaction of 1a–11a with sodium tetra-
chloropalladate in methanol at room temperature
afforded brown coloured complexes of composition
1b–11b (Scheme 1) as shown in (Chart 1). The orthopal-
ladated complexes are formed upon substitution of the
ortho aryl proton from the azobenzene fragment of the
ligand precursors 1a–11a. Eleven orthopalladated
complexes were prepared, where the binding modes
(C,N,N) of the ligands were identical (1H NMR and
X-ray, see below), unlike 2-(arylazo) aniline [6]. One of
the important observations is the coordination of the
secondary amino nitrogen without dissociating the
proton. In the case of other azoamine ligands, the sec-
ondary amino groups bind the metals only when the
amino proton gets dissociated [7]. Thus the complexes,
1b–11b, are the first family of orthopalladated azoamine
molecules. The formation of a metal–carbon bond has
been presumed to occur as a result of prior binding with
a suitable hetero donor atom fulfilling the electronic
criteria and appropriate geometry about the metal with
respect to the ortho carbon atom.
R
N
H
H
B
A
C
Chart 1.
structure of one of the complexes has been determined
to confirm the molecular structure. Weak unsupported
dimers have been recognized in the crystal lattice.
2. Results and discussion
2.1. Syntheses
The orange coloured 2-arylazo-1N-alkyl aniline,
1a–11a (Chart 2) ligands were prepared by refluxing
2-(arylazo) anilines with the appropriate alkyl halide in
ethanol or DMF in the presence of potassium carbonate
(Scheme 1). The product formations were monitored on
a TLC plate. Eleven ligands were prepared by modifying
R
Ligand
Complex
R
1a
CH3
CH3
1b
2b
H
CH3
2a
3a
4a
3b
H
C2H5
R
N
R
N
CH3
C2H5
4b
5b
6b
CH3
CH3
CH3
5a
6a
C8H17
Cl
Pd
CH2CHCH2
-MeOC H CH
N
N
N
7a
8a
7b
8b
2
N
H
6
4
2
R
R
H
CH2Ph
H
CH3
CH2Ph
CH2Ph
9a
Complex
9b
Ligand
10a
Cl
10b
11b
11a
CH3
CH2CO2C2H5
Chart 2.
R
R
R
Methanol
Cl
K2CO3
Ethanol or DMF
Pd
R X
NH2
N
N
N
Na2PdCl4
N
N
N
N
H
N
H
/
R
/
R
Scheme 1.

J. lal Pratihar et al. / Polyhedron 24 (2005) 1953–1960
1955
2.2. Characterisation
complexes are similar, with a low energy split band in
the range 490–470 nm and a structured band within
the range 410–360 nm. The spectral data for all the li-
gands and complexes are collected in Table 1.
The ligands, 1a–11a, and the corresponding orthopal-
ladated complexes, 1b–11b, exhibit characteristic UV–
Vis spectra. Representative spectra for 9a and 9b have
been shown in Fig. 1. It is interesting to observe that
the UV–Vis spectra of all the brown orthopalladated
The ligands, 1a–11a, displayed a mN–H absorption as a
single band in the range of 3488–3413 cmꢁ1, whereas for
the complexes 1b–11b, the mN–H band appeared within
the range 3283–3071 cmꢁ1 in the IR spectra. The mN@N
band (1518–1506 cmꢁ1) of all the ligands shifted to lower
frequency (1394–1383 cmꢁ1) in the complexes, consistent
with coordination of the azo nitrogen. The mPd–Cl absorp-
tion of the palladium complexes was observed in the range
296–288 cmꢁ1. The spectral data for all the ligands and
complexes are collected in Table 1.
1
The H NMR spectra of all the ligands and com-
plexes were recorded. The spectra are consistent with
the composition and structure. However, to avoid
unnecessary inclusion, we have tabulated only the data
1
for the complexes in Table 2. The H NMR data of
the ligands are given in Table 3.
Some important features of the 1H NMR spectra that
occur upon palladation are as follows: (i) The N–H res-
onance of the ligands (d 9.58–8.60) is shifted to upfield
(d 8.12–6.38) in the complexes; (ii) The aromatic proton
count of the complexes is one less than that of the
ligands indicating orthometallation. Further, the com-
plexes where R is Me display a singlet within the range
(d 7.29–6.61) in the aromatic region, consistent with the
orthometallation. (iii) The equivalent methylene protons
Fig. 1. UV–Vis spectra of 9a (---) and 9b (—). The arrows indicate
scales of the corresponding spectra.
Table 1
UV–Visa and IRb spectral data
Compound
k
max/nm (e/Mꢁ1 cmꢁ1
)
m/cmꢁ1
mN–H
mN@N
mPd–Cl
1a
1b
2a
2b
3a
3b
4a
4b
5a
5b
6a
6b
7a
7b
8a
8b
9a
9b
10a
10b
11a
11b
a
450 (9500), 315 (18050), 250 (23840), 230 (21500)
490 (6300), 400 (14600), 370 (27700), 360 (28750), 248 (25540), 230 (29600)
450 (31400), 325 (53950), 250 (51620), 230 (56100)
490 (16100), 410 (29700), 370 (42900), 360 (44500), 260 (42800), 230(51300)
460 (9800), 320 (16000), 250 (16700), 230 (17500)
490 (6500), 410 (15300), 370 (29830), 360 (30700), 250 (27050), 230 (38100)
460 (13500), 325 (20900), 250 (20200), 230 (22000)
490 (8800), 410 (16850), 370 (24650), 360 (25500), 260 (23820), 230 (28800)
465 (27300), 315 (40300), 250 (59300), 230 (60800)
490 (13150), 410 (24900), 375 (36550), 360 (37300), 260 (36500), 230 (47650)
455 (18700), 320 (30650), 245 (35300), 230 (38200)
490 (12400), 410 (23500), 375 (33900), 360 (35000), 260 (34400), 230 (44200)
450 (8450), 320 (25400), 270 (31600), 230 (57200)
490 (6500), 410 (12700), 375 (18200), 360 (18000), 260 (20300), 230 (33400)
460 (6500), 315 (17600), 230(16600)
490 (2050), 406 (4800), 375 (8600), 360 (9100), 250 (8560), 230 (12000)
450 (12270), 325 (20503), 250 (22770), 230 (23000)
490 (11400), 410 (21811), 375 (30500), 360 (34200), 260 (36500)
450 (8614), 320 (14570), 250 (17000), 230 (16700)
480 (5237), 415 (11734), 375 (11800), 360 (16000), 260 (14200), 230 (23250)
430 (29600), 320 (52000), 245 (48050), 230 (50600)
490 (7500), 410 (14000), 370 (20200), 360 (20600), 260 (20000), 230 (25600)
3426
3238
3427
3236
3414
3225
3413
3229
3417
3099
3420
3097
3420
3283
3421
3231
3415
3205
3421
3219
3488
3071
1517
1391
1517
1386
1514
1388
1514
1383
1514
1391
1513
1394
1510
1387
1506
1384
1510
1393
1508
1386
1518
1390
293
294
296
294
290
290
289
289
293
290
296
In dichloromethane.
b
KBr disc.

1956
J. lal Pratihar et al. / Polyhedron 24 (2005) 1953–1960
Table 2
1H NMR spectra of the complexes, 1b–11b
Compound
da (X, nH)b
Aromatic protons
Non-aromatic protons
3.16(d, 3H)
R (CH3)
N–H
1bd
6.72(t, 1H), 6.87(d, 1H),
7.01(t, 1H), 7.22(t, 1H),
7.44(d, 1H), 7.52(m, 3H)
6.65(s, 1H), 6.80(d, 1H),
7.16(t, 1H), 7.37(d, 1H),
7.45(d, 1H), 7.49(t, 1H),
7.55(d, 1H)
6.38(b, 1H)
2bd
3bd
3.14(d, 3H)
2.00(s, 3H)
6.47(s, 1H)
6.69(s, 1H)
6.71(t, 1H), 6.85(d, 1H),
1.25(t, 3H), 3.52(m, 1H),
6.99(t, 1H), 7.15–7.22(m, 1H),
7.42(d, 1H), 7.53(d, 2H),
7.58(d, 1H)
6.68(s, 1H), 6.81(d, 1H),
7.16(t, 1H), 7.40(d, 1H),
7.47(d, 1H), 7.52(m, 2H)
6.61(s, 1H), 6.78(d, 1H),
7.11(t, 1H), 7.33(d, 1H),
7.44(d, 1H), 7.48(t, 1H),
7.52(d, 1H)
3.65(m, 1H)
4bd
5bd
1.24(t, 3H), 3.53(m, 1H),
3.65(m, 1H)
2.03(s, 3H)
1.99(s, 3H)
6.73(b, 1H)
6.82(s, 1H)
0.81(t, 3H), 1.16–1.40(m, 12H),
3.40(b, 1H), 3.54(b, 1H),
6bd
7bd
6.81(m, 2H), 7.15(t, 1H),
7.38(d, 1H), 7.46(d, 1H),
7.48(t, 1H), 7.54(d, 1H)
6.78(s, 1H), 6.81–6.86(m, 3H),
6.89(d, 1H), 7.10(t, 1H),
7.21(t, 1H), 7.27–7.32(m, 2H),
7.44(d, 1H), 7.50(d, 1H)
7.15–7.29(m, 5H), 7.44(t, 2H),
7.54(t, 3H), 7.74(t, 2H),
7.91(t, 1H)
7.02(d, 1H), 7.09–7.13(m, 3H),
7.29(s, 1H), 7.36(d, 1H), 7.53(d, 2H),
7.61(t, 1H), 7.68(d, 1H),
7.74(d, 1H), 7.80(s, 1H)
7.16(t, 3H), 7.31(d, 1H), 7.41(t, 2H),
7.52(t, 2H), 7.69(t, 1H), 7.78(d, 1H),
7.84(d, 2H)
4.05(b, 1H), 4.24(b, 1H),
5.08(d, 1H), 5.14(d, 1H), 6.13–6.19(m, 1H)
2.02(s, 3H)
2.10(s, 3H)
6.68(s, 1H)
6.65(t, 1H)
3.91(s, 3H), 4.17(b, 1H),
5.14(b, 1H)
8bc
9bc
4.51(s, 2H)
4.52(s, 2H)
7.93(s, 1H)
7.93(s, 1H)
2.30(s, 3H)
10bc
11bd
4.54(s, 2H)
8.12(s, 1H)
6.73(b, 1H)
6.82(s, 1H), 6.83(d, 1H),
7.23(t, 1H), 7.45–7.51(m, 3H)
7.55(d, 1H)
1.22(t, 3H), 4.20(m, 2H),
4.22(d, 1H), 4.40(d, 1H)
2.06(s, 3H)
a
In ppm.
b
X = multiplicity (m = multiplet, s = singlet, d = doublet, t = triplet, b = broad), n = proton count.
In DMSO-d6.
In CDCl3.
c
d
(N–CH2–) of R0 in the ligands become inequivalent in
in Fig. 3. Selected bond distances and angles are col-
lected in Table 4.
the complexes (excepting R0 = CH2Ph), diagnostic for
binding of the amino nitrogen. All of these features have
been shown in Fig. 2, in representative spectra for 6a
and 6b. (iv) The N–H proton resonance of the metal
complexes vanishes upon shaking with D2O, confirming
its non-dissociation upon coordination.
The asymmetric unit of 9b contains two molecules,
which are held as a weak dimer with a non-covalent
Pdꢀ ꢀ ꢀPd interaction. The geometry and bond parameters
are similar in the two molecules. The molecular struc-
ture of each monomer molecule exhibits a distorted
square planar geometry about the palladium, where
the anionic ligand (9a)ꢁ binds the metal in a tridentate
(C,N,N) fashion. A chloride ligand completes the tetrac-
oordination about Pd(II). The Pd–Cl and Pd–N(azo)
2.3. X-ray structure
The suitable crystals of 9b were grown by slow diffu-
˚
sion of hexane into a dichloromethane solution. The
distances (2.312(2) and 1.943(4) A, respectively), are
ꢀ
crystals are triclinic and the space group is P1. A per-
within the normal range [7b]. The Pd–C bond length
˚
spective view with the atom numbering scheme is given
(1.986(5) A) is also matched well with the Pd–C lengths

J. lal Pratihar et al. / Polyhedron 24 (2005) 1953–1960
1957
Table 3
1H NMR spectra of the ligands, 1a–11a
Compound
da (X, nH)b
Aromatic protons
Non-aromatic protons
p-CH3
N–H
1ac
2ac
3ac
4ac
5ac
6ac
7ac
8ac
9ac
6.72–6.80(m, 2H), 7.20–7.54(m, 9H),
7.79(d, 2H), 7.81(d, 1H)
6.74–6.84(m, 2H), 7.22–7.39(m, 8H),
7.68(d, 2H), 7.84(d, 1H)
6.87(t, 2H), 7.22–7.44(m, 8H),
7.72(d, 2H), 7.84(d, 1H)
6.77–6.84(m, 2H), 7.25–7.52(m, 4H),
7.80–7.87(m, 3H)
6.77(t, 2H), 7.29(t, 4H),
7.81(d, 2H), 8.10(d, 1H)
6.76(t, 2H), 7.34–7.56(m, 4H),
7.77–7.94(m, 3H)
6.77–6.87(m, 2H), 7.23–7.31(m, 3H),
7.75(d, 2H) 7.82(d, 1H)
4.54(s, 2H)
4.54(s, 2H)
4.54(s, 2H)
3.01(s, 3H)
2.99(s, 3H)
9.24(s, 1H)
9.20(s, 1H)
9.58(s, 1H)
8.60(s, 1H)
8.60(s, 1H)
8.80(s, 1H)
8.70(s, 1H)
8.72(s, 1H)
9.04(s, 1H)
2.41(s, 3H)
2.46(s, 3H)
3.33–3.35(m, 2H),
1.37(t, 3H)
3.30–3.40(m, 2H),
1.38(t, 3H)
3.94(s, 2H), 5.22(d, 1H),
5.35(d, 1H), 5.97–6.01(m, 1H),
3.79(s, 3H), 4.55(s, 2H)
2.43(s, 3H)
2.41(s, 3H)
2.43(s, 3H)
6.74–6.79(m, 2H), 7.23–7.30(m, 3H),
7.71(d, 2H), 7.83(d, 1H)
6.79(t, 1H), 6.86(d, 2H),
6.94(t, 2H), 7.17(t, 1H), 7.18(t, 1H),
7.21(m, 3H), 7.38(d, 1H),
7.70(d, 1H)
6.73–6.78(m, 2H), 7.24–7.30(m, 3H),
7.70(d, 2H), 7.82(d, 1H)
10ac
11ac
3.27(d, 2H), 1.69–1.75(m, 2H)
1.44–1.50(m, 2H), 1.25–1.39(m, 8H),
0.88(t, 3H)
1.25–1.36(m, 3H), 4.08(s, 2H),
4.28–4.32(m, 2H)
2.41(s, 3H)
2.42(s, 3H)
8.85(s, 1H)
8.93(b, 1H)
6.63(d, 1H), 6.86(t, 1H),
7.28(m, 3H), 7.81–7.90(m, 3H)
a
In ppm.
b
X = multiplicity (m = multiplet, s = singlet, d = doublet, t = triplet, b = broad), n = proton count.
In CDCl3.
c
C(9)
C(8)
C(10)
C(7)
N(1)
C(5)
N(2)
C(11)
C(6)
C(4)
H1/
C(12)
N(3)
C(3)
C(1)
Pd(1)
C(13)
C(2)
C(15)
C(16)
C(20)
C(14)
Cl(1)
C(19)
C(18)
C(17)
Fig. 3. Perspective view of 9b with the atom numbering scheme.
Hydrogen atoms excepting on N3 are omitted for clarity.
Fig. 2. The 1H NMR spectra of (a) 6a and (b) 6b in CDCl3, where n of
nH(Ar) stands for the proton count. The expansion of the aromatic
region (d 6.81–7.54) of 6b has been shown in the inset.
(177.06(13)°) bond angles deviate a little from linearity.
The chelate ring bite angles are also considerably smaller
[N(2)–Pd–N(3), 81.75(17)°; N(2)–Pd–C(1), 79.5(2)°]
than the ideal values (90°) of a square geometry,
although the atoms within the coordination sphere lie
in other orthopalladated azo benzene complexes [8]. The
˚
Pd–N(amine) bond length (2.194(1) A) is much longer
˚
on a plane (mean deviation 0.01 A). In fact the whole
than the Pd–N(azo) distance, presumably as a conse-
quence of the stronger trans influence of the aryl carbon
[9]. The N(3)–Pd–C(1) (161.17(19)°) and N(2)–Pd–Cl
molecule, excepting the benzyl group, is planar (mean
˚
deviation 0.05 A).

1958
J. lal Pratihar et al. / Polyhedron 24 (2005) 1953–1960
Table 4
˚
Selected bond distances (A) and angles (°) for 9b
Pd(1)–C(1)
Pd(1)–N(2)
Pd(1)–N(3)
Pd(1)–Cl(1)
N(1)–C(6)
N(1)–N(2)
N(2)–C(7)
C(7)–C(12)
C(1)–C(6)
N(3)–C(12)
1.986(1)
1.942(1)
2.194(1)
2.312(2)
1.399(1)
1.266(1)
1.431(1)
1.391(1)
1.413(1)
1.465(1)
N(2)–Pd(1)–C(1)
N(2)–Pd(1)–N(3)
C(1)–Pd(1)–N(3)
N(2)–Pd(1)–Cl(1)
C(1)–Pd(1)–Cl(1)
N(3)–Pd(1)–Cl(1)
C(12)–N(3)–Pd(1)
79.5(2)
81.7(2)
161.1(2)
177.0(1)
97.9(2)
100.7(1)
106.2(3)
The dimer contained in the asymmetric unit, is held in
a staggered conformation (dihedral angle is 60°) with
three non-bonding inter-monomeric interactions,
Fig. 5. Partial packing diagram of complex 9b along the c-axis.
The 2-(arylazo) anilines were prepared according to a re-
ported procedure [6]. Palladium chloride, benzyl chlo-
ride, methyl iodide, ethyl bromide and potassium
carbonate were purchased from E. Merck, Kolkata, In-
dia. Allyl chloride, ethyl chloroacetate, n-bromooctane
and o-cresol were purchased from SRL, Mumbay, India.
Disodium tetrachloropalladate was prepared by a re-
ported procedure [6].
˚
˚
Pdꢀ ꢀ ꢀPd, 3.301 A; N(amine)ꢀ ꢀ ꢀCl, 3.256 A and N(ami-
˚
ne)ꢀ ꢀ ꢀPd, 3.635 A. The dimeric unit with the non-bond-
ing interactions is shown in Fig. 4.
However, in the packing of the molecule, no infinite
stacking has been observed, where the discrete dimers
are arranged in a regular pattern in the crystal lattice.
A partial packing diagram has been shown in Fig. 5.
3.2. Syntheses of ligands
3. Experimental
3.2.1. 1a and 2a
To prepare the ligands 1a and 2a, methyl iodide
(0.095 cm3, 1.52 mmol) was refluxed for 2 h with
2-(phenylazo) aniline (0.3 g, 1.52 mmol) and 2-(p-tolylazo)
aniline (0.32 g, 1.52 mmol), respectively, in 30 cm3 etha-
nol in the presence of 1 g of K2CO3. From the orange
solid mass that was obtained after evaporation of etha-
nol, the ligands 1a and 2a were isolated by column chro-
matography on silica gel (60–120 mesh). The eluent was
petroleum ether. Upon evaporation of the solvent, the
orange-red semi-solid of pure ligand was obtained.
Yield: 1a, 65%; 2a, 70%. Anal. Calc. for C13H13N3, 1a:
C, 73.93; H, 6.16; N, 19.90. Found: C, 73.90; H, 6.10;
N, 19.85%. Calc. for C14H15N3, 2a: C, 74.66; H, 6.66;
N, 18.66. Found: C, 74.61; H, 6.68; N, 18.62%.
3.1. Materials
The solvents used in the reactions were of reagent
grade obtained from E. Merck, Kolkata, India, and
were purified and dried by reported procedures [6].
3.2.2. 3a and 4a
The ligands 3a and 4a were prepared following the
same procedure as described in the case of 1a and 2a
using ethyl bromide (0.114 cm3, 1.52 mmol) in place of
methyl iodide. The refluxing time was 4 h. Yield 3a,
50%; 4a, 65%. Anal. Calc. for C14H15N3, 3a: C, 74.66;
H, 6.66; N, 18.66. Found: C, 74.63; H, 6.65; N,
17.05%. Anal. Calc. for C15H17N3, 4a: C, 75.31; H,
7.11; N, 17.57. Found: C, 75.27; H, 7.10; N, 17.53%.
Fig. 4. A view of the dimeric unit of 9b. The broken lines indicate the
weak interactions.

J. lal Pratihar et al. / Polyhedron 24 (2005) 1953–1960
1959
3.2.3. 5a, 6a and 7a
3.3.2. 2b–11b
5a, 6a and 7a were prepared by refluxing 2-(p-toly-
lazo) aniline (0.32 g, 1.52 mmol) with n-bromooctane
(0.264 cm3, 1.52 mmol), allyl chloride (0.125 cm3,
1.52 mmol) and 2-bromomethyl anisole (0.305 g,
1.52 mmol), respectively, in 30 cm3 ethanol in the pres-
ence of 1 g of K2CO3for 4 h. The ligands were purified
by the same procedure as described above. Yield: 5a,
65%; 6a, 65%; 7a, 65%. Anal. Calc. for C21H29N3, 5a:
C, 78.01; H, 8.97; N, 13.00. Found: C, 78.00; H, 8.91;
N, 13.07%. Anal. Calc. for C16H17N3, 6a: C, 76.49; H,
6.77; N, 16.73. Found: C, 76.45; H, 6.75; N, 16.75%.
Anal. Calc. for C21H21N3O, 7a: C, 76.13; H, 6.34; N,
12.69. Found: C, 76.10; H, 6.30; N, 12.70%.
The complexes 2b–11b were prepared following a
similar procedure as described in the case of 1b, but
the durations of the reactions were different. These are
8 h for 2b–4b, 6 h for 5b, 7 h for 6b, 15 h for 7b, 5 h
for 8b–10b and 15 h for 11b.
Yield: 2b, 60%; 3b, 40%; 4b, 60%; 5b, 60%; 6b, 50%;
7b, 45%; 8b, 60%; 9b, 70%; 10b, 30%; 11b, 30%. Anal.
Calc. for C14H14N3PdCl, 2b: C, 45.91; H, 3.82; N,
11.47. Found: C, 45.90; H, 3.85; N, 11.95%. Anal. Calc.
for C14H14N3PdCl, 3b: C, 45.91; H, 3.82; N, 11.47.
Found: C, 45.87; H, 3.80; N, 11.45%. Anal. Calc. for
C15H16N3PdCl, 4b: C, 47.37; H, 4.21; N, 11.05. Found:
C, 47.35; H, 4.15; N, 11.00%. Anal. Calc. for
C21H28N3PdCl, 5b: C, 54.31; H, 6.03; N, 9.05. Found:
C, 54.35; H, 6.07; N; 9.00%. Anal. Calc. for C16H16-
N3PdCl, 6b: C, 48.98; H, 4.08; N, 10.71. Found: C,
48.95; H, 4.05; N, 10.70%. Anal. Calc. for C21H20N3-
OPdCl, 7b: C, 53.39; H, 4.23; N, 8.89. Found: C,
53.40; H, 4.25; N, 8.85%. Anal. Calc. for C19H16N3PdCl,
8b: C, 53.28; H, 3.77; N, 9.80. Found: C, 53.50; H, 4.00;
N, 9.70%. Anal. Calc. for C20H18N3PdCl, 9b: C, 54.27;
H, 4.07; N, 9.49. Found: C, 54.30; H, 4.10; N, 9.51%.
Anal. Calc. for C19H15N3PdCl2, 10b: C, 49.30; H, 3.27;
N, 9.00. Found: C, 49.70; H, 3.40; N, 9.31%. Anal. Calc.
for C17H18N3O2PdCl, 11b: C, 46.58; H, 4.11; N, 9.59.
Found: C, 46.55; H, 4.05; N, 9.56%.
3.2.4. 8a, 9a and 10a
8a, 9a and 10a ligands were prepared by refluxing
benzyl chloride (0.193 cm3, 1.52 mmol) with 2-(pheny-
lazo) aniline (0.3 g, 1.52 mmol), 2-(p-tolylazo) aniline
(0.32 g, 1.52 mmol) and 2-(p-chlorophenylazo) aniline
(0.352 g, 1.52 mmol), respectively, in 30 cm3 ethanol
and 1 g of K2CO3 for 4 h. The ligands were purified
by the same procedure as described above. Yield: 8a,
50%; 9a, 65%; 10a, 50%. Anal. Calc. for C19H17N3, 8a:
C, 79.44; H, 5.97; N, 14.63. Found: C, 79.70; H, 6.10;
N, 14.55%. Anal. Calc. for C20H19N3, 9a: C, 79.69; H,
6.36; N, 13.95. Found: C, 79.70; H, 6.40; N, 13.97%.
Anal. Calc. for C19H16N3Cl, 10a: C, 70.90; H, 5.00; N,
13.00. Found: C, 70.70; H, 5.30; N, 13.40%.
3.4. Physical measurements
3.2.5. 11a
Microanalyses (C,H,N) were performed using a
Perkin–Elmer 240C elemental analyzer. Infrared spectra
were recorded on a Perkin–Elmer L120-00A FT-IR
spectrometer with the samples prepared in KBr pellets.
Electronic spectra were recorded on a Shimadzu
UV-2401 PC spectrophotometer. 1H NMR spectra were
obtained on Brucker AC-200, Brucker Avance DPX
300, Brucker Avance DPX 400 and Brucker Avance
RPX 500 NMR spectrometers in CDCl3, DMSO-d6,
D2O using TMS as the internal standard.
2-(p-Tolylazo) aniline (0.32 g, 1.52 mmol) was mixed
with ethyl chloroacetate (0.185 cm3, 1.52 mmol) in
30 cm3 DMF. 1 g of K2CO3 was added to this mixture
and which was then refluxed for 4 h. From the orange
solid mass that was obtained after evaporation of
DMF, the ligand 11a was isolated by column chroma-
tography on silica gel (60–120 mesh). The eluent was
petroleum ether. Upon evaporation of solvent the or-
ange-red semi-solid of pure ligand was obtained. Yield:
65%. Anal. Calc. for C17H19N3O2, 11a: C, 68.68; H,
6.39; N, 14.14. Found: C, 68.65; H, 6.40; N, 14.10%.
3.5. Crystallography
3.3. Syntheses of complexes
Data of 9b was collected by the x-scan technique
on a Nicolet R3m/v diffractometer with Mo Ka radi-
ation monochromated by a graphite crystal. The
structure solution was done by direct methods with
the SHELXS-97 program. Full-matrix least-squares
refinements were performed using the SHELX-97 pro-
gram (PC version). All non-hydrogen atoms were re-
fined anisotropically using reflections I > 2r(I).
Hydrogen atoms were included at calculated positions.
The crystal data and data collection parameters are
listed in Table 5.
3.3.1. 1b
A solution of 1a (0.110 g, 0.52 mmol) in 10 cm3 meth-
anol was added to a solution of Na2PdCl4 (0.150 g,
0.52 mmol) in 5 cm3 methanol. The mixture was stirred
for 8 h. The dark solid precipitate was separated by fil-
tration and purified by column chromatography using
silica gel (60–120 mesh). The eluent was toluene-acetoni-
trile mixed solvent (90/10 v/v) and upon evaporation of
the solvent, dark red solid 1b was obtained. Yield: 55%.
Anal. Calc. for C13H12N3PdCl: C, 44.32; H, 3.40; N,
11.93. Found: C, 44.29; H, 3.35; N, 11.40%.

1960
J. lal Pratihar et al. / Polyhedron 24 (2005) 1953–1960
Table 5
Crystallographic data for 9b
References
[1] (a) W.D. Jones, Acc. Chem. Res. 36 (2003) 140, and references
Chemical formula
Formula weight
Space group
C20H18ClN3Pd
442.22
therein;
ꢀ
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P1
Crystal system
triclinic
10.802(5)
13.159(5)
14.397(8)
˚
a (A)
˚
b (A)
˚
c (A)
[2] (a) H. Rau, in: H. Durr, H. Bouas-Laurent (Eds.), In Studies in
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4
Temperature (K)
qcald (Mg/m3)
293(2)
1.614
1.173
888
l (mmꢁ1
F(000)
)
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R(all data)
R1 = 0.0730, wR2 = 0.1080
6770/6400 [Rint = 0.0277]
0.0419/1.065
Unique reflections/[I > 2r(I)]
R1a/GOFb
c
wR2 [I > 2r(I)]
0.0969
P
P
a
Observation criterion: I > 2r(I). R1 = iFoj ꢁ jFoi/ jFoj.
P
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1=2
b
c
GOF ¼ ½ ½wðF 2o ꢁ F 2c Þ ꢂ=ðn ꢁ pÞꢂ
.
P
P
2
2 1=2
wR2 ¼ ½ ½wðF 2o ꢁ F c2Þ ꢂ= ½wðF 2oÞ ꢂ
,
where w ¼ 1=r2ðF o2Þþ
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2
ðaPÞ þ bP; P ¼ ðF 2o þ 2F c2Þ=3.
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1656;
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Reference Number 212758. Copies
of this information may be obtained free from the Direc-
tor, CCDC, 12 Union Road, Cambridge CB2 1EW, UK
(fax: +44 1223 336 033; e-mail: deposit@ccdc.cam.ac.uk
or www: http://www.ccdc.com.ac.uk).
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We are thankful to the DST (New Delhi) for funding
and fellowship to JP under the DST-SERC Project. The
necessary laboratory and infrastructural facilities are
provided by the Dept. of Chemistry, University of Kaly-
ani. We acknowledge the National facility (X-ray diffrac-
tometer) at RSIC, IIT Madras for X-ray studies. We are
thankful to Dr. G. Saha (Chembiotek). The support of
DST under the FIST Program to the Department of
Chemistry, University of Kalyani is acknowledged.
(b) K.K. Kamar, S. Das, C.-H. Hung, A. Castineiras, M.D.
Kuzmin, C. Rillo, J. Bartolome, S. Goswami, Inorg. Chem. 42
(2003) 5367.
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