Schiff bases functionalized with PPh2 and SPh groups and their Ni(II) and Pd(II) complexes: Synthesis, crystal structures and applications of a Pd complex for Suzuki-Miyaura Coupling

Article abstract of DOI:10.1016/j.poly.2008.01.027

The reactions of 2-hydroxyacetophenone with NH₂CH₂CH₂SPh and NH₂CH₂CH₂PPh₂ have resulted in Schiff bases having the chemical formulae 2-HO-C₆H₄C(CH₃){double bond, long}N-CH₂CH₂Y (Y = SPh (L¹) or PPh₂ (L⁴)), which are potential (N, O, S) and (N, O, P) type ligands. Using an appropriate ketone, the Schiff base 2,4-(HO)₂-C₆H₄C(CH₃){double bond, long}N-CH₂CH₂SPh (L²) has also been synthesized in a similar fashion. L¹, L², L⁴ and the compounds obtained by borohydride reduction of L¹ and L², viz. 2-HO-C₆H₄CH(CH₃)-NHCH₂CH₂Y [Y = SPh (L³) or PPh₂ (L⁵)] have been explored as ligands. In their complexes with Pd(II) and Ni(II), all the five ligands coordinate in a uninegative tridentate mode (N, O^-, S/P). The proton, carbon-13 and phosphorus-31 (in the case of L⁴ and L⁵) NMR spectra of all the ligands and their Pd(II) and Ni(II) complexes have been found characteristic. Single crystal structures ofL¹, L², [PdCl(L¹-H)] (1), [PdCl(L³-H)] (3) and [NiCl(L⁴-H)] (6) have been solved. The bond distances are: Pd-N, 2.005(3)-2.042(7) ?; Pd-S, 2.257(2)-2.2644(11) ? and Pd-Cl, 2.3091(11)-2.321(2) ?. The Ni-P, Ni-N and Ni-Cl bond lengths in 6 are 2.1324(8) 1.896(2) and 2.1940(7) ? respectively. The geometries of complexes 1, 3 and 6 have been found to be square planar. [Pd(L²-H)Cl] has been immobilized on silica gel and used as a catalyst for Suzuki-Miyaura C-C coupling reactions of benzeneboronic acid with bromobenzene and substituted bromobenzenes. The yields are between 75% and 90%.

Full text of DOI:10.1016/j.poly.2008.01.027

Available online at www.sciencedirect.com
Polyhedron 27 (2008) 1610–1622
www.elsevier.com/locate/poly
Schiff bases functionalized with PPh2 and SPh groups and their
Ni(II) and Pd(II) complexes: Synthesis, crystal structures
and applications of a Pd complex for Suzuki–Miyaura Coupling
P. Raghavendra Kumar, Shailesh Upreti, Ajai K. Singh *
Department of Chemistry, Indian Institute of Technology, New Delhi 110016, India
Received 19 September 2007; accepted 21 January 2008
Available online 17 March 2008
Dedicated to Professor J.E. Drake, University of Windsor, Canada
Abstract
The reactions of 2-hydroxyacetophenone with NH2CH2CH2SPh and NH2CH2CH2PPh2 have resulted in Schiff bases having the
chemical formulae 2-HO–C6H4C(CH3)@N–CH2CH2Y (Y = SPh (L1) or PPh2 (L4)), which are potential (N,O,S) and (N,O,P) type
ligands. Using an appropriate ketone, the Schiff base 2,4-(HO)2–C6H4C(CH3)@N–CH2CH2SPh (L2) has also been synthesized in a sim-
ilar fashion. L1, L2, L4 and the compounds obtained by borohydride reduction of L1 and L2, viz. 2-HO–C6H4CH(CH3)–NHCH2CH2Y
[Y = SPh (L3) or PPh2 (L5)] have been explored as ligands. In their complexes with Pd(II) and Ni(II), all the five ligands coordinate in a
uninegative tridentate mode (N,Oꢀ,S/P). The proton, carbon-13 and phosphorus-31 (in the case of L4 and L5) NMR spectra of all the
ligands and their Pd(II) and Ni(II) complexes have been found characteristic. Single crystal structures of L1, L2, [PdCl(L1–H)] (1),
3
4
˚
[PdCl(L –H)] (3) and [NiCl(L –H)] (6) have been solved. The bond distances are: Pd–N, 2.005(3)–2.042(7) A; Pd–S, 2.257(2)–
˚
˚
˚
2.2644(11) A and Pd–Cl, 2.3091(11)–2.321(2) A. The Ni–P, Ni–N and Ni–Cl bond lengths in 6 are 2.1324(8) 1.896(2) and 2.1940(7) A
respectively. The geometries of complexes 1, 3 and 6 have been found to be square planar. [Pd(L2–H)Cl] has been immobilized on silica
gel and used as a catalyst for Suzuki–Miyaura C–C coupling reactions of benzeneboronic acid with bromobenzene and substituted
bromobenzenes. The yields are between 75% and 90%.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Schiff base; Metal complex; Palladium(II); Nickel(II), (N,O,S) ligand, (N,O,P) ligand; X-ray diffraction; Crystal structure Suzuki–Miyaura
C–C coupling; Catalysis
1. Introduction
show catalytic activity. Thiosemicarbazones and Schiff
bases of suitable aldehydes and ketones constitute a major
group of (N,O,S) ligands investigated in the recent past
[3–9]. The mixed ligand complexes of (N,O,S) ligands with
bipyridyl/phenanthroline have been investigated for DNA
cleavage [10]. The number of (N,O,P) ligands explored
for their complexation reactions with metal ions is limited,
but in last 6–7 years reports appearing on them have
increased [11–21]. The ligands N-[1-(20-hydroxy)phenyleth-
ylidene]-2-(phenylthio) ethyl amine (L1), N-[1-(20,40-di-
hydroxy)phenylethylidene]-2-(phenylthio) ethyl amine
Hybrid ligands, containing both ‘soft’ and ‘hard’ donor
sites, are not only academic curios but are also attractive
for catalyst designing as their hemilabile behaviour results
in facile and reversible generation of coordinatively unsatu-
rated metal centers. Palladium complexes of some (N,O,S)
and (N,O,P) type ligands belonging to this class, as they
have both type of donor sites, are already known [1,2] to
*
Corresponding author. Tel.: +91 11 26591379; fax: +91 11 26581102.
(L2),
N-(10-methyl)-10-(2-hydroxyphenyl)-2-(phenylthio)
E-mail addresses: aksingh@chemistry.iitd.ac.in, ajai57@hotmail.com
(A.K. Singh).
ethyl amine (L2), N-[1-(20-hydroxy)phenylethylidene]-2-
0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2008.01.027

P.R. Kumar et al. / Polyhedron 27 (2008) 1610–1622
1611
(diphenylphoshino) ethyl amine (L4) and N-(10-methyl)-10-
(2-hydroxyphenyl)-2-(diphenylphosphino) ethyl amine
(L5) are potentially of the (N,O,S) or (N,O,P) type
(Fig. 1) and their complexation reactions have not been
investigated so far. It was therefore was thought worthwhile
to investigate them. Additionally, the catalytic activity of
metal complexes [22–29] of ‘Salen’ type of ligands is a moti-
vating factor for exploring L1–L5, as the introduction of one
soft donor site in a framework of a tridentate ligand may
tune the activity towards a new direction. In this paper their
syntheses and complexation with Pd(II) and Ni(II) are
described. Single crystal structures of L1, L2, [PdCl (L1–
H)] (1), [PdCl(L3–H)] (3) and [NiCl(L4–H)] (6) have been
reported. The Pd(II) complex of L2 was immobilized on sil-
ica gel via a –CH2CH2CH2Si linker and the resulting matrix
was found suitable for the Suzuki–Miyaura reaction. These
results are also part of the present paper.
ture method [30,31] was modified as detailed below.
2-Chloroethylamine hydrochloride (0.58 g, 5 mmol) dis-
solved in 20 ml of freshly distilled THF was taken in a
Schlenk flask and stirred for 10 min under nitrogen atmo-
sphere at ꢀ78 °C. A freshly prepared solution of LiPPh2
(5 mmol) in THF (50 ml) was added to it dropwise with
stirring. After complete addition, the temperature of the
flask was slowly increased to room temperature and then
its contents were refluxed for 10 h under nitrogen atmo-
sphere. During this period the deep red solution became
colourless. The reaction mixture was cooled to room tem-
perature and the solvent was removed on a rotary evapora-
tor. The resulting semi-solid was treated with 10% HCl
solution and the solution was washed with benzene
(3 ꢁ 15 ml) and made alkaline with 10% NaOH solution.
The phosphinated amine from this solution was extracted
into benzene, washed with brine (2 ꢁ 25 ml) and dried with
anhydrous Na2SO4. After evaporation of the solvent on a
rotary evaporator, a colourless highly viscous liquid was
obtained. It was further purified by dissolving in 20 ml of
benzene and washing with brine (20 ml). The benzene layer
was dried with Na2SO4 and filtered through celite before
evaporating off the solvent again on a rotary evaporator
2. Experimental
The C and H analyses were carried out with a Perkin–
Elmer elemental analyzer 240 C. The 1H, 13C{1H} and
31P{1H} NMR spectra were recorded on a Bruker Spectro-
spin DPX-300 NMR spectrometer at 300.13, 75.47 and
121.49 MHz, respectively.
1
to get the viscous liquid. Yield: 60%; H NMR: 2.23–2.28
(t, 2H, CH2N), 2.82–2.89 (m, 2H, CH2P), 7.32–7.46 (m,
10H, ArH).
The 13C CPMAS NMR spectrum was recorded on a
Bruker FT-NMR Spectrometer (DSX 300) at 75.46 MHz.
IR spectra in the range 4000–250 cmꢀ1 were recorded on
2.1. Synthesis of L1
´
a Nicolet Protege 460 FT-IR spectrometer as KBr pellets.
The melting points were determined in open capillary,
and are reported as such. The conductivity measurements
were carried out in CH3CN (concentration ca. 1 mM) using
an ORION conductivity meter model 162.
PhSCH2CH2NH2 was synthesized by the literature
method [30,31]. To prepare Ph2PCH2CH2NH2 the litera-
o-Hydroxyacetophenone (0.71 g, 5.26 mmol) dissolved
in 20 ml of dry methanol was stirred for 30 min and mixed
with a solution of PhSCH2CH2NH2 (0.81 g, 5.26 mmol)
made in 10 ml of dry methanol, which was added dropwise
with stirring. The mixture, which became yellow instanta-
neously, was stirred further for ꢂ5–6 h at room tempera-
CH3
CH3
1
11
14
9
6
1
11
9
S
4
5
10
S
4
5
10
12
13
3
12
13
N
8
3
8
7
N
2
2
15
15
7
HO
OH
OH
6
9
14
11
L1
L2
CH3
1
CH3
S
4
5
10
1
11
9
12
13
3
8
7
N
P
4
10
2
12
13
H
3
8
N
2
15
OH
7
15
6
14
OH
5
L3
6
14
L4
CH3
1
11
14
9
6
P
4
5
10
12
13
3
8
N
2
H
7
15
OH
L5
Fig. 1. Structures of L1 to L5.

1612
P.R. Kumar et al. / Polyhedron 27 (2008) 1610–1622
ture. The solvent was evaporated off on a rotary evapora-
tor to yield a yellow solid. The single crystals of L1 were
grown from its solution in a chloroform–hexane (1:2) mix-
ture at low temperature (0–5 °C). Yield: 1.36 g; 95% m.p.
55 °C. Anal. Calc. for C16H17NOS: C, 70.82; H, 6.31; N,
5.16. Found C, 70.52; H, 6.26; N, 5.31%. NMR: (1H,
25 °C, CDCl3) d: 2.27 (s, 3H, CH3), 3.29 (t, J = 7.0 Hz,
2H, H2), 3.76 (t, J = 6.9 Hz, 2H, H1), 6.79 (t, J = 7.3 Hz,
2H, H13), 6.92–6.95 (d, d, J = 8.3 Hz, 1H, H6), 7.17–7.41,
(m, 6H, H11 to H15 and H7), 7.48–7.51 (d, J = 8.0 Hz,
1H, H9), 15.82 (bs, 1H, OH); (13C{1H}, 25 °C, CDCl3) d:
14.3 (CH3), 34.1 (C2), 48.3 (C1), 117.0 (C6), 118.2 (C8),
121.7 (C4), 126.1 (C13), 127.9 (C12,14), 129.4 (C11,15),
129.9 (C9), 132.1 (C7), 135.2 (C10), 163.0 (C5), 172.1 (C3).
119.0 (C8), 126.4 (C13), 127.9 (C7), 127.3 (C4), 128.3 (C9),
128.9 (C12,14), 129.7 (C11,15), 135.0 (C10), 157.0 (C5).
2.4. Synthesis of L4
(2-Aminoethyl)diphenylphosphine (1.2 g, 5.0 mmol) was
stirred for 0.5 h in 5 ml dry ethanol at room temperature.
o-Hydroxyacetophenone (0.13 g, 1.0 mmol) dissolved in
5 ml of dry ethanol was added to the above solution drop-
wise with stirring under a N2 atmosphere. The mixture was
stirred further for 6 h at room temperature. Its solvent was
evaporated off on a rotary evaporator resulting in L4 as a
viscous yellow liquid, which on recrystallization from a
chloroform–hexane mixture (1:10) gave L4 as a yellow
solid. Single crystals of L4 were grown by slow evaporation
of its solution made in a mixture of chloroform and hexane
(1:10). Yield 1.36 g; 78%; m.p. 82-83 °C Anal. Calc. for
C22H22NOP: C, 76.06; H, 6.38; N, 4.03. Found: C, 75.20;
H, 6.52; N, 4.25%. NMR: (1H, 25 °C, CDCl3) d: 2.21 (s,
3H, CH3), 2.51 (t, J = 8.0 Hz, 2H, H2), 3.59–3.67 (q,
J = 7.7 Hz, 2H, H1), 6.75 (t, J = 7.4 Hz, 2H, H13,19),
6.90–6.93 (d, J = 8.2 Hz, 1H, H6), 7.24–7.46, (m, 11H,
ArH), 16.27 (bs, 1H, OH); (13C{1H}, 25 °C, CDCl3) d:
14.3 (CH3), 29.4–29.6 (d, JP–C = 12 Hz, C2), 46.0–46.3 (d,
JP–C = 22.5 Hz, C1), 116.9 (C6), 118.7 (C8), 119.2 (C4),
127.9 (C13), 128.5–128.8 (C12,14), 132.4–132.5 (d, C11,15),
132.8 (C7), 137.8 (C10), 163.8 (C5), 171.4 (C3); (31P{1H},
25 °C, CDCl3): d ꢀ20.4.
2.2. Synthesis of L2
2,4-Dihydroxyacetophenone (0.61 g, 4.0 mmol) was dis-
solved in 20 ml of dry methanol and stirred for 30 min.
PhSCH2CH2NH2 (0.81 g, 5.26 mmol) dissolved in 10 ml
of methanol was added and the mixture was heated over
a water bath at 50 °C for 3 h. The solvent was evaporated
off on a rotary evaporator to give a light yellow solid L2.
Yellow single crystals of L2 were obtained by slow evapo-
ration of its solution made in a chloroform–hexane (2:1)
mixture. Yield: 1.04 g; 90%; m.p. 113 °C. Anal. Calc. for
C16H17NO2S: C, 66.87; H, 5.96; N, 4.87. Found: C,
66.52; H, 6.12; N, 4.71%. NMR: (1H, 25 °C, DMSO-d6)
d: 2.23 (s, 3H, CH3), 3.31 (t, J = 6.2 Hz, 2H, H2), 3.71
(t, J = 6.2 Hz, 2H, H1), 6.11 (s, 1H, H6), 6.17–6.19
(d, J = 10.5 Hz, 1H, H8), 7.20–7.30 (d, J = 9.0 Hz, 1H,
H9), 7.36–7.48 (m, 5H, H11ꢀ15), 9.82 (bs, 1H, OH p to
C@N), 16.43 (s, 1H, OH o to C@N); (13C{1H}, 25 °C,
DMSO-d6) d: 14.3 (CH3), 33.1 (C2), 46.5 (C1), 103.5 (C6),
105.7 (C8), 111.5 (C4), 125.9 (C13), 128.4 (C12,14), 129.1
(C11,15), 129.1 (C9), 135.6 (C10), 161.7 (C5), 167.4 (C7),
172.1 (C3).
2.5. Synthesis of L5
L4 (0.3474, 1 mmol) and NaBH4 (0.2 g, 5 mmol) were
refluxed together in 50 ml dry ethanol under a N2 atmo-
sphere for 12 h. The mixture was cooled and the solvent
was evaporated off on a rotary evaporator. L5 was
extracted from the residue into dry dichloromethane
(4 ꢁ 20 ml) and the extract was filtered through celite.
The filtrate was washed with distilled water (4 ꢁ 25 ml)
and dried with anhydrous sodium sulfate. L5 was obtained
from the dried extract as a viscous colourless oil by
evaporation of the solvent on a rotary evaporator. Yield
0.26 g; 75%. NMR: (1H, 25 °C, CDCl3) d: 1.34–1.37 (d,
J = 11.63 Hz, 3H, CH3), 2.16–2.35 (m, 2H, H1), 2.69–
2.77 (m, 2H, H2), 3.80–3.86 (q, J = 7.4 Hz, 1H, H3),
6.86–6.88 (d, J = 6.00 Hz, 2H, H11,15), 6.78–6.80 (d,
J = 6.00 Hz, 1H, H6), 7.09 (t, J = 7.7 Hz, 1H, H7), 7.28–
7.69 (m, 10H, ArH); (13C{1H}, 25 °C, CDCl3) d: 22.0
(CH3), 28.2–28.3 (d, JP–C = 12 Hz, C2), 46.0–46.3 (d, JP–C
= 21.9 Hz, C1), 61.4 (C3), 116.9 (C6), 118.7 (C8), 126.3
(C4), 127.8 (C7), 128.0 (C9), 128.3 (C12,14), 132.4 (C13),
137.4–137.6 (C11,15), 138.8 (C10), 157.0 (C5); (31P{1H},
25 °C, CDCl3): d ꢀ21.4.
2.3. Synthesis of L3
L1 (0.2714 g, 1 mmol) and NaBH4 (0.2 g, 5 mmol) were
taken in 50 ml of dry ethanol and refluxed for 24 h. The
reaction mixture was cooled and its solvent evaporated
off on a rotary evaporator to result in a semi-solid product.
L3 was leached out from this product with dry dichloro-
methane (5 ꢁ 25 ml). The combined dichloromethane
extract was filtered through celite, washed with distilled
water (4 ꢁ 25 ml) and dried with anhydrous sodium sul-
fate. The solvent from the extract was removed on a rotary
evaporator and L3 was obtained as a highly viscous color-
less oil. Yield: 0.23 g; 85%. NMR: (1H, 25 °C, CDCl3) d:
1.37–1.40 (d, J = 6.7 Hz, 3H, CH3), 2.75–2.45 (m, 2H,
H2), 2.92–3.00 (m, 1H, H1), 3.06–3.15 (m, 1H, H1),
3.80–3.87 (q, J = 6.5 Hz, 1H, CH), 6.71–6.90 (m, 3H, H6,
H7, H8), 7.01–7.27 (m, 5H, H11 to H15), 7.23–7.32 (d,
J = 6.3 Hz, 1H, H9); (13C{1H}, 25 °C, CDCl3) d: 22.12
(CH3), 33.41 (C2), 45.22 (C1), 58.31 (C3), 116.6 (C6),
2.6. Synthesis of [PdCl(L1–H)] (1)
To a stirred solution of Na2[PdCl4] (0.294 g, 1 mmol)
made in 5 ml of distilled water was added a solution of

P.R. Kumar et al. / Polyhedron 27 (2008) 1610–1622
1613
L1 (0.2714 g, 1 mmol) made in 10 ml of acetone. The mix-
ture was stirred for 30 min and thereafter it was poured
into 50 ml of distilled water. The complex was extracted
with 100 ml of chloroform. The chloroform extract was
washed with distilled water (3 ꢁ 20 ml) and dried with
anhydrous sodium sulfate. The solvent was evaporated
off on a rotary evaporator and the residue was dried under
vacuum to obtain an orange powder of 1. On recrystalliza-
tion of the powder from a mixture (1:1) of chloroform and
hexane, single crystals of 1 were obtained. Yield: 0.32 g;
78%; m.p. 140 °C. Anal. Calc. for C16H16NOSPdCl: C,
46.62; H, 3.91; N, 3.40. Found: C, 46.71; H, 3.92; N,
3.61%. NMR: (1H, 25 °C, CDCl3) d: 2.47 (s, 3H, CH3),
2.75–2.81 (td, J = 13.5 Hz, 1H, H1), 3.32–3.42 (dt,
J = 4.5 Hz, J = 13.4 Hz, 1H, H2), 3.72–3.82 (dt, J =
3.5 Hz, J = 14.0 Hz, 1H, H2), 4.03–4.11 (td, J = 13.4 Hz,
1H, H1), 6.64 (t, J = 7.7 Hz, 1H, H6), 7.14–7.24 (m, 3H,
sulfate. Slow evaporation of solvent from the dried extract
at room temperature gave orange-red single crystals of 3.
Yield 0.32 g; 78%; m.p. 185 °C. Anal. Calc. for C16H18NO
SPdCl: C, 46.39; H, 4.38; N, 3.38. Found: C, 46.52; H,
4.26; N, 3.43%. NMR: (1H, 25 °C, CDCl3) d: 1.60 (bs, 3H,
CH3), 2.86 (bs, 1H, NH), 3.14–3.26 (two bs, 2H, H2), 3.63
(bs, 2H, H1), 6.95 (bs, 2H, H12,14), 7.58 (bs, H11,13,15), 8.00
(bs, 1H, H7), 8.30 (bs, 1H, H9); (13C{1H}, 25 °C, CDCl3) d:
18.7 (CH3), 41.6 (C2), 51.8 (C1), 57.4 (C3), 114.2 (C6), 118.6
(C8), 127.3 (C4), 128.7 (C13), 129.4 (C7), 130.5 (C9), 129.9
(C12,14), 132.4 (C11,15), 135.0 (C10), 162.2 (C5).
2.9. Synthesis of [PdCl(L4–H)] (4)
Na2[PdCl4] (0.294 g, 1 mmol) was dissolved in 5 ml of
water. A solution of L4 (0.3474 g, 1 mmol) made in 10 ml
of acetone was added to it with stirring. The mixture was stir-
red for a further 30 min which resulted in a yellow coloured
solution. The complex was extracted into 50 ml of
chloroform. The chloroform layer was washed with 20 ml
of distilled water, dried with anhydrous sodium sulfate and
reduced in volume to 10 ml by evaporating off the solvent
on a rotary evaporator. The resulting precipitate was fil-
tered, washed with hexane and dried under vacuum to give
4 as a yellow solid. Yield: 0.39 g; 80%; m.p. 158 °C. Anal.
Calc. for C22H21NOPPdCl: C, 54.12; H, 4.34; N, 2.87.
Found: C, 54.01; H, 4.32; N, 2.81%. NMR: (1H, 25 °C,
CDCl3) d: 2.17 (s, 3H, CH3), 2.38–2.45 (two t, J = 6.5 Hz,
2H, H2), 3.81 (t, J = 6.2 Hz, 2H, H1), 3.92 (t, J = 6.2 Hz,
1H, H1), 6.57 (t, J = 7.9 Hz, 1H, H13), 7.14–7.17 (d,
J = 8.5 Hz, 1H, H6), 7.26 (t, merged with CHCl3 signal,
2H, H8), 7.44–7.53 (m, 8H, ArH o and m to P), 7.91–7.97
(m, 2H, H7,9); (13C{1H}, 25 °C, CDCl3) d: 21.2 (CH3),
30.1–30.5 (d, JP–C = 12 Hz C2), 56.6 (C1), 114.8 (C6), 119.2
(C4), 123.3 (C8), 128.0 (C9), 129.0–129.1 (C12,14), 130.4
(C13), 133.3–133.5 (C11,15), 132.4 (C7), 144.6 (C10), 158.0
(C5), 170.7 (C3); (31P{1H}, 25 °C, CDCl3): d 35.1.
H
8,12–14), 7.29–7.33 (m, H11,15,7), 8.17–8.21 (m, 1H, H9);
(13C{1H}, 25 °C, CDCl3) d: 18.6 (CH3), 39.7 (C2), 58.3
(C1), 114.7 (C6), 120.3 (C8), 121.7 (C4), 127.5 (C10), 128.8
(C12,14), 129.6 (C13), 129.9 (C9), 131.8 (C11,15), 132.5 (C7),
163.0 (C5), 167.2 (C3).
2.7. Synthesis of [PdCl(L2–H)] (2)
Na2[PdCl4] (0.294 g, 1 mmol) dissolved in 5 ml of water
was treated with L2 (0.2874 g, 1 mmol) dissolved in 10 ml
of acetone as described above for 1, except that the com-
plex was extracted into 50 ml of chloroform. The extract
was dried with anhydrous sodium sulfate. Its solvent was
evaporated off on a rotary evaporator resulting in an
orange coloured powder of 2. The orange coloured crystals
of 2 were grown by slow evaporation of its solution made
in a mixture of chloroform and methanol (10:1). Yield:
0.30 g; 70%; m.p. 170–172 °C. Anal. Calc. for C16H16NO2-
SPdCl: C, 44.88; H, 3.77; N, 3.27. Found: C, 44.75; H, 3.76;
N, 3.27%. NMR: (1H, 25 °C, DMSO-d6) d: 2.23 (s, 3H,
CH3), 2.70–2.74 (td, J = 13.3 Hz, 1H, H1), 3.30–3.46 (dt,
J = 4.4 Hz, J = 13.2 Hz, 1H, H2), 3.55–3.62 (dt,
J = 11.0 Hz, 1H, H2), 3.87–3.92 (td, J = 12.9 Hz, 1H,
H1), 7.15–7.19 (d, J = 9.2 Hz, 1H, H8), 7.4–7.44 (m, 4H,
2.10. Synthesis of [PdCl(L5–H)] (5)
Na2[PdCl4] (0.294 g, 1 mmol) dissolved in 5 ml of water
and a solution of L5 (0.35 g, 1 mmol) made in 10 ml of ace-
tone were mixed with vigorous stirring. The stirring was
continued further for 1 h. The complex was extracted into
40 ml of chloroform. The organic layer was washed with
distilled water (2 ꢁ 20 ml), dried with anhydrous sodium
sulfate and evaporated on a rotary evaporator. The result-
ing residue was recrystallized with a chloroform–hexane
mixture (1:10) to obtain 5 as a yellow solid, which was sep-
arated and dried under vacuo. Yield: 0.32 g; 65%; m.p.
169 °C. Anal. Calc. for C22H23NO PPdCl: C, 53.79; H,
4.92; N, 2.85. Found: C, 53.81; H, 4.86; N, 2.94%.
H
11,12,14,15), 6.13–6.17 (m, 1H, H13), 6.44–6.45 (d,
J = 3.0 Hz, 1H, H6), 8.08–8.11 (m, 1H, H9), 9.32 (bs, 1H,
OH); (13C{1H}, 25 °C, DMSO-d6) d: 17.6 (CH3), 39.3
(C2), 57.5 (C1), 103.0 (C6), 105.9 (C8), 114.5 (C4), 127.4
(C10), 129.1 (C9,13), 128.4 (C12,14), 131.3 (C11,15), 161.3
(C5), 164.1 (C7), 165.4 (C3).
2.8. Synthesis of [PdCl(L3–H)] (3)
A solution of Na2[PdCl4] (0.294 g, 1 mmol) made in 5 ml
of water was added to a solution of L3 (0.2734 g, 1 mmol)
prepared in 10 ml of acetone with vigorous stirring. The mix-
ture was stirred further for 2 h. It was then poured into 50 ml
of distilled water. Complex 3 was extracted into 100 ml of
chloroform. The chloroform extract was washed with dis-
tilled water (2 ꢁ 25 ml) and dried with anhydrous sodium
2.11. Synthesis of [NiCl(L4–H)] (6)
NiCl2 ꢃ 6H2O (0.284 g, 1 mmol) was dissolved in 2 ml of
dry methanol. A solution of L4 (0.3474 g, 1 mmol) made in

1614
P.R. Kumar et al. / Polyhedron 27 (2008) 1610–1622
10 ml of chloroform was added to it with vigorous stirring.
The mixture was stirred for a further 0.5 h. The resulting
red coloured solution was poured into 50 ml of distilled
water. The complex was extracted into 50 ml of chloro-
form. The chloroform layer was washed with 25 ml of dis-
tilled water and dried with anhydrous sodium sulfate. The
solvent of the extract was evaporated off on a rotary evap-
orator to get 6 as a red solid. Its single crystals were grown
in a chloroform and hexane mixture (2:1). Yield: 0.39 g;
88%; m.p. 140 °C. Anal. Calc. for C22H21NO PNiCl: C,
59.98; H, 4.80; N, 3.18. Found: C, 60.01; H, 4.92; N,
3.21%. NMR: (1H, 25 °C, CDCl3) d: 2.48 (s, 3H, CH3),
2.02–2.10 (two t, J = 6.78 Hz, 2H, H2), 3.50 (t,
J = 6.53 Hz, 1H, H1), 3.59 (t, J = 6.5 Hz, 1H, H1), 6.56,
(t, J = 7.3 Hz, 1H, H13), 7.08–7.11 (d, J = 8.4 Hz, 1H,
H6), 7.21 (t, J = 7.5 Hz, 1H, H8), 7.41–7.57 (m, 8H, ArH
o and m to P), 8.04–8.10 (m, 2H, H7,9); (13C{1H}, 25 °C,
CDCl3) d: 20.4 (CH3), 28.9–29.3 (d, JP–C = Hz C2), 55.0
(C1), 114.8 (C6), 121.7 (C8), 127.4 (C4), 128.9–129.2
(C12,14), 130.4 (C13), 131.5 (C9), 133.0 (C7), 133.1–133.4
(d, C11,15), 144.6 (C10), 158.0 (C5), 170.7 (C3); (31P{1H},
25 °C, CDCl3): d 37.0.
was filtered, washed with DMF (3 ꢁ 5 ml) and THF
(3 ꢁ 5 ml), dried in vacuo, to give a slippery orange-yellow
solid (Catalyst 1). The palladium content was found to be
0.08 mmol/g in Catalyst 1 by flame AAS after decomposing
0.1 g of it with 20 ml of concentrated HNO3 + HCl (1:3)
and 70% HClO4 (5 ml).
2.14. Coupling of aryl bromides with benzeneboronic acid
A mixture of bromobenzene or its derivative (1 mmol),
benzeneboronic acid (0.183 g, 1.5 mmol), Na2CO3 (0.212
g, 2 mmol), distilled water (0.5 ml), isopropanol (10 ml)
and Catalyst 1 (0.1 g, ꢂ0.008 mmol of Pd) was stirred
under reflux over an oil bath for 8–10 h under ambient con-
ditions. The reaction mixture was cooled to room temper-
ature. The solid was filtered off and the filtrate was
extracted with hexane/diethyl ether (25–50 ml). The solvent
from the extract was evaporated off to give a white crystal-
line solid product, which was authenticated by NMR. Fur-
ther details and results are given in Table 8.
2.15. X-ray diffraction analysis
2.12. Synthesis of [NiCl(L5–H)] (7)
Single crystal X-ray diffraction studies of L1, L2, 3 and 6
were carried out with a Bruker SMART CCD diffractom-
˚
NiCl2 ꢃ 6H2O (0.284 g, 1 mmol) was dissolved in 5 ml of
dry methanol. A solution of L5 (0.35 g, 1 mmol) made in
10 ml of methanol was added to it with vigorous stirring.
The mixture was stirred for a further 0.5 h. Complex 7
was extracted and treated further as given above in Section
2.11, to get it as a red solid. Yield: 0.35 g; 80%; m.p.
140 °C. Anal. Calc. for C22H23NO PNiCl: C, 59.57; H,
5.45; N, 3.16. Found: C, 59.54; H, 5.42; N, 3.25%. NMR:
(1H, 25 °C, CDCl3) d: 1.58–1.60 (d, J = 5.13 Hz, 3H,
CH3), 2.50 (bs, 1H, NH), 2.90 (bs, 2H, H2), 3.13 (bs, 2H,
H1), 4.46 (q, 1H, CH), 6.76 (t, J = 7.2 Hz, 2H, H13), 7.03
(d, 1H, H6), 7.12 (t, J = 6.91 Hz, 1H, H8), 7.60–7.90 (bs,
1H, H7,9), 7.24–7.48 (m, 8H, ArH o and m to P).
eter (at IIT Delhi) using Mo Ka (k = 0.71073 A) radiation
at 298(2) °C. The software SADABS was used for absorption
corrections and SHELXTL for space group, structure determi-
nation and refinements [33]. All non-hydrogen atoms were
located from a difference Fourier map using geometrical
constraints and were refined anisotropically. Hydrogen
atoms were included in idealized positions with isotropic
thermal parameters set at 1.2 times that of the carbon atom
to which they were attached. The least-squares refinement
cycles on F2 were performed until the model converged.
Data for 1 was collected (at the Instituto de Quimica,
UNAM, Mexico) on a Bruker Smart APEX CCD diffrac-
tometer, using graphite monochromatized Mo Ka radia-
˚
tion (k = 0.71073 A) at 293(2) K. An analytical face
2.13. [PdCl(L2–H)] (2) anchored silica gel (Catalyst 1)
indexed absorption correction was applied. The structure
was solved by direct methods. Refinement was carried
out by full-matrix least-squares analysis with anisotropic
thermal parameters for all non-hydrogen atoms. Hydrogen
atoms were placed into calculated positions and refined
using a riding model with fixed isotropic thermal parame-
ters. Calculations were carried out with SMART software
for data collection and reduction, and SHELXTL for solution
and refinement [34].
Activated silica gel [32] (30 g), suspended in 100 ml solu-
tion of (3-chloropropyl)triethoxysilane in dry xylene (15%
v/v), was refluxed with stirring for 72 h under a nitrogen
atmosphere. The solid 3-chloropropyl silica gel (CPSG),
separated by filtration, was washed (4 ꢁ 25 ml) successively
with xylene, ethanol and diethylether. It was dried and
degassed at 373 K under vacuum for 6 h, under anhydrous
conditions. The CPSG (1 g) was added to a mixture made
by stirring for about 15 min, 1 mmol (0.024 g) of sodium
hydride (60% in mineral oil), 10 ml of a DMF–THF mix-
ture (1:1) and an orange-red solution of complex 2
(1 mmol, 0.429 g) made in 2 ml of DMF (the solution of
2 was added dropwise with stirring with a magnetic bead
at room temperature to the other contents taken in a
100 ml round bottom flask). The mixture was stirred fur-
ther for 12 h. The silica gel became orange in colour. It
3. Results and discussion
The ligands L1 to L5 were synthesized by the reactions
given in Eqs. (1) and (2). They are soluble in common
organic solvents, except L2 which is sparingly soluble in
chloroform, dichloromethane and methanol and insoluble
in hexane and diethyl ether. L4 and L5 are highly viscous
oily liquids and consequently could not be subjected to

P.R. Kumar et al. / Polyhedron 27 (2008) 1610–1622
1615
elemental analyses. The Pd(II) and Ni(II) complexes (1–7)
of L1–L5 were synthesized according to Eqs. (3) and (4).
show a red shift of the order of 10–15 cmꢀ1 with respect
to those of the corresponding ligands.
CH3
CH3
CH3
SPh
SPh
NaBH4
O
N
N
H
SPh
+
H2N
ð1Þ
ð2Þ
dry EtOH
dry EtOH
R
OH
R
OH
OH
L3
R = H L1, OH L2
CH3
N
CH3
CH3
PPh
PPh2
2 NaBH4
O
N
PPh2
H
+
H2N
dry EtOH
dry EtOH
OH
OH
OH
L5
L4
Acetone
H2O
L1 to L5
[PdCl(
)]
L-H (1-5)
+ 2 NaCl +HCl
+
Na2PdCl4
ð3Þ
ð4Þ
Methanol
L4 to L5
[NiCl(
)]
L-H (6-7)
+
NiCl . H2O
6
+ HCl
2
All the complexes were soluble in common organic sol-
vents such as chloroform, dichloromethane, acetonitrile,
methanol, ethanol, DMF and DMSO, except 5. In hexane
and diethyl ether all the complexes were sparingly soluble.
However, the solubility of 7 in common organic solvents
was to be found relatively low. The molar conductance
(KM) of the ligands and the complexes was measured in
acetonitrile at a concentration of about 1 mM at room tem-
perature. The values of 0.5–10 Omegaꢀ1 cm2 molꢀ1 suggest
that they are non-electrolytic in nature.
3.1. NMR spectra
The 1H NMR spectra of the ligands L1 to L5 were found
to be characteristic. The OH (ortho to azomethine) proton
appears as a singlet at 15.82 ppm in the spectrum of L1 and
at 16.43 ppm in that of L2. They are highly deshielded due
to OHꢃ ꢃ ꢃN intra-molecular hydrogen bonding (supported
by their single crystal structures). In the 1H NMR spectrum
of L2, the OH (para to azomethine) proton appears as a
broad singlet at 9.82 ppm. The OH proton appears as a sin-
glet at 16.27 ppm in the spectrum of L4, which is also
highly deshielded due to OHꢃ ꢃ ꢃN intra-molecular hydrogen
bonding. The OH signal could not be observed in the spec-
tra of L3 and L5, which have reduced ˜C–NH rather than
˜C@N groups. Most probably the OH proton is not stabi-
lized by intra-molecular hydrogen bonding in L3 and L5
and consequently intermolecular exchange between the
phenolic protons broadens the OH signal so that it is not
In the IR spectra of L1, L2 and L4 the ˜C@N stretching
vibration appears at 1612, 1618 and 1605 cmꢀ1 respec-
tively, while the C–S stretching band in the case of L1 to
L3 appears between 782 and 797 cmꢀ1. The N–H bending
absorption appears at 1595 cmꢀ1 in the IR spectrum of
L3. In the IR spectra of 1, 2 and 6, the ˜C@N stretching
band shows a red shift with respect to those of the corre-
sponding free ligands by ꢂ15 cmꢀ1. In the IR spectra of
the complexes of L1–L3, the C–S stretching bands appear
at around 745 cmꢀ1 (red shifted in comparison to those
of the corresponding free ligands). In the IR spectra of 3,
5 and 7 the N–H stretching and bending absorptions also
1
identifiable. In the H NMR spectra of 1 and 2 the CH3
protons were deshielded by ꢂ0.2 ppm relative to those of
the corresponding free ligand protons. The two protons
of each CH2 in the S–CH2–CH2–N system i.e. H2 and H1

1616
P.R. Kumar et al. / Polyhedron 27 (2008) 1610–1622
are diastereotopic and magnetically non-equivalent, thus
producing a group of four signals, each one corresponding
to a single proton. The H2 protons give two doublets of a
triplet in which one signal is deshielded by 0.2–0.3 ppm and
the other one by 0.3–0.4 ppm with respect to those of the
free ligand. The H1 protons give two triplets of a doublet
in which one signal is deshielded by ꢂ0.3–0.4 ppm and
the other is shielded by ꢂ1 ppm (relative to those of free
L1/L2). The signals of the H6 proton appear shielded
thine carbon atom was shielded by ꢂ5 and 7 ppm, respec-
tively, (relative to the ligands) in the spectra of 1 and 2. The
signals of C10 show a deshielding of ꢂ7–8 ppm in compar-
ison to those of the ligands. In the carbon-13 spectrum of 3
the signals of the C1 and C2 carbon atoms were deshielded
by ꢂ5 and 7 ppm respectively. The 13C{1H} NMR spectra
of 4 and 6 exhibit signals for C1, C2 and CH3 which are
deshielded by ꢂ6–7 ppm with respect to those of the
ligands. Thus the above mentioned deshielding of the sig-
1
1
(ꢂ0.3 ppm) compared to those of free ligands. In the H
nals in the 13C{1H} and H NMR spectra suggests that
NMR spectrum of 3 the signals were somewhat broad.
The CH3 protons were deshielded (ꢂ0.3 ppm) with respect
to the corresponding protons of L3. The H2 and H1 protons
also appear deshielded (ꢂ0.2 and 0.5 ppm, respectively) rel-
ative to the corresponding protons of the ligand L3. Addi-
tionally, the NH proton signal has been observed at
2.86 ppm. The signal of the H6 proton was shielded
(ꢂ0.3 ppm) whereas the signals of the other aromatic pro-
tons were deshielded (0.2–1.0 ppm) in comparison to the
corresponding protons of L3. In the proton NMR spec-
trum of 4 the H2 protons were shielded (ꢂ0.1 ppm). The
H1 protons give two characteristic triplets which were
deshielded by ꢂ0.4 and 0.5 ppm compared to the corre-
sponding L4 protons. The OH signal present in the spectra
of ligands L1, L2 and L4 was found to be absent in the spec-
tra of complexes 1, 2, 4 and 6. In the 1H NMR spectra of 6
and 7, the CH3 protons were deshielded by ꢂ0.3 ppm com-
pared to those of the ligands. The H2 protons in the spec-
trum of 6 give two triplets (due to P–H coupling) merged
with each other, but these signals are shielded by 0.5 ppm
with respect to the signals of the corresponding ligand pro-
tons. The H1 protons also gave characteristic triplets (due
to coupling with P) at 3.50 and 3.59 ppm. The signals of
the H2 and H1 protons were also deshielded by ꢂ0.7 ppm
in the spectrum of 7 with respect to the signals of the cor-
responding ligand protons. The solubility of 5 was inade-
quate even for proton NMR.
ligands L1 to L5 behave as (N,Oꢀ,S/P) donors in all the
complexes. This is corroborated by the single crystal struc-
tures of 1, 3 and 6, indicating similarity in the solid state
and solution structures. The 13C{1H} NMR spectrum of
7 could not be recorded due to its inadequate solubility.
In the 31P{1H} NMR spectra of L4 and L5 a sharp sin-
glet was observed at ꢀ20.2 and ꢀ21.4 ppm, respectively,
indicating the presence of only one type of phosphorus
Table 1
Crystal data and structure refinement parameters of L1 and L2
L1
L2
Empirical formula
Formula weight
Colour
C16H17NOS
271.38
yellow
C16H17NO2S ꢃ 1/6C6H6
1808.5
yellow
Crystal size (mm)
Crystal system
Space group
0.312 ꢁ 0.109 ꢁ 0.098 0.312 ꢁ 0.192 ꢁ 0.056
monoclinic
rhombohedral
ꢀ
P21/c
R3
Unit cell dimensions
˚
a (A)
14.938(3)
5.4453(10)
18.138(3)
90
104.619(4)
90
1427.7(5)
4
1.263
15.1642(10)
15.1642(10)
15.1642(10)
112.35
112.35
112.35
2355.0(3)
1
1.275
0.210
960
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
3
˚
V (A )
Z
qcalc (Mg/m3)
l (mmꢀ1
F(000)
)
0.218
576
The carbon-13 NMR spectra of L1–L5 and their metal
complexes are characteristic. In the spectrum of L3, the sig-
nal of the C3 carbon atom appears shielded by about
113.8 ppm relative to that of L1. The methyl carbon peak
was also deshielded by 7.8 ppm with respect to that of
L1. In the carbon-13 NMR spectrum of L4, the signals of
the C2 and C1 carbon atoms appear as doublets at 29.4–
29.6 and 46.0–46.3 ppm, respectively. The splitting of these
peaks into doublets is due to coupling with phosphorous.
The signal of the azomethine carbon atom has been
observed at 171.4 ppm. On reduction of L4 to L5 the signal
of the azomethine carbon was replaced with a signal of a
CH carbon atom, shielded by 110 ppm with respect to
the signal of the corresponding carbon of L4. In the
13C{1H} NMR spectra of 1 and 2 the signals of C1 and
C2 carbon atoms were deshielded by ꢂ10 and 5–6 ppm,
respectively, relative to the signals of the corresponding
carbon atoms of the ligands. The signals of the CH3 carbon
atoms were also deshielded by ꢂ4 ppm on complexation,
with respect to those of L1 and L2. The signal of the azome-
h Range (°)
Index ranges
1.41–25.50
ꢀ18 6 h 6 18,
ꢀ6 6 k 6 6,
ꢀ21 6 l 6 21
8719
1.62–25.50
ꢀ17 6 h 6 17,
ꢀ17 6 k 6 17,
ꢀ17 6 l 6 17
15893
Reflections collected
Independent reflections 1836 [0.0535]
[Rint
2937 [0.0493]
]
Maximum and
minimum
0.971–0.981
none
transmission
Completeness to
maximum h (%)
Data/restraints/
parameters
100
98.6
2467/0/150
2343/0/193
Goodness-of-fit on F2
Final R indices
[I > 2r(I)]
1.238
1.298
R1 = 0.0710,
wR2 = 0.1686
R1 = 0.0796,
wR2 = 0.1840
0.200 and ꢀ0.178
R1 = 0.0904,
wR2 = 0.2255
R1 = 0.1018,
wR2 = 0.2447
0.423 and ꢀ0.371
R indices (all data)
Largest difference in
peak and hole
ꢀ3
˚
(e A
)

P.R. Kumar et al. / Polyhedron 27 (2008) 1610–1622
1617
containing species. In the 31P{1H} NMR spectra of com-
3.2. Single crystal structures
plexes 4 and 6 sharp signals at 35 and 37 ppm were
observed, deshielded by ꢂ55–57 ppm in comparison to
those of the corresponding ligands. This supports the
ligation of L4 and L5 through phosphorus in solution as
well.
The crystal structures of L1, L2, 1, 3 and 6 have been
determined by X-ray diffraction on their single crystals.
The twinning in crystals of 2 restricted us from solving its
structure. The crystal data and structure refinement details
Table 2
Crystal data and structure refinement parameters of 1, 3 and 6
1
3
6
Empirical formula
Formula weight
Colour
C16H16ClNOPdS
412.21
orange
C16H18ClNOPdS
414.22
red
C22H21ClNNiOP
440.53
red
Crystal size (mm)
Crystal system
Space group
0.446 ꢁ 0.072 ꢁ 0.048
monoclinic
P21/n
0.219 ꢁ 0.138 ꢁ 0.089
0.319 ꢁ .102 ꢁ 0.089
monoclinic
P21/c
triclinic
ꢀ
P1
Unit cell dimensions
˚
a (A)
12.6507(8)
8.7952(6)
15.566(1)
90
112.904(1)
90
1595.2(2)
4
1.716
10.6388(12)
11.6769(14)
14.9603(17)
76.857(2)
64.884(2)
71.233(2)
1584.3(3)
4
1.737
1.469
10.7188(12)
12.0840(13)
16.4529(18)
90.00
100.520(2)
90
2095.3(4)
4
1.397
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
3
˚
V (A )
Z
Dcalc (Mg/m3)
l (mmꢀ1
F(000)
)
1.458
824
1.141
912
832
h Range (°)
Index ranges
1.77–25.03
ꢀ15 6 h 6 15,
ꢀ10 6 k 6 10,
ꢀ18 6 l 6 18
12699
1.45–25.11
ꢀ12 6 h 6 12,
ꢀ13 6 k 6 13,
ꢀ17 6 l 6 17
14715
0.997–25.27
ꢀ11 6 h 6 11,
ꢀ13 6 k 6 13,
ꢀ18 6 l 6 18
12711
Reflections collected
Independent reflections [Rint
]
2819 [0.0510]
0.9397 and 0.6681
99.9
2891/0/191
0.957
4755 [0.0515]
0.782 and 0.879
98.3
5554/0/393
1.312
3811 [0.0284]
0.868 and 0.905
99.7
3000/0/245
1.024
Maximum and minimum transmission
Completeness to maximum h (%)
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R1 = 0.0326,
wR2 = 0.736
R1 = 0.0429,
wR2 = 0.0759
1.048 and ꢀ0.295
R1 = 0.0810,
wR2 = 0.1674
R1 = 0.1034,
wR2 = 0.1846
1.132 and ꢀ2.068
R1 = 0.0315,
wR2 = 0.0809
R1 = 0.0365
wR2 = 0.0842
0.208 and ꢀ0.195
R indices (all data)
ꢀ3
˚
Largest difference in peak and hole (e A
)
C10
C9
C7
C6
C8
N1
C5
C4
1.787(4) Å
H1
C1
S1
C11
C12
C13
C2
C3
O1
C16
C14
C15
Fig. 2. ORTEP diagram of L1 (thermal ellipsoids are drawn with 30% probability).

1618
P.R. Kumar et al. / Polyhedron 27 (2008) 1610–1622
C8
C10
C12
N1
C9
C13
C11
C16
C7
C3
C4
1.806(3) Å
H2
S1
C14
C2
C15
C5
O2
C1
H1
C6
O1
Fig. 3. ORTEP diagram of L2 (thermal ellipsoids are drawn with 30% probability).
are given in Tables 1 and 2. The molecular structures of L1
and L2 are shown in Figs. 2 and 3. Selected bond lengths
and bond angles are given in Tables 3 and 4. The S–C
(alkyl) bond length is longer than the S–C (aryl) bond, as
expected. The geometry around the sulfur is V-shaped.
The C–S–C bond angle is almost normal. The bond lengths
and angles in the benzene ring and alkyl chain were also
found to be normal. There exists a strong O–Hꢃ ꢃ ꢃN intra-
molecular H-bond in L1 and L2.
ment with the reported values [35] for [PdCl{EtNHC
ꢀ
˚
(@S)NH–N@CH–C6H4-2-O }] [Pd–N = 1.965(2) A, Pd–
˚
˚
O = 2.019(2) A, Pd–S = 2.2456 (9) A and Pd–Cl =
˚
2.3078(8) A]. The Pd–S and Pd–Cl bond length of 1 are
C13
C14
The molecular structure of 1 is shown in Fig. 4. Selected
bond lengths and bond angles are given in Table 5. The Pd
centre has a square planar geometry in 1. The ligand is coor-
dinated with Pd in a monoanionic tridentate (O,N,S) mode,
forming a six membered chelate ring with Oꢀ and N (azo-
methine) and a five membered ring with S and N (azome-
thine). The Pd–N, Pd–O, Pd–S and Pd–Cl bond lengths
C15
C12
C11
C9
C10
C16
C8
C3
N1
C7
S1
˚
2.005(3), 1.971(2), 2.2644(11) and 2.3091(11) A are in agree-
Pd
C2
Table 3
Cl
C4
1
˚
Selected bond lengths (A) and bond angles (°) of L
˚
Bond lengths (A)
O1
C1
S(1)–C(1)
N(1)–C(9)
O–H(1)ꢃ ꢃ ꢃN(1)
Bond angles (°)
C(9)–N(1)–C(8)
C(2)–C(1)–S(1)
C(1)–C(2)–C(3)
C(1)–S(1)–C(7)
1.771(6)
1.279(6)
1.787(4)
S(1)–C(7)
N(1)–C(8)
1.794(6)
1.461(6)
C5
C6
Fig. 4. ORTEP diagram of 1 (thermal ellipsoids are drawn with 30%
probability).
121.4(5)
C(2)–C(1)–C(6)
C(6)–C(1)–S(1)
C(8)–C(7)–S(1)
118.4(5)
124.3(5)
109.4(4)
117.3(4)
120.8(6)
104.1(3)
Table 5
˚
Selected bond lengths (A) and bond angles (°) of 1
˚
Bond lengths (A)
Pd(1)–O(1)
Pd(1)–S(1)
S(1)–C(10)
N(1)–C(7)
O(1)–C(1)
1.971(2)
2.2644(11)
1.788(4)
1.289(4)
1.311(4)
Pd(1)–N(1)
Pd(1)–Cl(1)
S(1)–C(11)
N(1)–C(9)
2.005(3)
2.3091(11)
1.793(4)
1.484(4)
Table 4
2
˚
Selected bond lengths (A) and bond angles (°) of L
˚
Bond lengths (A)
S(1)–C(1)
O(2)–C(14)
N(1)–C(8)
1.763(7)
1.341(8)
1.466(10)
S(1)–C(7)
N(1)–C(9)
1.818(5)
1.304(8)
1.806(3)
Bond angles (°)
O(1)–Pd(1)–N(1)
N(1)–Pd(1)–S(1)
N(1)–Pd(1)–Cl(1)
C(10)–S(1)–C(11)
O(2)–H(2)ꢃ ꢃ ꢃN(1)
93.00(11)
89.27(9)
178.60(9)
104.8(2)
O(1)–Pd(1)–S(1)
O(1)–Pd(1)–Cl(1)
S(1)–Pd(1)–Cl(1)
177.70(8)
87.74(8)
89.99(4)
Bond angles (°)
C(1)–S(1)–C(7)
C(2)–C(1)–S(1)
102.55(28)
124.91(55)
C(9)–N(1)–C(8)
C(1)–C(2)–C(3)
124.72(50)
120.35(76)

P.R. Kumar et al. / Polyhedron 27 (2008) 1610–1622
1619
˚
Table 6
consistent with the values (2.268(4) and 2.316(4) A)
˚
Selected bond lengths (A) and bond angles (°) of 3
reported for [PdCl2{4-MeOC6H4TeCH2CH2SEt}] [36].
˚
Bond lengths (A)
Surprisingly, the Pd–S bond distance in cis-Pd(SNNMe2-
Pd(1)–O(1)
Pd(1)–S(1)
Pd(1)–N(1)
Pd(1)–Cl(1)
O(1)–C(1)
S(1)–C(10)
S(1)–C(11)
N(1)–C(7)
1.996(6)
2.257(2)
2.042(7)
2.321(2)
1.322(11)
1.807(10)
1.780(9)
1.487(12)
1.500(12)
2.407(3)
Pd(2)–O(2)
Pd(2)–S(2)
Pd(2)–N(2)
Pd(2)–Cl(2)
O(2)–C(17)
S(2)–C(26)
1.996(6)
˚
S)(AsPh3)Cl2 (2.249(1) A) is some what shorter [37] than
2.263(2)
2.035(7)
2.329(2)
1.317(11)
1.832(9)
1.797(9)
1.477(12)
1.490(11)
2.502(5)
that of 1. In trans-[Pd(SCN)2[P(OPh)3]2] the Pd–S bond
˚
length is 2.352 A [38], longer than that of 1, probably due
to the trans influence of S. The four bond lengths of 1
involving Pd are also consistent with the sum of the covalent
radii for Pd–Cl, Pd–N, Pd–O and Pd–S (2.27, 1.98, 2.01 and
S(2)–C(27)
N(2)–C(23)
N(2)–C(25)
N(2)–H(2)ꢃ ꢃ ꢃCl(2)
˚
2.32 A respectively).
N(1)–C(9)
The molecular structure of 3 is shown in the Fig. 5.
Selected bond lengths and bond angles are given in Table
6. The crystal of 3 contains two types of molecules, conse-
quently there are two types of N–Hꢃ ꢃ ꢃCl intermolecular
N(1)–H(1)ꢃ ꢃ ꢃCl(1)
Bond angles (°)
O(1)–Pd(1)–N(1)
N(1)–Pd(1)–S(1)
N(1)–Pd(1)–Cl(1)
O(1)–Pd(1)–S(1)
O(1)–Pd(1)–Cl(1)
S(1)–Pd(1)–Cl(1)
C(11)–S(1)–C(10)
91.7(3)
88.1(2)
O(2)–Pd(2)–N(2)
N(2)–Pd(2)–S(2)
N(2)–Pd(2)–Cl(2)
O(2)–Pd(2)–S(2)
O(2)–Pd(2)–Cl(2)
S(2)–Pd(2)–Cl(2)
C(27)–S(2)–C(26)
91.0(3)
88.0(2)
˚
hydrogen bonds (2.407(3) and 2.502(5) A) (Fig. 5a and
178.8(2)
179.7(2)
89.45(18)
90.78(9)
101.8(4)
179.2(2)
176.5(2)
88.97(19)
92.03(9)
101.3(4)
5b). The Pd–N, Pd–O, Pd–S and Pd–Cl bond lengths
2.042(7)/2.035(7), 1.996(6), 2.257(2)/2.263(2) and 2.321(2)/
˚
2.329(2) A are in agreement with the reported values [35]
for [PdCl{EtNHC(@S)NH–N@CH–C6H4-2-Oꢀ}] men-
tioned above as well as with those of 1. The Pd–S and
Pd–Cl bond lengths of 3 are also consistent with those of
C8
C14
C15
[PdCl2{4-MeOC6H4TeCH2CH2SEt}]
[36], mentioned
C5
C2
C13
C12
C7
C9
above. They are also consistent with the sum of covalent
radii mentioned above. The Pd in 3 also has a square pla-
nar geometry. Generally the Pd–N bond distance [39–42] is
C6
C1
C4
C3
N1
C16
C11
H1
C10
˚
close to 2.0 A, however the values 1.857(4) [43] and
O1
˚
2.461(3) A [44] have also been reported. Thus the Pd–N
S1
bond distance values in the present complexes 1 and 3
Pd1
2.407(3) Å
Cl1
˚
(2.005(3)–2.042(7) A) fall in the common range. Pd–S bond
Cl1
˚
lengths are commonly between 2.25 and 2.30 A [45–47].
2.407(3) Å
˚
Our values (2.257(2)–2.2644(11) A) are closer to the lower
Pd1
O1
C1
S1
C2
end as the uninegative ligands coordinate with Pd strongly
due to the formation of two chelate rings. Pd–O bond dis-
C3
H1
C10
˚
C11
tances are generally observed between 2.0 and 2.1 A [48–
C16
C15
N1
50]. These distances in the case of the present complexes
C9
C4
C6
C12
C5
C7
C14
C8
C15
C13
C13
C14
Fig. 5a. NHꢃ ꢃ ꢃCl weak interactions in 3 (H atoms have been omitted for
clarity).
C16
C12
C8
C11
C9
C10
˚
1 and 3 (1.971(2)–1.999(6) A) are somewhat on the lower
side, suggesting strong chelation by the uninegative triden-
tate ligand.
N1
S1
C7
The molecular structure of 6 is shown in Fig. 6. Selected
bond lengths and bond angles are given in Table 7. The
geometry around Ni is square planar. The ligand is coordi-
nated with Ni in a monoanionic tridentate mode, forming a
six membered chelate ring with Oꢀ and N (azomethine)
and a five membered ring with P and N (azomethine).
The Ni–P, Ni–N, Ni–O and Ni–Cl bond lengths
C6
Pd1
C5
C4
Cl1
O1
C1
C3
C2
˚
2.1324(8), 1.896(2) 1.8428(19) and 2.1940(7) A are consis-
˚
tent with the earlier reported values, Ni–P = 2.142(2) A,
Fig. 5. ORTEP diagram of 3 (thermal ellipsoids are drawn with 30%
˚
˚
probability).
Ni–N = 1.900(7) A, Ni–O = 1.875(5) A and Ni–Cl =

1620
P.R. Kumar et al. / Polyhedron 27 (2008) 1610–1622
13
the C CPMAS NMR spectrum of ‘Catalyst 10 and the
C30
C24
C31
solution 13C{1H} NMR spectrum of 2. Additional signals
for the propyl group (-Si-CH2CH2CH2–O–) have been
observed in the case of the 13C CPMAS NMR spectrum.
The SiCH2, middle CH2 and OCH2 carbon atom signals
appear at 10.5, 26.4 and 47.0 ppm respectively. The methyl
carbon signal appears at 18.6 ppm. The signals for the C2
and C1 atoms appear at 38.8 and 60.5 ppm, respectively.
The signals of C10, C9, C13, C12 and C14 merge and appear
as a broad peak at 130.5 ppm. The signals for C11 and
C15 appear at 132.0 ppm, for C3 and C7 at 164.1 ppm
and for C5, C6/C8 and C4 at 158.8, 106.6 and 119.8 ppm,
respectively (see Fig. 1 for the numbering of the carbon
atoms).
C21
C23
C20
C22
C17
C29
C25
C32
C26
N2
C28
C27
C19
H2
O2
C18
Pd2
Pd2
2.502(5) Å
S2
Cl2
Cl2
S2
2.502(5) Å
C17
C18
O2
H2
C19
C26
C27
C28
C29
C30
N2
C25
C22
C20
C32
H3C
C23
C21
N
O
SPh
C24
C31
Pd
Cl
Fig. 5b. NHꢃ ꢃ ꢃCl weak interactions in 3 (H atoms have been omitted for
O
O
O
clarity).
Si
O
2.148(3) A for [NiCl(2-PPh2C6H4–CH@N–C6H4-2-Oꢀ)]
˚
Catalyst 1.
[19]. The Ni–P bond distance of 6 is shorter than that of
bis[1,2-bis(diphenylphosphino)ethene]nickel(II) diperchlo-
‘Catalyst 1’ was used in the Suzuki–Miyaura C–C
coupling reactions of benzeneboronic acid with bromoben-
zene and substituted bromobenzenes (Eq. (5)) in an iso-
propanol and water mixture using Na2CO3 as a base at
90 °C.
˚
rate (2.2374(7) A) [51] but longer than that of tetrakis-
˚
(2-thienyldifluorophosphine)nickel (2.092(3) A) [52]. The
sum of the covalent radii for Ni–P, Ni–O, Ni–N and Ni–
˚
Cl are 2.21, 1.88, 1.90 and 2.14 A, respectively. The values
IPA + H2O + Na2CO3
+
Br
R
(OH)2B
R
Cat. 1, 12h, 90 0C
ð5Þ
where R = CH3O, CH3, H, NO2, CO2H
IPA = isopropanol
of the bond lengths of 6 are consistent with the sum of the
The yields were maximal when 0.001 mol% of catalyst
(Pd) was taken. The catalytic activity was dependent on
radii, except Ni–P which is somewhat shorter. Generally
˚
the Ni–O bond distance is around 2.0 or 2.1 A [53–55]. Val-
˚
ues around 1.82 A have also been reported for this bond
˚
length [56,57]. The Ni–O distance in 6 (1.8428(19) A) is clo-
C17
C18
ser to the later value, which is interesting and indicates
strong chelation of Ni by the (P,N,Oꢀ) ligand. The Ni–
C19
˚
Cl1
C16
C15
N bond length of 6 (1.896(2) A) is also shorter than the
˚
commonly observed value of around 2.05/2.10 A [58,59],
O1
C2
C20
C7
Ni1
indicating its strong nature. On the contrary the commonly
C8
C6
P1
˚
found value of around 2.15 A for the Ni–P bond [60,61] is
C14
C9
˚
similar to that of 6 (2.1324(8) A).
C13
C12
C21
N1
C3
C22
C5
3.3. Catalytic coupling reaction
C4
C1
C10
C11
‘Catalyst 1’ is stable under ambient conditions. Its IR
spectrum has bands at 2943 (mC–H), 1600 (b, mC@N), 1219
(mC–O) and 799 (mC–S) cmꢀ1. There are similarities between
Fig. 6. ORTEP diagram of 3 (thermal ellipsoids are drawn with 30%
probability).

P.R. Kumar et al. / Polyhedron 27 (2008) 1610–1622
1621
ligands as evidenced in the case of [PdCl(L1–H)] (1),
[PdCl(L3–H)] (3) and [NiCl(L4–H)] (6) by their single crys-
tal structures. The palladium complex of L2 has been
grafted on silica gel to prepare ‘Catalyst 1’, which was used
for Suzuki–Miyaura C–C coupling reactions with good
yields.
Table 7
˚
Selected bond lengths (A) and bond angles (°) of 6
˚
Bond lengths (A)
Ni(1)–O(1)
Ni(1)–P(1)
P(1)–C(9)
P(1)–C(15)
N(1)–C(2)
1.8428(19) Ni(1)–N(1)
1.896(2)
2.1940(7)
1.810(3)
1.308(3)
1.493(4)
2.1324(8)
1.809(3)
1.815(3)
1.310(3)
Ni(1)–Cl(1)
P(1)–C(21)
O(1)–C(8)
N(1)–C(22)
Acknowledgements
Bond angles (°)
O(1)–Ni(1)–N(1)
N(1)–Ni(1)–P(1)
N(1)–Ni(1)–Cl(1)
C(9)–P(1)–C(21)
C(21)–P(1)–C(15)
C(21)–P(1)–Ni(1)
C(8)–O(1)–Ni(1)
C(2)–N(1)–Ni(1)
N(1)–C(2)–C(3)
C(20)–C(15)–P(1)
95.10(9)
89.15(7)
O(1)–Ni(1)–P(1)
O(1)–Ni(1)–Cl(1)
P(1)–Ni(1)–Cl(1)
C(9)–P(1)–C(15)
C(9)–P(1)–Ni(1)
C(15)–P(1)–Ni(1)
C(2)–N(1)–C(22)
C(22)–N(1)–Ni(1)
N(1)–C(2)–C(1)
C(16)–C(15)–P(1)
C(22)–C(21)–P(1)
175.72(6)
89.07(6)
86.68(3)
106.87(13)
117.53(9)
116.62(10)
117.9(2)
116.02(17)
119.2(3)
A.K.S. is grateful to Professor John E. Drake, Univer-
sity of Windsor, Canada for his valuable help in solving
the single crystal structures of the compounds synthesized
in the research group of AKS at IIT Delhi, for more than
one and a half decades. To acknowledge it further, this pa-
per is dedicated to John. He thanks Department of Science
and Technology (India) for research project SR/S1/IC-23/
06. The authors also thank the Department of Science and
Technology (India) for partial financial assistance given to
establish the single crystal X-ray diffraction facility under
its FIST program at IIT Delhi. R.K.P. thanks the Univer-
sity Grants Commission (India) for a Senior Research
Fellowship.
175.81(7)
106.88(13)
107.32(14)
100.60(10)
126.79(19)
125.9(2)
123.1(2)
121.0(2)
120.4(2)
106.4(2)
N(1)–C(22)–H(22A) 109.6
N(1)–C(22)–H(22B) 109.6
C(10)–C(9)–P(1)
C(14)–C(9)–P(1)
P(1)–C(21)–H(21A) 110.5
P(1)–C(21)–H(21B) 110.5
N(1)–C(22)–C(21)
118.2(2)
123.4(2)
110.3(2)
Table 8
Suzuki–Miyaura coupling reaction with Catalyst 1
Appendix A. Supplementary data
Aryl bromide
Product
% Yield of
biphenyl
CCDC numbers 639950, 639951, 639952, 639953 and
639954 contain the supplementary crystallographic data
for L1, L2, 1, 3 and 6, respectively. These data can be
obtained free of charge at www.ccdc.cam.ac.uk/conts/
retrieving.html [or from the Cambridge Crystallographic
Data Centre, 12, Union Road, Cambridge CB2 1EZ,
UK; fax: (internat.) +44-1223/336-033; E-mail: deposit@
ccdc.cam.ac.uk]. Supplementary data associated with this
article can be found, in the online version, at
doi:10.1016/j.poly.2008.01.027.
75
78
89
80
90
Br
Br
OMe
CH3
MeO
H3C
Br
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