Synthesis, characterization and catalytic properties of novel palladium(II) complexes containing aromatic sulfonamides: Effective catalysts for the oxidation of benzyl alcohol

Article abstract of DOI:10.1002/aoc.2938

In this article, N-(2-aminophenyl)arylsulfonamides (1-5) were successfully synthesized by the reaction of o-phenylenediamine and various benzenesulfonyl chlorides. The Schiff base derivatives (1a-f; 4e) of those compounds were obtained using different ald

Full text of DOI:10.1002/aoc.2938

Full Paper
Received: 28 April 2012
Revised: 3 September 2012
Accepted: 24 September 2012
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/aoc.2938
Synthesis, characterization and catalytic
properties of novel palladium(II) complexes
containing aromatic sulfonamides: effective
catalysts for the oxidation of benzyl alcohol
Serkan Dayan and Nilgun Ozpozan Kalaycioglu*
In this article, N-(2-aminophenyl)arylsulfonamides (1–5) were successfully synthesized by the reaction of o-phenylenediamine
and various benzenesulfonyl chlorides. The Schiff base derivatives (1a–f; 4e) of those compounds were obtained using differ-
ent aldehydes. Then, a series of neutral-four coordinate Pd(II) complexes (6–10) were prepared from the reaction of Pd(OAc)2
and 1–5. On the other hand, when we tried to synthesize Pd(II) complexes containing Schiff base/sulfonamide ligands, two
different situations were observed. Generally, when an electron-donating group was attached to the imine fragment (1a–d)
except for 1f, the Schiff base hydrolyzed and 6 was isolated. When an electron-withdrawing group was attached to the imine
fragment (1e, 4e), neutral four-coordinate Pd(II) complexes (11–13) bearing Schiff base/sulfonamide ligands were isolated. The
synthesized compounds were characterized by FT-IR, elemental analysis and NMR spectroscopy. The complexes were used as a
catalyst in the oxidation reaction of benzyl alcohol to benzaldehyde in the presence of H5IO6 in acetonitrile. All complexes
showed satisfactory catalytic activity. The highest catalytic activity was obtained with 9. Copyright © 2012 John Wiley &
Sons, Ltd.
Supporting information may be found in the online version of this article.
Keywords: oxidation reaction; Pd(II) complexes; catalyst; aromatic sulfonamides; Schiff base
The catalytic properties of these materials were investigated for the
Introduction
aerobic oxidation of benzyl alcohol.[43]
In general, sulfonamides are obtained from the reaction of sulfonyl
chloride with primary or secondary amines in alkaline.[1]
Sulfonamides and their derivatives have attracted the interest
of many researchers’ owing to their importance in the development
of coordination chemistry, and their application in medicinal
chemistry, catalytic fields, etc.[2–18] For example, metal complexes
containing sulfonamide ligands have been used as catalysts in
various organic reactions.[19–32]
Herein, a series of Pd(II) complexes containing sulfonamide
ligands was synthesized and characterized by various spectro-
scopic techniques. The synthesized complexes (6–13) were used
as catalysts in the oxidation of benzyl alcohol to benzaldehyde.
Experimental
Materials and Methods
The catalytic oxidation of simple alcohols to aldehydes is a
fundamentally important laboratory and commercial procedure.[33]
There are many methods in the oxidation of alcohols, but most of
them are not preferred due to environmental contamination and
provide a by-product. Palladium-catalyzed oxidation of alcohols
has been attracting because of both environmental contamination
and the formation of a little by-product.[34] Moreover, the
palladium-catalyzed oxidation reaction was found dominated by
high activity and high selectivity under mild conditions.[35–39]
In recent times, high-activity ultra-fine Pd catalyst was
synthesized and used in solvent-free selective aerobic oxidation
All reagents and solvents were obtained from commercial suppli-
ers and used without any additional purification. NMR spectra
were recorded at 297 K on a Bruker 400 NMR spectrometer at
400 MHz (1H) and 100.56 MHz (13C). The NMR studies were carried
out in high-quality 5 mm NMR tubes. Signals are quoted in parts
per million as d downfield from tetramethylsilane (d 0.00) as an
internal standard. Coupling constants (J-values) are given in
hertz. NMR multiplicities are abbreviated as follows: br = broad,
s = singlet, d = doublet, t = triplet, m = multiplet signal. The C, H,
and N analyses were performed using a Truspec MICRO (LECO)
instrument. Infrared spectra were measured with a PerkinElmer
Spectrum 400 FT-IR system and recorded using a universal ATR
of toluene.[40]
A Pd(OAc)2/pyridine/K2CO3 system selectively
converted terpenic alcohols to respective aldehydes in the presence
of dioxygen.[41] A series of oligomeric methylsiloxane compounds
functionalized with pyridyl groups was synthesized and used as
ligands in the aerobic Pd(OAc)2-catalyzed oxidation of benzyl alcohol
to benzaldehyde at 80ꢀC.[42] The immobilization of palladium
complexes or nanoparticles in N-heterocyclic carbene (NHC)-modified
mesoporous SBA-15 materials was carried out by a post-grafting route.
*
Correspondence to: N. O. Kalaycioglu Department of Chemistry, Faculty of Science,
Erciyes University, Kayseri 38039, Turkey. E-mail: nozpozan@erciyes.edu.tr
Department of Chemistry, Faculty of Science, Erciyes University, Kayseri, 38039,
Turkey
Appl. Organometal. Chem. 2013, 27, 52–58
Copyright © 2012 John Wiley & Sons, Ltd.

Palladium(II) complexes containing aromatic sulfonamides
Compound 4
(attenuated total reflectance) sampling accessory within the
range 550–4000 cmꢁ1. Melting points were determined in open
capillary tubes on a digital Electrothermal 9100 melting point
apparatus. Gas chromatographic measurements for catalytic
experiments were performed using a Younglin Acme 6100 gas
chromatograph with a flame ionization detector and an Optima
5MS capillary column (The gas chromatographic parameters
were as follows: oven 80ꢀC (isothermal); carrier gas H2 (split ratio
15:1); flow rate: 4 ml minꢁ1; injector port temperature 220ꢀC;
detector temperature 280ꢀC; injection volume 6.0 ml).
Color light brown; yield 82%; m.p. 175–178ꢀC. 1H NMR (CDCl3,
d ppm): 3.77 (br., 2H, -NH2), 3.86 (s, 3H, -OCH3), 6.54–7.05
(m, 4H, -H1–4), 6.92 (d, 2H, J=8Hz, -Hb), 7.68 (d, 2H, J=8Hz, -Ha).
13C NMR (CDCl3, ppm); 55.6 (-OCH3), 114.1 (arom. -CH), 117.2
(arom. -CH), 118.7 (arom. -CH), 121.3 (arom. -CH), 128.7 (arom. -CH),
128.9 (arom. -CH), 129.7 (arom. -CH), 130.4 (arom. -CH), 144.4
(arom. -CH), 163.2 (arom. -CH). IR (cmꢁ1): 3465, 3369, 3239, 3075,
2979, 2947, 2846, 1615, 1593, 1576, 1496, 1462, 1439, 1415,
1383, 1323, 1302, 1259, 1214, 1193, 1183, 1153, 1112, 1090, 1008,
928, 897, 828, 801, 743, 727, 717, 684, 667, 643, 629, 605, 578,
555, 534.
General Procedure for the Synthesis of Compounds 1–5
N-(2-Aminophenyl)arylsulfonamides (1–5) were prepared
by modifying of the published procedure.[44]
Compound 5
A solution of arylsulfonyl chlorides (10 mmol) in THF (10 ml)
was added dropwise to a solution of triethylamine (20 mmol) in
THF (5 ml) in a Schlenk tube. After a few minutes, a THF (5 ml)
solution of o-phenylenediamine (10 mmol) was added slowly at
room temperature because the reaction is an exothermic
reaction, and the reaction continued for a period of 12 h. The
reaction mixture was then stirred and heated at 70ꢀC for 1 h
(in order to obtain a high yield), after which it was cooled and filtered.
The volatiles were removed under reduced pressure. The product
was recrystallized from chloroform–diethyl ether (15 ml, 1:3, v/v).
Color light-brown; yield 74%; m.p. 178–180ꢀC. 1H NMR (CDCl3,
d ppm): 0.94 (t, 3H, J= 8 Hz, -CH2CH2CH3), 1.66 (m, 2H, -CH2CH2CH3),
2.65 (t, 2H, J = 8 Hz, -CH2CH2CH3), 3.84 (br., 2H, -NH2), 6.47–7.67
(m, 8H, -H1-4 and -Ha–b).13C NMR (CDCl3, ppm); 13.9 (-CH2CH2CH3),
24.4 CH2CH2CH3), 38.1 (-CH2CH2CH3), 117.4 (arom. -CH), 118.9 (arom.
-CH), 121.5 (arom. -CH), 127.8 (arom. -CH), 128.8 (arom. -CH),
129.1 (arom. -CH), 129.3 (arom. -CH), 136.3 (arom. -CH), 144.6
(arom. -CH), 148.8 (arom. -CH). IR (cmꢁ1): 3445, 3364, 3235, 3036,
2961, 2928, 2867, 1622, 1597, 1505, 1495, 1465, 1409, 1376, 1325,
1313, 1250, 1213, 1184, 1159, 1116, 1089, 1033, 1019, 929, 902,
876, 843, 817, 804, 743, 733, 692, 666, 611, 593, 559, 533, 501.
Data for Compounds 1–5
Color light-brown; yield 92%; m.p. 170–172ꢀC. 1H NMR (CDCl3,
d ppm): 4.18 (br., 2 H, -NH2), 6.48 (d, 1H, J = 8 Hz, -H1), 6.56
(t, 2H, J=8Hz, -H3), 6.80 (d, 1H, J =8Hz, -H4), 7.06 (t, 1H, J=8Hz, -H2),
7.48 (t, 2H, J= 8 Hz, -Hb), 7.59 (t, 1H, J = 8 Hz, -Hc), 7.77
(d, 2H, J = 8 Hz, -Ha). 13C NMR (CDCl3, ppm): 117.6 (arom. -CH),
119.2 (arom. -CH), 121.4 (arom. -CH), 127.6 (arom. -CH), 128.6 (arom.
-CH), 129.0 (arom. -CH), 129.1 (arom. -CH), 132.1 (arom. -CH), 138.8
(arom. -CH), 143.6 (arom. -CH). IR (cmꢁ1): 3479, 3390, 3204, 3071,
2863, 2791, 2720, 1621, 1584, 1498, 1464, 1449, 1406, 1313, 1295,
1262, 1214, 1181, 1146, 1091, 1030, 1000, 971, 941, 911, 853, 754,
732, 716, 687, 666, 608, 558, 535, 477.
General Procedure for the Synthesis of Compounds 1a–f and 4e
A
solution of N-(2-aminophenyl)arylsulfonamides (10 mmol)
in methanol (10 ml) was added to solutions of aromatic
aldehydes (10 mmol) in methanol (5 ml) in a Schlenk tube. The
reaction mixture was stirred at room temperature for a period
of 24 h. The volatiles were removed under reduced pressure.
The residue was recrystallized from chloroform (5 ml)–diethyl
ether (10 ml).
Data for Compounds 1a–f and 4e
Compound 1a
Compound 2
Color light-brown; yield 86%; m.p. 120–123ꢀC. 1H NMR (CDCl3,
d ppm): 7.01–7.73 (m, 14H, -H1–4, -Ha–c and -Hx–z), 7.82 (s, 1H, -NH-),
8.21 (s, 1H, -N CH-). 13C NMR (CDCl3, ppm): 117.0 (arom. -CH), 121.2
(arom. -CH), 125.5 (arom. -CH), 127.1 (arom. -CH), 127.5 (arom. -CH),
127.7 (arom. -CH), 128.5 (arom. -CH), 128.7 (arom. -CH), 128.9
(arom. -CH), 129.0 (arom. -CH), 132.1 (arom. -CH), 132.8 (arom. -CH),
135.5 (arom. -CH), 140.9 (arom. -CH), 159.7 (-N CH-). IR (cmꢁ1): 3227,
3057, 3030, 2964, 2886, 1619, 1596, 1577, 1498, 1483, 1448, 1406,
1383, 1371, 1336, 1323, 1313, 1292, 1273, 1211, 1169, 1158, 1091,
1072, 1047, 1027, 999, 989, 967, 940, 918, 880, 856, 846, 835, 812,
757, 729, 685.
Color yellow; yield 75%; m.p. 180–182ꢀC. 1H NMR (CDCl3, d ppm):
4.03 (br., 2H, -NH2), 6.46–7.10 (m, 4H, -H1–4), 7.95 (d, 2H, J = 8 Hz, -Ha),
8.32 (d, 2H, J = 8 Hz, -Hb), 13C NMR (CDCl3, ppm): 117.4 (arom. -CH),
118.8 (arom. -CH), 124.2 (arom. -CH), 124.3 (arom. -CH), 128.5
(arom. -CH), 129.0 (arom. -CH), 129.6 (arom. -CH), 130.5
(arom. -CH), 144.7 (arom. -CH), 170.9 (arom. -CH). IR (cmꢁ1):
3469, 3380, 3240, 3122, 3105, 3036, 3859, 1615, 1517, 1498, 1475,
1463, 1399, 1378, 1369, 1348, 1332, 1310, 1253, 1207, 1162, 1107,
1087, 1030, 1009, 975, 960, 948, 934, 904, 853, 846, 817, 790, 739, 678.
Compound 3
Color yellow; yield 85%; m.p. 180–182ꢀC. 1H NMR (CDCl3, d ppm):
1.33 (s, 9H, -C(CH3)3), 3.69 (br., 2H, -NH2), 6.51–7.05 (m, 4H, -H1-4),
7.47 (d, 2H, J = 8 Hz, -Hb); 7.68 (d, 2H, J = 8 Hz, -Ha).13C NMR
(CDCl3, ppm): 31.1 (-C(CH3)3), 35.2 (-C(CH3)3), 117.1 (arom. -CH),
118.6 (arom. -CH), 121.2 (arom. -CH), 126.0 (arom. -CH), 127.4
(arom. -CH), 128.5 (arom. -CH), 128.9 (arom. -CH), 135.9 (arom. -CH),
144.4 (arom. -CH), 156.9 (arom. -CH). IR (cmꢁ1): 3465, 3386, 3066,
3039, 2960, 2908, 2868, 2792, 1623, 1596, 1500, 1463, 1405, 1368,
1362, 1322, 1293, 1267, 1258, 1215, 1197, 1153, 1111, 1087, 1030,
1015, 943, 915, 852, 831, 755, 734, 661, 624, 572, 547, 517, 472.
Compound 1b
Color light-yellow; yield 80%; m.p. 145–146ꢀC. 1H NMR (CDCl3,
d ppm): 2.47 (s, 3H, -CH3), 7.01–7.73 (m, 13H, -H1–4, -Ha–c and -Hx–y),
7.82 (s, 1H, -NH-), 8.16 (s, 1H, -N CH-). 13C NMR (CDCl3, ppm): 21.7
(-CH3), 117.0 (arom. -CH), 125.4 (arom. -CH), 127.1 (arom. -CH), 127.5
(arom. -CH), 128.7 (arom. -CH), 129.1 (arom. -CH), 129.7 (arom. -CH),
129.7 (arom. -CH), 129.9 (arom. -CH), 132.0 (arom. -CH), 132.7
(arom. -CH), 139.1 (arom. -CH), 159.6 (-N CH-). IR (cmꢁ1):
3230, 3072, 3060, 3029, 2887, 1620, 1606, 1588, 1567,
Appl. Organometal. Chem. 2013, 27, 52–58
Copyright © 2012 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

S. Dayan and N. O. Kalaycioglu
1511, 1484, 1446, 1390, 1332, 1310, 1291, 1280, 1214, 1168,
1094, 1042, 970, 921, 881, 842, 815, 771, 754, 726, 691, 665.
7.65 (s, 1H, -NH-), 7.98 (d, 2H, J = 8 Hz, -Ha); 7.12–8.35 (m, 8H, H1–4
and -Hx–y), 8.37 (s, 1H, -N CH-).13C NMR (CDCl3, ppm); 55.5 (-OCH3),
114.0 (arom. -CH), 116.9 (arom. -CH), 121.4 (arom. -CH), 124.2
(arom. -CH), 125.3 (arom. -CH), 127.4 (arom. -CH), 129.0 (arom. -CH),
129.3 (arom. -CH), 129.6 (arom. -CH), 130.7 (arom. -CH), 132.9
(arom. -CH), 139.7 (arom. -CH), 140.7 (arom. -CH), 149.5 (arom. -CH),
156.5 (-N CH-). IR (cmꢁ1): 3219, 3070, 3001, 2944, 2894, 2838, 1628,
1593, 1575, 1520, 1495, 1484, 1464, 1454, 1437, 1415, 1392, 1341,
1331, 1304, 1278, 1258, 1214, 1161, 1157, 1105, 1092, 1026, 1010,
986, 969, 950, 916, 886, 869, 855, 838, 800, 764, 752, 738, 722, 710,
688, 680, 648, 623, 612, 587, 571, 553, 538, 505, 490, 467.
Compound 1c
Color light-yellow; yield 85%; m.p. 130–132ꢀC. 1H NMR (CDCl3,
d ppm): 2.41 (s, 3H, -(CH3)p), 2.50 (s, 3H, -(CH3)o), 6.99–7.79
(m, 12H, H1–4, -Ha–c, and -Hx–y), 7.84 (s, 1H, -NH-), 8.45 (s, 1H, -
N CH-). 13C NMR (CDCl3, ppm): 19.6 (- (CH3)p), 21.6 (- (CH3)o),
117.0 (arom. -CH), 121.0 (arom. -CH), 125.4 (arom. -CH), 127.1
(arom. -CH), 127.2 (arom. -CH), 127.4 (arom. -CH), 127.4 (arom. -CH),
127.6 (arom. -CH), 128.5 (arom. -CH), 128.7 (arom. -CH), 129.0
(arom. -CH), 132.0 (arom. -CH), 132.7 (arom. -CH), 138.9 (arom. -CH),
158.5 (-N CH-). IR (cmꢁ1): 3225, 3066, 3002, 2921, 1623, 1606,
1583, 1498, 1482, 1463, 1446, 1405, 1395, 1372, 1322, 1313, 1295,
1274, 1251, 1230, 1213, 1170, 1150, 1113, 1089, 1037, 1000, 938,
912, 871, 847, 825, 801, 753, 729, 686, 672.
General Procedure for the Synthesis of Compounds 6–10
A solution of 1–5 (0.50 mmol) in DMSO (2 ml) was added to a
solution of Pd(OAc)2 (0.25 mmol) in DMSO(2 ml) in a Schlenk
tube. The reaction mixture was stirred and heated at 70ꢀC for
12 h, and then cooled. The volatiles were removed under reduced
pressure. The residue was washed with diethyl ether (20 ml) and
dried under vacuum.
Compound 1d
Color light yellow; yield 92%; m.p. 145–148ꢀC. 1H NMR
(CDCl3, d ppm): 2.35 (s, 3H, -(CH3)p), 2.50 (s, 6H, - (CH3)o,m), 6.96
(s, 2H, -Hy) 7.02–7.76 (m, 9H, -H1–4 and -Ha–c), 7.84 (s, 1H, -NH-),
8.71 (s, 1H, -N CH-). 13C NMR (CDCl3, ppm): 21.3 (- (CH3)p), 21.7
(- (CH3)o), 116.6 (arom. -CH), 119.9 (arom. -CH), 125.1 (arom. -CH),
127.1 (arom. -CH), 127.4 (arom. -CH), 127.7 (arom. -CH), 128.8
(arom. -CH), 129.1 (arom. -CH), 129.4 (arom. -CH), 130.3 (arom. -CH),
132.1 (arom. -CH), 132.8 (arom. -CH), 139.3 (arom. -CH), 141.0
(arom. -CH), 160.1 (-N CH-). IR (cmꢁ1): 3254, 3065, 2970, 2952, 2910,
2848, 1621, 1607, 1586, 1562, 1488, 1461, 1449, 1433, 1404, 1390,
1379, 1329, 1312, 1278, 1210, 1165, 1152, 1090, 1074, 1037, 1027,
998, 979, 9441, 914, 853, 829, 755, 743, 718, 687, 667, 654, 603, 580,
566, 551, 540, 519, 500, 473, 458.
Data for Compounds 6–10
Compound 6
Color brown; yield 73%; m.p. 300–301ꢀC (dec.). 1H NMR (DMSO-d6,
d ppm): 6.55 (s, 4H, -NH2), 6.68–6.74 (m, 2H, -H1,3), 6.90 (t, 2H,
J = 8 Hz, -H2), 7.03 (d, 2H, J = 8 Hz, -H4), 7.41–7.96 (m, 10H, -Hx–z),
13C NMR (DMSO-d6, ppm): 115.2 (arom. -CH), 121.5 (arom. -CH),
127.2 (arom. -CH), 129.2 (arom. -CH), 129.5 (arom. -CH), 130.0
(arom. -CH), 130.2 (arom. -CH), 133.1 (arom. -CH), 135.7 (arom. -CH),
143.5 (arom. -CH). IR (cmꢁ1): 3228, 3217, 2987, 2906, 2838, 2799,
1616, 1575, 1488, 1455, 1445, 1429, 1414, 1399, 1299, 1264, 1242,
1165, 1155, 1121, 1107, 1080, 1039, 1023, 948, 926, 893, 866, 847,
817, 775, 753, 718, 688, 652, 624, 584, 556.
Compound 1e
1
Color yellow; yield 72%; m.p. 225–227ꢀ. H NMR (CDCl3, d ppm):
7.10–7.79 (m, 9H, -H1–4 and -Ha–c), 7.81 (s, 1H, -NH-), 7.97 (d, 2H,
J = 8 Hz, -Hx), 8.35 (d, 2H, J = 8 Hz, -Hy), 8.36 (s, 1H, -N CH-). 13C
NMR (CDCl3, ppm): 116.8 (arom. -CH), 121.4 (arom. -CH), 124.2
(arom. -CH), 125.5 (arom. -CH), 127.1 (arom. -CH), 127.2
(arom. -CH), 127.4 (arom. -CH), 127.7 (arom. -CH), 128.8 (arom. -CH),
128.9 (arom. -CH), 129.0 (arom. -CH), 129.6 (arom. -CH), 132.9
(arom. -CH), 133.2 (arom. -CH), 156.7 (-N CH-). IR (cmꢁ1): 3287, 3103,
3077, 3055, 2841, 1623, 1590, 1507, 1494, 1484, 1462, 1447, 1378,
1338, 1313, 1288, 1277, 1209, 1182, 1154, 1104, 1090, 1076, 1047,
1025, 1014, 1000, 977, 956, 923, 885, 850, 825, 757, 728, 716, 693,
685, 626, 583, 559, 534, 512, 501, 460.
Compound 7
1
Color brown; yield 68%; m.p. >350ꢀC (dec.). H NMR (DMSO-d6,
d ppm): 6.53 (s, 4H, -NH2), 6.78–7.59 (m, 8H, -H1–4), 8,14 (d, 4H,
J = 12 Hz, -Hb), 8,33 (d, 4H, J = 8 Hz, -Ha). 13C NMR (DMSO-d6, ppm):
121.8 (arom. -CH), 122.5 (arom. -CH), 124.6 (arom. -CH), 126.5
(arom. -CH), 127.1 (arom. -CH), 128.4 (arom. -CH), 136.7
(arom. -CH), 146.9 (arom. -CH), 149.3 (arom. -CH), 149.4 (arom. -CH).
IR (cmꢁ1): 3253, 3184, 3099, 3074, 3034, 3867, 2795, 1605,
1581, 1522, 1489, 1452, 1430, 1400, 1349, 1312, 1297, 1280, 1258,
1243, 1196, 1151, 1122, 1109, 1085, 1030, 1015, 966, 950, 931,
846, 824, 790, 752, 744, 733, 702, 686, 648, 631, 622, 599, 561, 536,
493, 461.
Compound 1f
Color light-yellow; yield 88%; m.p. 120–123ꢀC. 1H NMR (CDCl3,
d ppm): 3.92 (s, 3H, -OCH3), 7.73 (s, 1H, -NH-), 7.00–7.80 (m, 13H,
H1–4, -Ha–c and -Hx–y), 8.10 (s, 1H, -N CH-). 13C NMR (CDCl3, ppm):
55.5 (-OCH3); 114.4 (arom. -CH), 117.0 (arom. -CH), 121.5
(arom. -CH), 125.5 (arom. -CH), 127.1 (arom. -CH), 127.3 (arom. -CH),
127.6 (arom. -CH), 128.5 (arom. -CH), 128.7 (arom. -CH), 129.0
(arom. -CH), 131.1 (arom. -CH), 131.9 (arom. -CH), 132.7 (arom. -CH),
139.2 (arom. -CH), 159.2 (-N CH-). IR (cmꢁ1): 3208, 3065, 2997, 2961,
2836, 1619, 1608, 1591, 1572, 1511, 1499, 1485, 1464, 1448, 1424,
1406, 1386, 1314, 1295, 1276, 1246, 1214, 1149, 1111, 1092, 1034,
1000, 974, 943, 914, 883, 831, 803, 756, 733, 688, 666.
Compound 8
1
Color brown; yield 70%; m.p. 315–316ꢀC (dec.). H NMR (DMSO-
d6, d ppm): 1.27 (s, 18H, -C(CH3)3), 6.63 (s, 4H, -NH2), 6.72–6.78
(m, 4, -H1,3), 6.94 (t, 2H, J = 8 Hz, -H2), 7.08 (d, 2H, J = 8 Hz, -H4),
7.50 (d, 4H, J = 8 Hz, -Hb), 7.94 (d, 2H, J = 8 Hz, -Ha). 13C NMR
(DMSO-d6, ppm): 29.1 (-C(CH3)3), 31.3 (-C(CH3)3), 116.1 (arom. -CH),
118.5 (arom. -CH), 122.7 (arom. -CH), 126.0 (arom. -CH), 127.2
(arom. -CH), 128.1 (arom. -CH), 129.0 (arom. -CH), 135.5
(arom. -CH), 143.8 (arom. -CH), 154.6 (arom. -CH). IR (cmꢁ1): 3241,
3188, 3158, 3111, 2969, 2958, 2869, 1611, 1595, 1573, 1516, 1486,
1463, 1452, 1396, 1361, 1301, 1284, 1262, 1238, 1192, 1161, 1138,
1107, 1097, 1080, 1035, 1015, 979, 954, 849, 828, 813, 774, 750,
735, 704, 652, 633, 615, 573, 566, 552, 537.
Compound 4e
Color light-yellow; yield 79%; m.p. 183–185ꢀC. 1H NMR
(CDCl3, d ppm): 3.75 (s, 3H, -OCH3), 6.75 (d, 2H, J = 8 Hz, -Hb),
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Copyright © 2012 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2013, 27, 52–58

Palladium(II) complexes containing aromatic sulfonamides
Compound 9
Compound 13
1
Color brown; yield 74%; m.p. 270–272ꢀC (dec.). H NMR (DMSO-d6,
Color dark-red; yield 68%; m.p. 265–266ꢀC (dec.). 1H NMR (CDCl3,
d ppm): 3.74 (s, 6H, -OCH3), 6.85 (d, 4H, J = 8 Hz, -Hb); 7.83 (d, 4H,
J = 8 Hz, -Ha), 7.09–8.92 (m, 16H, -H1–4 and -Hx–y), 8.48 (s, 2H,
-N CH-).13C NMR (CDCl3, ppm); 55.6 (-OCH3), 113.3 (arom. -CH),
117.9 (arom. -CH), 121.2 (arom. -CH), 124.7 (arom. -CH), 125.7
(arom. -CH), 127.5 (arom. -CH), 128.3 (arom. -CH), 129.6 (arom. -CH),
129.8 (arom. -CH), 131.1 (arom. -CH), 134.2 (arom. -CH), 141.1
(arom. -CH), 141.6 (arom. -CH), 150.5 (arom. -CH), 159.8 (-N CH-). IR
(cmꢁ1): 3070, 3011, 2970, 2912, 2837, 1593, 1578, 1516, 1495, 1454,
1339, 1304, 1249, 1152, 1119, 1087, 1020, 1001, 949, 853, 829, 801,
745, 715, 681, 667, 629, 551, 489, 477, 452.
d ppm): 3.79 (s, 6H, -OCH3), 6.58 (s, 4H, -NH2), 7.45 (d, 4H, J=8Hz, -Hb),
7.91 (d, 4H, J = 8 Hz, -Ha), 6.71–7.06 (m, 8H, -H1-4).13C NMR
(DMSO-d6, ppm): 56.0 (-OCH3), 114.3 (arom. -CH), 121.2 (arom. -CH),
121.4 (arom. -CH), 126.2 (arom. -CH), 127.0 (arom. -CH), 129.2
(arom. -CH), 135.4 (arom. -CH), 135.7 (arom. -CH), 147.8 (arom. -CH),
161.9 (arom. -CH). IR (cmꢁ1): 3247, 3228, 3196, 3155, 3129, 2975,
2947, 2846, 1616, 1592, 1574, 1496, 1484, 1448, 1410, 1308, 1284,
1259, 1237, 1197, 1185, 1176, 1155, 1137, 1112, 1101, 1081, 1034,
1020, 946, 869, 838, 810, 800, 770, 718, 670, 649, 628, 617, 571, 554,
538, 520, 486, 457.
Compound 10
Catalytic Experiments
1
Color brown; yield 81%; m.p. 275–277ꢀC (dec.). H NMR (CDCl3,
In a typical oxidation reaction, a Schlenk tube was charged with a
solvent solution of alcohol, oxidant and complex. This mixture
was stirred at 70ꢀC for an appropriate time. After completion of
the reaction, the mixture was cooled to room temperature and
the products extracted with diethyl ether (10 ml); they were then
filtered through a pad of silica gel with copious washing and the
removed volatiles were concentrated. Reactions were monitored
by gas chromatography (GC) and thin-layer chromatography.
d ppm): 0.87 (t, 6H, J = 8 Hz, -CH2CH2CH3), 1.58 (m, 4H, -CH2CH2CH3),
2.59 (t, 4H, J = 8 Hz, -CH2CH2CH3), 6.59 (s, 4H, -NH2), 6.69–7.97
(m, 16H, -H1–4 and -Ha–b).13C NMR (CDCl3, ppm): 13.7 (-CH2CH2CH3),
23.7 (-CH2CH2CH3), 37.0 (-CH2CH2CH3), 120.6 (arom. -CH), 120.9
(arom. -CH), 125.7 (arom. -CH), 126.6 (arom. -CH), 126.8 (arom. -CH),
128.6 (arom. -CH), 135.1 (arom. -CH), 140.5 (arom. -CH), 145.8
(arom. -CH), 147.3 (arom. -CH). IR (cmꢁ1): 3244, 3183, 3150, 3095,
2954, 2927, 2867, 1610, 1596, 1573, 1488, 1454, 1406, 1379, 1302,
1288, 1261, 1239, 1207, 1140, 1105, 1080, 1037, 1017, 977, 950,
861, 849, 799, 772, 745, 705, 679, 647, 624, 583, 558, 516.
Results and Discussion
General Procedure for the Synthesis of Compounds 11–13
N-(2-Aminophenyl)arylsulfonamides, their Schiff base derivatives
and novel Pd(II) complexes were successfully synthesized (Fig. 1). The
synthesized compounds were characterized by elemental analysis,
1H-NMR, 13C NMR and IR spectroscopy.
Compounds 1–5 were obtained by the reaction of o-phenylene-
diamine with R-arylsulfonyl chloride in the presence of triethyla-
mine in THF. Benzensulfonyl chloride, p-nitrobenzenesulfonyl
chloride, p-isobutyl-benzenesulfonyl chloride, p-methoxyben-
zenesulfonyl chloride and 4-n-propylbenzenesulfonyl chloride
compounds were used as R-arylsulfonyl chloride. Then, the novel
Pd(II) complexes (6–10) were synthesized by the reaction of 1–5
with Pd(OAc)2 in DMSO.
A solution of 1a–f and 4e (0.50 mmol) in DMSO (2 ml) was added
to a solution of Pd(OAc)2 (0.25 mmol) in DMSO (2 ml) in a reaction
flask. The reaction mixtures were stirred and heated at 70ꢀC for
72 h and then cooled. The volatiles were removed under reduced
pressure. The residues were washed with diethyl ether (30 ml)
and dried under vacuum.
Data for Compounds 11–13
Compound 11
Color dark-red; yield 72%; m.p. 281–282ꢀC (dec.). 1H NMR (CDCl3,
d ppm): 6.64–7.71 (m, 18H, H1–4 and -Ha–c), 7.70 (d, 4H, J = 8 Hz, -Hx),
7.90 (d, 4H, J = 8 Hz, -Hy), 8.78 (s, 2H, -N CH-). 13C NMR (CDCl3, ppm):
118.1 (arom. -CH), 121.7 (arom. -CH), 123.3 (arom. -CH), 126.2
(arom. -CH), 127.1 (arom. -CH), 127.4 (arom. -CH), 127.6 (arom. -CH),
128.1 (arom. -CH), 129.5 (arom. -CH), 129.7 (arom. -CH), 131.7
(arom. -CH), 132.0 (arom. -CH), 133.5 (arom. -CH), 137.6 (arom. -CH),
165.6 (-N CH-). IR (cmꢁ1): 3093, 3065, 1621, 1595, 1571, 1509, 1489,
1477, 1445, 1334, 1306, 1287, 1266, 1236, 1218, 1157, 1118, 1080,
1048, 999, 954, 918, 872, 851, 827, 809, 749, 730, 719, 702, 686,
641, 629, 586, 567, 556, 547, 516, 475.
On the other hand, 1a–f and 4e were synthesized by the
reaction of R0-benzaldehyde with appropriate N-(2-aminophenyl)
arylsulfonamides in methanol. Benzaldehyde, 4-methylbenzal-
dehyde, 2,4-dimethylbenzaldehyde, 2,4,6-trimethylbenzaldehyde,
4-nitrobenzaldehyde and 4-methoxybenzaldehyde were used as
R0-benzaldehyde. Then, we studied to synthesis of Pd(II) complexes
of those ligands (1a–f, 4e). Two different situations occurred from
the reaction of 1a-f and 4e with Pd(OAc)2. In the first, when 1a–d
were used as ligands, they were hydrolyzed and the Pd(II) complex
(6) of N-(2-aminophenyl)benzenesulfonamide was obtained. This
situation is considered to be caused by water molecules from the
solvent.[45a,b] In the second, when 1e–f, 4e were used as ligands,
the Pd(II) complexes (11–13) containing Schiff base ligands were
obtained. The formation of these two different situations is related
to the electronic parameters.
Satisfactory elemental analysis was obtained for all compounds
(Table 1). The structure of all the compounds was determined on
the basis of FT-IR and NMR spectroscopy. From the 1H NMR spectra,
the formation of compounds (1–13) could clearly be seen.
In the 1H NMR spectra, the -Ha, -Hb and -Hc protons were
observed as doublets, triplets and triplets, respectively, in a 2:2:1
ratio around d 7.43–7.81 ppm in N-(2-aminophenyl)benzene-
sulfonamide (1). Similarly, other N-(2-aminophenyl)arylsulfonamide
Compound 12
Color dark-red; yield 78%; m.p. 275–277ꢀC (dec.). 1H-NMR (CDCl3,
d ppm): 3.90 (s, 6H, -OCH3), 7.00–7.95 (m, 26H, H1–4, -Ha-c and -Hx,y),
9.89 (s, 2H, -N CH-). 13C NMR (CDCl3, ppm): 55.6 (-OCH3), 114.3
(arom. -CH), 126.1 (arom. -CH), 126.7 (arom. -CH), 127.1 (arom. -CH),
127.3 (arom. -CH), 128.4 (arom. -CH), 128.9 (arom. -CH), 129.2
(arom. -CH), 130.0 (arom. -CH), 130.3 (arom. -CH), 131.8 (arom. -CH),
132.0 (arom. -CH), 132.7 (arom. -CH), 137.1 (arom. -CH), 164.9
(-N CH-). IR (cmꢁ1): 3054, 2996, 2935, 2909, 2834, 1578, 1539, 1509,
1468, 1444, 1430, 1330, 1307, 1265, 1231, 1155, 1121, 1108, 1080,
1015, 949, 926, 848, 751, 718, 687, 652, 624, 610, 583, 555, 478.
Appl. Organometal. Chem. 2013, 27, 52–58
Copyright © 2012 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

S. Dayan and N. O. Kalaycioglu
R
NH2
NH2
O
S
Cl
O
N(C2H5)3
-N(C2H5)3.HCl
THF, 25oC, 12 h.
RI
R
O
H
Pd(OAc)2
N
S
O
O
NH2
25oC, 12 h.
MeOH
1-5
70 oC, 12 h.
DMSO
-AcOH
RI
-H
R
a
b
c
1
2
-H
-4-Me
-4-NO2
-4- tBu
R
-2,4-(Me)2
O
S
3
4
5
H
N
d
e
f
-2,4,6-(Me)3
-4-NO2
-4-OCH3
R
-4- n
Pr
O
-4-OCH3
Pd(OAc)2
N
O
S
N
O
c
if 1e, 1f, 4e
70 oC, 72 h.
DMSO
-AcOH
H2N
RI
b
a
R
Pd
or cis-Pd complex
RI
1a-1f, 4e
NH2
N
S
O
S
N
O
O
O
1
N
2
Pd
or cis-Pd complex
if 1a-1d
3
R
70 oC, 72 h.
DMSO
N
N
S
4
x
O
O
-AcOH
6-10
y
R
z
6
RI
11-13
Figure 1. Synthesis of the compounds together with NMR numbering scheme.
Table 1. Analytical data for the synthesized compounds
Compound
No.
C (%)
H (%)
N (%)
S (%)
Calc.
Calc.
Found
Calc.
Found
Calc.
Found
Found
(C12H12N2O2S)
(C12H11N3O4S)
(C16H20N2O2S)
(C13H14N2O3S)
(C15H18N2O2S)
(C19H16N2O2S)
(C20H18N2O2S)
(C21H20N2O2S)
(C22H22N2O2S)
(C19H15N3O4S)
(C20H18N2O3S)
(C20H17N3O5S)
Pd[C12H11N2O2S]2
Pd[C12H10N3O4S]2
Pd[C16H19N2O2S]2
Pd[C13H13N2O3S]2
Pd[C15H17N2O2S]2
Pd[C19H14N3O4S]2
Pd[C20H17N2O3S]2
Pd[C20H16N3O5S]2
1
2
58.05
49.14
63.13
56.10
62.04
67.84
68.55
69.20
69.81
59.83
65.55
58.38
47.96
41.72
53.89
47.24
52.59
52.63
57.38
51.81
57.13
49.20
63.15
56.13
62.07
67.90
68.53
69.22
69.84
59.80
65.40
58.43
48.02
41.81
53.83
47.31
52.50
52.70
57.45
51.85
4.87
3.78
6.62
5.07
6.25
4.79
5.18
5.53
5.86
3.96
4.95
4.16
3.69
2.92
5.37
3.96
5.00
3.25
4.09
3.48
4.91
3.72
6.59
5.11
6.22
4.85
5.20
5.50
5.90
4.01
4.85
4.18
3.76
3.00
5.43
3.92
4.92
3.28
4.12
3.50
11.28
14.33
9.20
10.06
9.65
8.33
7.99
7.69
7.40
11.02
7.64
10.21
9.32
12.16
7.86
8.48
8.18
9.69
6.69
9.06
11.25
14.30
9.24
10.05
9.64
8.30
7.98
7.72
7.41
11.03
7.70
10.20
9.38
12.20
7.90
8.50
8.16
9.70
6.75
9.10
12.91
10.93
10.53
11.52
11.04
9.53
9.15
8.80
8.47
8.41
8.75
7.79
10.67
9.28
8.99
9.70
9.36
7.39
7.66
6.92
12.90
10.95
10.48
11.57
11.06
9.55
9.17
8.84
8.50
8.45
8.81
7.82
10.74
9.28
8.93
9.73
9.40
7.44
7.62
6.85
3
4
5
1a
1b
1c
1d
1e
1f
4e
6
7
8
9
10
11
12
13
ligands (2–5), the -Ha and -Hb protons were observed as doublets
in a 2:2 ratio around d 6.92–8.32 ppm. -NH2 protons were found
at around d 3.69–4.18 ppm in compounds 1–5. In (c) position,
the -p-C(CH3)3, -p-OCH3 and -CH2CH2CH3 protons were observed
as singlet in 9 proton eq. at d 1.33 ppm for compound 3, singlet
in 3 proton eq. at d 3.86 ppm for compound 4, triplet, and
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Copyright © 2012 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2013, 27, 52–58

Palladium(II) complexes containing aromatic sulfonamides
multiplet and quartet in a 2:2:3 ratio at round d 0.94–2.65 ppm for
compound 5, respectively. In the 13C NMR spectra for 3–5, the -C
(CH3)3, -OCH3 and -CH2CH2CH3 carbons were found at 35.2, 31.1,
55.6, 38.1, 24.4 and 13.9ppm, respectively. In the 1H NMR spectra
1 mmol benzyl alcohol and 1 mmol H5IO6 in acetonitrile (5 ml) at 70ꢀC
led to the best conversions at 120 min. Under these conditions, benz-
aldehyde was observed as a single product. The reactions were per-
formed under identical conditions to allow comparison of results.
All the complexes showed good activity as catalysts.
1
for 6–10, the H NMR signals shifted to lower field for the -NH2
protons compared with free ligands (1–5) and were found around
d 6.53–6.63 ppm.
In the H NMR spectra for the Schiff base ligands (1a–f and 4e);
The catalytic experiments showed that complex 9 was a more
active catalyst than 6–8 or 10. This situation was observed to be
associated with electron-donating properties of the R-group. At
the same time, complex 7 bearing a nitro group was observed
to be more active compared to complex 6: 9 > 8 > 10 > 7 > 6.
On the other hand, complex 11, containing nitro group (elec-
tron-withdrawing) at the 4- position of -N CH-R0, showed better
activity compared to complex 12. Therefore, Schiff base deriva-
1
the -NH- protons were observed around d 7.65–7.84 ppm. Similarly,
-N CH- proton peaks appeared around d 8.10–8.71 ppm. In the
13C NMR spectra for the Schiff base ligands (1a–f and 4e),
the -N CH- carbons were observed around 156.5–160.1 ppm. In the
1H NMR spectra of Pd(II) complexes (11–13) bearing Schiff base
ligands, the -NH- protons belonging to the sulfonamide groups
1
disappeared. H NMR signals shifted to lower fields for the -N CH-
protons compared with 1e–f and 4e and were observed around
d 8.48–9.89 ppm in 11–13. These observations show that 1e–f
and 4e coordinate to the Pd(II) through the imine nitrogen atom
and the deprotonated nitrogen of the sulfonamide group. In the
13C NMR spectra of 11–13, the signals for the -N CH- carbons shifted
to lower fields compared with 1e–f and 4e and appeared around
d 159.8–165.6ppm.
Table 2. Catalytic activity for the oxidation reaction of benzyl alcohol
to benzaldehyde in using Pd(II) complexes
Entry Catalyst Yielda (%) Time
Oxidant TONb TOFc (hꢁ1
)
In the IR spectra for 1–5, N-H stretching frequency peaks
appeared around 3204–3240 cmꢁ1 and NH2 stretching frequency
peaks were observed around 3479–3364 cmꢁ1. In the Pd(II)
complexes (6–10), the NH2 stretching frequency peaks appeared
around 3247–3150 cmꢁ1. These bands are shifted approximately
200 cmꢁ1 to a lower wavenumber which supports the participa-
tion of the -NH2 group of these ligands in binding to the Pd (II).
Also, in 1a–f and 4e, N-H stretching frequency peaks appeared
around 3219–3208 cmꢁ1 and -N CH- frequency peaks were
observed around 1619–1628 cmꢁ1. In the Pd(II) complexes
(11–13), N-H stretching frequency peaks belonging to sulfonamide
groups were not observed and -N CH- frequency peaks were
observed around 1621–1576 cmꢁ1. -N CH- frequency peaks are
shifted 2–50 cmꢁ1 to a lower wavenumber which supports the
participation of the -N CH- group of these ligands in binding to
Pd(II). In addition, in all the compounds (1–13) SO2 stretch peaks
were observed at around 1339–1105 cmꢁ1. All the measurements
and interpretations are compatible with the proposed structure of
ligands. The NMR data are consistent with a transoid or cisoid type
of complex because they the same symmetry elements which
would give the same degree of magnetic equivalence in the
NMR. Therefore, the transoid or cisoid structures of the complexes
have not been determined since single crystals have not
been obtained. The representative IR and NMR spectra are shown
in Figs S1 and S2 as supporting information.
1
6
32
46
90 min
H5IO6
32
46
21
31
56
62
51
61
33
28
35.5
50
50
50
38
—
2
7
3
8
84
84
4
9
93
93
5
10
76
76
6
11
91
91
7
12
49
49
8
13
42
42
9
6
71
120 min
71
10
11
12
13
14
7
100
100
100
57
100
100
100
57
10
12
13
Absence of
Trace
—
catalyst
15
16
9
9
Traced
Traced
H2O2
—
—
—
—
O2 of air
aGC yields; yields are based on benzaldehyde.
bTON, moles of product/moles of catalyst.
cTOF, moles of product/(moles of the catalyst) ꢂ (hour).
dH2O2 or O2 of air used as oxidant.
Reaction conditions: 1.0mmol C6H5CH2OH, 1.0mmol H5IO6, 0.01mmol
Pd(II) complexes, CH3CN (5ml); all reactions were monitored by TLC
and GC; temperature 70ꢀC.
Catalytic Studies
In recent times, oxidation reactions have been studied in a wide range
of new ligands and their transition metal complexes as catalysts.[46–53]
In this study, we described the synthesis of a series of novel Pd(II)
complexes containing sulfonamide ligands (6–13) which were
employed as catalysts for the oxidation reaction of benzyl alcohol to
benzaldehyde. The rate of oxidation is dependent on a variety of
parameters such as temperature, solvent, oxidant and catalyst loading.
For the choice of oxidant, we examined H2O2, H5IO6 and O2 of
air. Experiments were also carried out in the absence of catalyst.
To find the optimum conditions, a series of experiments was
performed. Finally, we found that the use of 0.01 mmol
novel Pd(II) complexes containing aromatic sulfonamide ligands,
Pd(II)
H5IO6
O
HIO3 + 2 H2O
HO
O
Pd(IV)
Figure 2. Proposed mechanism for oxidation of benzyl alcohol to
benzaldehyde-catalyzed palladium complexes in the presence of H5IO6.
Appl. Organometal. Chem. 2013, 27, 52–58
Copyright © 2012 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

S. Dayan and N. O. Kalaycioglu
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tive 4e was synthesized using 4 and 4-nitrobenzaldehyde. Pd(II)
complexes of 4e were then synthesized (13). In this way, we
hoped to synthesize the best catalyst. However, compound 13
as not as good a catalyst as expected. The results are summarized
in Table 2.
All the experiments were carried out in an air atmosphere since
there was no change in conversion if the reaction is carried out
under argon. This indicates that air is not involved in the oxidation
process and palladium complexes are air-stable. A plausible mech-
anism has been proposed for the above described results (Fig. 2).
The mechanistic studies suggest that an initial carbonyl-bound
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concomitant loss of water molecules. The loaded catalysts then
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Acknowledgments
The financial support of Erciyes University (ERUBAP) (FBA-11-3547,
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Çanakkale Onsekiz Mart University, 17020 Çanakkale, Turkey) for
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Appl. Organometal. Chem. 2013, 27, 52–58