Synthesis of triethylphosphite complexes of nickel(II) and palladium(II) with tridentate Schiff base ligand for catalytic application in carbon-carbon coupling reactions

Article abstract of DOI:10.1016/j.inoche.2012.08.016

Air stable Ni(II) and Pd(II) complexes viz. [Ni(LS)(P(OEt)₃)] (1), [Ni(LN)(P(OEt)₃)] (2), [Pd(LS)(P(OEt)₃)] (3) and [Pd(LN)(P(OEt)₃)] (4) [where LS and LN are dianions of N-(2-mercaptophenyl)salicylideneimine and N-(2-mercaptophenyl)naphthylideneimine respectively] have been synthesized and characterized by analytical and spectral (electronic, FT-IR, ¹H, ¹³C and ³¹P NMR) methods. The ¹H-³¹P HMBC spectrum established the coupling of phosphorus with the azomethine proton of the Schiff base and the aliphatic protons of triethylphosphite. Novel Ni(II) and Pd(II) complexes exhibited good catalytic activity in Kumada-Tamao-Corriu and Suzuki-Miyaura coupling reactions respectively.

Full text of DOI:10.1016/j.inoche.2012.08.016

Inorganic Chemistry Communications 25 (2012) 30–34
Contents lists available at SciVerse ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Synthesis of triethylphosphite complexes of nickel(II) and palladium(II) with
tridentate Schiff base ligand for catalytic application in carbon–carbon
coupling reactions
⁎
M. Muthu Tamizh, R. Karvembu
Department of Chemistry, National Institute of Technology, Tiruchirappalli 620015, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Air stable Ni(II) and Pd(II) complexes viz. [Ni(LS)(P(OEt)3)] (1), [Ni(LN)(P(OEt)3)] (2), [Pd(LS)(P(OEt)3)] (3) and
[Pd(LN)(P(OEt)3)] (4) [where LS and LN are dianions of N–(2–mercaptophenyl)salicylideneimine and N–(2–
mercaptophenyl)naphthylideneimine respectively] have been synthesized and characterized by analytical and
spectral (electronic, FT–IR, 1H, 13C and 31P NMR) methods. The 1H–31P HMBC spectrum established the coupling
of phosphorus with the azomethine proton of the Schiff base and the aliphatic protons of triethylphosphite.
Novel Ni(II) and Pd(II) complexes exhibited good catalytic activity in Kumada–Tamao–Corriu and Suzuki–
Miyaura coupling reactions respectively.
Received 16 May 2012
Accepted 14 August 2012
Available online 19 August 2012
Keywords:
Nickel(II)
Palladium(II)
Triethylphosphite
Schiff base
© 2012 Elsevier B.V. All rights reserved.
Coupling reaction
The chemistry of transition metal complexes with coordinated
phosphorus ligands has been known for a long time [1]. A significant
amount of work has been carried out on the syntheses and reactivity
of phosphine complexes of transition metals, particularly with plati-
num group metals [2,3]. Alkyl phosphites are in some respects more
tractable than the phosphines, but still only little attention has been
paid to phosphite complexes [4]. Phosphite ligands posses good π–
acceptor property owing to the availability of vacant 3dπ orbitals on
the phosphorus atom, which makes possible back bonding with filled
dπ orbitals of metal ions [5]. Phosphite complexes have been used as
catalysts for hydrocyanation [6,7], hydroformylation [8], alkene oligo-
merization [9,10] and isomerization [11,12] reactions. Recently,
Takeda et al. have applied Ni[P(OEt)3]4 as catalyst for the transforma-
tions of (E)–alkenyl halides into sulphides [13] and allylic acetates
into allylic sulphides [14].
Schiff base ligands which can accommodate various substituents
play an important role in tuning the electronic property of metal ions
in its complexes [15]. Many transition metal Schiff base complexes
have been utilized as catalysts for important organic transformations
[16,17]. Of which, considerable amount of Schiff base complexes con-
tain tertiary phosphine as auxillary ligand [18,19]. We could not find
any report on Schiff base complexes incorporating phosphite ligand
eventhough phosphite ligands are inexpensive compared to tertiary
phosphines. Moreover, most of the homogeneous catalysts containing
phosphite ligand exist in low valent state i.e. zero [13,14,20]. In this
paper, we report the synthesis and characterization of Ni(II) and
Pd(II) complexes containing ONS donor tridentate Schiff base (Fig. 1)
and triethylphosphite ligands. Carbon–carbon bond forming reactions
involving aryl halides are important synthetic transformations in syn-
thetic chemistry [21–26]. Interestingly, new air stable Ni(II) and Pd(II)
complexes act as good catalysts for Kumada–Tamao–Corriu and
Suzuki–Miyaura coupling reactions respectively.
As shown in Scheme 1, the reactions of tridentate Schiff base ligand
(H2LS/H2LN) [27,28], metal salt (NiBr2/PdCl2) and triethylphosphite in
presence of few drops of triethyl amine yielded the corresponding
metal complexes in moderate yield [29]. All the prepared complexes
were air stable and non‐hygroscopic. They were found to be soluble in
CH2Cl2, CHCl3, DMSO and DMF. The Schiff bases behave as dianionic
tridentate ligands using phenolic oxygen, azomethine nitrogen and
thiolate sulfur atoms for bonding with Ni(II)/Pd(II).
The UV–Visible spectra of all the complexes in dichloromethane
showed four bands in the region 231–446 nm. The bands appearing
in the region 231–289 nm have been assigned to intraligand transi-
tions. A less intense band in the region 322–336 nm corresponds to
metal-to-ligand charge transfer transition (MLCT). The UV–Visible
spectra of Ni(II) and Pd(II) complexes also showed d-d transition in
the region 413–446 nm. The results are in accordance with the elec-
tronic spectra of other similar square planar Ni(II) and Pd(II) com-
plexes [30,31].
The IR spectra of Ni(II) and Pd(II) complexes of the Schiff base are
compared with that of the free Schiff base in order to determine the co-
ordination sites. The spectra of ligands showed a strong band around
1614–1621 cm−1 due to ν(C_N). As a result of coordination, this
band has been shifted to a lower wave number (1605–1615 cm−1) in
the complexes, indicating participation of the azomethine nitrogen in
⁎
Corresponding author. Tel.: +91 431 2503636; fax: +91 431 2500133.
E-mail address: kar@nitt.edu (R. Karvembu).
1387-7003/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.inoche.2012.08.016

M.M. Tamizh, R. Karvembu / Inorganic Chemistry Communications 25 (2012) 30–34
31
Fig. 1. Structure of ligands.
coordination [32,33]. The band in the region 1304–1316 cm−1, which is
assigned to phenolic oxygen in the free ligand is shifted to a higher
wave number (1310–1334 cm−1) in complexes, suggesting the coordi-
nation through phenolic oxygen to Pd(II) and Ni(II) ions [32,33]. How-
ever, participation of thiolato sulfur atom in coordination is ascertained
from the negative shift of ν(C\S) in complexes by 5–9 cm−1 compared
to ligands [34–37]. Bands due to triethylphosphite are appeared in the
expected region [38].
Fig. 3. 1H–1H COSY spectrum of [Ni(LS)(P(OEt)3)](1).
The disappearance of signals due to phenolic and thiolato hydro-
gen atoms in the 1H NMR spectra of all the Ni(II) and Pd(II) complexes
indicates the deprotonation of these groups and the Schiff bases are
coordinated to metal ions as dianionic ligands. A doublet observed in
resonance. 1H–31P HMBC spectrum (Fig. 2) of 1 revealed that this dou-
blet is due to four bond coupling of phosphorus in triethylphosphite
with the azomethine proton [39]. The strong coupling of azomethine
proton in Pd(II) complexes (~23 Hz) compared to corresponding
Ni(II) complexes (~15 Hz) is due to the fact that π electron cloud of
azomethine group in Pd(II) complexes is attracted towards the large
1
the H NMR spectra of all the complexes in the region 8.87–9
88 ppm (4JP,H=15.4–23.6 Hz) has been assigned to the HC_N
8
9
10
13
12
11
Scheme 1. Synthesis of nickel(II) and palladium(II) complexes.
Fig. 2. 1H–31P HMBC spectrum of [Ni(LS)(P(OEt)3)](1).

32
M.M. Tamizh, R. Karvembu / Inorganic Chemistry Communications 25 (2012) 30–34
Fig. S8). The 31P NMR spectra of the complexes exhibit only one signal
at 99.54–108.0 ppm suggesting the presence of one coordinated
triethylphosphite in the present Ni(II) and Pd(II) complexes
(Fig. S9–Fig. S12).
Complex 1 was first employed in the Kumada–Tamao–Corriu
(KTC) coupling reaction of 4-bromo toluene with phenylmagnesium
bromide at 90 °C in 1,4‐dioxane (Table 1, entries 1, 2 and 3) under
air atmosphere, in 0.25, 0.5 and 1.0 mol%. Results have shown that
% conversion increases significantly when catalyst amount increases
from 0.25 to 0.5 mol%. But the conversion increases only by 3 %
while doubling the catalyst amount to 1.0 mol%. Hence 0.5 mol% of
catalyst was used for further KTC reactions. The catalytic efficiency
of all the Ni(II) (1 and 2) and Pd(II) (3 and 4) complexes for KTC re-
action was evaluated. It was found that Ni(II) complexes (1 and 2) ex-
hibit better efficiency (Table 1, Entries 2, 4-6) compared to Pd(II)
complexes (3 and 4). Among the two Ni(II) complexes, complex 1
was efficient and used for KTC reactions with different aryl halides.
The % conversion of 4-bromo toluene is comparable with that of
same reaction catalyzed by trans-dichloro-tetrakis-(N-R-imidazole)
nickel(II) complexes [40]. Complex 1 effected 91% conversion of
4-bromo anisole in KTC reaction (Table 1, Entry 7), which is higher
than the conversion exhibited by [Ni(COD)2]/triaryl phosphine [41]
and polymer supported Ni(II) Schiff base complexes [42]. Entries
8 and 9 in Table 1 show the reaction of 4-bromonitrobenzene and
4-chloronitrobenzene with phenylmagnesium bromide to yield
4-nitrobiphenyl with 94 and 82% respectively. Silica immobilized
Ni(II)‐catalyzed KTC reaction with the same substrates produced al-
most equal conversion but with 2 mol% catalyst loading [43]. Using
0.5 mol% of 1, 1-bromo-4-(trifluoromethyl)benzene, 2-bromopyridine
and 2-bromonaphthalene were converted into corresponding biaryl
compounds with 89, 97 and 82 % conversion respectively after 6 h at
90 °C (Table 1, entries 10-12).
Complexes 1–4 were applied to the Suzuki–Miyaura cross-coupling
reaction of phenylboronic acid with 4-bromoacetophenone at 100 °C
for 12 h in dimethylacetamide (DMAc) solvent under aerobic conditon
(Table 2, entries 1–4). As expected, Pd(II) complexes (3 and 4) showed
good catalytic activity compared to Ni(II) complexes (1 and 2). Among
Pd(II) complexes, 3 showed good catalytic property in Suzuki–Miyaura
cross-coupling reaction with 4-bromoacetophenone. Complex 3 was
then used for optimizing the mol% of catalyst and extending the scope
of the substrates. The yield was maximum when 1.0 mol% of 3 was
taken (Table 2, entries 3, 5 and 6). 4-Iodoacetophenone reacted with
phenylboronic acid in presence of 3 (1 mol%) to give 4-acetylbiphenyl
in 95 % yield (Table 2, entry 8) which is higher than bromo analogue.
This may be due to the fact that iodo is a better leaving group compared
to bromo. The yield of 4-acetylbiphenyl is comparable with other
Fig. 4. 1H–13C HSQC spectrum of [Ni(LS)(P(OEt)3)](1).
and energetic 4d-orbital of Pd(II) ion, which decreases the distance
between phosphorus and azomethine proton. All the complexes ex-
hibit signals around 6.75−7.79 ppm which are assigned as due to
the aromatic protons of Schiff base ligand. Assignments to individual
aromatic protons have been made with the help of 1H–1H COSY spec-
trum of 1 (Fig. 3). The individual 1H NMR spectra with complete as-
signment were given in supporting information (Fig. S1–Fig. S4). The
signals appeared at 1.41–1.43 ppm and 4.43–4.45 ppm are due to
methyl and methine protons of the triethylphosphite and they
appeared as triplet and doublet of quartet (3JP,H=8.5–8.8; JH,H
=
1
7.0–7.1 Hz) respectively. In the 13C NMR spectra of all the complexes,
azomethine carbon resonance is observed in the 147.62–154.77 ppm
range. The resonance for C\S, C\N and C\O are observed in the re-
gions 142.82–144.07, 147.67–149.10 and 164.41–166.07 ppm respec-
tively. The signals at 62.81–63.03 and 16.36–16.48 ppm are assigned
to methyl and methine carbons of triethylphosphite. The assignment
of all the aromatic carbon resonances is made on the basis of 1H–13C
HSQC spectrum of 1 (Fig. 4) and individual 13C NMR spectra with com-
plete assignment are provided in the supporting information (Fig. S5–
Table 1
Ni(II) and Pd(II)-catalyzed Kumada–Tamao–Corriu cross coupling reactionsa
Catalyst
ArX þ PhMgBr −−−−−−−−−−−−→ Ar−Ph þ Ar−Ar.
THF=1; 4−dioxane
Entry
Catalyst
(mol%)
Ar-X
Ar\Ph
Conversion
(%)b
Ar\Ph
(%)
Ar\Ar
(%)
1
2
3
4
5
6
7
8
1 (0.25)
1 (0.5)
1 (1.0)
2 (0.5)
3 (0.5)
4 (0.5)
1 (0.5)
1 (0.5)
1 (0.5)
1 (0.5)
1 (0.5)
1 (0.5)
p-Me\Ph\Br
p-Me\Ph\Ph
59
68
71
59
46
26
91
94
82
89
97
82
55
63
65
53
42
24
85
85
79
73
96
82
4
5
6
6
4
2
6
9
3
p-MeO\Ph\Br
p-O2N\Ph\Br
p-O2N\Ph\Cl
p-F3C\Ph\Br
2-Br\Pyridine
2-Br\Naphthalene
p-MeO\Ph\Ph
p-O2N\Ph\Ph
p-O2N\Ph\Ph
p-F3C\Ph\Ph
2-Ph\Pyridine
2-Ph\Naphthalene
9
10
11
12
16
1
0
a
Reaction conditions: 4-bromoarene (0.5 mmol), catalyst in 1,4−dioxane, phenylmagnesium bromide (1 mmol; 1 M in THF), stirring for 6 h, 90 °C.
Conversion is determined by GC.
b

M.M. Tamizh, R. Karvembu / Inorganic Chemistry Communications 25 (2012) 30–34
33
Table 2
Ni(II) and Pd(II)-catalyzed Suzuki-Miyaura cross coupling reactionsa
Catalyst
K2CO3ð2mmolÞ
.
ArX þ PhBðOHÞ2−−−−−−−−−−−−→ Ph−Ar
DMAC=EtOH=H2O
∘
100 C
Entry
Catalyst
(mol%)
Ar-X
Ar-Ph
Yieldb
(%)
1
2
3
4
5
6
7
8
1 (1.0)
2 (1.0)
3 (1.0)
4 (1.0)
3 (0.25)
3 (0.5)
3 (1.0)
3 (1.0)
3 (1.0)
3 (1.0)
3 (1.0)
3 (1.0)
3 (1.0)
3 (1.0)
3 (1.0)
p-MeOC\Ph\Br
p-MeOC\Ph\Ph
23
24
92
81
75
85
72
95
73
52
92
73
36
54
53
p-MeO\Ph\I
p-MeOC\Ph\I
p-OHC\Ph\Br
p-NC\Ph\Br
p-HO2C\Ph\Br
p-O2N\Ph\Br
p-Me\Ph\Br
p-F3C\Ph\Br
2-Br\Pyridine
p-MeO\Ph\Ph
p-MeOC\Ph\Ph
p-OHC\Ph\Ph
p-NC\Ph\Ph
p‐HO2C\Ph\Ph
p-O2N\Ph\Ph
p-Me\Ph\Ph
p-F3C\Ph\Ph
2-Ph\Pyridine
9
10
11
12
13
14
15
a
Reaction conditions: 4-bromoarene (1 mmol), phenylboranic acid (1.5 mmol) in 1 mL ethanol, catalyst, DMAc (5 mL), stirring for 12 h, 100 °C.
Yield is determined by GC with area normalization.
b
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The lower catalytic activity of 2 and 4 may be explained on the
basis of steric effect caused by the extra ring present in the aldehydic
part of the Schiff base ligand. Both the coupling reactions presented
here are expected to proceed through the formation of M(0)
(M_Ni/Pd) species followed by oxidative addition, transmetalation
and reductive elimination. In this case, triethylphosphite released
from complex, when it is dissolved in solvent, might help for the re-
duction of M(II) to M(0) as phosphines do in many cases [46].
We have successfully prepared and characterized new Ni(II) and
Pd(II) complexes containing ONS donor tridentate Schiff base and
triethylphosphite. One of the Ni(II) complexes can serve as good cata-
lyst for Kumada–Tamao–Corriu cross coupling reaction. Pd(II) complex
containing salicylaldimine ligand was found to be an effective catalyst
for Suzuki–Miyaura cross coupling reaction. These complexes are ther-
mally and air stable, and offer the advantage of carbon–carbon coupling
reactions for the synthesis of biaryls under aerobic conditions.
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[16] C.M. Che, J.S. Huang, Metal complexes of chiral binaphthyl Schiff-base ligands and
their application in stereoselective organic transformations, Coord. Chem. Rev.
242 (2003) 97–113.
Acknowledgements
Funding from DST, Government of India through FIST Programme
is acknowledged. We also thank SAIF, IIT-Madras, Chennai for NMR
measurements.
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plexes, Coord. Chem. Rev. 252 (2008) 1420–1450.
Appendix A. Supplementary data
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tivity of ruthenium(III) Schiff base complexes derived from 3-acetyl-6-methyl-
2H-pyran-2,4(3H)-dione, Polyhedron 25 (2006) 3095–3103.
Supplementary data to this article can be found online at http://
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446. FT–IR (KBr disk), cm−1
: ν(C=N) 1615, ν(C\O) 1314, ν(C\S) 745,
ν(Pd\O) 532, ν(Pd\N) 457, bands due to P(OEt)3 2924, 1385, 1019. 1H NMR
(500 MHz, CDCl3): δ=1.41 (t, J=7.1 Hz, 9H, Ha), 4.37 (dq, J=8.8, 7.1 Hz, 6H,
Hb), 7.05–7.12 (m, 2H, H10 and H11), 7.18 (d, J=9.1 Hz, 1H, H2), 7.27 (t,
J=7.3 Hz, 1H, H3’), 7.52 (t, J=7.3 Hz, 1H, H3), 7.60 (d, J=8.8 Hz, 1H, H4’),
7.67 (t, J=7.3 Hz, 1H, H6’), 7.72–7.80 (m, 2H, H9 and H12), 8.17 (d, J=8.5 Hz,
1H, H5’), 9.88 (d, JPH=23.6 Hz, 1H) ppm. 13C{1H} NMR (125.76 MHz, CDCl3):
δ=16.44 (d, JPC=6.4 Hz, Ca), 63.13(Cb), 109.61 (C6), 115.36 (C9), 119.6 (C5’),
122.59 (C10), 122.71 (C3’), 124.97 (C2), 126.69 (C6), 127.23 (C4), 127.89
(C11), 129.44 (C4), 129.46 (C6), 129.25 (C4’), 135.44 (C5), 136.13 (C3), 142.85
(d, JPC=7.3 Hz, C13), 147.62 (C7), 149.12 (C8), 166.07 (C1) ppm. 31P{1H} NMR
(202.46 MHz, CDCl3): δ=108.00 (s) ppm.
[29] Synthesis and characterization of Ni(II) and Pd(II) complexes:To the hot and clear solu-
tion of metal halide (0.5 mmol) in acetonitrile (20 mL), H2LS or H2LN (0.5 mmol)
dissolved in dichloromethane (5 mL), triethylphosphite (0.75 mmol) and
triethylamine (0.2 mL) were added slowly and successively with stirring. The so-
lution was allowed to stir for 3 h at 27 °C. Then the solvent was removed under
reduced pressure and the resulting residue was washed several times with
hexane. The residue was passed through silica gel column and eluted with ethyl
acetate/hexane (1:5) mixture to obtain brown or red color low melting
solid.[Ni(LS)(P(OEt)3)] (1): 1 was prepared from NiBr2 (0.109 g; 0.5 mmol),
H2LS (0.114 g; 0.5 mmol) and P(OEt)3 (130 μL; 0.124 g; 0.75 mmol). Yield:
142 mg (61%). Anal. Calcd for C20H27NNiO4PS: C, 51.42; H, 5.83; N, 3.00; S, 6.86.
Found: C, 51.25; H, 5.67; N, 2.70; S, 6.51%. UV–Vis (CH3CN), λmax/nm: 253, 289,
336, 413. FT–IR (KBr disk), cm−1: ν(CN) 1606, ν(C\O) 1330, ν(C\S) 750,
ν(Ni\O) 558, ν(Ni\N) 471, bands due to P(OEt)3 2923, 1375, 1021. 1H NMR
(500 MHz, CDCl3): δ=1.40 (t, J=7.1 Hz, 9H, Ha), 4.43 (dq, J=8.5, 7.1 Hz, 6H,
Hb), 6.75 (ddd, J=8.0, 6.8, 1 Hz, 1H, H4), 6.96–7.04 (m, 2H, H2 and H10), 7.07
(ddd, J=7.9, 6.9, 1.0 Hz, 1H, H11), 7.36 (ddd, J=8.7, 6.8, 1.6 Hz, 1H, H3), 7.48
(dd, J=8.0, 1.6 Hz, 1H, H5), 7.52 (dd, J=7.9, 1.3 Hz, 1H, H12), 7.68 (d, J=7.9
Hz, 1H, H9), 8.90 (d, JPH=15.5 Hz, 1H, H7) ppm. 13C{1H} NMR (125.76 MHz,
CDCl3): δ=16.57 (d, JPC=5.4 Hz, Ca), 63.05 (d, JPC=1.8 Hz, Cb), 114.89 (C9),
115.88 (C4), 119.20 (C6), 121.48 (C2), 122.12 (C10), 127.10 (C11) 128.82 (d,
JPC=3.6 Hz, C12) 134.50 (C3) 134.58 (C5) 144.01 (d, JPC=13.6 Hz, C13) 149.10
(C8) 154.76 (C7) 164.42 (C1) ppm. 31P{1H} NMR (202.46 MHz, CDCl3):
δ=99.54 (s) ppm. [Ni(LN)(P(OEt)3)] (2): 2 was prepared from NiBr2 (0.109 g;
0.5 mmol), H2LN (0.140 g; 0.5 mmol) and P(OEt)3 (130 μL; 0.124 g;
0.75 mmol). Yield: 172 mg (66%). Anal. Calcd for C24H29NNiO4PS: C, 55.73; H,
5.65; N, 2.71; S, 6.20. Found: C, 55.62; H, 5.45; N, 2.41; S, 6.02%. UV–Vis
(CH3CN), λmax/nm: 231, 281, 329, 429. FT–IR (KBr disk), cm−1: ν(C=N) 1615,
ν(C\O) 1310, ν(C\S) 746, ν(Ni\O) 550, ν(Ni\N) 464, bands due to P(OEt)3
2924, 1373, 1023. 1H NMR (500 MHz, CDCl3): δ=1.43 (t, J=7.1 Hz, 9H, Ha),
4.45 (dq, J=8.5, 7.1 Hz, 6H, Hb), 7.04–7.11 (m, 2H, H10 and H11), 7.13 (d,
J=9.1 Hz, 1H, H2), 7.34 (t, J=7.3 Hz, 1H, H3), 7.52–7.60 (m, 2H, H3 and H6’),
7.74 (m, 2H, H4’ and H12), 7.79 (dd, J=7.6, 1.7 Hz, 1H, H12), 8.22 (d, J=8.5
Hz, 1H, H5’), 9.83 (d, JPH=15.4 Hz, 1H, H7) ppm. 13C{1H} NMR (125.76 MHz,
CDCl3): δ=16.58 (d, JPC=6.4 Hz, Ca) 62.95 (d, JPC=2.7 Hz, Cb) 110.24 (C6),
114.90 (C9), 119.13 (C5’), 122.23 (C10), 123.12 (C3’), 124.08 (C2), 126.45 (C6),
127.28 (C4), 127.94 (C11), 128.75 (d, JPC=3.6 Hz, C12), 129.33 (C4’), 134.43
(C5), 135.36 (C3), 143.17 (d, JPC=13.6 Hz, C13), 148.58 (C8), 150.44 (C7),
165.42 (C1) ppm. 31P{1H} NMR (202.46 MHz, CDCl3): δ=102.72 (s) ppm.
[Pd(LS)(P(OEt)3)] (3): 3 was prepared from PdCl2 (0.088 g; 0.5 mmol), H2LS
(0.114 g; 0.5 mmol) and P(OEt)3 (130 μL; 0.124 g; 0.75 mmol). Yield: 156 mg
(60%). Anal. Calcd for C20H27NPdO4PS: C, 46.65; H, 5.29; N, 2.72; S, 6.23. Found:
C, 46.30; H, 5.04; N, 2.49; S, 6.01%. UV–Vis (CH3CN), λmax/nm: 238, 274, 325,
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427. FT–IR (KBr disk), cm−1
:
ν(C=N) 1605, ν(C\O) 1330, ν(C\S) 750,
ν(Pd\O) 553, ν(Pd\N) 471, bands due to P(OEt)3 2922, 1383, 1022. 1H NMR
(500 MHz, CDCl3): δ=1.41 (t, J=7.1 Hz, 9H, Ha), 4.37 (dq, J=8.7, 7.1 Hz, 6H,
Hb), 6.72 (ddd, J=8.0, 6.8, 1.0 Hz, 1H, H4), 7.03–7.08 (m, 2H, H2 and H10),
7.11 (ddd, J=7.9, 6.8, 1.3 Hz, 1H, H11), 7.42 (ddd, J=8.6, 6.8, 1.8 Hz, 1H, H3),
7.49 (dd, J=8.0, 1.7 Hz, 1H, H5), 7.59 (dd, J=8.0, 1.3 Hz, 1H, H12), 7.73 (d,
J=8.2 Hz, 1H, H9), 8.94 (d, JPH=23.0 Hz, 1H, H7) ppm. 13C{1H} NMR (125.76
MHz, CDCl3): δ=16.42 (d, JPC=6.4 Hz, Ca), 63.26 (Cb), 115.22 (C4), 115.33
(C9), 119.30 (C6), 121.98 (C2), 122.47 (C10), 127.34 (C11), 129.53 (C12),
135.48 (C3), 136.23 (C5), 143.82 (d, JPC=7.3 Hz, H13), 147.69 (C7), 154.11
(C7), 165.31 (C1) ppm. 31P{1H} NMR (202.46 MHz, CDCl3): δ=106.36 (s) ppm.
[Pd(LN)(P(OEt)3)] (4): 4 was prepared from PdCl2 (0.088 g; 0.5 mmol), H2LN
(0.140 g; 0.5 mmol) and P(OEt)3 (130 μL; 0.124 g; 0.75 mmol). Yield: 181 mg
(64%). Anal. Calcd for C24H29NPdO4PS: C, 51.02; H, 5.17; N, 2.48; S, 5.68. Found:
C, 50.81; H, 5.02; N, 2.18; S, 5.36%. UV–Vis (CH3CN), λmax/nm: 230, 270, 322,
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