Schiff bases of 1′-hydroxy-2′-acetonaphthone containing chalcogen functionalities and their complexes with and (p-cymene)Ru(II), Pd(II), Pt(II) and Hg(II): Synthesis, structures and applications in C-C coupling reactions

Article abstract of DOI:10.1016/j.jorganchem.2008.07.024

Schiff bases of 1′-hydroxy-2′-acetonaphthone (HAN) containing chalcogen functionalities, 1-HO-C₁₀H₆-2-CH₃)C{double bond, long}N-(CH₂)_nEC₆H₄-4-R (R = H or OMe; n = 2 or 3; E = S (L¹-L²), Se (L³-L⁴) or Te (L⁵-L⁶)) have been synthesized in yield 90-95%. They show characteristic ¹H, ¹³C{¹H} ⁷⁷Se{¹H} and ¹²⁵Te{¹H} (in case of selenated and tellurated species, respectively) NMR spectra. Their complexation with Pd(II), Pt(II), Hg(II) and (p-cymene)Ru(II) has been explored. The single-crystal structures of ligands L¹, L³ and L⁶ and complexes of Pd(II) with L¹, L², L³ and L⁵ have been determined. The geometry of Pd is close to square planar in all the complexes and the ligands coordinate in a uni-negative tridentate mode. The Pd-N bond lengths are in the range 1.996(7)-2.019(5) ?. The Pd-Se bond distance is 2.3600(5) ? whereas Pd-Te is 2.5025(7) ?. The Pd(II) complexes of L¹-L⁵ have been found promising as homogeneous catalyst for Heck and Suzuki reactions. The yields obtained were up to 85%.

Full text of DOI:10.1016/j.jorganchem.2008.07.024

Journal of Organometallic Chemistry 693 (2008) 3533–3545
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Schiff bases of 10-hydroxy-20-acetonaphthone containing chalcogen functionalities
and their complexes with and (p-cymene)Ru(II), Pd(II), Pt(II) and Hg(II): Synthesis,
structures and applications in C–C coupling reactions
*
Arun Kumar, Monika Agarwal, Ajai K. Singh
Department of Chemistry, Indian Institute of Technology, New Delhi 110 016, India
a r t i c l e i n f o
a b s t r a c t
Schiff bases of 10-hydroxy-20-acetonaphthone (HAN) containing chalcogen functionalities, 1-HO–C10H6-
2-CH3)C@N–(CH2)nEC6H4-4-R (R = H or OMe; n = 2 or 3; E = S (L1–L2), Se (L3–L4) or Te (L5–L6)) have been
synthesized in yield 90–95%. They show characteristic 1H, 13C{1H} 77Se{1H} and 125Te{1H} (in case of sel-
enated and tellurated species, respectively) NMR spectra. Their complexation with Pd(II), Pt(II), Hg(II) and
(p-cymene)Ru(II) has been explored. The single-crystal structures of ligands L1, L3 and L6 and complexes
of Pd(II) with L1, L2, L3 and L5 have been determined. The geometry of Pd is close to square planar in all
the complexes and the ligands coordinate in a uni-negative tridentate mode. The Pd–N bond lengths are
in the range 1.996(7)–2.019(5) AÅ. The Pd–Se bond distance is 2.3600(5) AÅ whereas Pd–Te is 2.5025(7) AÅ.
The Pd(II) complexes of L1–L5 have been found promising as homogeneous catalyst for Heck and Suzuki
reactions. The yields obtained were up to 85%.
Article history:
Received 25 April 2008
Received in revised form 19 July 2008
Accepted 22 July 2008
Available online 29 July 2008
Keywords:
0
0
0
Chalcogenated Schiff bases
Platinum metals
Synthesis
Crystal structure
Heck reaction
Ó 2008 Elsevier B.V. All rights reserved.
Suzuki reaction
1. Introduction
ples of Schiff bases of 10-hydroxy-20-acetonaphthone containing
chalcogen functionalities (L1–L6) are reported here. Their com-
10-Hydroxy-20-acetonaphthone (HAN) is an important mole-
cule. It has been studied as a proton transfer prototype molecule
in gas, solution and nanocavities. The internal hydrogen bonding
photoreaction in this molecule leads to keto type structure, and
following its formation, an internal twisting motion gives birth
to keto rotamers [1]. Its skeleton is very photostable and used
for polymer photoprotection [2]. It has also been used for prepar-
ing photosensitive ZrO2 films [3]. Its Schiff bases with diamines
and amine having an arm of pyrrolidine have been synthesized
[4–6]. Their dioxovanadium(V) complexes have also been synthe-
sized, structurally characterized and found promising for several
catalytic oxidation reactions. To the best of our knowledge no
Schiff base of HAN having chalcogen functionalities has been
studied so far. The presence of chalcogen may tune the catalytic
activity of its complex in a new direction. Therefore first exam-
plexes having stoichiometries [PdCl(LꢀH)] (L = L1ꢀL6; L–
H = deprotonated ligand.), [PtCl(L3–H/L5ꢀH)], [PtCl2(L4/L6)2], [(p-
cymene)RuCl(L5/L6)]Cl and [HgBr2(L5/L6)2] have been synthesized.
The ligands and their complexes have been characterized using
multinuclei NMR, IR and mass spectral data and single-crystal
structures (in case of some ligands and palladium(II) complexes).
These results and potential of some of Pd(II) complexes as homo-
geneous catalysts for Heck and Suzuki reactions are the subject of
the present paper.
2. Experimental
The C and H analyses were carried out with a Perkin–Elmer
2400 Series II C, H, N analyzer. The 1H, 13C{1H}, 77Se{1H} NMR
and 125Te{1H} NMR spectra were recorded on a Bruker Spectrospin
DPX-300 NMR spectrometer at 300.13, 75.47, 57.24 and
94.69 MHz, respectively. Mass spectra (ion spray) were recorded
on Hybrid Quadrupole-TOF LC/MS/MS mass spectrometer (QSTAR
XL System), Model 1011273/A, AB Sciex Instruments (Applied Bio-
systems, Canada).
* Corresponding author. Tel.: +91 11 26591379; fax: +91 11 26581102.
E-mail
addresses:
aksingh@chemistry.iitd.ac.in,
ajai57@hotmail.com
(A.K. Singh).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.07.024

3534
A. Kumar et al. / Journal of Organometallic Chemistry 693 (2008) 3533–3545
2
3
1
CH3
CH3
6
3
6
5
17
17
8
9
8
9
E
16
15
16
15
2
4
7
E
7
N
N
4
a
5
1
14
13
14
13
OH
OH
L2
10
11
10
11
L4
12
12
E = Se
L3
E = S
;
L1 E = S ; E = Se
2
OMe
3
CH3
CH3
1
6
17
5
6
3
17
8
8
Te
4
16
15
16
15
2
7
Te
N
4
7
N
a
5
9
14
13
OH
14
13
9
OMe
OH
1
10
11
10
11
12
L6
12
L5
IR spectra in the range 4000–250 cmꢀ1 were recorded on a
Nicolet Protége 460 FT-IR spectrometer as KBr pellets. The melt-
ing points determined in open capillary are reported as such.
The conductivity measurements were carried out in CH3CN
(concentration ca. 1 mM) using ORION conductivity meter model
162.
2.22 (s, 3H, CH3), 3.18 (t, J = 7.2 Hz, 6.9 Hz, 2H, H5), 3.59ꢀ3.63
(m, 2H, H6), 6.78 (d, J = 9.3 Hz, 1H, H16), 7.19ꢀ7.24 (m, 2H, H1,
H17), 7.28 (t, J = 7.4 Hz, 2H, H2), 7.37ꢀ7.41 (m, 3H, H3 and H12),
7.49 (t, J = 6.9 Hz, 1H, H13), 7.57 (d, J = 7.8 Hz, 1H, H14) 8.50 (d,
J = 8.1 Hz, 1H, H11), 16.38 (bs, 1H, OH); (13C{1H}, CDCl3, 25 °C,
vs. TMS): d 14.08 (CH3), 33.62 (C5), 44.24 (C6), 108.57 (C8),
113.45 (C16), 124.66 (C17 and C12), 125.38 (C11), 126.85 (C14),
126.87 (C1), 129.08 (C2), 129.52 (C13), 130.17 (C10), 130.25 (C3),
134.26 (C4), 137.07 (C15), 170.93 (C9), 175.12 (C7); HRMS (ESI+)
Single-crystal diffraction studies were carried out with a Bruker
AXS SMART Apex CCD diffractometer using Mo K
a (0.71073 Å)
radiations at 298(2) K The software SADABS was used for absorption
correction (if needed) and SHELXTL for space group, structure deter-
mination and refinements [7,8]. All non-hydrogen atoms were re-
fined 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 are attached. The least-squares
refinement cycles on F2 were performed until the model con-
verged. The precursor chalcogenated amines PhS(CH2)2NH2, PhS-
(CH2)3NH2, PhSe(CH2)2NH2, PhSe(CH2)3NH2, ArTe(CH2)2NH2 and
ArTe(CH2)3NH2 [Ar = 4-CH3O–C6H4] were synthesized by the liter-
ature methods [9–11].
calc. for KC20H19NOS (M+K)+ 360.0824, found m/z 360.0820 (
D
1.2334 ppm). IR(KBr, cmꢀ1): 3423, 1612, 785.
2.1.2. Ligand L2
Yield 1.543 g (ꢁ92%); m.p. 64 °C. KM = 0.8 cm2 molꢀ1 ohmꢀ1
.
Anal. Calc. for C21H21NOS: C, 75.12; H, 6.26; N, 4.17. Found: C,
75.19; H, 6.23; N, 4.13%. NMR (1H, CDCl3, 25 °C, vs. TMS): d 2.01
(quintet, J = 6.6 Hz, 2H, Ha), 2.24 (s, 3H, CH3), 3.01 (t, J = 6.6 Hz,
2H, H5), 3.50ꢀ3.52 (m, 2H, H6), 6.76 (d, J = 9.3 Hz, 1H, H16),
7.13ꢀ7.27 (m, 4H, H1, H2, H17), 7.32 (d, J = 7.5 Hz, 2H, H3), 7.39 (t,
J = 7.2 Hz, 1H, H12), 7.49 (t, J = 7.5 Hz, 1H, H13), 7.57 (d, J = 7.8 Hz,
1H, H14) 8.50 (d, J = 8.1 Hz, 1H, H11), 16.22 (bs, 1H, OH); (13C{1H},
CDCl3, 25 °C, vs. TMS): d 13.94 (CH3), 28.55 (Ca) 30.59 (C5), 43.07
(C6), 108.26 (C8), 112.99 (C16), 124.55 (C17), 124.71 (C12), 125.32
(C11), 126.16 (C1), 126.86 (C14), 128.88 (C2), 129.31 (C3), 129.46
(C13), 130.43 (C10), 135.21 (C4), 137.11 (C15), 171.00 (C9), 175.70
(C7); IR(KBr, cmꢀ1): 3421, 1612, 786.
2.1. Synthesis of L1–L6
2-(Phenylsulphanyl)ethylamine (0.765 g, 5.0 mmol)/2-(phe-
nylseleno)ethylamine (1.00 g, 5.0 mmol)/2-(4-methoxyphenyl-
telluro)ethylamine (1.39 g, 5.0 mmol)/3-(phenylsulphanyl)propyl-
amine (0.835 g, 5.0 mmol)/3-(phenylseleno)propylamine (1.07 g,
5.0 mmol) /3-(4-methoxyphenyl telluro)propylamine (1.46 g,
5.0 mmol) was stirred in dry ethanol (20 mL) at room tempera-
ture for 0.5 h. HAN (0.93 g, 5.0 mmol), dissolved in dry ethanol
(20 mL), was added dropwise with stirring. The mixture was stir-
red further at room temperature for 2 h. The solvent was evapo-
rated off on a rotary evaporator. The L1–L4 and L6 were obtained
as a yellow precipitate and L5 as yellow coloured highly viscous
liquid. The precipitates were recrystallized with chloroform–hex-
ane mixture (1:1). It gave yellow coloured single crystals in the
case of L1, L3 and L6. The L5 was purified by washing it with
10 mL hexane–chloroform mixture (3:1). All ligands L1–L6 were
finally dried in vacuo.
2.1.3. Ligand L3
Yield 1.694 g (ꢁ92%); m.p. 78 °C. KM = 0.8 cm2 molꢀ1 ohmꢀ1
.
Anal. Calc. for C20H19NOSe: C, 65.16; H, 5.15; N, 3.80. Found: C,
65.08; H, 5.17; N, 3.89%. NMR (1H, CDCl3, 25 °C, vs. TMS): d 2.37
(s, 3H, CH3), 3.19 (t, J = 7.2 Hz, 7.5 Hz, 2H, H5), 3.78ꢀ3.84 (m, 2H,
H6), 6.82 (d, J = 9.3 Hz, 1H, H16), 7.26ꢀ7.29 (m, 4H, H1, H2, H17),
7.41 (t, J = 6.6 Hz, 8.1 Hz, 1H, H12), 7.50ꢀ7.61 (m, 4H, H3, H13
,
H14), 8.50 (d, J = 8.1 Hz, 1H, H11), 16.43 (bs, 1H, OH); (13C{1H},
CDCl3, 25 °C, vs. TMS): d 14.11 (CH3), 26.53 (C5), 45.21 (C6),
108.59 (C8), 113.53 (C16), 124.67 (C17), 124.72 (C12), 125.47 (C11),
126.92 (C14), 127.61 (C1), 128.39 (C4), 129.27 (C2), 129.58 (C13),
130.31 (C10), 133.41 (C3), 137.14 (C15), 170.62 (C9), 175.35 (C7);
2.1.1. Ligand L1
Yield 1.446 g (ꢁ90%); m.p. 62 °C. KM = 0.6 cm2 molꢀ1 ohmꢀ1
.
(
77Se{1H}, CDCl3, 25 °C, vs. Me2Se): d 287.7. HRMS (ESI+) calc. for
HC20H19NOSe (M+H)+ 370.0710, found m/z 370.0709
(D
Anal. Calc. for C20H19NOS: C, 74.66; H, 5.91; N, 4.35. Found: C,
74.82; H, 5.89; N, 4.41%. NMR (1H, CDCl3, 25 °C, vs. TMS): d
0.2971 ppm). IR(KBr, cmꢀ1): 3438, 1612, 472, 740.

A. Kumar et al. / Journal of Organometallic Chemistry 693 (2008) 3533–3545
3535
2.1.4. Ligand L4
C, 51.87; H, 3.91; N, 3.09%. NMR (1H, CDCl3, 25 °C, vs. TMS): d
2.29 (s, 3H, CH3), 2.69ꢀ2.73 (m, 1H, H5), 3.49ꢀ3.89 (m, 3H,
H5 + H6), 6.96 (d, 3J = 9.0 Hz, 1H, H16), 7.27 (d, 3J = 9.0 Hz, 1H,
H17), 7.40ꢀ7.46 (m, 4H, H1, H2 and H12), 7.55 (t, 3J = 7.2 Hz, 1H,
H13), 7.63 (d, 3J = 7.8 Hz, 1H, H14), 8.17ꢀ8.20 (m, 2H, H3), 8.73 (d,
3J = 8.1 Hz, 1H, H11), (13C{1H}, CDCl3, 25 °C, vs. TMS): d 19.61
(CH3), 41.36 (C5), 58.84 (C6), 115.17 (C8), 115.66 (C16), 125.15
(C12), 126.36 (C14), 126.56 (C11), 127.17 (C17), 128.16 (C10),
128.57 (C4), 129.15 (C13), 129.77 (C2), 130.60 (C1), 133.02 (C3),
136.09 (C15), 162.59 (C9), 167.00 (C7); IR(KBr, cmꢀ1): 1596, 745.
Yield 1.739 g (ꢁ91%); m.p. 82 °C. KM = 0.7 cm2 molꢀ1 ohmꢀ1
.
Anal. Calc. for C21H21NOSe: C, 65.92; H, 5.49; N, 3.66. Found: C,
65.90; H, 5.47; N, 3.69%. NMR (1H, CDCl3, 25 °C, vs. TMS): d 1.97
(quintet, J = 7.2 Hz, 2H, Ha), 2.01 (s, 3H, CH3), 2.90 (t, J = 7.2 Hz,
2H, H5), 3.25 (t, J = 6.9 Hz, 2H, H6), 6.74 (d, J = 9.3 Hz, 1H, H16),
7.13 (d, J = 9.0 Hz, 1H, H17), 7.18ꢀ7.21 (m, 3H, H1 + H2), 7.38ꢀ7.56
(m, 4H, H3, H12, H13), 7.57 (d, J = 7.2 Hz, 1H, H14), 8.57 (d,
J = 8.1 Hz, 1H, H11), 16.09 (bs, 1H, OH); (13C{1H}, CDCl3, 25 °C, vs.
TMS): d 13.46 (CH3), 23.92 (C5), 29.09 (Ca), 43.65 (C6), 107.91 (C8),
112.41 (C16), 124.14 (C17), 124.60 (C12), 125.04 (C11), 126.56 (C14
as well as C1), 128.72 (C2), 129.00 (C4), 129.09 (C13), 130.16 (C10),
132.07 (C3), 136.81 (C15), 170.68 (C9), 175.23 (C7); (77Se{1H}, CDCl3,
25 °C, vs. Me2Se): d 288.8. IR(KBr, cmꢀ1): 3435, 1612, 740, 472.
2.2.2. [PdCl(L2ꢀH)] (2)
Yield 0.400 g (ꢁ84%); m.p. 162 °C. KM = 6.0 cm2 molꢀ1 ohmꢀ1
.
Analy. Calc. for C21H20NOSPdCl: C, 52.91; H, 4.20; N, 2.94. Found:
C, 52.87; H, 4.23; N, 2.90%. NMR (1H, CDCl3, 25 °C, vs. TMS): d
2.16ꢀ2.22 (m, 2H, Ha), 2.44 (s, 3 H, CH3), 2.99 (m, 2H, H5),
3.70ꢀ3.74 (m, 2H, H6), 7.03 (d, 3J = 9.0 Hz, 1H, H16), 7.33 (d,
3J = 9.0 Hz, 1H, H17), 7.39ꢀ7.43 (m, 4H, H1, H2 and H12), 7.51 (t,
3J = 6.9 Hz, 1H, H13), 7.63 (d, 3J = 8.1 Hz, 1H, H14), 8.06ꢀ8.09 (m,
2H, H3), 8.66 (d, 3J = 8.1 Hz, 1H, H11), (13C{1H}, CDCl3, 25 °C, vs.
TMS): d 19.64 (CH3), 25.77 (Ca), 34.53 (C5), 51.58 (C6), 115.70 (C8
as well as C16), 121.71 (C4), 125.37 (C17), 125.80 (C14), 126.60
(C12), 127.03 (C11), 129.11 (C13), 129.68 (C2), 129.86 (C10), 130.11
(C1), 132.40 (C3), 136.52 (C15), 162.54 (C9), 167.30 (C7); IR(KBr,
cmꢀ1): 1598, 748.
2.1.5. Ligand L5
Yield 2.1232 g (ꢁ95%); KM = 0.9 cm2 molꢀ1 ohmꢀ1. Anal. Calc.
for C21H21NO2Te: C, 56.37; H, 4.69; N, 3.13. Found: C, 56.24; H,
4.72; N, 3.09%. NMR (1H, CDCl3, 25 °C, vs. TMS): d 2.25 (s, 3H,
CH3), 3.00 (t, J = 8.1 Hz, 2H, H5), 3.72 (s, 3H, OMe), 3.79 (m, 2H,
H6), 6.71 (d, J = 8.7 Hz, 2H, H2), 6.77 (d, J = 9.3 Hz, 1H, H16), 7.21
(d, J = 9.0 Hz, 1H, H17), 7.39 (t, J = 6.9 Hz, 1H, H12), 7.50 (t,
J = 6.6 Hz, 1H, H13), 7.57 (d, J = 8.4 Hz, 1H, H14), 7.70 (d, J = 8.7 Hz,
2H, H3) 8.48 (d, J = 8.1 Hz, 1H, H11), 16.19 (bs, 1H, OH); (13C{1H},
CDCl3, 25 °C, vs. TMS): d 6.23 (C5), 13.97 (CH3), 46.91 (C6), 55.00
(OCH3), 99.22 (C4) 108.37 (C8), 113.29 (C16), 115.28 (C2), 124.65
(C17), 124.68 (C12), 125.49 (C11), 126.87 (C14), 129.56 (C13) 130.46
(C10), 137.17 (C15), 141.46 (C3), 160.01 (C1), 170.17 (C9), 175.79
(C7); (125Te{1H}, CDCl3, 25 °C, vs. Me2Te): d 466.1. IR(KBr, cmꢀ1):
3438, 1613, 518.
2.2.3. [PdCl(L3ꢀH)] (3)
Yield ꢁ0.397 g (ꢁ78%); m.p. 142 °C KM = 5.0 cm2 molꢀ1 ohmꢀ1
Anal. Calc. for C20H18NOSePdCl: C, 47.14; H, 3.53; N, 2.74. Found: C,
47.09; H, 3.49; N, 2.81%. NMR (1H, CDCl3, 25 °C, vs. TMS): d 2.07 (s,
3H, CH3), 2.66ꢀ2.71 (m, 1H, H5), 3.54ꢀ3.61 (m, 2H, H5 + H6),
4.15ꢀ4.20 (m, 1H, H6), 6.99 (d, 3J = 9.0 Hz, 1H, H16), 7.22 (d,
3J = 9.3 Hz, 1H, H17), 7.41ꢀ7.45 (m, 4H, H1, H2, H12), 7.54 (t,
3J = 6.6 Hz, 6.9 Hz, 1H, H13), 7.64 (d, 3J = 7.5 Hz, 1H, H14),
8.18ꢀ8.22 (m, 2H, H3), 8.74 (d, 3J = 8.1 Hz, 1H, H11), (13C{1H}, CDCl3,
25 °C, vs. TMS): d 19.66 (CH3), 32.71 (C5), 60.29 (C6), 115.27 (C16),
115.78 (C8), 125.10 (C12), 125.54 (C4), 126.36 (C14), 127.00 (C11),
127.18 (C17), 128.11 (C10), 129.10 (C13), 129.93 (C2) 130.16 (C1),
133.64 (C3), 136.06 (C15), 162.85 (C9), 167.26 (C7); (77Se{1H}, CDCl3,
25 °C, vs. Me2Se): d 445.7. IR(KBr, cmꢀ1): 1571, 468, 742.
2.1.6. Ligand L6
Yield 2.189 g (ꢁ95%); KM = 0.9 cm2 molꢀ1 ohmꢀ1. Anal. Calc.
for C22H23NO2Te: C, 57.26; H, 4.99; N, 3.04. Found: C, 57.24; H,
4.91; N, 3.09%. NMR (1H, CDCl3, 25 °C, vs. TMS): d 2.13 (quintet,
J = 7.2 Hz, 2H, Ha), 2.24 (s, 3H, CH3), 2.88 (t, J = 7.5 Hz, 2 H, H5),
3.45 (m, 2H, H6), 3.69 (s, 3H, OMe), 6.68 (d, J = 9.0 Hz, 2H, H2),
6.75 (d, J = 9.0 Hz, 1H, H16), 7.20 (d, J = 9.3 Hz, 1 H, H17), 7.39 (t,
J = 7.5 Hz, 1H, H12), 7.49 (t, J = 6.9 Hz, 1H, H13), 7.56 (d, J = 7.8 Hz,
1H, H14), 7.64 (d, J = 8.4 Hz, 2H, H3) 8.49 (d, J = 8.1 Hz, 1H, H11),
16.12 (bs, 1H, OH); (13C{1H}, CDCl3, 25 °C, vs. TMS): d 4.78 (C5),
14.04 (CH3), 31.05 (Ca), 46.09 (C6), 54.95 (OCH3), 99.73 (C4)
108.23 (C8), 112.92 (C16), 115.14 (C2), 124.53 (C17), 124.70 (C12),
125.38 (C11), 126.85 (C14), 129.46 (C13) 130.53 (C10), 137.15 (C15),
140.80 (C3), 159.68 (C1), 170.83 (C9), 175.86 (C7); (125Te{1H}, CDCl3,
25 °C, vs. Me2Te): d 460.3. HRMS (ESI+) calc. for HC22H23NO2Te
2.2.4. [PtCl(L3ꢀH)] (4)
Yield ꢁ0.531 g (ꢁ89%); m.p. 168 °C; KM = 8.0 cm2 molꢀ1 ohmꢀ1
Anal. Calc. for C20H18NOSePtCl: C, 40.15; H, 3.01; N, 2.34. Found: C,
40.09; H, 3.04; N, 2.31%. NMR (1H, CDCl3, 25 °C, vs. TMS): d 2.41 (s,
3H, CH3), 3.22ꢀ3.28 (m, 1H, H5), 3.77ꢀ3.96 (m, 3H, H5 + H6), 6.99 (d,
3J = 9.3 Hz, 1H, H16), 7.31 (d, 3J = 9.3 Hz, 1H, H17), 7.34ꢀ7.44 (m, 4H,
H1, H2, H12), 7.52 (t, 3J = 6.9 Hz, 1H, H13), 7.64 (d, 3J = 6.9 Hz, 1H,
H14), 8.07ꢀ8.09 (m, 2H, H3), 8.78 (d, 3J = 8.1 Hz, 1H, H11), (13C{1H},
CDCl3, 25 °C, vs. TMS): d 20.54 (CH3), 34.22 (C5), 61.88 (C6),
114.16 (C8), 115.83 (C16), 125.32 (C12), 125.92 (C4), 126.76 (C14),
127.43 (C11), 127.58 (C17), 128.51 (C10), 129.54 (C13), 129.97 (C2),
130.46 (C1), 133.84 (C3), 136.86 (C15), 162.98 (C9), 163.46 (C7);
(M+H)+ 464.0869, found m/z 464.0862 (
D 1.5800 ppm). IR(KBr,
cmꢀ1): 1645, 504, 292.
2.2. Synthesis of [PdCl(LꢀH)] and [PtCl(LꢀH)]
Na2[PdCl4] (0.294 g, 1 mmol) was dissolved in water (5 mL) and
mixed with the solution of 1 mmol of L1 (0.321 g)/L2 (0.335 g)/L3
(0.368 g)/L4 (0.382 g)/L5 (0.447 g)/L6 (0.461 g) in acetone (10 mL).
Similarly K2[PtCl4] (0.415 g, 1 mmol) was mixed with the solutions
of L3 and L5. The mixture was vigorously stirred for 0.5 h. An or-
ange precipitate was immediately obtained, which was filtered,
washed with hexane (10 mL) and dried in vacuo. Its recrystalliza-
tion with chloroform–hexane (60:40) mixture gave red coloured
single crystals of [PdCl(LꢀH)] (L = L1–L3, L5).
(
77Se{1H}, CDCl3, 25 °C, vs. Me2Se): d 388.6. IR(KBr, cmꢀ1): 1582,
468, 740.
2.2.5. [PdCl(L4ꢀH)] (5)
Yield ꢁ0.455 g (ꢁ87%); m.p. 148 °C KM = 7.0 cm2 molꢀ1 ohmꢀ1
Anal. Calc. for C21H20NOSePdCl: C, 48.17; H, 3.82; N, 2.68. Found: C,
48.13; H, 3.79; N, 2.63%. NMR (1H, CDCl3, 25 °C, vs. TMS): d
1.97ꢀ2.06 (m, 1H, Ha), 2.27ꢀ2.37 (m, 4H, CH3 + Ha), 2.75 (t of d,
2J = 12.9 Hz, 3J = 5.4 Hz, 1H, H5), 3.07 (d of t, 3J = 9.6 Hz, 3J = 4.5 Hz,
1H, H5), 3.51ꢀ3.65 (m, 2H, H6), 6.95 (d, 3J = 9.0 Hz, 1H, H16), 7.27 (d,
3J = 9.0 Hz, 1H, H17), 7.33ꢀ7.41 (m, 4H, H1, H2, H12), 7.49 (t,
3J = 7.8 Hz, 1H, H13), 7.62 (d, 3J = 8.1 Hz, 1H, H14), 8.06 (d, 3J = 7.8 Hz,
2.2.1. [PdCl(L1ꢀH)] (1)
Yield 0.360 g (ꢁ78%); m.p. 160 °C. KM = 5.0 cm2 molꢀ1 ohmꢀ1
.
Anal. Calc. for C20H18NOSPdCl: C, 51.92; H, 3.89; N, 3.03. Found:

3536
A. Kumar et al. / Journal of Organometallic Chemistry 693 (2008) 3533–3545
2H, H3), 8.64 (d, 3J = 8.1 Hz, 1H, H11), (13C{1H}, CDCl3, 25 °C, vs. TMS): d
19.35 (CH3), 26.23 (Ca), 29.48 (C5), 53.03 (C6), 115.11 (C16), 121.96
(C8), 125.04 (C12), 126.37 (C17), 126.63 (C14), 126.88 (C4 as well as
C11), 128.79 (C10), 128.87 (C13), 129.72 (C2), 129.79 (C1), 133.37 (C3),
136.47 (C15), 163.86 (C9), 167.72 (C7); (77Se{1H}, CDCl3, 25 °C, vs.
Me2Se): d 297.01. IR(KBr, cmꢀ1): 1576, 741, 469.
2.3.1. Compound 9
Yield ꢁ0.83 g (ꢁ80%); m.p. 156 °C; KM = 6.6 cm2 molꢀ1 ohmꢀ1
.
Anal. Calc. for C42H42N2O2Se2PtCl2: C, 48.91; H, 4.08; N, 2.72.
Found: C, 49.10; H, 4.05; N, 2.78%. NMR (1H, CDCl3, 25 °C, vs.
TMS):
d
2.08ꢀ2.18 (m, 4H, Ha), 2.38ꢀ2.44 (4s, 6H, CH3),
3.09ꢀ3.68 (m, 8H, H5 + H6), 6.81ꢀ6.86 (m, 2H, H16), 7.22ꢀ7.54
(m, 12H, H17 + H13 + H12 + H1 + H2), 7.22ꢀ7.59 (m, 3J = 7.5 Hz, 2H,
H14), 7.88 (m, 4H, H3), 8.46 (d, 3J = 7.8 Hz, 2H, H11), 16.44 (bs, 2H,
OH), (13C{1H}, CDCl3, 25 °C, vs. TMS): d 14.41 (CH3), 27.61 (C5),
30.70 (Ca), 44.61 (C6), 108.11 (C8), 113.79 (C16), 124.62 (C17),
124.89 (C12), 125.42 (C11), 127.06 (C14), 129.68 (C2), 129.75 (C13),
130.43 (C1), 130.91 (C10), 132.94, 132.99 (C3), 133.17 (C4), 136.87
(C15), 170.63 (C9), 175.28 (C7); (77Se{1H}, CDCl3, 25 °C, vs. Me2Se):
2.2.6. [PdCl(L5ꢀH)] (6)
Yield ꢁ0.564 g (ꢁ96%); m.p. 173 °C KM = 9.0 cm2 molꢀ1 ohmꢀ1
.
Anal. Calc. for C21H20NO2TePdCl: C, 42.87; H, 3.40; N, 2.38. Found:
C, 42.81; H, 3.47; N, 2.31%. NMR (1H, CDCl3, 25 °C, vs. TMS): d 1.86
(s, 3H, CH3), 2.35 (t of d, 2J = 12 Hz, 3J = 4.8 Hz, 1H, H5), 3.40 (d of t,
3J = 12 Hz, 3J = 4.8 Hz, 1H, H5), 3.78 (s, 3H, OCH3), 3.86 (d of t,
3J = 12.9 Hz, 3J = 3.9 Hz, 1H, H6), 5.19 (t of d, 2J = 13.2 Hz,
3J = 3.9 Hz, 1H, H6), 6.84 (d, 3J = 8.4 Hz, 2H, H2), 6.93 (d, 3J = 9.3
Hz, 1H, H16), 7.11 (d, 3J = 9.0 Hz, 1H, H17), 7.40 (t, 3J = 7.2 Hz, 1H,
H12), 7.52 (t, 3J = 7.2 Hz, 1H, H13), 7.64 (d, 3J = 7.8 Hz, 1H, H14),
7.98 (d, 3J = 8.7 Hz, 2H, H3), 8.71 (d, 3J = 8.1 Hz, 1H, H11), (13C{1H},
CDCl3, 25 °C, vs. TMS): d 14.65 (C5), 19.72 (CH3), 55.28 (OCH3),
63.09 (C6), 104.36 (C4), 114.22 (C16), 115.66 (C2), 116.63 (C8),
124.67 (C12), 126.35 (C14), 126.70 (C11), 128.13 (C10), 128.16
(C17), 128.78 (C13), 135.98 (C15), 138.69 (C3), 161.10 (C1), 162.77
(C9), 167.98 (C7); (125Te{1H}, CDCl3, 25 °C, vs. Me2Te): d 764.1.
IR(KBr, cmꢀ1): 1596, 515, 292.
d
339.02, 340.27. HRMS (ESI+) calc. for C42H42N2O2Se2Pt
(M+ꢀ2Cl) 961.1225, found m/z 961.1240 (
D 1.6075 ppm). IR(KBr,
cmꢀ1): 3444, 1595, 795, 742, 690, 467, 338.
2.3.2. Compound 10
Yield ꢁ0.97 g (ꢁ82%); m.p. 154 °C KM = 7.2 cm2 molꢀ1 ohmꢀ1
.
Anal. Calc. for C44H46N2O4Te2PtCl2: C, 44.45; H, 3.87; N, 2.36.
Found: C, 44.76; H, 3.87; N, 2.40. NMR (1H, CDCl3, 25 °C, vs.
TMS): d 1.94ꢀ1.98 (m, 4H, Ha), 2.28 (s, 3H, CH3), 2.35 (s, 3H,
CH3), 2.92ꢀ3.43 (m, 8H, H5 + H6), 3.63, 3.68, 3.73 (s, 6H, OCH3)
6.461, 6.641 (d, 3J = 8.4 Hz, 4H, H2), 6.74ꢀ6.80 (m, 2H, H16),
7.22ꢀ7.59 (m, 12H, H17, H14, H13, H12, H3), 8.40ꢀ8.46 (2 merging
d, 2H, H11), 16.03 (bs, 2H, OH), (13C{1H}, CDCl3, 25 °C, vs. TMS): d
14.48, 14.68 (CH3), 16.19, 16.31 (C5), 28.13, 28.24 (Ca), 45.50 (C6)
55.08, 55.16 (OCH3), 101.61, 102.61 (C4), 108.68, 108.86 (C8),
113.23, 113.39 (C16), 115.14, 115.25 (C2), 124.64 (C17), 124.95
(C12), 125.38 (C11), 126.99 (C14), 129.57 (C13), 130.36, 130.40
(C10), 137.21 (C15), 137.42, 137.68 (C3), 161.15, 161.40 (C1),
171.67, 171.85 (C9), 175.22, 175.37 (C7); (125Te{1H}, CDCl3, 25 °C,
vs. Me2Te): d 550.9, 563.1. HRMS (ESI+) calc. for C44H46N2O4-
2.2.7. [PtCl(L5ꢀH)] (7)
Yield ꢁ0.6020 g (ꢁ89%); m.p. 178 °C KM = 10.0 cm2 molꢀ1
ohmꢀ1. Anal. Calc. for C21H20NO2TePtCl: C, 37.25; H, 2.96; N, 2.07.
Found: C, 37.19; H, 2.91; N, 2.09%. NMR (1H, CDCl3, 25 °C, vs. TMS):
d 1.69 (s, 3H, CH3), 2.11ꢀ2.15 (m, 1H, H5), 3.36ꢀ3.53 (m, 2H, 2H,
H5 + H6), 3.77 (s, 3H, OCH3), 4.61ꢀ4.65 (m, 1H, H6), 6.81 (d,
3J = 8.4 Hz, 2H, H2), 6.99 (d, 3J = 9.0 Hz, 1H, H16), 7.19 (d, 3J = 9.0 Hz,
1H, H17), 7.42 (t, 3J = 6.9 Hz, 1H, H12), 7.57 (t, 3J = 6.9 Hz, 1H, H13),
7.65 (d, 3J = 7.8 Hz, 1H, H14), 7.94 (d, 3J = 8.4 Hz, 2H, H3), 8.78 (d,
3J = 8.1 Hz, 1H, H11), (13C{1H}, CDCl3, 25 °C, vs. TMS): d 15.09 (C5),
20.74 (CH3), 55.24 (OCH3), 63.84 (C6), 101.12 (C4), 115.09 (C16 + C2),
116.31 (C8), 125.06 (C12), 126.43 (C14), 126.56 (C11), 127.58 (C17),
128.01 (C10), 128.66 (C13), 135.50 (C15), 138.16 (C3), 160.41 (C9),
161.17 (C1), 163.73 (C7); (125Te{1H}, CDCl3, 25 °C, vs. Me2Te) 624.9.
IR(KBr, cmꢀ1): 1582, 512, 280.
Te2PtCl2 (M+) 1191.0607, found m/z 1191.0636 (
D
2.4290 ppm),
(M+ꢀ2Cl) 1121.1230, found m/z 1121.1171
(D 5.2638 ppm).
IR(KBr, cmꢀ1): 3451, 1593, 798, 742, 692, 585, 518, 414, 308.
2.4. Synthesis of [(p-cymene)RuClL5]Cl (11) [(p-cymene)RuClL6]Cl (12)
The [RuCl2(p-cymene)]2 (0.306 g, 0.5 mmol) dissolved in dichlo-
romethane (10 mL) and a solution of 1 mmol of L5 (0.447 g,) or L6
(0.461 g) in dichloromethane (20 mL) were stirred together vigor-
ously for 3 h. The solvent was removed on a rotary evaporator
which gave 11 or 12 as an orange coloured solid. It was washed
with hexane and dried in vacuo.
2.2.8. [PdCl(L6ꢀH)] (8)
Yield ꢁ0.536 g (ꢁ89%); m.p. 176 °C KM = 10.0 cm2 molꢀ1
ohmꢀ1. Anal. Calc. for C22H22NO2TePdCl: C, 43.86; H, 3.66; N, 2.33.
Found: C, 43.81; H, 3.69; N, 2.24%. NMR (1H, CDCl3, 25 °C, vs.
TMS): d 2.02 (m, 1H, Ha), 2.24 (s, 3H, CH3), 2.39 (m, 1H, Ha),
2.55ꢀ2.59 (m, 1H, H5), 2.84ꢀ2.87 (m, 1H, H5), 3.64ꢀ3.66 (m, 2H,
H6), 3.79 (s, 3H, OCH3), 6.83 (d, 3J = 8.1 Hz, 2H, H2), 6.92 (d,
3J = 9.0 Hz, 1H, H16), 7.25 (d, 3J = 9.3 Hz, 1H, H17), 7.37 (t,
3J = 7.2 Hz, 1H, H12), 7.48 (t, 3J = 7.8 Hz, 1H, H13), 7.62 (d,
3J = 8.1 Hz, 1H, H14), 8.00 (d, 3J = 8.1 Hz, 2H, H3), 8.64 (d, 3J = 8.4 Hz,
1H, H11), (13C{1H}, CDCl3, 25 °C, vs. TMS): d 15.60 (C5), 19.20 (CH3),
26.48 (Ca) 55.31 (OCH3), 57.56 (C6), 104.49 (C4), 114.45 (C16),
115.64 (C2), 121.95 (C8), 124.89 (C12), 126.64 (C14), 126.71 (C17),
126.93 (C11), 128.76 (C13), 129.14 (C10), 136.54 (C15), 138.70 (C3),
161.06 (C1), 164.17 (C9), 168.21 (C7); (125Te{1H}, CDCl3, 25 °C, vs.
Me2Te): d 484.75. IR(KBr, cmꢀ1): 1598, 513, 292.
2.4.1. Compound 11
Yield ꢁ0.587 g (ꢁ78%); m.p. 168 °C KM = 42 cm2 molꢀ1 ohmꢀ1
.
Anal. Calc. for C31H35NO2TeRuCl2: C, 49.39; H, 4.65; N, 1.86. Found:
C, 49.31; H, 4.61; N, 1.81%. NMR (1H, CDCl3, 25 °C, vs. TMS): d
1.25ꢀ1.29 (m, 6H, CH3 of i-pr), 2.13 (s, 3H, CH3), 2.33 (s, 3H, CH3 p
to i-pr), 2.85 (m, 1H, CH of i-pr), 3.20ꢀ3.26 (m, 1H, H5), 3.57ꢀ3.61
(m, 1H, H5), 3.72ꢀ3.82 (m, 5H, OCH3 + H6), 4.88 (d, 3J = 5.4 Hz, 1H,
ArH of p-cymene), 5.24 (d, 3J = 5.4 Hz, 1H, ArH of p-cymene), 5.36
(d, 3J = 5.7 Hz, 1H, ArH of p-cymene), 5.45 (d, 3J = 5.4 Hz, 1H, ArH
of p-cymene), 6.75ꢀ6.81 (m, 3H, H2 + H16), 7.26 (d, 3J = 9.3 Hz, 1H,
H17), 7.41 (t, 3J = 7.5 Hz, 1H, H12), 7.52 (t, 3J = 8.1 Hz, 1H, H13), 7.59
(d, 3J = 7.5 Hz, 1H, H14), 7.90 (d, 3J = 8.4 Hz, 2H, H3), 8.48 (d,
3J = 8.1 Hz, 1H, H11), 16.36 (bs, 1 H, ꢀOH), (13C{1H}, CDCl3, 25 °C,
vs. TMS): d 14.48 (CH3), 17.30 (C5), 18.44 (p-cymene CH3), 22.06
and 22.31 (CH3 of i-pr of p-cymene), 30.80 (CH of of i-pr of p-cym-
ene), 43.74 (C6), 55.09 (OCH3), 81.09, 81.26, 85.05 and 85.15 (ArC
of p-cymene m and o to i-pr), 98.41 (ArC of p-cymene attached to
CH3), 104.28 (ArC of p-cymene attached to i-pr), 106.14 (C4),
2.3. Synthesis of [PtCl2(L4)2 ] (9) and [PtCl2(L6)2 ] (10)
K2[PtCl4] (0.415 g, 1 mmol) dissolved in water (5 mL) and a
solution of 2 mmol of L4 (0.764 g)/L6 (0.922 g) in acetone (10 mL)
were stirred together vigorously. An orange precipitate of 9 or 10
was immediately obtained, which was filtered, washed with hex-
ane (10 mL) and dried in vacuo.

A. Kumar et al. / Journal of Organometallic Chemistry 693 (2008) 3533–3545
3537
108.69 (C8), 113.34 (C16), 115.32 (C2), 124.51 (C17), 124.75 (C12),
2.5.2. Compound 14
Yield ꢁ1.064 g (ꢁ83%); m.p. 170 °C KM = 10.0 cm2 molꢀ1
ohmꢀ1. Anal. Calc. for C44H46N2O4Te2HgBr2: C, 41.17; H, 3.59; N,
2.18. Found: C, 41.21; H, 3.51; N, 2.16%. NMR (1H, CDCl3, 25 °C, vs.
TMS): d 2.19 (Quintet, J = 6.9 Hz, 4H, Ha), 2.25 (s, 6H, CH3), 3.28 (t,
3J = 7.5 Hz, 4H, H5), 3.47 (t, 3J = 6.9 Hz, 4H, H6), 3.66 (s, 6H, OMe),
6.71ꢀ6.77 (m, 6H, H2 + H16), 7.20 (d, 3J = 9.3 Hz, 2H, H17), 7.35 (t,
3J = 7.2 Hz, 2H, H12), 7.47 (t, 3J = 7.8 Hz, 2H, H13), 7.55 (d,
3J = 7.8 Hz, 2H, H14), 7.64 (d, 3J = 8.4 Hz, 4H, H3) 8.42 (d, 3J = 8.1 Hz,
2H, H11), 16.16 (bs, 2H, OH); (13C{1H}, CDCl3, 25 °C, vs. TMS): d
14.55 (CH3), 17.92 (C5), 29.45 (Ca), 46.08 (C6), 55.18 (OCH3),
101.76 (C4) 108.63 (C8), 113.33 (C16), 116.08 (C2), 124.67 (C17),
124.88 (C12), 125.40 (C11), 126.98 (C14), 129.55 (C13), 130.30 (C10),
137.19 (C15), 139.01 (C3), 161.24 (C1), 171.51 (C9), 175.22 (C7);
125.36 (C11), 126.84 (C14), 129.39 (C13), 130.14 (C10), 137.07 (C15),
137.68 (C3), 161.30 (C1), 171.31 (C9), 174.93 (C7); (125Te{1H}, CDCl3,
25 °C, vs. Me2Te): d 515.33. HRMS (ESI+) calc. for C31H35NO2TeRuCl
(M+ꢀCl) 720.0462, found m/z 720.0472 (
D 1.3764 ppm). IR(KBr,
cmꢀ1): 3440, 1604, 1249, 1179, 1026, 825, 761, 705.
2.4.2. Compound 12
Yield ꢁ0.65 g (ꢁ85%); m.p. 131 °C. KM = 54 cm2 molꢀ1 ohmꢀ1
.
Anal. Calc. for C32H37NO2TeRuCl2: C, 50.06; H, 4.82; N, 1.82. Found:
C, 49.88; H, 4.87; N, 1.85%. NMR (1H, CDCl3, 25 °C, vs. TMS): d
1.17ꢀ1.23 (m, 6H, CH3 of i-pr), 2.05ꢀ2.14 (m, 5H, CH3 + Ha), 2.31
(s, 3H, CH3 p to i-pr), 2.74ꢀ2.83 (multiplet, 1H, CH of i-pr), 3.10
(m, 1H, H5), 3.23 (m, 1H, H5), 3.46ꢀ3.48 (m, 2H, H6), 3.79 (s, 3H,
OCH3), 4.97 (d, 3J = 5.1 Hz, 1H, ArH of p-cymene), 5.20 (d,
3J = 5.1 Hz, 1H, ArH of p-cymene), 5.33 (d, 3J = 5.4 Hz, 1H, ArH of
p-cymene), 5.43 (d, 3J = 5.4 Hz, 1H, ArH of p-cymene), 6.77 (d,
3J = 9.0 Hz, 1H, H16), 6.87 (d, 3J = 8.4 Hz, 2H, H2), 7.24 (d,
3J = 9.0 Hz, 1H, H17), 7.36 (t, 3J = 6.9 Hz, 1H, H12), 7.49 (t,
3J = 7.5 Hz, 1H, H13), 7.57 (d, 3J = 7.8 Hz, 1H, H14), 7.84 (d,
3J = 8.4 Hz, 2H, H3), 8.45 (d, 3J = 8.1 Hz, 1H, H11), 16.18 (bs, 1H,
–OH); (13C{1H}, CDCl3, 25 °C, vs. TMS): d 14.20 (CH3), 14.72 (C5),
18.31 (p-cymene CH3), 21.79 and 22.79 (CH3 of i-pr of p-cymene),
28.62 (Ca), 30.65 (CH of of i-pr of p-cymene), 45.76 (C6), 55.15
(OCH3), 80.96, 81.48, 84.65 and 85.23 (ArC of p-cymene m and o
to i-pr), 97.54 (ArC of p-cymene attached to CH3), 104.24 (ArC of
p-cymene attached to i-pr), 106.12 (C4), 108.34 (C8), 113.04 (C16),
115.50 (C2), 124.46 (C17), 124.73 (C12), 125.26 (C11), 126.84 (C14),
129.40 (C13), 130.39 (C10), 137.04 (C3), 137.11 (C15), 161.27 (C1),
171.05 (C9), 175.59 (C7); (125Te{1H}, CDCl3, 25 °C, vs. Me2Te): d
535.8 ppm. HRMS (ESI+) calc. for C32H37NO2TeRuCl (M+ꢀCl)
(
125Te{1H}, CDCl3, 25 °C, vs. Me2Te): d 367.4. HRMS (ESI+) calc. for
C44H46N2O4Te2HgBr (M+ꢀBr) 1207.0472, found m/z 1207.0450 (
D
1.8098 ppm). IR(KBr, cmꢀ1): 3427, 1592, 1249, 1179, 1023, 794,
742, 691, 587, 515, 415.
2.6. Procedure for catalytic Suzuki reaction
Bromobenzene or its derivative (1 mmol), benzeneboronic acid
(0.183 g, 1.5 mmol), K2CO3 (0.276 g, 2 mmol), distilled water
(0.5 mL), DMF (4 mL) and catalyst (complex 1/2/3/5/6)
(0.001 mmol) were stirred together under reflux on an oil bath
for 24 h at 100 °C under ambient conditions. The reaction mixture
was cooled to room temperature and mixed with 20 mL of water.
The product was extracted from the aqueous mixture with hex-
ane/diethyl ether (25–50 mL). The solvent was partly evaporated
on a rotary evaporator to get white crystalline solid products,
which were filtered and washed with 3–4 mL of hexane. The
NMR (1H and 13C{1H}) spectra and m.p.’s identified the products.
734.0619, found m/z 734.0593 (
D
3.4861 ppm) IR(KBr, cmꢀ1):
3427, 1591, 1456, 1247, 1179, 1023, 795, 744, 691, 586, 518,
414, 283.
2.7. Procedure for catalytic Heck reaction
The mixture of alkene (1.5 mmol), aryl halide (1 mmol), Na2CO3
(0.212 g, 2.0 mmol), DMF (4.0 mL) and catalyst (complex 1/2/3/5/
6) (0.001 mmol) was stirred under reflux on an oil bath for 24 h
at 100 °C under nitrogen atmosphere. It was cooled to room tem-
perature. To obtain (E)-1-(4-chloro/nitrophenyl)-2-phenylethene,
it was treated with chloroform (40 mL) and filtered. The filtrate
was washed with water (3 ꢂ 25 mL) and evaporated on rotary
evaporator. The product was further purified chromatographically
(silica gel column) using hexane–ethylacetate mixture (9:1). For
(E)-3-(4-chloro/nitrophenyl)acrylic acid the cooled reaction mix-
ture was mixed with NaHCO3 (0.50 g) and water (30 mL). The mix-
ture was stirred for 1 h at room temperature. The aqueous phase
was separated and acidified with 5 N HCl. On cooling to 0 °C, the
solid precipitate was formed which was filtered, washed and air
dried.
2.5. Synthesis of [HgBr2(L5)2] (13) and [HgBr2(L6)2] (14)
The HgBr2 (0.360 g, 1.0 mmol) was dissolved in 5 mL of acetone.
The solution of L5 (0.894 g, 2.0 mmol)/L6 (0.922 g, 2.0 mmol) in
10 mL of chloroform was added to it with stirring. The mixture
was stirred further for 3 h. The solvent was evaporated off to dry-
ness on a rotary evaporator. The resulting residue was washed
with acetone, redissolved in minimum amount of chloroform and
mixed with hexane. The resulting precipitate of 13 or 14 was fil-
tered, washed with hexane (10 mL) and dried in vacuo.
2.5.1. Compound 13
Yield ꢁ0.953 g (ꢁ76%); m.p. 161 °C KM = 10.0 cm2 molꢀ1
ohmꢀ1. Anal. Calc. for C42H42N2O4Te2HgBr2: C, 40.18; H, 3.35; N,
2.23%. Found: C, 40.13; H, 3.39; N, 2.28%. NMR (1H, CDCl3, 25 °C,
vs. TMS): d 2.30 (s, 6H, CH3), 3.50 (t, 3J = 7.2 Hz, 4H, H5), 3.65 (s,
6H, OMe), 4.00 (t, 3J = 6.9 Hz, 4H, H6), 6.71 (d, 3J = 8.7 Hz, 4H, H2),
6.82 (d, 3J = 9.0 Hz, 2H, H16), 7.21 (d, 3J = 9.3 Hz, 2H, H17), 7.36 (t,
3J = 6.9 Hz, 2H, H12), 7.49 (t, 3J = 7.8 Hz, 2H, H13), 7.57 (d,
3J = 7.8 Hz, 2H, H14), 7.71 (d, 3J = 8.7 Hz, 4H, H3) 8.38 (d, 3J = 8.1 Hz,
2H, H11), 16.21 (bs, 2H, OH); (13C{1H}, CDCl3, 25 °C, vs. TMS): d
14.87 (CH3), 20.60 (C5), 44.85 (C6), 55.17 (OCH3), 101.73 (C4)
109.21 (C8), 114.07 (C16), 116.05 (C2), 124.85 (C17 + C12), 125.35
(C11), 127.01 (C14), 129.55 (C13) 129.70 (C10), 137.05 (C15), 139.58
(C3), 161.28 (C1), 171.80 (C9), 173.78 (C7); (125Te{1H}, CDCl3, 25 °C,
vs. Me2Te): d 362.6. HRMS (ESI+) calc. for C42H42N2O4Te2HgBr
3. Results and discussion
The ligands L1–L6 synthesized by the reactions given in Scheme
1 are stable and can be stored under ambient conditions up to 6
months easily. They have good solubility in CHCl3, CH2Cl2, CH3CN,
CH3OH, C2H5OH and acetone. In hexane all the ligands are spar-
ingly soluble. They behave as non-electrolytes. The complexes 1–
14 are stable under ambient conditions and soluble in CHCl3,
CH2Cl2, CH3CN, EtOH, MeOH and acetone but insoluble in hexane.
The stoichiometry of complexes formed by four metal ions with
L1–L6 does not change on varying the metal:ligand ratio. When
M:L ratio is 1:2, [PdCl2L2] is not formed. The [PtCl(L–H)] species
are not formed in case of L4 and L6 even when Pt:L ratio is 1:1. Sim-
ilarly in case of L3 and L5, [PtCl2L2] is not formed when M:L is 1:2.
(M+ꢀBr) 1179.0159, found m/z 1179.0170 (
D 0.9463 ppm). IR(KBr,
cmꢀ1): 3412, 1589, 1250, 1179, 1024, 796, 748, 689, 587, 515, 422,
321.

3538
A. Kumar et al. / Journal of Organometallic Chemistry 693 (2008) 3533–3545
CH3
L1, L3, L5
[Dry EtOH, r.t]
R
( n =2)
( n =3)
O
H2N(CH2)nE
+
2
4
6
L , L , L
OH
E = S, Se, Te
R = H, OR
Scheme 1.
All of them are nonionic in nature except 11 and 12 for which the
values of molar conductance at room temperature are 42.0 and
54.0 S cm2 molꢀ1, respectively, which are less than the KM value
(120–160 S cm2 molꢀ1) expected for a 1:1 electrolyte in MeCN,
probably due to some ion association or partial change in the den-
tate character of ligand (from two to one). In IR spectra of all the
complexes except that of 9, 10, 13 and 14, ˜C@N– stretching fre-
quency has been observed red shifted (10ꢀ55 cmꢀ1) with respect
to those of corresponding ligands indicating the involvement of
its nitrogen in coordination or somewhat weaker interaction.
Table 1
125Te or 77Se NMR signals of metal complexes of L3–L6 and their shielding/deshielding
S.no. Complex
Chemical shift d (ppm)
Change in chemical shift
relative to ligand (ppm)
in 125Te or 77Se NMR
1
2
3
4
5
6
7
8
9
PdCl(L3ꢀH)] (3)
445.7
388.6
297
764.1
624.9
484.8
339.0 and 340.3
550.9 and 563.1
515.3
+158
+100.9
+8.2
+298
+158.8
+24.5
+50.2 and +51.5
+90.6 and +102.8
+49.2
[PtCl(L3ꢀH)] (4)
[PdCl(L4ꢀH)](5)
[PdCl(L5–H)] (6)
[PtCl(L5–H)] (7)
[PdCl(L6–H)] (8)
[PtCl2(L4)2] (9)
[PtCl2(L6)2] (10)
[(p-
3.1. Ligands
Cymene)RuClL5]Cl
(11)
In 77Se{1H} NMR spectra of L3 and L4 the signals appears almost
at the same position (287.7 and 288.8 ppm, respectively). The sig-
nal in 125Te{1H} NMR spectrum of 2-(4-methoxyphenyltelluro)eth-
ylamine gets deshielded by 72 ppm when Schiff base L5 is formed
but in case of L6, its position remains similar to that of precursor
amine. 13C{1H} NMR spectra of all the ligands were found charac-
teristic. On comparing the spectra of six ligands, it is observed that
signal of C4 (bonded to E = S, Se or Te) is most high field in case of
Te, followed by Se and S. Similar trends are observed for the signal
of carbon atom of CH2E also. The signal of ꢀCH3 carbon appears al-
most at the same position in the spectra of L1 to L6. The 1H NMR
spectra of all the ligands were found characteristic. The signals of
H5 protons of ligands containing E–(CH2)2–N system are deshield-
ed by 0.12–0.29 ppm in comparison to those ligands containing E–
(CH2)3–N system. The signal of –OH proton in the 1H NMR spectra
of all the ligands has been found most deshielded due to intramo-
lecular O–Hꢃ ꢃ ꢃN hydrogen bonding.
10
[(p-
535.8
+75.5
Cymene)RuClL6]Cl
(12)
11
12
[HgBr2(L5)2] (13)
[HgBr2(L6)2] (14)
362.6
367.4
ꢀ103.5
ꢀ92.9
NMR spectrum shows deshielding of 8.42–10.82 ppm on complex-
ation with Pd. The carbon signal of CH2Se is deshielded between
5.56 and 6.18 ppm. The deshielding in CH2S carbon signal on com-
plexation (3.94–7.74 ppm) also indicates the coordination of L1ꢀL2
through sulphur. The deshieldings of signal of C4 are in the ranges
4.76ꢀ5.14, 2.1ꢀ2.9, 5.7ꢀ13.50 ppm, respectively, for E = Te, Se
and S and imply the formation of Pd–chalcogen bond. In 13C{1H}
NMR spectra of each palladium complex the signal of ꢀCH3 appears
deshielded (5ꢀ6 ppm) with respect to that of corresponding ligand
which indicates the involvement of ˜C@N group in coordination
with the Pd. The deshielding of signal of @NCH2 in 13C{1H} NMR
spectra not only indicates coordination of Pd with ˜C@N group
but changes with chelate ring size. When out of two chelate rings
formed around the central metal atom, one ring is five-membered
and the other is six-membered (1, 3 and 6), the deshielding in the
signal of @NCH2 carbon is between 14.60 and 16.18 ppm, whereas
when both the rings around the central metal atom are six-mem-
bered (2, 5 and 8), the deshielding of signal of @NCH2 carbon is
between 8.51 and 11.47 ppm.
3.2. [PdCl(LꢀH)] complexes
The complexes 1, 2, 3, 5, 6 and 8 are of the stoichiometry
[PdCl(LꢀH)], which is supported by crystal structures of 1, 2, 3
and 6 given below (Section 3.2). The chemical shifts observed in
77Se{1H} and 125Te{1H} NMR spectra of palladium(II) complexes of
L3ꢀL6 and change in their positions with respect to those of corre-
sponding ligands are compared in Table 1. The signal of L3 in 77Se
NMR spectrum shows deshielding of 158 ppm on complexation
with Pd(II), whereas in case of L4 the deshielding is of the order of
8 ppm only (Table 1). This difference is due to formation of five-
and six-membered rings, respectively, with L3 and L4. On compar-
ing P-31 NMR spectra of various metal–phosphine complexes, sim-
ilar observations have been made earlier [12a]. These deshieldings
on formation of complexes 3 and 5 indicate that the coordination of
ligands in them occurs through Se. The deshielding of 298 ppm has
been observed in the 125Te{1H} NMR signal of L5 on the complexa-
tion with Pd(II), which is much higher than the one shown by L6 on
complexation with the same metal (Table 1). It may also be attrib-
uted to chelate ring size effect as mentioned in case of Se analogues.
As in the case of 3 and 5 the coordination of L5 and L6 with Pd(II)
through Te can be easily inferred from these deshieldings of signals
in Te-125 NMR spectra of 6 and 8. This is further supported by
13C{1H} NMR spectral data. The signal of CH2Te (C5) in 13C{1H}
The signal of ꢀOH does not appear in the 1H NMR spectra of
complexes 1, 2, 3, 5, 6 and 8 indicating the coordination of ꢀOH
group to palladium(II) in the deprotonated form (Oꢀ). On consider-
ing the Se-77, Te-125 and C-13 NMR data with this observation, it
may be inferred that L1ꢀL6 coordinate in uni-negative tridentate
mode in all Pd-complexes as supported by single-crystal structures
of 1, 2, 3 and 6.
The signal of CH3 in proton NMR spectra does not show ex-
pected deshielding uniformly for all Pd-complexes. It shows
shielding (0.30ꢀ0.38 ppm) on comparing the spectra of 3 and 6
with those of corresponding ligands. In the spectra of 1, 2 and
5, CH3 signal shows deshielding (0.08ꢀ0.31 ppm) with respect
to those of corresponding free ligands. However, in the case of
8 the signal of CH3 appears at a position identical to that of ligand
L6. In 1H NMR spectra the H5 protons of all the ligands on com-
plexation with Pd(II), show two multiplets, each corresponds to

A. Kumar et al. / Journal of Organometallic Chemistry 693 (2008) 3533–3545
3539
one proton, except in case of L5 where one H5 appears as triplet of
doublet and other doublet of triplet. In all cases the signal for H5
is expected to be ‘ddd’ as two protons of each CH2 group are ex-
pected to be diastereotopic. However, due to overlap of signals
such splittings are masked. Of two one signal is
shielded (ꢁ0.15ꢀ0.65 ppm) and the other one deshielded
(ꢁ0.17ꢀ0.51 ppm) in comparison to corresponding ligand signals,
except for 8, which exhibits both signals shielded in comparison
to that of corresponding ligand, and 2 which gives only one com-
plex multiplet at higher field relative to that of ligand. The gem-
inal @NCH2 protons (H6) also give two different signals (one for
each) in case of 3 and 6. One signal is shielded (ꢁ0.07ꢀ0.23 ppm)
and the other deshielded (ꢁ0.37ꢀ1.40 ppm) in comparison to
those of the corresponding ligands. In the proton NMR spectra
of 1, 2, 5 and 8, @NCH2 protons appear as a complex multiplet,
deshielded (ꢁ0.08ꢀ0.33 ppm) with respect to those of corre-
sponding free ligands. The proton NMR spectra are affected more
by spatial interactions and conformational influences which may
be responsible for some of these divergences. Therefore, 5 and 8
can also be formulated as [PdCl(LꢀH)] like other Pd-complexes
characterized structurally.
form. However, in the proton NMR spectra of 9 and 10 signal of
OH group has been observed. This rules out formulation of type
[Pt(L–H)2Cl] ꢃ 2HCl for 9 and 10. Thus most probably in 9 and
10 the Schiff base ligands coordinate through Se or Te only (uni-
dentate mode) and the complexes are cis–trans isomeric mixtures,
whereas in 4 and 7 Schiff base ligands bind in a tridentate uni-
negative mode as in the case of Pd-complexes.
Proton NMR spectral data generally support the conclusions
made above for 4, 7, 9 and 10. In proton NMR spectrum of 9
the CH3 protons give four singlets of similar heights. This is due
to its existence as a cis–trans isomeric mixture and probably also
contributed by non-equivalence of the two Schiff base ligand
molecules in each isomer. In mass spectra of 9 and 10 appearance
of [M+ꢀ2Cl] peak suggest that there are other interactions in
these molecules which make Pt–Cl bond weak and probably make
two ligands non-equivalent. The possibility of impurity in the
samples of 9 and 10 was ruled out on the basis of elemental anal-
ysis and mass spectra. In 1H NMR spectra, both the geminal H5
protons of 4 as well as 7 appear at different positions. In case
of 7, one H5 proton signal appears shielded (0.87 ppm) and the
other one deshielded (ꢁ0.44 ppm) in comparison to that of ligand
but in case of 4, both the signals are deshielded (0.06 and
0.67 ppm). On complexation of L4 and L6 with Pt(II) signals for
H5 protons appear overlapped with those of H6 protons. The pro-
ton NMR spectrum of 10 exhibits double number of signals for
some protons. This further supports the existence of this complex
as a cis–trans isomeric mixture. In 1H NMR spectra of 7 the two
geminal @NCH2 protons (H6) give two different signals (one for
each). One signal is shielded (0.35 ppm) and the other deshielded
(0.84 ppm) in comparison to that of the corresponding ligand. But
in case of 4, 9 and 10, @NCH2 protons appear as a complex mul-
tiplet, overlapped with other signals so shielding or deshielding
cannot be quantified explicitly. The L4 and L6 ligate with Pd and
Pt differently due to several reasons. The Pt–Cl bond is more
covalent and strong than Pd–Cl bond which makes its reactivity
lower towards OH group. The Pt(II) is more ‘Soft’ Lewis acid than
Pd(II) therefore its coordination with N of ˜C@N resulting in six-
membered ring does no become very stable. Consequently L4 and
L6 ligate through Se or Te only.
3.3. Platinum complexes
There are two type of platinum complexes formed. It is inter-
esting to note that on varying metal: ligand ratio same species are
formed. One has composition [PtCl(L–H)] (4 and 7) and the other
[PtCl2(L)2] (9 and 10). The later ones are supported by HRMS data.
The structural diagnosis of Pt-complexes is largely based on the
NMR spectral data only, as single crystals could not be grown
for any Pt-complex. The deshielding of 50–100 ppm (Table 1)
has been observed in 77Se{1H} NMR signal of L3 and L4 when they
coordinate with Pt(II). The appearance of two very close signals in
the spectrum of 9 may be due to the presence of both cis and
trans isomeric forms together as it has two ligand molecules.
The chemical shifts observed in the 125Te{1H} NMR spectra of
Pt-complexes of L5 and L6 and their relative positions with re-
spect to those of corresponding ligands are also given in Table
1. On complexation with Pt(II), the deshielding is ꢁ158.8 ppm
in case of L5 and is 90.6/102.8 for L6. The appearance of two sig-
nals takes place in the case of L6, which may be due to the pres-
ence of cis and trans forms together. Attempts made for column
chromatographic separation of the isomeric forms of 9 and 10
failed. These deshieldings indicate that in 4, 7, 9 and 10, L3ꢀL6
coordinate with Pt(II) through Se or Te. This is supported by car-
bon-13 NMR data as signal of C5 (CH2E; E = Se or Te) in the spec-
tra shows deshielding of 7.69, 3.69, 8.86, and 11.41/11.53 ppm in
case of 4, 7, 9 and 10, respectively, with respect to those of free
ligands. The signal of C4 (attached to Se or Te) also gets deshield-
ed on the formation of 9, 7 and 10 (1.88ꢀ4.17 ppm), supporting
the coordination of ligands in the Pt-complexes through Se or
Te. The signal of –CH3 in carbon-13 NMR appears deshielded
(6.43–6.77 ppm) for complexes 4 and 7 but in 9 and 10 it appears
nearly at the position observed in the corresponding ligand. This
probably implies that in 9 and 10 the ligands L4 and L6 do not
coordinate through ˜C@Nꢀ group. The doubling of signals of
some carbon atoms in 13C{1H} NMR spectra of 9 and 10 further
supports the existence of cis–trans isomeric forms inferred from
Se-77 and Te-125 NMR spectra. In carbon-13 NMR of 4 and 7,
the deshielding in the signal of @NCH2 is found between 16.67
and 16.93 ppm, respectively, whereas in case of 9 and 10, the sig-
nal of @NCH2 appears almost at the same position at which it ap-
pears in the corresponding ligand. This indicates that in 9 and 10,
@NCH2 is not involved in coordination. The signal of –OH does
not appear in 1H NMR spectra of complexes 4 and 7 indicating
the coordination of –OH group with Pt(II) in the deprotonated
3.4. Ruthenium complexes
The single crystals could not be grown for any Ru-complex.
Therefore for species [Ru(p-cymene)ClL5/L6)]Cl, NMR spectral data
(with support of mass) are mainly correlated with the possible
structural features. On complexation with ruthenium L5 and L6
show deshielding in Te-125 NMR spectra (Table 1). It is
49.2 ppm in the case of L5 and 75.5 ppm when L6 coordinates
with Ru(II). In 13C{1H} NMR spectra of 11 and 12 the signals of
CH2Te (C5) show deshielding (11.07 and 9.94 ppm, respectively)
in comparison to those of free ligands. The signal of C4 carbon
atom also appears deshielded (6ꢀ7 ppm) in both 11 and 12 with
respect to those of corresponding ligands. Thus ligation of L5 and
L6 with Ru through Te may be inferred. In 13C{1H} NMR spectra,
the position of signal of ꢀCH3 carbon remains almost unchanged
on the formation of 11 and 12. Moreover in 13C{1H} NMR spectra
of 11 and 12, @NCH2 carbon signal shows shielding (up to
ꢁ3 ppm). This suggest that ˜C@N group does not coordinate
strongly with Ru. A strong association between complex and chlo-
ride ion, facilitated by weak interaction between Ru and ˜C@N
group, seems to lower conductance values for 11 and 12. The
appearance of [M+ꢀCl] peak in HRMS concurs with this proposi-
tion. In 1H NMR spectra of 11 as well as 12, the presence of signal
of OH proton indicates that –OH group does not coordinate with
metal. In 1H NMR spectra of 11 and 12 both the geminal H5 pro-
tons show two multiplets (one for each) but both are deshielded

3540
A. Kumar et al. / Journal of Organometallic Chemistry 693 (2008) 3533–3545
Table 2
Crystal data and structural refinements for L1, L3 and L6
Compound
L1
L3
L6
Empirical formula
Formula weight
Crystal size (mm)
Crystal system
Space group
Unit cell dimensions
a (Å)
C20H19NOS
321.43
C20H19NOSe
368.32
C22H23NO2Te
461.0
0.407 ꢂ 0.289 ꢂ 0.196
0.463 ꢂ 0.215 ꢂ 0.167
0.423 ꢂ 0.298 ꢂ 0.178
Triclinic
Triclinic
Triclinic
ꢀ
ꢀ
ꢀ
P1
P1
P1
7.8504(15)
10.336(2)
11.594(2)
73.700(3)
834.7(3)
8.0693(14)
10.2505(17)
11.5208(19)
72.878(4)
842.6(2)
2
1.440
2.232
376.00
6.3152(5)
8.7203(7)
18.3132(14)
85.8362(11)
976.85(13)
2
1.567
1.538
460.0
b (Å)
c (Å)
b (°)
Volume (Å3)
Z
2
Dcalc. (Mg mꢀ3
)
1.279
0.198
340.00
Absorption coefficient (mmꢀ1
F(000)
)
h Range (°)
Index ranges
1.84–25.49
ꢀ9 ꢄ h ꢄ 9
ꢀ12 ꢄ k ꢄ 12
ꢀ14 ꢄ l ꢄ 14
8365
1.85–28.32
ꢀ10 ꢄ h ꢄ 10
ꢀ13 ꢄ k ꢄ 13
ꢀ15 ꢄ l ꢄ 15
10087
2.23–25.49
ꢀ7 ꢄ h ꢄ 7
ꢀ10 ꢄ k ꢄ 10
ꢀ22 ꢄ l ꢄ 22
9616
Reflections collected
Independent reflections (Rint
)
3096(0.0983)
99.7
0.965/0.931
3096/0/209
1.061
4014(0.0965)
95.8
0.645/0.456
4014/0/210
0.907
3610(0.0205)
98.8
0.764/0.581
3610/0/254
1.064
Completeness to maximum h (%)
Maximum/minimum transmission
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0564, wR2 = 0.1469
R1 = 0.0603, wR2 = 0.1529
0.462/ꢀ0.333
R1 = 0.0577, wR2 = 0.0990
R1 = 0.0964, wR2 = 0.1110
0.621/ꢀ0.526
R1 = 0.0251, wR2 = 0.0660
R1 = 0.0270, wR2 = 0.0671
0.436/ꢀ0.385
Largest difference in peak/hole (e Åꢀ3
)
Table 3
Crystal data and structural refinements for 1, 2, 3 and 6
Compound
1
2
3
6
Empirical formula
Formula weight
Crystal size (mm)
Crystal system
Space group
Unit cell dimensions
a (Å)
C20H18ClNOPdS
462.26
C21H20ClNOPdS
476.32
C20H18ClNOPdSe
509.18
C21H20ClNO2PdTe
664.74
0.34 ꢂ 0.28 ꢂ 0.26
Orthorhombic
C2cb
0.52 ꢂ 0.18 ꢂ 0.15
0.298 ꢂ 0.165 ꢂ 0.076
0.463 ꢂ 0.215 ꢂ 0.167
Triclinic
Monoclinic
Monoclinic
ꢀ
P1
P2(1)/c
P2(1)/c
9.689(2)
12.429(4)
15.677(4)
77.09(2)
1838.4(9)
4
1. 670
1.276
16.038(9)
10.536(6)
12.351(7)
110.369(11)
1956.5(19)
4
1.617
1.201
9.6820(14)
12.2362(18)
15.813(2)
101.645(2)
1834.8(4)
9.7664(3)
b (Å)
c (Å)
16.1747(6)
27.8791(9)
90.00(2)
4404.0(3)
8
2.005
2.525
2568.0
b (°)
Volume (Å3)
Z
4
Dcalc (Mg mꢀ3
)
1.843
3.148
1000.0
Absorption coefficient (mmꢀ1
F(000)
)
928.0
960.0
h Range (°)
Index ranges
4.49–32.57
ꢀ14 ꢄ h ꢄ 14
ꢀ18 ꢄ k ꢄ 18
ꢀ23 ꢄ l ꢄ 22
28871
1.35–28.32
ꢀ21 ꢄ h ꢄ 21
ꢀ14 ꢄ k ꢄ 14
ꢀ16 ꢄ l ꢄ 16
11519
2.12–25.50
ꢀ11 ꢄ h ꢄ 11
ꢀ14 ꢄ k ꢄ 14
ꢀ19 ꢄ l ꢄ 19
17812
3.28–25.00
ꢀ11 ꢄ h ꢄ 11
ꢀ17 ꢄ k ꢄ 19
ꢀ32 ꢄ l ꢄ 33
12537
Reflections collected
Independent reflections (Rint
)
12020 (0.0371)
89.9
0.82300/0.75740
12020/0/453
1.111
4850 (0.1000)
99.5
0.915/0.787
4850/0/200
1.318
3412 (0.0377)
100.0
0.593/0.445
3412/0/227
1.230
3851 (0.0274)
1.86(0.99)
0.521/0.429
3851/1/270
1.068
Completeness to maximum h (%)
Maximum/minimum transmission
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2
r
(I)]
R1 = 0.0636, wR2 = 0.1782
R1 = 0.0883, wR2 = 0.1903
2.551/ꢀ1.114
R1 = 0.0796, wR2 = 0.1705
R1 = 0.0929, wR2 = 0.1869
0.676/ꢀ1.248
R1 = 0.0295, wR2 = 0.0744
R1 = 0.0343, wR2 = 0.0781
0.454/ꢀ0.360
R1 = 0.0406, wR2 = 0.0953
R1 = 0.0475, wR2 = 0.0985
1.764/ꢀ1.916
R indices (all data)
Largest difference peak/hole (e Åꢀ3
)
(ꢁ0.22–0.59 ppm) in comparison to those of corresponding free
ligands. This supports the binding of ligands L5 and L6 with Ru(II)
through Te. In 1H NMR spectra of 11, the geminal @NCH2 protons
signal overlaps with the signal of OMe and consequently its
shielding/deshielding cannot be quantified. But in the case of
12, @NCH2 protons appear as a complex multiplet, little deshield-
ed (ꢁ0.023 ppm) with respect to those of corresponding free li-
gands. This supports the possibility of weak interaction between
Ru and ˜C@N group as suggested above but also suggest that
Schiff base ligands in 11 and 12 both are behaving as a monoden-
tate ligand.
3.5. Mercury complexes
Single crystals could not be grown for any Hg-complex also.
Contrary to deshielding (Table 1) observed in 125Te{1H} NMR signal
of L5 and L6 on complexation with Pd(II), Pt(II) and (p-cymene)-
Ru(II), there is a shielding of 103.5 ppm when L5 complexes with

A. Kumar et al. / Journal of Organometallic Chemistry 693 (2008) 3533–3545
3541
mation of metal–chalcogen bond. In 13C{1H} NMR spectra the
position of signal of @NCH2 has been found deshielded
(2.06 ppm) when 13 is formed while it appears exactly at the same
position in 14 at which it appears in the spectrum of free ligand L6.
Thus possibility of existence of weak interaction between Hg and
˜C@N group cannot be ruled out completely. In the 1H NMR spec-
tra of both 13 and 14, ꢀOH appears indicating that –OH group does
not coordinate with metal. High resolution mass spectra supports
metal to ligand ratio as 1:2, which suggest that ligands are bonded
with Hg, mainly through Te and weak interactions with N of ˜C@N
group may exist.
C12
C13
C14
S1
C16
N1
C17
C11
C8
C15
C9
C5
H1A
C18
C20
C19
C7
C6
C10
C4
O1
In the 1H NMR spectra of both 13 and 14, a triplet just like that
of ligand appears for H5 protons. This triplet is deshielded by
0.50 ppm in case of 13 and 0.40 ppm in case of 14 in comparison
to that of corresponding ligand. In 1H NMR spectra the position
of @NCH2 proton signal has been found deshielded (0.21 ppm) in
case of 13 while it appears almost at the same position in 14 at
which it appears in the spectrum of free L6. This supports the pos-
sibility of weak interactions between Hg and ˜C@N group, particu-
larly in the case of 13.
C1
C3
C2
Fig. 1. ORTEP diagram of L1 with 50% probability ellipsoids.
C21
C15
3.6. Crystal structures
C14
C2
C11
The crystal structures of L1, L3, L6, 1, 2, 3 and 6 were solved.
Crystal data and structural refinements are given in Tables 2 and
3. Molecular structures of L1, L2 and L3 are shown in Figs. 1–3,
respectively, and their bond lengths and angles are available as
C4
N1
C16
C13
C17
C3
O1
C12
Supplementary material. The S–C, Se–C and Te–C bond lengths
0
H1
1.7648(19)/1.801(2), 1.915(3)/1.942(3) and 2.116(2)/2.160(3) ÅA,
respectively, are consistent with the earlier reports [13–15]. The
order of E–C(alkyl/aryl) bond distances is S < Se < Te. The E–C(aryl)
bond distances (E = S, Se and Te) are somewhat shorter than E–
C(alkyl) distances in all the three ligands L1, L2 and L3. The C(al-
kyl)–S–C(aryl) bond angle was found to be maximum 102.67(9)o
followed by C(alkyl)–Se–C(aryl) 99.23(15)o and C(alkyl)–Te–
C(aryl) 95.15(9)o. The intramolecular hydrogen bonding O–Hꢃ ꢃ ꢃN
have been observed in the structure of all the three ligands L1, L3
and L6.
Se1
C5
C20
C18
C6
C19
C7
C10
C8
C9
Fig. 2. ORTEP diagram of L3 with 50% probability ellipsoids.
The molecular structures of 1 and 2 are shown in Fig. 4 and.
Fig. 5, respectively, and their selected bond distances and angles
are given in Table 4. The unit cell has nearly similar two molecules
of 1. Their slightly different bond lengths and bond angles are in-
dexed as A and B in the Table 4. The geometry around Pd is square
planar in 1 as well as 2. The ligands are coordinated with Pd in a
monoanionic tridentate (S, N, Oꢀ) mode in both the complexes.
This kind of coordination mode forms a six-membered chelate ring
with Oꢀ and N (azomethine) and a five-membered ring with S and
N (azomethine) in case of 1 but both the rings are six-membered in
Hg(II) (Table 1). The shielding is however less (ꢁ93 ppm) in case of
L6. For a d10 system such shieldings have been reported earlier as
well [12b–d].
In 13C{1H} NMR spectra of both 13 and 14, the signal of –CH3
carbon appears almost at the same position at which it appears
in L5 and L6, respectively. However, signal of CH2Te (C5) shows
deshielding of 14.37 and 13.14 ppm in the carbon-13 NMR spectra
of 13 and 14, respectively, in comparison to those of free ligands.
The signal of C4 also gets deshielded by 2.51 ppm in the spectra
of 13 and 2.03 ppm in the case of 14. These deshieldings in the po-
sition of signals of C4 and C5 on complex formation imply the for-
0
0
case of 2. The Pd–S bond length in 1 (2.2704(16) ÅA/2.2631(16) ÅA)
C12
C8
C7
C1
C11
C10
N1
C2
C13
C6
C14
C22
C18
O2
C9
C17
H1
C5
O1
C19
C15
C3
Te1
C4
C20
C16
C21
Fig. 3. ORTEP diagram of L6 with 50% probability ellipsoids.

3542
A. Kumar et al. / Journal of Organometallic Chemistry 693 (2008) 3533–3545
Table 4
0
C12A
N1A
Bond length (ÅA) and bond angle (°) of (1), (2), (3) and (7)
C9A
C14A
S1A
Bond length
Bond angle
C10A
C13A
1
Pd(1)–O(1A)
Pd(2)–O(1B)
Pd(1)–N(1A)
Pd(2)–N(1B)
Pd(1)–S(1A)
Pd(2)–S(1B)
Pd(1)–Cl(1A)
Pd(2)–Cl(1B)
S(1A)–C(15A)
S(1B)–C(15B)
S(1A)–C(14A)
S(1B)–C(14B)
O(1A)–C(1A)
O(1B)–C(1B)
N(1A)–C(11A)
N(1B)–C(11B)
N(1A)–C(13A)
N(1B)–C(13B)
1.982(4)
1.987(4)
2.019(5)
2.012(5)
2.2704(16)
2.2631(16)
2.3290(15)
2.3219(15)
1.807(6)
1.784(6)
1.817(7)
1.826(6)
1.298(6)
1.303(7)
1.295(8)
1.301(7)
1.486(7)
1.484(7)
O(1A)ꢀPd(1)ꢀN(1A)
O(1B)ꢀPd(2)ꢀN(1B)
O(1A)ꢀPd(1)ꢀS(1A)
O(1B)ꢀPd(2)ꢀS(1B)
N(1A)ꢀPd(1)ꢀS(1A)
N(1B)ꢀPd(2)ꢀS(1B)
O(1A)ꢀPd(1)ꢀCl(1A)
O(1B)ꢀPd(2)ꢀCl(1B)
N(1A)ꢀPd(1)ꢀCl(1A)
N(1B)ꢀ Pd(2)ꢀCl(1B)
S(1A)ꢀPd(1)ꢀCl(1A)
S(1B)ꢀPd(2)ꢀCl(1B)
C(15A)ꢀS(1A)ꢀC(14A)
C(15B)ꢀS(1B)ꢀC(14B)
C(15A)ꢀS(1A)ꢀPd(1)
C(15B)ꢀS(1B)ꢀPd(2)
C(14A)ꢀS(1A)ꢀPd(1)
C(14B)ꢀS(1B)ꢀPd(2)
C(1A)ꢀO(1A)ꢀPd(1)
C(1B)ꢀO(1B)ꢀPd(2)
C(11A)ꢀN(1A)ꢀC(13A)
C(11B)ꢀN(1B)ꢀC(13B)
C(11A)ꢀN(1A)ꢀPd(1)
C(11B)ꢀN(1B)ꢀPd(2)
C(13A)ꢀN(1A)ꢀPd(1)
C(13B)ꢀN(1B)ꢀPd(2)
O(1)–Pd(1)–N(1)
O(1)–Pd(1)–S(1)
N(1)–Pd(1)–S(1)
O(1)–Pd(1)–Cl(1)
N(1)–Pd(1)–Cl(1)
S(1)–Pd(1)–Cl(1)
C(20)–N(1)–C(1)
C(20)–N(1)–Pd(1)
C(1)–N(1)–Pd(1)
C(11)–O(1)–Pd(1)
C(4)–S(1)–C(3)
91.99(18)
91.92(18)
176.17(14)
177.25(13)
89.82(15)
89.29(14)
88.06(13)
88.85(13)
178.51(14)
178.65(13)
90.23(6)
89.99(6)
103.9(3)
102.7(3)
103.81(19)
106.9(2)
94.8(2)
C11A
C8A
C7A
C16A
C1A
Pd1
C6A
C15A
C20A
C2A
O1A
C1 7 A
C18A
C3A
C5A
Cl1A
C4A
C19A
Fig. 4. ORTEP diagram of 1 with 50% probability ellipsoids.
C21
96.0(2)
126.0(4)
124.5(3)
120.0(5)
120.6(5)
126.6(4)
125.7(4)
113.4(4)
113.7(4)
C1
C2
C20
N1
C19
C10
C11
C3
C4
C18
S1
O1
2
Pd(1)–O(1)
Pd(1)–N(1)
Pd(1)–S(1)
Pd(1)–Cl(1)
N(1)–C(20)
N(1)–C(1)
O(1)–C(11)
S(1)–C(4)
1.998(8)
2.015(10)
2.266(4)
2.309(4)
1.305(16)
1.495(16)
1.287(15)
1.792(14)
1.830(14)
87.5(4)
174.9(3)
97.5(3)
C17
Pd1
C9
C5
C6
C12
89.3(2)
C16
176.6(3)
85.67(14)
116.0(11)
121.5(8)
122.3(9)
115.2(8)
103.9(7)
106.4(5)
105.5(5)
C8
C13
Cl1
C7
C15
C14
S(1)–C(3)
Fig. 5. ORTEP diagram of 2 with 50% probability ellipsoids.
C(4)–S(1)–Pd(1)
C(3)–S(1)–Pd(1)
0
3
Pd(1)ꢀCl(1)
Pd(1)ꢀN(1)
Pd(1)ꢀO(1)
Pd(1)ꢀSe(1)
Se(1)ꢀC(14)
Se(1)ꢀC(15)
N(1)ꢀC(11)
N(1)ꢀC(13)
2.3156(9)
2.010(3)
1.973(2)
2.3600(5)
1.952(4)
1.935(4)
1.308(4)
1.488(5)
O(1)ꢀPd(1)ꢀN(1)
O(1)ꢀPd(1)ꢀCl(1)
N(1)ꢀPd(1)ꢀCl(1)
O(1)ꢀPd(1)ꢀSe(1)
N(1)ꢀPd(1)ꢀSe(1)
Cl(1)ꢀPd(1)ꢀSe(1)
C(15)ꢀSe(1)ꢀC(14)
C(15)ꢀSe(1)ꢀPd(1)
C(14)ꢀSe(1)ꢀPd(1)
C(11)ꢀN(1)ꢀPd(1)
C(13)ꢀN(1)ꢀPd(1)
C(1)ꢀO(1)ꢀPd(1)
N(1)–Pd(1)–O(1)
N(1)–Pd(1)–Cl(1)
O(1)–Pd(1)–Cl(1)
N(1)–Pd(1)–Te(1)
O(1)–Pd(1)–Te(1)
Cl(1)–Pd(1)–Te(1)
C(15)–Te(1)–C(14)
C(15)–Te(1)–Pd(1)
C(14)–Te(1)–Pd(1)
C(11)–N(1)–C(13)
C(11)–N(1)–Pd(1)
C(13)–N(1)–Pd(1)
C(1)–O(1)–Pd(1)
C(18)–O(2)–C(19)
92.57(11)
88.63(7)
178.78(9)
175.43(7)
90.49(9)
88.32(3)
100.19(16)
99.43(11)
91.64(12)
125.5(2)
114.8(2)
125.6(2)
and 2 (2.266(4) ÅA) are similar. The Pd–N bond lengths of 2.019(5)/
0
2.012(5) and 2.015(10) 0ÅA, respectively, in 1 and 2 are little higher
than that of 1.965(2) ÅA reported [16] for [PdCl{EtNHC(@S)NH–
N@CH–C6H4–2–Oꢀ}], but the Pd–O distances of 1.982(4)/1.987(4)
0
and 1.998(8) ÅA in
1 and 2, respectively, are comparable to
0
2.019(2) ÅA reported [16] for [PdCl{EtNHC(@S)NH–N@CH0–C6H4–2–
Oꢀ}]. The Pd–S bond distances, 2.2704(16)–2.2631(16) ÅA and Pd–
0
Cl bond distances, 2.3290(15)–2.309(4) ÅA of 1 and 2 are consistent
with the values [16] reported for [PdCl{EtNHC(@S)NH–N@CH–
0
0
C6H4–2–Oꢀ}] [Pd–S = 2.2456(9) ÅA and Pd–Cl = 2.3078(8) ÅA] and
[PdCl2{4–0MeOC6H4TeCH2CH2SEt}] [Pd–S = 2.268(4) and Pd–Cl
2.316(4) ÅA] [17]. The Pd–S bond0 distance observed in cis-
Pd(SNNMe2–S)(AsPh3)Cl2 (2.249(1) ÅA) [18] is also in agreement
6
Pd(1)–N(1)
Pd(1)–O(1)
Pd(1)–Cl(1)
Pd(1)–Te(1)
O(1)–C(1)
O(2)–C(18)
O(2)–C(19)
N(1)–C(11)
N(1)–C(13)
Te(1)–C(14)
Te(1)–C(15)
1.996(7)
2.061(6)
2.293(2)
2.5025(7)
1.311(11)
1.343(10)
1.430(11)
1.298(11)
1.488(10)
2.150(8)
2.133(9)
90.0(2)
177.0(2)
92.59(16)
89.2(2)
176.65(15)
88.30(6)
96.2(3)
with Pd–S bond distances of 1 and 2. In trans-[Pd(SCN)2[P(OPh)3]2]
0
the Pd–S bond length is reported [19] as 2.352 ÅA, longer than that
of 1 and 2, probably due to the trans influence of S. The metal–li-
gand bond lengths of 1 and 2 are also consistent with the sum of
102.3(2)
89.0(2)
the covalent radii for Pd–Cl, Pd–N, Pd–O and Pd–S (2.27, 2.03,
0
121.7(7)
123.9(6)
114.2(5)
114.9(5)
118.6(7)
2.01 and 2.30 ÅA, respectively).
The molecular structure of 3 is shown in Fig. 6. The selected bond
lengths and angles are given in Table 4. The ligand is coordinated with
Pd in a monoanionic tridentate (Se, N, Oꢀ) mode forming a six-mem-
bered chelate ring with Oꢀ and N (azomethine) and a five-membered
ring with Se and N (azomethine) around the central metal atom. The
0
Pd–Se, Pd–N, Pd–O and Pd–Cl bond distances, 2.3600(5) ÅA, 2.010(3),
0
0
1.973(2) and 2.3156(9) ÅA, respectively, of 3 are consistent with the
O = 2.017(4) and Pd–Cl = 2.323(2) ÅA] [14b]. The Pd–N, Pd–O and Pd–
earlier reports [14] for [PdCl{PhSe–(CH2)2–N@C(CH3)–C6H4–2–Oꢀ}]
Cl bond distances of 3 are also consistent with the earlier reports
0
0
0
0
[Pd–Se = 2.3669(11) ÅA, Pd–N = 2.003(7), Pd–O = 1.977(6) and Pd–
[Pd–N = 2.01(1) AÅ, Pd–O = 2.03(1) ÅA, Pd–Cl = 2.290(4) ÅA] on Pd(II)
0
Cl = 2.305(2) ÅA] and [PdCl{PhSe–(CH2)2–N@C(CH3)–C6H3-3-R-2–
complex of a tridentate ligand of (Te, N, Oꢀ) type [20]. The Pd–Se bond
0
0
Oꢀ}] [R = CH(CH2CH3)2; Pd–Se = 2.365(1) ÅA, Pd–N = 1.985(4), Pd–
length of complex 3, 2.3600(5) ÅA is shorter than those reported for

A. Kumar et al. / Journal of Organometallic Chemistry 693 (2008) 3533–3545
3543
Table 5
C14
Conversions (%) in Suzuki and Heck reactions
C13
N1
Substituents on reactants
Conversion (%)
C12
Se1
1
2
3
5
6
C20
C11
C2
R
Suzuki reaction
C3
OMe
H
NO2
25
45
80
10
20
70
15
40
85
10
25
82
10
40
75
C19
C18
C15
C16
C4
Pd1
Ar–X
Y
Heck reaction
C5
O1
C1
O2N
Cl
I
C6
C17
COOH
78
70
68
65
80
74
72
68
75
65
C10
Cl1
C7
COOH
COOH
C9
I
C8
Fig. 6. ORTEP diagram of 3 with 50% probability ellipsoids.
O2N
O2N
Cl
Br
I
35
75
78
30
25
68
60
32
38
78
70
35
30
70
65
30
32
75
75
32
C12
C9
C8
Ph
Ph
Ph
C10
C13
C7
N1
C11
C14
Te1
C6
I
C1
C2
C3
Pd1
C5
O1
C15
O2N
Br
C16
C18
C4
C17
O2
C21
Cl1
C20
0
with sum of their covalent radii 2.03, 2.01, 2.27, 2.44 and 2.64 ÅA,
respectively, the bonding between L3/L5 and Pd seems to be strong
in nature. The geometry around chalcogen atoms in 1, 2, 3 and 6 is
pyramidal.
C19
Fig. 7. ORTEP diagram of 6 with 50% probability ellipsoids.
It is interesting to note the effect on bond lengths/angles of
chalcogenated Schiff bases when they coordinate with metal ions.
The C(alkyl)–S–C(aryl) bond angle in L1 is 102.67(9)° and remains
almost unchanged on the formation of 1 (102.7(3)°/103.9(3)°).
Similarly is the case with L3 C(alkyl)–Se–C(aryl) bond angle is
99.23(15)° and becomes 100.19(16)° on the formation of 3. The
S–C(aryl) 0and S–C(alkyl) bond distances in L1 are 1.7648(19) and
1.801(2) ÅA, respectively, but on formation of 1, the distances for
0
[Pd(PEt3)2(SePh)(PO(OPh)2)] (2.518(9)0 ÅA) [21] and [Pd(Me2PCH2CH2-
PMe2)(Me) (SeC6H4-4-Cl)] (2.4483(8) ÅA) [22]. The possible reason for
shortening of Pd–Se bond in 3 may be the tridentate nature of ligand
L3 which makes two chelate rings and forces Se to bind with Pd(II)
some what strongly in comparison to those complexes in which sele-
nium ligand is monodentate one. Similar observation has been made
for (N, Se, Oꢀ) ligands earlier [14]. The bond angles at N are consistent
with their trigonal pyramidal geometry.
these bonds get increased to 1.807(6)/1.784(6) and 1.817(7)/
0
The ORTEP diagram of 6 given in Fig. 7 reveals its molecular
structure. The selected bond lengths and angles are given in Table
5. In this case also the ligand is coordinated with Pd in a monoan-
ionic tridentate (Te, N, Oꢀ) mode forming a six-membered chelate
ring with Oꢀ and N (azomethine) and a five-membered ring with
Te and N (azomethine) around the central metal atom. The lengths
of Pd–Te, Pd–N, Pd0–O and Pd–Cl bonds of 6, 2.5025(7), 1.996(7),
2.061(6), 2.293(2) ÅA, respectively, are consistent with the earlier
reports [20] for [PdCl{MeO–C6H4–Te–(CH2)2–N@C(CH3)–C6H4–2–
1.826(6) ÅA, respectively. Similarly, the Se–C(aryl) and Se–C(alkyl)
0
bond distances in L3 are 1.915(3) and 1.942(4) ÅA, respectively,
but on formation of 3, the distances for these bonds becomes
0
1.935(4) and 1.952(4) ÅA, respectively. Th0e ˜C@N– bond distances
in L1 and L3 are 1.304(2) and 1.314(4) ÅA, respectively. However,
these distances remains almost unchanged on complexation with
0
Pd(II) [1.295(8)/1.301(7) and 1.308(4) ÅA, respectively, in 01 and 3].
However, N–CH2 bond distance [1.467(2) and 1.472(4) ÅA, respec-
tively, in L1 and L3] gets slightly increased on the formation of 1
0
Oꢀ}] [Pd–Te = 2.504(1), Pd–N = 2.01(1), Pd–O = 2.03(1) and Pd–
and 3 and becomes 1.486(7)/1.484(7) and 1.488(5) ÅA, respectively.
0
0
Cl = 2.290(4) ÅA]. The Pd–Te bond length in the present complex
The O–C distances, 1.276(2) and 1.285(4) ÅA, respectively, for L1
0
2.5025(7) ÅA is shorter in comparison to earlier reports, 2.5873(2)
[23] in di[bis(2-{1,3-dioxan-2-yl}ethyl)telluride)dichloro palla-
dium(II) and 2.5865(2)–2.6052(2) [24] in di[N-{2-(4-methoxyphe-
nyltelluro)ethyl}morpholine]dichloropalladium(II) [PdCl2(OC4H8-
N–(CH2)2–Te–C6H4–p-OMe)2]. This appears due to combined effect
of tridentate nature of hybrid organotellurium ligand and the ab-
sence of strong trans influence in the present complex molecule.
On comparing Pd–N, Pd–O, Pd–Cl, Pd–Se and Pd–Te bond lengths
and L3 also get slightly increased on the formation of 1 and 3
0
and become 1.298(6)/1.303(7) and 1.303(4) ÅA, respectively.
3.7. Applications in Suzuki and Heck reactions
TheSuzukiand Heckreactionwere carriedout using complexes 1–
3, 5 and 6 as summarized in Scheme 2. The percentage conversions
were found up to 85 (Table 5). Heck reaction is among the most

3544
A. Kumar et al. / Journal of Organometallic Chemistry 693 (2008) 3533–3545
Complex
1/2/3/5/7
R
R
Br
+
(OH)2B
K2CO3, DMF/H2O, 24h, 100ºC
Ar
Complex
1/2/3/5/7
+
Ar
X
Na2CO3, DMF, N2 atm, 24h at 100ºC
Y
Y
Scheme 2.
powerful tools in organic synthesis for carbon–carbon bond forma-
tion. The complexes used as catalysts are based on phosphorus
ligands as well as involve phosphorus-free ligands. The improved
catalytic activity of transition metal complexes with hemilabile
ligands has been reported [25]. But many phosphine based catalysts
are often water- and air-sensitive. Therefore, catalysis under phos-
phine-free conditions is a challenge of high importance, and a num-
ber of Pd-complexes of phosphine-free ligands [26] have been
reported to exhibit promising catalytic activity for Heck reaction.
Recently Pd–Se bond containing complexes [27] have been found
very promising for Heck reaction. This has motivated us to examine
palladium(II) complexes 1–3, 5 and 6 of tridentate chalcogenated
Schiff bases [(N, O, E) type ligands, where E = S, Se or Te)]. The advan-
tage of using complexes of 1–3, 5 and 6 is that they are air stable and
also not moisture sensitive. Investigations on Pd(II) complexes of a
tellurated ligand for Heck reaction have been made for the first time.
A good selectivity for trans-products has been observed. The cata-
lytic activity depends on the halide, while electron-withdrawing
groups on the aryl ring increase the reaction rate. The reactivity de-
creases drastically in the order ArI > ArBr > ArCl. For Aryl bromides
(1 mmol) also, a very little amount (0.001 mmol) of complex was
sufficient to catalyze the Heck reaction.
‘n’ in the ligand backbone ˜C@N–(CH2)n–E changes from 2 to 3.
In Se-77 and Te-125 NMR spectra of Pd(II)/Pt(II) complexes shift
of signal relative to free ligand depends on the size of chelate ring
(five-membered > six-membered) The Pd–N, Pd–O, Pd–Cl, Pd–S,
Pd–Se and Pd–Te bond lengths observed in the crystal structures
of Pd-complexes of these Schiff bases are very close to the sum
of their covalent radii, indicating strong binding of uni-negative tri-
dentate ligands with Pd(II). The complexes of 1–3, 5 and 6 have
been found promising for homogeneous catalysis of Heck and Su-
zuki reactions. The advantage of using them is that they are air sta-
ble and also not moisture sensitive. A 1:1000 catalyst: aryl halide
molar ratio was found optimum for Heck as well as Suzuki
reactions.
Acknowledgements
Authors thank Department of Science and Technology (India)
for research Project No. SR/S1/IC–23/06 and for partial financial
assistance given to establish single-crystal X-ray diffraction facility
at IIT Delhi, New Delhi (India) under its FIST programme. A.K.
thanks Council of Scientific and Industrial Research (India) for
the award of Junior/Senior Research Fellowship.
Suzuki–Miyaura reaction, is also among the most important
palladium-catalyzed cross-coupling reactions of both academic
and industrial interest. [28–29]. In view of air and moisture sensi-
tivity of complexes of phosphorus ligands there is an interest in
phosphine-free ligands for the Suzuki–Miyaura reaction. Com-
plexes 1ꢀ3, 5 and 6 offer the advantage of stability under ambient
conditions for Suzuki–Miyaura reactions of aryl bromides with
phenylboronic acid which were carried out under aerobic condi-
tions at 100 °C for 24 h, using K2CO3 as base, without addition of
free ligand or any promoting additive and in the presence of a
small amount of water (ꢁone equivalent with respect to the sub-
strates). Homocoupling of phenylboronic acid to give unsubstitut-
ed biphenyl was negligible. The reaction was performed using a
1:1000 catalyst: aryl halide molar ratio. The catalytic activity de-
pended on the halide, while electron-withdrawing groups on the
aryl ring increased the reaction rate. The activity follows in the or-
der NO2 > H > OMe. The conversions were found up to 85%, partic-
ularly for activated 1-bromo-4-nitrobenzene the conversions were
usually about 80% or higher. The use of aryl chlorides as substrates
remains the goal in cross-coupling reactions due to their inexpen-
sive cost and convenient availability, but unfortunately, the oxida-
tive addition in these cases is difficult due to the comparatively
high C–Cl bond strength. Evaluation of palladium complexes of
tellurated Schiff base ligand in the Suzuki–Miyaura reaction has
also been made for the first time and results are promising. Thus
chalcogenated Schiff bases of 10-hydroxy-20-acetonaphthone
(HAN) may result in efficient catalysts for Suzuki–Miyaura cross-
coupling and Heck reactions.
Appendix A. Supplementary material
CCDC 685767, 685768, 685769, 685770, 685771, 661338 and
685772 contain supplementary crystallographic data for L1, L3,
L6, 1, 2, 3 and 7. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.a-
c.uk/data_request/cif. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.jorganchem.2008.07.024.
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