Activation of ortho C-H bond by nickel(II) acetate or sodium tetrachloropalladate(II) in naphthyl imino derivatives of azobenzene

Article abstract of DOI:10.1016/j.poly.2012.12.011

The reactions of 1-{[2-(arylazo)phenyl]iminomethyl}-2-naphthol, H ₂L_nap [where H represents the dissociable proton upon complexation and aryl groups of H₂L_nap are phenyl for H₂L¹_nap

Full text of DOI:10.1016/j.poly.2012.12.011

Polyhedron 51 (2013) 46–53
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Activation of ortho C–H bond by nickel(II) acetate or sodium
tetrachloropalladate(II) in naphthyl imino derivatives of azobenzene
Debprasad Patra a,b, Poulami Pattanayak a, Jahar Lal Pratihar a,c, Surajit Chattopadhyay a,
⇑
a Department of Chemistry, University of Kalyani, Kalyani 741235, India
b Department of Chemistry, East Calcutta Girls’ College, Kolkata 700089, India
c Department of Chemistry, Kandi Raj College, Murshidabad 742137, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The reactions of 1-{[2-(arylazo)phenyl]iminomethyl}-2-naphthol, H2Lnap [where H represents the disso-
ciable proton upon complexation and aryl groups of H2Lnap are phenyl for H2L1nap; p-methyl phenyl for
Received 5 November 2012
Accepted 15 December 2012
Available online 23 December 2012
H2L2
and p-chloro phenyl for H2L3nap] with nickel acetate tetra hydrate or disodium tetrachloropalla-
nap
date in methanol afforded M–C(aryl) bonded species of composition [M(Lnap)] (M = Ni(II) and Pd (II)). The
dinegative (Lnap
)
2ꢀ ligands bind the Ni(II) or Pd(II) in tetradentate (C, N, N, O) fashion in distorted square
Keywords:
1-{[2-(Arylazo)phenyl]iminomethyl}-2-
naphthol
Orthometallation
O-insertion
Luminescent property
planar geometry. Ligands and complexes were characterized by spectroscopic methods. The X-ray struc-
tures of H2L1nap, [Ni(L1nap)] and [Pd(L1nap)] were determined to authenticate the characterization. Reac-
tions with metachloroperbenzoic acid (mCPBA), TBHP and hydrogen peroxide leading to oxygen
insertion into the M-C bond have been examined. Luminescent properties of ligands and complexes have
been reported.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
bond between M = Ni(II) and M = Pd(II) is also relevant to realize
the advantages.
Catalytic conversion of C–H bonds into C–C, C–N, C–O and C–
halogen bonds by means of metal assisted C–H activation is one
of the important areas in current chemical research to search for
suitable catalyst [1,2]. Studies are ongoing to develop appropriate
low cost alternative catalysts, with comparatively cheap and abun-
dant metal ions, that are capable of C–H activation. Recently, first
[Ni(COD)2] catalyzed chemical transformation via activation of
ortho C–H bond has been reported with a mention that there
was no such example though chelation assisted orthonickelation
of azobenzene was achieved by treating with [Ni(Cp)2] quite a long
ago [3]. Facile activation of ortho C–H bond and stoichiometric C–O
bond formation under ordinary condition using the common re-
agent nickel acetate has been reported [4]. Although, the reaction
was not catalytic but provided the clue toward use of commonly
available nickel compound as catalyst for the transformations
involving ortho C–H activation. Thus, having realized the impor-
tance, we were encouraged to study the hydroxylation of different
organic substrates through chelation assisted activation of ortho
C–H bond by nickel acetate. Comparison of the reactivity of M–C
This work stems from our interest on synthesis of metalloazosa-
lophens 1 [4–6]. As reported earlier, synthesis of metalloazosalo-
phens can be carried out in two ways – first, synthesis of M–C
(aryl) bonded complex (ortho C–H cleavage) using nickel acetate
R2
O
N
O
N
R1
M
N
1
or sodium tetrachloropalladate followed by oxygen insertion into
M–C bond i.e. C–O bond formation (Scheme 1). This procedure
was shown to be applicable for the compound H2Lsal, 2 [4,6]. Sec-
ondly, Synthesis of authentic azosalophen ligand, H2OLsal, 3, via
nickel assisted hydroxylation followed by complexation with
appropriate transition metal substrates (Scheme 2) [4–8].
Synthesis of new analogs of H2Lsal, 2 and its conversion to an
analog of H2OLsal, 3, using nickel acetate or sodium tetrachloropal-
ladate were contemplated to illustrate that the C–H activation by
nickel acetate or sodium tetrachloropalladate can also take place
in the analogs of H2Lsal. As a sequel, the new analog, containing
naphthyl group, H2Lnap, shown in 4, have been used for the present
purpose [9]. Incorporation of naphthyl group within the ligand
⇑
Corresponding author. Tel.: +91 33 25828750; fax: +91 33 25828282.
E-mail address: scha8@rediffmail.com (S. Chattopadhyay).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.12.011

D. Patra et al. / Polyhedron 51 (2013) 46–53
47
R
R
R
Ni(CH3COO)2.4H2O
O
OH
N
O
N
O
[O]
or
M
M
Na2PdCl4
N N
N N
N
N N
2
= Ni / Pd
M
M
= Ni / Pd
H L
sal
2
Scheme 1.
backbone was conceived with the expectation that the complexes
prepared with 4 might exhibit interesting absorption and/or emis-
sion properties due to the inherent luminescent property of naph-
thyl group [9–19].
have been reported. Emission properties of the ligands and corre-
sponding complexes have been compared and delineated in this
paper.
R
2. Results and discussion
HO
N
2.1. Syntheses
N
N
Reaction of 1-{[2-(arylazo)phenyl]iminomethyl}-2-naphthol,
H2Lnap, with Ni(OAc)2ꢁ4H2O in refluxing methanol afforded green
precipitate which upon purification by washing with methanol
gave pure complexes of Ni(II) of composition [Ni(L1nap)], 5. Simi-
larly the reaction of Na2PdCl4 with H2Lnap in stirring methanol
afforded brown complexes of Pd(II) of composition (Lnap)Pd, 6.
The synthetic reactions are shown in Eq. (1) below:
4
Herein we have described the orthometallation in H2Lnap by
treating with Ni(CH3COO)2ꢁ4H2O or Na2PdCl4. The products were
characterized by UV–Vis, IR and 1H NMR spectroscopic data. The
ð1Þ
X-ray structures of H2L1nap and newly synthesized Ni(II) and Pd(II)
orthometallated complexes have been determined for unequivocal
characterization. The reactions of new Ni–C and Pd–C bonded com-
plexes with peroxo compounds, leading to C–O bond formation,
2.2. Reactions with oxidants
The newly synthesized orthometallated complexes [Ni(L1nap)],
5, and [Pd(L1nap)], 6, transformed into the oxygenated products

48
D. Patra et al. / Polyhedron 51 (2013) 46–53
[Ni(OL1nap)], 7, and [Pd(OL1nap)], 8, respectively upon reaction
with meta chloroperbenzoic acid (mCPBA) as given in Eqs. (2)
and (3).
2.3. Preparation of authentic H2OL1nap, 9, and their complexes
Authentic H2OL1nap ligand was synthesized by the condensation
of HOL1–NH2 with 2-hydroxy-1-napthaldehyde as shown in Eq.
O
O
N
O
N
(i) or (ii) or (iii)
Ni
Ni
N
N
N
N
ð2Þ
[Ni(L1nap)], 5
[Ni(OL1nap)],
TBHP, CH2Cl2 or tBuOH
2 ; (iii)
7
Aqueous H O ,CH Cl
m-CPBA, CH Cl
; (ii)
2
(i)
2
2
2
2
(i) or (ii)
O
N
O
N
O
Pd
Pd
N
N
N
N
ð3Þ
[Pd(OL1 )],
[Pd(L1 )],
8
nap
6
nap
CH Cl
TBHP, VO(acac)2, CH2Cl2 or tBuOH
m-CPBA,
; (ii)
2
(i)
2
Although the oxygen insertion was relatively slower for
[Pd(L1nap)] but it was very fast in the case of [Ni(L1nap)]. Gradual
change in absorption spectrum with time could be measured spec-
trophotometrically for [Pd(L1nap)] adding quantitative amount of
mCPBA (Fig. 1) in dichloromethane solution.
(4). HOL1–NH2 was prepared by the procedure described earlier
[4,6]. Subsequently authentic H2OL1
was utilized for the prepa-
nap
ration of [Ni(OL1nap)] and [Pd(OL1nap)] complexes upon reaction
with Ni(OAc)2ꢁ4H2O and Na2PdCl4 respectively in methanol. Char-
acterization data, spectral features and other physical characteris-
tics of these complexes were identical with the products obtained
after oxidation of [Ni(L1nap)] and [Pd(L1nap)] with peroxo reagents
(see above).
Moreover, [Ni(L1nap)] complex underwent oxygen insertion
with TBHP in tBuOH solution (Eq. (2)) whereas [Pd(L1nap)] required
VO(acac)2 along with TBHP for effective oxygen insertion (Eq. (3)).
CHO
OH
OH
N
HO
O H
N
H2
N
N
N
N
ð4Þ
9
H2OL1
nap
Milder and greener reagent containing Mixture of aqueous hydro-
gen peroxide and dichloromethane afforded oxygenated product
only in the case of [Ni(L1nap)] at room temperature (Eq. (2)). There-
fore, in general, C–O bond formation after ortho C–H bond activa-
tion is more facile for nickel acetate than the sodium tereachloro
palladate. Isolation and unequivocal characterization of [Ni(L1nap)]
than [Pd(L1nap)] complexes provided the necessary evidence in fa-
vor of ortho C–H cleavage prior to C–O bond formation to predict
the plausible mechanism.
2.4. Characterization
All the H2Lnap, 4, ligands displayed characteristic UV–Vis spectra
in dichloromethane solution with absorptions near 465 nm and
near 315 nm [4–8]. In dichloromethane solution [Ni(L1nap)] com-
plexes, 5, exhibited low energy absorption near 620 nm and
[Pd(Lnap)] complexes, 6, displayed characteristic UV–Vis spectra
having several structured absorption bands within 250–450 nm.
The orange solution of authentic H2OL1nap in dichloromethane dis-
played overlapped absorptions within 420–320 nm. Oxidised com-

D. Patra et al. / Polyhedron 51 (2013) 46–53
49
plexes, [Ni(OL1nap)] exhibited low energy bands at 630 and 520 nm
whereas [Pd(OL1nap)] showed one absorption with maxima at
530 nm. Relevant data are included in Section 4.
In the IR spectra, the mN@N band of H2Lnap ligands (near
1482 cmꢀ1) shifted to lower frequency (1353–1361 cmꢀ1) after
formation of [Ni(Lnap)] and [Pd(Lnap)] chelates, consistent with
R
R
OH
N
O
N
O
N
N
Ni
[H+]
N
NH2
OH
CHO
the coordination of the azo nitrogen [4–8,20]. The mC@N band with-
in 1615–1624 cmꢀ1 of the H2Lnap ligands moved to 1613–
1616 cmꢀ1 region in [Ni(Lnap)] and [Pd(Lnap)] complexes. A broad
signal near 3290 cmꢀ1 for mOH of H2Lnap was absent in the spectra
of the complexes signifying the dissociation of –OH proton and
its coordination to the metal centre as Oꢀ [4–8,20]. The mN@N
(1473 cmꢀ1) of H2OL1nap shifted to lower frequency in [Ni (OL1nap)]
and [Pd(OL1nap)] at 1372 and 1375 cmꢀ1, respectively. The mC@N
R
R
O
N
O
HO
OH
M
N
N
N
N
N
M = Ni/Pd/Fe/V/Mn/Ru etc.
bands of H2OL1
(1628 cmꢀ1) appeared within 1603–1605 cmꢀ1
3
nap
H
OL
in complexes. Relevant data are collected in Section 4.
sal
2
A repeat 1H NMR experiments of the H2Lnap ligands exhibited
two doublets near d 15.9 (for H2L1
and H2L3nap) and d 9.16,
Scheme 2.
nap
whereas H2L2
displayed a broad signal at d 15.87 and a doublet
nap
at d 9.16. Therefore a revisit to the 1H NMR spectra of H2Lnap be-
came necessary [7]. Rationale of these resonances has been real-
ized by considering the intramolecular hydrogen bonded
structures shown in I. The doublet near d 15.9 for H2L1
and H2-
nap
L3
were assigned for hydrogen bonded –OH.
nap
R2
O
N
O
N
R1
M
N
1
Doublet nature was attributed to coupling with aldimino –C–H
proton through imino nitrogen as shown in I. On the other hand
the aldimine –C–H proton appears near d 9.20 as a doublet indicat-
ing significant coupling with the hydrogen bonded proton on N.
This rationale can be supported by the fact that the doublet reso-
nance for aldimino proton appeared as sharp singlet near d 9.16
on D2O shaking. Crystal structure of H2L1nap indicated the intramo-
lecular hydrogen bond in solid state also (see below).
Fig. 1. Graphical change in UV–Vis spectra during oxidation of [Pd(L1nap)] to
[Pd(OL1nap)] by mCPBA. Concentration of complex was 2.63 ꢂ 10ꢀ5(M) and of
mCPBA was 4.6 ꢂ 10ꢀ4(M).
The 1H NMR spectra of [Ni(Lnap)] and [Pd(Lnap)] complexes did
not display any –OH resonance near d 15.9 signifying the dissocia-
tion of –OH proton and its coordination to the metal centre as
phenoxide and the aldimino (–N@CH–) proton resonance appear
as a sharp singlet near d 9.40. The proton counts obtained from
1H NMR spectra and the spectral patterns of the cyclometallated
complexes are consistent with their formula and structures in
Fig. 3. Perspective view of H2L1nap with atom numbering scheme. Hydrogen atoms
(except H3a and H13) are omitted for clarity.
Fig. 2. Emission spectra of H2L1nap, [Pd(L1nap)] and [Ni(L1nap)].

50
D. Patra et al. / Polyhedron 51 (2013) 46–53
Table 2
0
Selected bond distances (AÅ) and angles (°) for [Ni(L1nap)], 5a.
Bond distances
Ni–O1
Ni–N2
Ni–N3
Ni–C2
O1–C15
N2–C7
1.8204(17)
1.799(2)
1.884(2)
1.880(2)
1.303(3)
1.419(3)
C11–C12
C15–C16
N1–N2
N1–C1
N3–C13
N3–C12
1.385(4)
1.426(4)
1.284(3)
1.404(3)
1.300(3)
1.422(3)
Bond angles
O1–Ni–N2
O1–Ni–N3
O1–Ni–C2
N2–Ni–N3
N2–Ni–C2
N3–Ni–C2
Ni–O1–C15
N2–N1–C1
O1–C15–C16
177.98(10)
96.05(8)
96.18(10)
85.58(9)
82.16(11)
167.69(10)
126.07(16)
107.5(2)
Ni–N2–N1
Ni–N2–C7
N1–N2–C7
Ni–N3–C12
Ni–N3–C13
N1–C1–C6
Ni–C2–C1
N1–C1–C2
Ni–C2–C3
123.91(17)
116.21(17)
119.9(2)
112.24(15)
125.85(17)
120.3(2)
110.07(18)
116.4(2)
133.4(2)
115.8(2)
Fig. 4. Perspective view of [Ni(L1nap)] with atom numbering scheme. Hydrogen
atoms are omitted for clarity.
Table 3
0
Selected bond distances (AÅ) and angles (°) for [Pd(L1nap)], 6a.
Bond distances
Pd–O1
Pd–N2
Pd–N3
Pd–C2
O1–C15
N1–N2
N1–C1
N2–C7
1.9939(15)
1.9172(17)
2.0131(15)
1.992(2)
1.312(3)
1.278(2)
C7–C12
C8–C9
1.422(3)
1.383(3)
1.390(3)
1.376(3)
1.399(3)
1.421(3)
1.420(3)
1.314(2)
C9–C10
C10–C11
C11–C12
C13–C14
N3–C12
N3–C13
1.408(3)
1.420(3)
Bond angles
O1–Pd–N2
O1–Pd–N3
O1–Pd–C2
N2–Pd–N3
N2–Pd–C2
N3–Pd–C2
Pd–O1–C15
N2–N1–C1
176.56(7)
93.76(6)
102.73(7)
83.71(6)
Pd–C2–C1
Pd–C2–C3
N1–N2–C7
Pd–N3–C12
Pd–N3–C13
N2–C7–C8
Pd–N2–N1
Pd–N2–C7
109.25(15)
134.33(16)
121.45(17)
111.05(11)
125.18(14)
124.19(19)
123.40(13)
115.14(12)
79.71(8)
163.31(7)
123.23(13)
108.89(16)
Fig. 5. Perspective view of [Pd(L1nap)] with atom numbering scheme. Hydrogen
atoms are omitted for clarity.
[Pd(OL1nap)] and [Ni(OL1nap)] complexes, prepared by reacting
H2OL1
with Na2PdCl4 and Ni(OAc)2 respectively, did not display
nap
the resonances for two phenolic protons consistent with phenolato
binding. The aldimino C–H appeared as singlets at d 9.60 for
[Pd(OL1nap)] and at d 9.29 for [Ni(OL1nap)]. All other resonances
for aromatic protons appeared as overlapped signals within d
6.8–8.4. The 1H NMR of oxidized products of [Ni(L1nap)] and
[Pd(L1nap)] matched well with the authentic complexes.
Table 1
0
Selected bond distances (ÅA) and angles (°) for H2L1nap, 4a.
Bond distances
O1–C15
N1–N2
N1–C1
N2–C7
N3–C12
1.2630(18)
1.2556(16)
1.4269(18)
1.4233(18)
1.4040(16)
C14–C15
C14–C19
N3–C13
N3–H3a
C1–C2
1.4533(19)
1.4627(18)
1.3298(17)
0.8595
1.3926(18)
2.5. Emission spectra
Bond angles
N2–N1–C1
N1–N2–C7
C12–N3–C13
C13–N3–H3a
C12–N3–H3a
N1–C1–C6
C2–C1–C6
114.64(11)
113.66(11)
126.25(12)
116.87
N3–C12–C7
N3–C12–C11
N3–C13–C14
N2–C7–C12
N2–C7–C8
O1–C15–C14
C1–C2–C3
O1–C15–C16
118.04(12)
122.57(12)
124.10(13)
115.40(11)
124.77(12)
122.48(13)
120.16(12)
120.08(13)
The
p
-conjugated chromophore containing ligand, H2L1nap, 4a,
exhibited emission maxima at 380 nm in dilute dichloromethane
solution (10ꢀ5 M) when excited at 320 nm. In dichloromethane
solution (10ꢀ5 M), The Ni(II) complex, [(L1nap)Ni], exhibited
quenched emission at 390 nm but the emission intensity of Pd(II)
complex, [Pd(L1nap)], was larger than the corresponding ligand at
405 nm. The emission spectra of H2L1nap, [Ni(L1nap)] and [Pd(L1nap)]
are shown in Fig. 2. The augmented emission intensity of Pd(II)
complex can be attributed to chelation-enhanced fluorescence
(CHEF) [10,11]. Whereas decrease in emission intensity for Ni(II)
complex can be ascribed as ‘‘heavy atom effect’’ [9,21]. It was men-
tioned elsewhere that the ‘‘heavy atom effect’’ does not induce
CHEF and causes the quenching through two well defined mecha-
116.88
125.20(12)
120.46(13)
114.34(11)
N1–C1–C2
solution. The 1H NMR data for all the ligands and complexes are gi-
ven in Section 4.
The 1H NMR results of authentic H2OL1nap ligand exhibited two
singlets at d 12.39, d 10.76 for two phenolic protons and at d 9.33
for one aldimino C–H proton. Resonances for other fourteen
nism
–
either naphthyl?metal energy transfer (ET) or
aromatic protons appeared within
d 7.0–8.1. Corresponding
metal?naphthyl electron transfer (et) [10,11].

D. Patra et al. / Polyhedron 51 (2013) 46–53
51
2.6. X-ray structures
Sodiumtetrachloropalladate (II) was prepared by reported proce-
dure [22].
Unequivocal characterizations of the ligands, H2Lnap, and corre-
sponding metal complexes, (Lnap)M (M = Ni, Pd), were performed
by X-ray structure analysis of H2L1nap, [Ni(L1nap)] and [Pd(L1nap)]
respectively. Figs. 3–5 show perspective views of their molecular
structures. Tables 1–3 respectively contain the selected bond dis-
tances and angles. The X-ray structure of H2L1nap reveals the planar
4.2. Physical measurements
Microanalyses (C, H, N, O/S) were performed using a Perkin-El-
mer 2400 elemental analyzer. Infrared spectra were recorded on a
Perkin-Elmer L120-00A FT-IR spectrometer with the samples pre-
pared as KBr pellets. Electronic spectra were recorded on a Shima-
dzu UV-1800 & UV-2401PC spectrophotometer. 1H NMR spectra
were obtained on Bruker RPX 500 NMR & Bruker DPX 400 spec-
trometers in CDCl3.
geometry of the ligand. All the non hydrogen atoms of H2L1
nap
0
make a goo0d plane (mean deviation 0.251 ÅA). The N(1)–C(1),
0
(1.4266(18) ÅA); N(2)–C(7), (1.4237(18) ÅA) and N(3)–C(12),
0
(1.4039(17) ÅA) lengths of the free ligand are close to C–N single
0
bond length. The N(3)–C(13) length (1.3309(17) ÅA) is similar to
the imine (C@N) distance [4–8,22–25]. The N(1)–N(2) length
0
(1.2556(16) ÅA) is very similar to azo (–N@N–) bond length [4–
4.3. Syntheses of compounds
0
8,22–25]. The distance (2.577 ÅA) between aryl O(1) and aldimine
N(3) signify the intramolecular H-bond [19–26]. H(3a) was located
by Fourier mapping indicating significant interaction with imine
nitrogen giving rise to considerable coupling with aldimine
(–N@CH–) proton as observed in 1H NMR spectra of the ligands
4.3.1. Synthesis of [Ni(L1nap)] complex (5a)
A solution of H2L1nap (0.2 g, 0.57 mmol) in 10 cm3 methanol was
added to a 5 cm3 methanolic solution of Ni(OAc)2ꢁ4H2O (0.142 g,
0.57 mmol). The mixture was then heated to reflux for 12 h to ob-
tain green precipitate of [Ni(L1nap)]complex. The solid product was
then filtered and washed with methanol. The volume of the filtrate
was reduced to ꢃ10 cm3 and kept in a beaker covering with a glass.
It was kept for few days. A little more crop of product was
collected.
(vide supra). In the X-ray structures of metal complexes the
2ꢀ
dinegative anion of ligands, (Lnap
)
bind Ni(II) and Pd(II) in
distorted square planer geometry. The [Ni(L1nap)]molecule has a
planar structure with a maximum deviation of 0.131 Å from the
least square plane. The planar molecules [Ni(L1nap)] in the
asymmetric units are held as weak staggered unsupported dimers
where Ni–Ni distances are 3.410 Å. The dimers are arranged in a
stair-like manner where the inter dimer Ni–Ni distance is
6.837 Å. The Ni–N(azo) [Ni–N2; 1.799(2) Å] and Ni–N(imine)
[Ni–N3; 1.884(2) Å] distances are different due to stronger trans
influence of aryl carbon than the phenolic oxygen [4]. The Ni–C2
distance (1.880(2) Å) is comparable with Ni–C distance of ortho-
metallated Ni(II) complex of azobenzene [17]. Ni–O1 distance
(1.8204(17) Å) is within the normal range of Ni–O distances
(1.83(1) Å) in salen complexes [27,28]. The X-ray structure of
palladium complex, [Pd(L1nap)], was similar to [Ni(L1nap)]. Pd–C
(1.993(2) Å) and Pd–O (1.9949(15) Å) distances are within the nor-
mal range [6,29,30]. Between the Pd–N(azo) (1.9175(17) Å) and
Pd–N(im) (2.0156(16) Å) distances, the former is shorter due to
5a: Yield: 0.258 g (65%). Anal. Calc. for C23H15N3NiO (408.07): C,
67.6; H, 3.7; N, 10.2. Found: C, 67.7; H, 3.6; N, 10.3%. UV–Vis
(CH2Cl2): [kmax, nm (e
, Mꢀ1 cmꢀ1)]: 622 (434), 478 (4644), 356
(5945). IR (KBr): 1374 (N@N); 1605 (C@N). 1H NMR (CDCl3):
d = 9.49 (s, 1H; N@CH), 8.02 (d, 1H; Ar), 7.66–7.62 (m, 5H; Ar),
7.48 (t, 1H; Ar), 7.43–7.27 (m, 4H; Ar), 7.12–7.08 (m, 3H; Ar) ppm.
4.3.2. Synthesis of [Ni(L2nap)] (5b) and [Ni(L3nap)] (5c)
Complexes [Ni(L2nap)] and [Ni(L3nap)] were prepared using the
ligand H2L2
and H2L3
in place of H2L1nap, respectively.
nap
nap
5b: Yield: 0.276 g (70%). Anal. Calc. for C24H17N3NiO (422.07): C,
68.2; H, 4.0; N, 9.9. Found: C, 68.3; H, 4.0; N, 9.9%. UV–Vis (CH2Cl2):
[kmax, nm (e
, Mꢀ1 cmꢀ1)]: 623 (1207), 480 (12691), 380 (15012). IR
(KBr): 1378 (N@N), 1603 (C@N). 1H NMR (CDCl3): d = 9.44 (s, 1H;
N@CH), 7.98 (d, 1H; Ar), 7.63–7.47 (m, 6H; Ar), 7.36 (t, 1H; Ar),
7.14–7.06 (m, 4H; Ar), 6.87 (d, 1H; Ar), 2.43 (s, 3H; Me) ppm.
5c: Yield: 0.255 g (60%). Anal. Calc. for C23H14N3NiOCl (443.57):
C, 62.4; H, 3.1; N, 9.4. Found: C, 62.4; H, 3.2; N, 9.4%. UV–Vis
either stronger
p-backbonding or stronger trans influence of car-
bon than the phenoxide oxygen [6]. In general, all the metal–ligand
bond distances of [Pd(L1nap)] are larger than those in [Ni(L1nap)]
complex due to larger size of Pd(II) than Ni(II).
(CH2Cl2): [kmax, nm (e
, Mꢀ1 cmꢀ1)]: 622 (729), 475 (7851), 384
3. Conclusion
(10212). IR (KBr pellets, cmꢀ1): 1375 (N@N), 1602 (C@N). 1H
NMR (CDCl3): d = 9.40 (s, 1H; N@CH), 7.96 (d, 1H; Ar), 7.63 (d,
2H; Ar), 7.57 (t, 2H; Ar), 7.50–7.46 (m, 3H; Ar), 7.41 (t, 1H; Ar),
7.09 (t, 2H; Ar), 7.05 (d, 1H; Ar) ppm.
Orthometallated complexes, of Ni(II) and Pd(II) have been pre-
pared with a naphthyl moiety within the ligand framework. All
the orthometallated complexes underwent oxygen insertion upon
rection with peroxy acids to form the complexes incorporating
azo ligands having salen like coordination sites –(O, N, N, O). Lumi-
nescence properties of the complexes and ligands are discussed
considering heavy atom effect and ‘‘chelation enhanced fluoro-
scence (CHEF)’’. The oxygenated products display very weak
emission.
4.3.3. Synthesis of [Pd(L1nap)] complex (6a)
A solution of H2L1nap (0.2 g, 0.57 mmol) in 10 cm3 methanol was
added to
a
5 cm3 methanolic solution of Na2PdCl4 (0.168 g,
0.57 mmol). The mixture was then stirred for 20 h to obtain brown
precipitate of [Pd(L1nap)] complex. The solid product was then fil-
tered and washed with methanol. The product was then purified
by preparative TLC using benzene–acetonitrile (19:1) mixed sol-
vent. Upon evaporation of solvent, the pure desired brown com-
plex [Pd(L1nap)] was isolated.
4. Experimental
4.1. Materials
6a: Yield: 0.310 g (65%). Anal. Calc. for C23H15N3PdO (455.80): C,
60.6; H, 3.3; N, 9.2. Found: C, 60.5; H, 3.3; N, 9.2%. UV–Vis (CH2Cl2):
The solvents used in the reactions were of reagent grade
obtained from Merck, Kolkata, India and purified and dried by
reported procedures [31]. 2-(Arylazo)anilines and 1-{[2-(ary-
lazo)phenyl]iminomethyl}-2-naphthol were prepared according
to reported procedure [7,22,31]. Palladium chloride, nickel acetate
tetra hydrate were purchased from Merck, Kolkata, India.
[kmax, nm (e
, Mꢀ1 cmꢀ1)]: 450 (5068), 374 (5908), 274 (9835), 245
(11611). IR (KBr pellets, cmꢀ1): 1357 (N@N), 1603 (C@N). 1H NMR
(CDCl3): d = 9.54(s, 1H; N@CH), 8.03 (d, 1H; Ar), 7.79 (d, 1H; Ar),
7.75 (d, 2H; Ar), 7.68 (d, 1H; Ar) 7.64 (d, 1H; Ar), 7.54–7.41 (m,
4H; Ar), 7.35 (d, 2H; Ar), 7.26–7.13 (m, 2H; Ar) ppm.

52
D. Patra et al. / Polyhedron 51 (2013) 46–53
4.3.4. Synthesis of[Pd (L2nap)] (6b) and [Pd(L3nap)] (6c)
Table 4
Crystallographic data for H2L1nap, 4a, [Ni(L1nap)], 5a and [Pd(L1nap)], 6a.
Complexes [Pd(L2nap)] and [Pd(L3nap)] were prepared using the
ligands H2L2
and H2L3
in place of H2L1nap, respectively.
Chemical formula
C23H17N3O
C23H15N3NiO
C23H15N3PdO
nap
nap
6b: Yield: 0.260 g (55%). Anal. Calc. for C24H17N3PdO (469.80): C,
Formula weight
Space group
351.40
P212121 (No.
19)
orthorhombic
5.5597(2)
408.07
P21/n (No.
14)
monoclinic
12.4865(2)
455.80
P21/n (No.
14)
monoclinic
12.5071(7)
61.3; H, 3.6; N, 8.9. Found: C, 61.3; H, 3.6; N, 8.9%. UV–Vis (CH2Cl2):
[kmax, nm (e
, Mꢀ1 cmꢀ1)]: 450 (4788), 374 (5321), 274 (8376), 245
(9819). IR (KBr pellets, cmꢀ1): 1353 (N@N); 1602 (C@N). 1H NMR
(CDCl3): d = 9.40 (s, 1H; N@CH), 8.19 (d, 1H; Ar), 8.08–8.04 (m,
1H; Ar), 7.92 (d, 1H; Ar) 7.67–7.56 (m, 3H; Ar), 7.40–7.26 (m,
2H; Ar), 7.22–7.12 (m, 2H; Ar), 7.05 (t, 2H; Ar), 6.84 (d, 1H; Ar),
2.28(s, 3H; Me) ppm.
Crystal system
0
a (ÅA)
0
11.3742(5)
8.6827(2)
8.5743(5)
b (AÅ)
0
27.1976(13)
17.2322(3)
17.4363(10)
c (AÅ)
a
(°)
90
90
90
0.71073
90
90
b (°)
109.8440(10)
90
0.71073
109.8980(10)
90
0.71073
6c: Yield: 0.234 g (50%). Anal. Calc. for C23H14N3PdOCl (491.30):
C, 56.3; H, 2.8; N, 8.5. Found: C, 56.3; H, 2.8; N, 8.6%. UV–Vis
c
(°)
0
(CH2Cl2): [kmax, nm (e
, Mꢀ1 cmꢀ1)]: 450 (5044), 374 (5960), 274
k (AÅ)
0
1719.90(13)
1757.32(6)
1758.23(17)
V (AÅ3)
(8940), 245 (10440). IR (KBr): 1353 (N@N), 1602 (C@N). 1H NMR
(CDCl3): d = 9.38(s, 1H; N@CH), 7.94 (d, 1H; Ar), 7.68 (d, 1H; Ar),
7.62 (d, 2H; Ar), 7.58 (d, 1H; Ar), 7.54 (d, 2H; Ar), 7.47–7.40 (m,
3H; Ar), 7.13 (t, 1H; Ar), 7.06–7.03 (m, 2H; Ar) ppm.
Z
4
293
4
293
4
293
T (K)
Dcalc (Mg/m3)
1.357
0.085
736
0.0354
0.0973
1.08
1.542
1.123
840
0.0302
0.0712
1.03
1.722
1.075
912
0.0240
0.0615
1.05
l
(mmꢀ1
)
F(000)
R[all data]
wR2[I > 2 (I)]
4.4. Synthesis of complex, (OL1nap)Ni (7)
r
Goodness-of-fit GOF on
The details for the preparation of (OL1nap)Ni are given.
F2
4.4.1. Reaction of [Ni(L1nap)] with mCPBA
A solution of mCPBA (0.143 g, 0.824 mmol) in dichloromethane
(5 mL) was added drop wise to a stirred solution of [Ni(L1nap)]
(0.100 g, 0.245 mmol) in dichloromethane (25 mL). Immediately
the color of the solution began to change from deep green to
brown. The stirring was continued for 10 min. Evaporation of the
solvent in vacuo afforded a brown solid mass. The solid mass
was washed with diethyl ether (30005 mL). The product was then
purified by preparative TLC using a benzene/acetonitrile (19:1)
mixture as eluent. Upon evaporation of the solvent, the pure target
complex [Ni(OL1nap)] was obtained.
4.5. Syntheses of complex, [Pd(OL1nap)] (8)
The details for the preparation of [Pd(OL1nap)] are given.
4.5.1. Reaction of [Pd (L1nap)] with mCPBA
A solution of (0.144 g, 0.824 mmol) mCPBA was added dropwise
to a stirred solution of [Pd(L1nap)] (0.100 g, 0.219 mmol) in 25 mL
dichloromethane. Immediately, the color of the solution began to
change from brown to pink. The stirring was continued for
30 min. Evaporation of the solvent under vaccuo afforded a pink
solid mass. The solid mass thus obtained was washed thrice with
diethyl ether, taking 5 mL for each wash. The product was then
purified by preparative TLC using benzene as the eluent. The pink
band was collected.
4.4.2. Reaction of (L1nap)Ni with TBHP
To a stirred solution of [Ni(L1nap)] (0.571 g, 0.140 mmol) in
25 cm3 dichloromethane or tert-butanol, TBHP (0.30 mL,
2.76 mmol) was added dropwise. Immediately the color of the
solution began to turn from deep green to brown. The stirring
was continued for 30 min. Evaporation of the solvent under vaccuo
afforded a brown solid mass. The solid mass, thus obtained, was
washed with water and diethyl ether. The product was then puri-
fied by preparative TLC using benzene–acetonitrile (19:1) mixed
solvent. Upon evaporation of solvent the pure desired complex
[Ni(OL1nap)] was obtained.
4.5.2. Reaction of [Pd (L1nap)] with TBHP
To a stirred solution of [Pd(L1nap)] (0.100 g, 0.219 mmol) in
25 cm3 dichloromethane or tert-butanol, TBHP (0.40 mL,
3.68 mmol) was added drop wise in presence of catalytic amount
VO(acac)2. Immediately the color of the solution began to turn
from brown to pink. The stirring was continued for 1 h. Evapora-
tion of the solvent under vaccuo afforded a pink solid mass. The so-
lid mass, thus obtained, was washed with water and diethyl ether.
The product was then purified by preparative TLC using benzene–
acetonitrile (19:1) mixed solvent. Upon evaporation of solvent the
pure desired complex [Pd (OL1nap)] was obtained.
4.4.3. Reaction of [Ni(L1nap)] with H2O2
To a stirred solution of [Ni(L1nap)] (0.34 g, 0.083 mmol) in
15 cm3 dichloromethane, 10 cm3 of 6% H2O2 was added drop wise.
The color of the organic layer began to turn from deep green to
brown after 15 min. The stirring was continued for 45 min. Evapo-
ration of the organic solvent, after separation from the aqueous
layer, under vaccuo afforded a dark solid mass. The solid mass, thus
obtained, was washed with water. The product was then purified
by preparative TLC using benzene–acetonitrile (19:1) mixed sol-
vent. Upon evaporation of solvent the pure desired complex
[Ni(OL1nap)] was obtained.
Yield: 0.138 g (50%). Anal. Calc. for C23H15N3PdO2 (471.80): C,
58.5; H, 3.2; N, 8.9. Found: C, 58.5; H, 3.2; N, 8.8%. UV–Vis (CH2Cl2):
[kmax, nm (e
, Mꢀ1 cmꢀ1)]: 538 (3779), 420 (3400), 379 (6100), 244
(12100). IR (KBr): 1384 (N@N), 1605 (C@N). 1H NMR (CDCl3):
d = 9.58 (s, 1H; N@CH), 8.36 (d, 1H; Ar), 8.11 (d, 1H; Ar), 7.98 (d,
1H; Ar), 7.90 (d, 1H; Ar) 7.76 (d, 1H; Ar), 7.56–7.50 (m, 1H; Ar),
7.48–7.39 (m, 2H; Ar), 7.36–7.7.34 (m, 2H; Ar), 7.33–7.30 (m, 2H;
Ar), 6.87 (m, 1H; Ar).
Yield: 0.205 g (70%). Anal. Calc. for C23H15N3NiO2 (424.07): C,
65.1; H, 3.5; N, 9.9. Found: C, 65.1; H, 4.0; N, 9.9%. UV–Vis (CH2Cl2):
[kmax, nm (e
, Mꢀ1 cmꢀ1)]: 646 (8935), 531 (2207), 478 (4516), 353
(6014), 256 (11523). IR (KBr): 1371 (N@N); 1603 (C@N). 1H NMR
(CDCl3): d = 9.29 (s, 1H; N@CH), 8.22 (d, 1H; Ar), 8.08 (d, 1H; Ar),
7.84 (d, 1H; Ar), 7.78 (d, 1H; Ar), 7.70 (t, 2H; Ar), 7.54 (t, 1H; Ar),
7.43–7.39 (m, 2H; Ar), 7.36–7.35 (m, 2H; Ar), 7.30–7.22 (m, 1H;
Ar), 6.89 (t, 1H; Ar) ppm.
4.6. Syntheses of authentic H2OL1nap, 9
To a solution of (0.100 g, 0.469 mmol) HOL1–NH2 in 50 cm3
diethyl ether 2-hydroxy 1-napthaldehyde (0.0573 g, 0.333 mmol)
was added. The mixture of solution was heated to reflux for 12 h.

D. Patra et al. / Polyhedron 51 (2013) 46–53
53
The solvent was evaporated in vaccuo. The solid product was kept
Appendix A. Supplementary material
in a vacuum desiccator for 24 h before use and characterization.
Yield: 0.155 g (90%). Anal. Calc. for C23H17N3O2 (367): C, 75.2; H,
4.6; N, 11.4. Found: C, 75.1; H, 4.6; N, 11.5%. UV–Vis (CH2Cl2):
CCDC 889016, 889017 and 889018 contain the supplementary
crystallographic data forH2L1nap, [Ni(L1nap)] and [Pd(L1nap)], respec-
tively. 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.
Figs. S1–S18 show the UV–Vis and IR spectra Figs. S19–S31 show
1H NMR spectra of all the ligands and complexes. Supplementary
data associated with this article can be found, in the online version,
at http://dx.doi.org/10.1016/j.poly.2012.12.011.
[kmax, nm (e
, Mꢀ1 cmꢀ1)]: 320 (30000), 232 (53000). IR (KBr):
1473 (N@N), 1628 (C@N). 1H NMR (CDCl3): d = 12.39 (s, OH),
10.76 (s, OH), 9.33 (s, 1H; N@CH), 8.046 (d, 1H; Ar), 7.97 (d, 1H;
Ar), 7.90 (d, 1H; Ar), 7.76 (d, 1H; Ar) 7.65 (d, 1H; Ar), 7.49 (t, 2H;
Ar), 7.44 (t, 1H; Ar), 7.34 (d, 2H; Ar), 7.28–7.22 (m, 3H; Ar), 7.10
(d, 1H; Ar), 7.02–6.98 (m, 2H; Ar).
4.7. Syntheses of authentic [Ni(OL1nap)], 7
References
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methanol (5 mL), solution of H2OL1
(0.100 g, 0.272 mmol) in
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added dropwise to a stirred solution of (0.100 g, 0.219 mmol)
Na2PdCl4 in 5 mL methanol. The color of the solution began to
change from brown to pink. The stirring was continued for
30 min. Evaporation of the solvent under vaccuo afforded a pink
solid mass. The product was then purified by preparative TLC using
benzene as the eluent. The pink band was collected. Upon
evaporation of the solvent, the pure target complex [Pd(OL1nap)]
was obtained.
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Data for the crystals H2L1nap, 4a, [Ni(L1nap)], 5a and [Pd(L1nap)],
6a were collected by the
CCD diffractometer with Mo K
x
-scan technique on a Brucker smart
radiation monochromated by a
a
graphite crystal. The structure was solved by direct method with
SHELXS-97 program. Full matrix least square refinements were per-
formed using the SHELX-97 program (PC version) [32,33]. All non-
hydrogen atoms were refined anisotropically using reflections
I > 2r(I). Hydrogen atoms were included at the calculated posi-
tions. The crystal data and data collection parameters for H2L1
[Ni(L1nap)] and [Pd(L1nap)] are listed in Table 4.
,
nap
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Acknowledgments
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We are thankful to the DST (New Delhi) for funding and fellow-
ship to PP under DST-WOS-A project (No. SR/WOS-A/CS-140/
2011). The necessary laboratory and infrastructural facility are pro-
vided by the Dept. of Chemistry, University of Kalyani. The support
of DST under FIST program to the Department of Chemistry, and
PURSE to the University of Kalyani is acknowledged.