Synthesis and characterization of SiO2-supported ruthenium complexes containing aromatic sulfonamides: As catalysts for transfer hydrogenation of acetophenone

Article abstract of DOI:10.1039/c3dt32876g

3-Amino-N-aryl-benzenesulfonamides (1-3) were successfully synthesized by the reaction of m-phenylenediamine and various benzenesulfonyl chlorides. Then, a series of ruthenium complexes (4-6) were prepared from the reaction of [RuCl₂(p-cymene)]₂ and 1-3. Finally, SiO ₂-supported Ru(ii) complexes (7-9) were prepared by an impregnation method. The synthesized compounds and materials were characterized by different methods such as NMR, FT-IR, TG/DTA, nitrogen adsorption-desorption (BET), SEM and EDX. Also, the solid state structures of 4-6 were determined by single-crystal X-ray diffraction. 4-9 were used as catalysts for the transfer hydrogenation of acetophenone. 4-9 showed good catalytic activity and so the effects of the different groups were also examined. For the transfer hydrogenation of acetophenone, 7-9 had similar activity to 4-6. However, the longer lifetime of 7-9 makes them more advantageous than the non-supported catalysts (4-6) in terms of catalytic cycle. Therefore, the effect of SiO ₂ was investigated as a catalyst and the results show that excess silicon(iv) oxide was a surprisingly active catalyst for the hydrogenation of acetophenone under these conditions.

Full text of DOI:10.1039/c3dt32876g

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Synthesis and characterization of SiO2-supported
ruthenium complexes containing aromatic
sulfonamides: as catalysts for transfer hydrogenation
of acetophenone†
Cite this: Dalton Trans., 2013, 42, 4957
Serkan Dayan,a Nilgün Özpozan Kalaycıoğlu,*a Osman Dayan,b Namık Özdemir,c
Muharrem Dinçerc and Orhan Büyükgüngörc
3-Amino-N-aryl-benzenesulfonamides (1–3) were successfully synthesized by the reaction of m-phenylene-
diamine and various benzenesulfonyl chlorides. Then, a series of ruthenium complexes (4–6) were
prepared from the reaction of [RuCl2(p-cymene)]2 and 1–3. Finally, SiO2-supported Ru(II) complexes (7–9)
were prepared by an impregnation method. The synthesized compounds and materials were character-
ized by different methods such as NMR, FT-IR, TG/DTA, nitrogen adsorption–desorption (BET), SEM and
EDX. Also, the solid state structures of 4–6 were determined by single-crystal X-ray diffraction. 4–9 were
used as catalysts for the transfer hydrogenation of acetophenone. 4–9 showed good catalytic activity
and so the effects of the different groups were also examined. For the transfer hydrogenation of aceto-
phenone, 7–9 had similar activity to 4–6. However, the longer lifetime of 7–9 makes them more advan-
tageous than the non-supported catalysts (4–6) in terms of catalytic cycle. Therefore, the effect of SiO2
was investigated as a catalyst and the results show that excess silicon(IV) oxide was a surprisingly active
catalyst for the hydrogenation of acetophenone under these conditions.
Received 30th November 2012,
Accepted 14th January 2013
DOI: 10.1039/c3dt32876g
www.rsc.org/dalton
catalysts in various organic reactions.13–15 At the same time,
properties of sulfonamides have been investigated in the field
Introduction
Due to their containing different donor atoms, sulfonamides of luminescence, antimicrobial and analytical application.16a–c
are used in coordination chemistry.1 The importance of sulfon- In addition, sulfonamides have recently been studied in detail
amides has given rise to a variety of synthetic methods. Sulfon- by our research team.17a,b
amides are formed by the reaction of primary or secondary
The transfer hydrogenation (TH) of ketones catalyzed by Ru(II)
amines with sulfonyl chloride in basic media,2 from sulfinic complexes containing N-donors ligands has been attracting
acid salts with hydroxylamine-o-sulfonic acid,3 the reduction considerable attention from the catalysis community18–29 after
of arylsulfonyl azides,4,5 from aromatic and aliphatic sulfinic the great success of Noyori’s catalyst, containing 1,2-diamine
acid salts using bis(2,2,2-trichloroethyl)azodicarboxylate6 etc. ligands.30 Since Noyori et al. developed a highly active Ru(II)
Recently many sulfonamide derivatives have been synthesized complex, many modifications of the Ru(II) complexes contain-
and their complexes have been reported.7–12 Further, ing N-donor ligands have aimed to identify a good Ru(II) cata-
complexes containing sulfonamide groups have been used as lyst for TH of ketones. In this respect, sulfonamide ligands
have led to significant success.
In recent times, quite remarkable studies have been carried
aDepartment of Chemistry, Faculty of Science, Erciyes University, 38039 Kayseri,
out in the TH of acetophenone. These studies investigated the
Turkey. E-mail: nozpozan@erciyes.edu.tr; Fax: +90 352 437 49 33;
effects of the period of catalysis without base,31 under mild
Tel: +90 505 644 11 70
conditions,32 on the mechanism of functional groups33–35 and
bLaboratory of Inorganic Synthesis and Molecular Catalysis,
on the use of support materials as catalysts in water.36 Thus,
Çanakkale Onsekiz Mart University, 17020 Çanakkale, Turkey
cDepartment of Physics, Faculty of Art and Sciences, Ondokuz Mayıs University,
55139 Samsun, Turkey
†Electronic supplementary information (ESI) available. CCDC 872787–872789
these studies are envisaged to be preliminary studies for the
TH of α,β-unsaturated ketones.
Ruthenium-based catalysts, especially those supported by
contain the supplementary crystallographic data (excluding structure factors) for
Al2O3, SiO2, TiO2, ZnO, MWCNT, or activated carbon etc., have
been prepared by various methods (such as deposition–
the structures reported in this article. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c3dt32876g
This journal is © The Royal Society of Chemistry 2013
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precipitation, impregnation and co-precipitation, immobiliza- thermal analysis (DTA) were carried out by using the DTA/TG
tion etc.) and used in many organic transformations.37–40
system (Perkin-Elmer Diamond type). Melting points were
The selection of support material is very important because determined in open capillary tubes on a digital Electrothermal
the catalytic activity and/or selectivity may be modified 9100 melting point apparatus and a DTA/TG system. Scanning
depending on the nature of the support. Among these electron microscopy (SEM) and EDX analysis were performed
materials, ruthenium supported by SiO2 has attracted atten- on a LEO 440 model scanning electron microscope using an
tion because of its inexpensiveness, high activity/selectivity accelerating voltage of 20 kV. GC measurements for the cata-
and well-defined and tunable structure. In particular, metallic lytic experiments were performed using a Younglin Acme 6100
nanoparticles supported on SiO2 have been widely employed GC instrument with a flame ionization detector and an Optima
in recent years in the hydrogenation reactions of organic 5MS capillary column (the GC parameters were as follows: oven
compounds.41–43
80 °C (isothermal); carrier gas: H2 (split ratio 15 : 1); flow rate:
The hydrogenation of benzaldehyde over Pd/CNTs, Pd/r- 4 ml min−1; injector port temperature: 220 °C; detector temp-
Al2O3 and Pd/SiO2 was carried out under atmospheric pressure erature: 280 °C; injection volume: 6.0 µL).
to test the activity and selectivity of the catalysts.44 Gómez
et al. describe the immobilization of ruthenium nanoparticles,
performed by organometallic compound decomposition in the
General procedure for the synthesis of ligands (L), 1–3
N-(3-Aminophenyl)arylsulfonamides (1–3) were prepared by
modifying the published procedure.50
presence of a pyridine derivative stabilizer and placed on
different supports (functionalized multi-walled carbon nano-
tubes, silica and activated carbon).45 A Cu(II)-based catalyst
supported by SiO2 was used as a catalyst for the oxidation of
ethyl benzene into acetophenone with molecular oxygen under
atmospheric pressure.46 Recently, SiO2-supported Ru(III)-based
catalysts were used for the oxidation of alcohols.47
On the other hand, C2-symmetric bis(sulfonamide) ligands
derived from chiral trans-(1R,2R)-cyclohexane-1,2-diamine were
immobilized on silica gel and complexed to RhIIICp*. The
complexes were used as catalysts in the asymmetric transfer
hydrogenation (ATH) of acetophenone.48 A core–shell struc-
tured heterogeneous rhodium catalyst exhibited good catalytic
activity in the asymmetric transfer hydrogenation of aromatic
ketones in aqueous medium.49
In the present work, a series of novel Ru(II) complexes con-
taining sulfonamide ligands (4–6) were synthesized and then
these complexes were supported on SiO2 (7–9). Additionally,
4–9 were used as catalysts for TH of acetophenone. Experimen-
tal results show that 4–9 are active catalysts for TH of ketones,
but, surprisingly, SiO2 was also an active catalyst under
working conditions.
A 50 ml Schlenk tube containing a magnetic stirring bar is
charged with
a solution of benzenesulfonyl chlorides
(10 mmol) in THF (10 ml). The addition, slowly, of a solution
of triethylamine (20 mmol) in THF (5 ml) and m-phenylenedi-
amine (10 mmol) in THF (5 ml), respectively, gives rise to the
immediate precipitation of a white solid (HCl·N(C2H5)3). After
being stirred for 12 hours at room temperature, the solid is
collected by filtration using a fine sintered-glass filter. Then,
the solvent is completely removed under reduced pressure.
The crude product can be used without further purification.
An analytically pure sample can be obtained by recrystalliza-
tion from chloroform–diethyl ether (15 ml 1 : 3, v/v) (Fig. 1).
(1) N-(3-Aminophenyl)-4-t-butyl-sulfonamides. Color: white;
yield: 92%; Mp: 150–152 °C. 1H-NMR (CDCl3, δ ppm): 1.30
(s, 9H, –C(CH3)3), 3.46 (br., 2H, –NH2), 6.41 (m, 2H, –H2,4), 6.54
(s, 1H, –H1), 6.97 (t, 1H, J = 8 Hz, –H3), 7.12 (s, 1H, –NH–), 7.44
(d, 2H, J = 8 Hz, –Hb), 7.76 (d, 2H, J = 8 Hz, –Ha). 13C-NMR
(CDCl3, ppm): 31.1 (–C(CH3)3), 35.2 (–C(CH3)3), 107.3 (Ar.
–CH), 110.8 (Ar. –CH), 111.8 (Ar. –CH), 126.1 (Ar. –CH), 127.1
(Ar. –CH), 130.1 (Ar. –CH), 136.3 (Ar. –CH), 137.7 (Ar. –CH),
147.4 (Ar. –CH), 156.7 (Ar. –CH). IR (cm−1): 3407 (NH2), 3382
(NH2), 3330 (N–H), 3072, 2958, 2902, 2866, 2769, 1610, 1590,
1504, 1487, 1438, 1397, 1364, 1344, 1330, 1311 (SO2), 1292,
1268, 1185, 1152 (SO2), 1110, 1085, 980, 910, 861, 835, 773,
750, 688, 620, 571, 545, 528, 516. Anal. Calcd for: C: 63.13;
H: 6.62; N: 9.20; O: 10.51; S: 10.53. Found: C: 63.29; H: 6.54;
N: 9.30; S: 10.44.
Experimental
Materials and methods
All reagents and solvents were obtained from commercial sup-
pliers and used without any additional purification. The NMR
spectra were recorded at 297 K on a Bruker 400 NMR spec-
trometer 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 δ downfield from
tetramethylsilane (δ 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 infrared spectra were
measured with a Perkin-Elmer Spectrum 400 FTIR system and
recorded using a universal ATR sampling accessory within the
range 550–4000 cm−1. Thermogravimetry (TG) and differential Fig. 1 Synthesis of the ligands together with the NMR numbering scheme.
4958 | Dalton Trans., 2013, 42, 4957–4969
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(2) N-(3-Aminophenyl)-benzene-sulfonamides. Color: white; 18.5 (–CH3), 22.0 (–CH(CH3)2), 30.5 (–CH(CH3)2), 31.0
1
yield: 90%; Mp: 100–102 °C. H-NMR (DMSO-d6, δ ppm): 5.11 (–C(CH3)3), 35.1 (–C(CH3)3), 79.7 (Ar. –CH), 80.5 (Ar. –CH), 81.7
(br., 2H, –NH2), 6.21 (m, 2H, –H2,4), 6.37 (s, 1H, –H1), 6.80 (Ar. –CH), 103.5 (Ar. –CH), 116.2 (Ar. –CH), 116.9 (Ar. –CH),
(t, 1H, J = 8 Hz, –H3), 7.55 (m, 3H, –Hb,c), 7.76 (d, 2H, J = 8 Hz, 126.3 (Ar. –CH), 127.2 (Ar. –CH), 127.3 (Ar. –CH), 130.4 (Ar.
–Ha), 9.97 (s, 1H, –NH–). 13C-NMR (DMSO-d6, ppm): 105.8 –CH), 136.3 (Ar. –CH), 138.2 (Ar. –CH), 146.2, 157.0 (Ar. –CH).
(Ar. –CH), 107.9 (Ar. –CH), 110.4 (Ar. –CH), 127.1 (Ar. –CH), IR (cm−1): 3213 (N–H), 3121 (NH2), 3055 (NH2), 2966, 2907,
129.6 (Ar. –CH), 129.8 (Ar. –CH), 133.2 (Ar. –CH), 138.8 (Ar. 2873, 2823, 1612, 1575, 1533, 1499, 1484, 1411, 1363, 1350,
–CH), 140.3 (Ar. –CH), 149.8 (Ar. –CH). IR (cm−1): 3410 (NH2), 1323 (SO2), 1295, 1270, 1198, 1178, 1158 (SO2), 1113, 1088,
3339 (NH2), 3226 (N–H), 3086, 3058, 2984, 2894, 2832, 2770, 1031, 1016, 1003, 980, 870, 833, 805, 792, 750, 694, 661, 644,
1609, 1596, 1495, 1447, 1429, 1404, 1335, 1309 (SO2), 1290, 627, 573, 546, 528, 474. Anal. Calcd for: C: 51.14; H: 5.61;
1266, 1183, 1176, 1150 (SO2), 1090, 1072, 1032, 1000, 976, 870, Cl: 11.61; N: 4.59; O: 5.24; Ru: 16.55; S: 5.25. Found: C: 55.75;
848, 779, 754, 715, 683, 635, 622, 579, 562, 549. Anal. Calcd H: 7.33; N: 3.85; S: 4.61.
for: C: 58.05; H: 4.87; N: 11.28; O: 12.89; S: 12.91. Found:
C: 58.15; H: 4.80; N: 11.20; S: 12.98.
(5) {[N-(3-Aminophenyl)-benzene-sulfonamides]-(p-cymene)-
di-chloro-ruthenium(II)}. Color: dark red; yield: 89%; Mp:
(3) N-(3-Aminophenyl)-4-methoxy-sulfonamides. Color: 220 °C (dec.). 1H-NMR (DMSO-d6, δ ppm): 1.18 (d, 6H,
white; yield: 80%; Mp: 118–120 °C. 1H-NMR (CDCl3, δ ppm): J = 8 Hz, –Hm), 2.07 (s, 3 H, –Hk), 2.82 (m, 1H, –Hl), 5.11 (br.,
3.71 (br., 2H, –NH2), 3.81 (s, 3H, –OCH3), 6.41 (d, 2H, J = 8 Hz, 2H, –NH2), 5.77 (d, 2H, J = 4 Hz, –Hy), 5.81 (d, 2H, J = 4 Hz, –Hx),
–H2,4), 6.52 (s, 1H, –NH–), 6.84 (s, 1H, –H1), 6.87 (d, 2H, 6.20 (m, 2H, –H2,4), 6.35 (s, 1H, –H1), 6.79 (t, 1H, J = 8 Hz, –H3),
J = 8 Hz, Hb), 6.97 (t, 1H, J = 8 Hz, –H3), 7.74 (d, 2H, J = 8 Hz, 7.54 (m, 3H, –Hb,c), 7.74 (d, 2H, J = 8 Hz, –Ha), 9.94 (s, 1H,
–Ha). 13C-NMR (CDCl3, ppm): 55.6 (–OCH3), 107.6 (Ar. –CH), –NH–). 13C-NMR (DMSO-d6, ppm): 18.3 (–CH3), 22.0 (–CH
111.0 (Ar. –CH), 111.9 (Ar. –CH), 114.2 (Ar. –CH), 129.4 (CH3)2), 30.5 (–CH(CH3)2), 86.0 (Ar. –CH), 86.6 (Ar. –CH), 100.6
(Ar. –CH), 130.0 (Ar. –CH), 130.1 (Ar. –CH), 137.7 (Ar. –CH), (Ar. –CH), 105.8 (Ar. –CH), 106.9 (Ar. –CH), 107.9 (Ar. –CH),
147.4 (Ar. –CH), 163.1 (Ar. –CH). IR (cm−1): 3391 (NH2), 3338 110.4 (Ar. –CH), 127.1 (Ar. –CH), 129.6 (Ar. –CH), 129.7 (Ar.
(NH2), 3238 (N–H), 3071, 2976, 2894, 2839, 2749, 2699, 1592, –CH), 133.1 (Ar. –CH), 138.7 (Ar. –CH), 140.3 (Ar. –CH), 149.8
1576, 1494, 1462, 1438, 1414, 1310 (SO2), 1296, 1260, 1171, (Ar. –CH). IR (cm−1): 3283 (N–H), 3210 (NH2), 3129 (NH2),
1146 (SO2), 1090, 1019, 978, 902, 859, 831, 802, 780, 716, 688, 3064, 2967, 2915, 2871, 2855, 1607, 1588, 1502, 1478, 1450,
661, 626, 551. Anal. Calcd for: C: 56.10; H: 5.07; N: 10.06; 1429, 1391, 1375, 1341, 1323, 1308 (SO2), 1282, 1257, 1174,
O: 17.25; S: 11.52. Found: C: 56.22; H: 4.98; N: 10.18; S: 11.39.
1154 (SO2), 1089, 1028, 1000, 973, 892, 876, 868, 846, 806, 780,
759, 718, 690, 661, 628, 615, 581, 557, 499. Anal. Calcd for:
C: 47.65; H: 4.73; Cl: 12.79; N: 5.05; O: 5.77; Ru: 18.23; S: 5.78.
Found: C: 47.87; H: 4.51; N: 5.16; S: 5.68.
General procedure for the synthesis of [(p-cymene)RuLCl2], 4–6
A solution of 1–3 (0.50 mmol) in methyl alcohol (5 ml) was
added to a solution of [RuCl2(p-cymene)]2 (0.25 mmol) in
methyl alcohol (5 ml) in a Schlenk tube. The reaction mixture
was stirred for 12 hours at 60 °C. The volatiles were removed
under reduced pressure. The residue was washed with diethyl
ether (20 ml) and dried under vacuum. The desired products
were recrystallized in MeOH and dark red-colored crystals were
obtained (Fig. 2).
(4) {[N-(3-Aminophenyl)-4-t-butyl-sulfonamides]-(p-cymene)-
di-chloro-ruthenium(II)}. Color: dark red; yield: 86%; Mp:
191 °C (dec.). 1H-NMR (CDCl3, δ ppm): 1.16 (d, 6H, J = 8 Hz, –Hm),
1.26 (s, 9H, –C(CH3)3), 2.06 (s, 3 H, –Hk), 2.81 (m, 1H, –Hl),
4.88 (br., 2H, –NH2), 4.91 (d, 2H, J = 4 Hz, –Hy), 5.02 (d, 2H,
J = 4 Hz, –Hx), 7.05 (d, 2H, J = 8 Hz, –H2,4), 7.22 (t, 1H, J = 8 Hz,
–H3), 7.29 (s, 1H, –H1), 7.25 (s, 1H, –NH–), 7.50 (d, 2H, J = 8 Hz,
–Hb), 7.91 (d, 2H, J = 8 Hz, –Ha). 13C-NMR (CDCl3, ppm):
(6) {[N-(3-Aminophenyl)-4-methoxy-sulfonamides]-(p-cymene)-
di-chloro-ruthenium(II)}. Color: dark red; yield: 81%; Mp:
1
200 °C. H-NMR (CDCl3, δ ppm): 1.18 (d, 6H, J = 8 Hz, –Hm),
2.08 (s, 3 H, –Hk), 2.82 (m, 1H, –Hl), 3.78 (s, 3H, –OCH3), 5.08
(br., 2H, –NH2), 5.77 (d, 2H, J = 4 Hz, –Hy), 5.81 (d, 2H,
J = 4 Hz, –Hx), 6.19 (m, 2H, –H2,4), 6.34 (s, 1H, –H1), 6.78 (t, 1H,
J = 8 Hz, –H3), 7.04 (d, 2H, J = 8 Hz, Hb), 7.67 (d, 2H, J = 8 Hz,
–Ha), 9.80 (s, 1H, –NH–). 13C-NMR (CDCl3, ppm): 18.4 (–CH3),
22.0 (–CH(CH3)2), 30.5 (–CH(CH3)2), 56.1 (–OCH3), 86.0
(Ar. –CH), 86.8 (Ar. –CH), 100.6 (Ar. –CH), 105.6 (Ar. –CH),
106.9 (Ar. –CH), 107.8 (Ar. –CH), 110.2 (Ar. –CH), 114.7 (Ar.
–CH), 129.3 (Ar. –CH), 129.7 (Ar. –CH), 131.9 (Ar. –CH), 139.0
(Ar. –CH), 149.8 (Ar. –CH), 162.7 (Ar. –CH). IR (cm−1): 3272
(N–H), 3208 (NH2), 3128 (NH2), 3061, 2966, 2910, 2841, 1602,
1499, 1473, 1450, 1423, 1392, 1339, 1321, 1307 (SO2), 1264,
1151 (SO2), 1095, 1057, 1026, 1002, 970, 895, 879, 864, 847,
823, 805, 782, 758, 718, 689, 667, 627, 567, 556, 519. Anal.
Calcd for: C: 44.87; H: 4.28; Cl: 18.06; N: 4.76; O: 5.43;
Ru: 17.16; S: 5.44. Found: C: 44.69; H: 4.34; N: 4.87; S: 5.33.
General procedure for the preparation of SiO2 supported
[(p-cymene)RuLCl2], 7–9
[(p-Cymene)RuLCl2]–SiO2 (7–9) were prepared by modifying
Fig. 2 Synthesis of the complexes together with the NMR numbering scheme.
the published procedure.32
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least-squares method using SHELXL-9752 implemented in the
WinGX53 program suite. All H atoms were positioned geometri-
cally and treated using a riding model, fixing the bond lengths
at 0.82, 0.86, 0.90, 0.93, 0.98 and 0.96 Å for OH, NH, NH2,
aromatic CH, methine CH and CH3 atoms, respectively.
The displacement parameters of the H atoms were fixed at
Uiso(H) = 1.2Ueq (1.5Ueq for OH and CH3) of their parent atoms.
4 crystallizes with a methanol solvent molecule which is dis-
ordered about the inversion center and was refined with
the occupancy of all atoms fixed at 0.5. In 6, there is a
disordered solvent water molecule with very large displace-
ment parameters which was difficult to model. Therefore,
the SQUEEZE command of PLATON54 was used to model
the electron density in the void regions. There are two cavities
of volume 91 Å3 per unit cell centered at (0.5, 0.5, 0.5)
and (0.5, 1, 0). Each cavity contains approximately 15 electrons
which were assigned to one solvent water molecule. With
Z = 4, each Ru complex has a 0.5 solvent water equivalent.
In the final refinement, these contributions were removed
from the intensity data to produce better refinement results.
Data collection: X-AREA,55 cell refinement: X-AREA, data
reduction: X-RED32.55 Details of the data collection conditions
and the parameters of the refinement process are given in
Table 1.
Fig. 3 Preparation of the materials.
Typically, 85 mg of 99.5% SiO2 was added to 15 mg of 4–6
in 3 ml diethyl ether (this ratio was selected randomly with the
aim of setting the amount of catalyst used in each catalytic
experiment). The system was stirred and sonicated for 3 hours
to form a stable brown suspension. The solvent was then evap-
orated under vacuum. The resulting orange solid was dried
under reduced pressure (Fig. 3).
X-ray analysis
The single-crystal X-ray data were collected on a STOE diffracto-
meter with an IPDS II image plate detector. All diffraction
measurements were performed at room temperature (296 K)
using graphite monochromated Mo Kα radiation (λ = 0.71073 Å)
in ω-scanning mode. The structures were solved by direct
methods using SHELXS-9751 and refined through the full-matrix
Table 1 Crystal data and structure refinement parameters for complexes (4), (5) and (6)
Parameters
4
5
6
CCDC deposition no.
Color/shape
Chemical formula
872 787
Prism/dark red
[RuCl2(C10H14)(C16H20N2O2S)]2·
(CH4O)
872 788
Prism/dark red
[RuCl2(C10H14)(C12H12N2O2S)]
872 789
Prism/dark red
[RuCl2(C10H14)(C13H14N2O3S)]·
0.5(H2O)
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell parameters
a, b, c (Å)
1253.21
296
554.48
296
0.71073 Mo Kα
Monoclinic
P21/c (no. 14)
593.51
296
0.71073 Mo Kα
Monoclinic
P21/c (no. 14)
0.71073 Mo Kα
Triclinic
ˉ
P1 (no. 2)
8.9631(5), 10.8459(6), 15.7706(8)
86.897(4), 79.499(4), 69.104(4)
1408.19(13)
1
1.478
0.849
10.4066(5), 13.3274(6), 18.0147(10) 10.8448(3), 15.2091(6), 17.3707(5)
90, 112.566(4), 90
2307.2(2)
4
1.596
1.023
α, β, γ (°)
90, 116.359(2), 90
2567.23(14)
4
1.536
0.929
Volume (Å3)
Z
Dcalc (g cm−3
)
μ (mm−1
)
Absorption correction
Tmin, Tmax
Integration
0.7203, 0.8739
646
0.38 × 0.31 × 0.18
STOE IPDS II/rotation (ω scan)
Integration
0.6570, 0.8919
1128
0.71 × 0.33 × 0.14
STOE IPDS II/rotation (ω scan)
Integration
0.7233, 0.8723
1212
0.44 × 0.29 × 0.19
STOE IPDS II/rotation (ω scan)
F000
Crystal size (mm3)
Diffractometer/measurement
method
Index ranges
−11 ≤ h ≤ 11, −14 ≤ k ≤ 14,
−20 ≤ l ≤ 20
−13 ≤ h ≤ 13, −17 ≤ k ≤ 17, −20 ≤ −14 ≤ h ≤ 14, −19 ≤ k ≤ 19,
l ≤ 23
−22 ≤ l ≤ 22
1.87 ≤ θ ≤ 27.57
25 379
θ range for data collection (°)
Reflections collected
Independent/observed
reflections
2.01 ≤ θ ≤ 27.58
33 213
1.96 ≤ θ ≤ 27.59
14 002
5251/4155
6504/5356
5906/4427
Rint
0.038
0.027
0.045
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I)]
R indices (all data)
Full-matrix least-squares on F2
6504/0/331
Full-matrix least-squares on F2
5251/0/272
Full-matrix least-squares on F2
5906/0/293
1.035
1.007
1.007
R1 = 0.0315, wR2 = 0.0758
R1 = 0.0440, wR2 = 0.0793
0.493, −0.372
R1 = 0.0285, wR2 = 0.0552
R1 = 0.0446, wR2 = 0.0582
0.361, −0.337
R1 = 0.0341, wR2 = 0.0672
R1 = 0.0567, wR2 = 0.0719
0.418, −0.414
Δρmax, Δρmin (e Å−3
)
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Results and discussion
The synthesis and reaction routes of the Ru(II) complexes are
presented in Fig. 2. The synthesized compounds and materials
were characterized by 1H-NMR, 13C-NMR, IR spectroscopy,
nitrogen adsorption–desorption (BET) analysis, scanning elec-
tron microscopy (SEM) and EDX analysis techniques. The
solid state structures of 4–6 were also confirmed by X-ray
crystallography.
1–3 were obtained by the reaction of m-phenylenediamine
with R-arylsulfonyl chloride in the presence of triethylamine in
THF. Benzenesulfonyl chloride, p-isobutylbenzenesulfonyl
chloride and p-methoxybenzenesulfonyl chloride compounds
were used as R-arylsulfonyl chloride. Then, the novel ruthe-
nium complexes (4–6) were synthesized by the reaction of 1–3
with [RuCl2(p-cymene)]2 in methyl alcohol. The synthesized
complexes were supported on commercial silicon(IV) oxide
(99.5%) (7–9). Additionally, [(p-cymene)RuLCl2] (4–6) and
[(p-cymene)RuLCl2]–SiO2 (7–9) were used as catalysts for the
TH of acetophenone.
◆
Fig. 4 IR spectra of amorphous SiO2 appear as (a) black, for 7 as (b) green,
●
■
for 8 as (c) red, for 9 as (d) blue.
approximately 200–350 cm−1 to a lower wavenumber which
supports the participation of the –NH2 group of these ligands
in binding to the ruthenium. In addition, the SO2 stretch
peaks appeared at 1311–1152 for 1, 1309–1150 for 2,
1310–1146 for 3, 1323–1158 for 4, 1308–1154 for 5, and
1307–1151 for 6.
In Fig. 4, the IR spectra of the synthesized [(p-cymene)-
RuLCl2]–SiO2 (7–9) and SiO2 are given. Herein, although the
formation of peaks belonging to [(p-cymene)RuLCl2] did not
show in the initial curve as amorphous, the SiO2 appears
black, and the formation of peaks belonging to [(p-cymene)-
RuLCl2] are clearly seen in 7 as green, in 8 as red, and in 9 as
blue. Consequently, the complexes supported on SiO2 were
observed after the impregnation method.
NMR spectra
In the 1H-NMR spectra, respectively, the –Ha, –Hb and –Hc
protons were observed as doublets, triplets and triplets in a
2 : 2 : 1 ratio at around δ 7.55–7.76 ppm in N-(3 aminophenyl)-
benzenesulfonamide. Similarly, in other N-(3-aminophenyl)-
arylsulfonamide ligands, the –Ha and –Hb protons were
observed as doublets in a 2 : 2 ratio at around δ 6.87–7.76 ppm.
–NH2 and –NH protons were found at around δ 3.46–5.11 ppm
and δ 6.62–9.97 in those compounds in 1–3, respectively. In (c)
position, the –C(CH3)3, and –OCH3 protons were observed as
singlets, in a 9 : 3 ratio at around δ 1.30 and 3.81 ppm in com-
pounds 1 and 3, respectively. In the 13C-NMR spectra for 1, the
–C(CH3)3 carbons were found at δ 31.1 and 35.2 ppm. Simi-
Structural description of 4–6
larly, –OCH3 carbon was found at δ 55.6 ppm for 3. In the The solid-state structures of 4–6 were verified by single-crystal
1
1H-NMR spectra for 4–6, the H-NMR signals shifted to lower X-ray analysis. The perspective ORTEP-356 views of the com-
fields for the –NH2 protons compared with free ligands (1–3) plexes with the atomic numbering scheme are depicted in
and were found at around δ 4.88, 5.11 and 5.08 ppm, respecti- Fig. 5–7, respectively, while selected geometric parameters
vely. Additionally, –Hk, –Hx, –Hy, –Hl and –Hm protons relating are given in Table 2. The three complexes are composed of an
to p-cymene exhibited at 2.06, 5.02, 4.91, 2.81, 1.16 ppm in 4, N-(3-aminophenyl)benzenesulfonamide ligand with an Ru(II)
at 2.07, 5.81, 5.77, 2.82, 1.18 ppm in 5 and at 2.08, 5.81, 5.77, metal center, one p-cymene ligand and two Cl ligands. The
2.82, 1.18 ppm in 6, respectively. In the 13C-NMR spectra for 4 difference in the composition of the complex structures orig-
and 6, the –C(CH3)3 carbons were observed at 31.0 and inates from the monodentate N-(3-aminophenyl)benzenesulfon-
35.1 ppm for 4 and –OCH3 carbon was observed at 56.1 ppm amide ligand. In addition, the crystallization characteristics of
for 6.
the complexes are not the same, with 5 and 6 crystallizing in
monoclinic space group P21/c while 4 crystallizes in the
Infrared spectra
ˉ
triclinic space group P1.
In the IR spectra for 1–3, N–H stretching frequency peaks
The complexes have the familiar half-sandwich “three-
belonging to the sulfonamide groups appeared at 3330, 3226 legged piano-stool” geometry with the η6 π-bound arene ring
and 3238 cm−1 and NH2 stretching frequency peaks were forming the seat and the σ-bonded nitrogen atom of the
observed at 3407–3382, 3410–3339 and 3391–3338 cm−1
,
N-(3-aminophenyl)benzenesulfonamide ligand and two term-
respectively. In the ruthenium complexes 4–6, N–H stretching inal chloride ligands as the legs of the piano-stool. The
frequency peaks belonging to the sulfonamide groups rotational orientation of the arene ring is such that atoms Cl1,
appeared at 3213, 3283 and 3272 cm−1 and NH2 stretching fre- Cl2 and N1 are staggered with respect to the arene C atoms,
quency peaks were observed at 3121–3055, 3210–3129 and i.e. when viewed along the arene centroid–Ru bond axis, the
3208–3128 cm−1
, respectively. These bands are shifted atoms eclipse the arene C–C bonds rather than the C atoms.
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Fig. 7 Perspective view of the asymmetric unit of 6 showing the atom-num-
bering scheme. Displacement ellipsoids are drawn at the 30% probability level
and H atoms have been omitted for clarity.
Fig. 5 Perspective view of the asymmetric unit of 4 showing the atom-num-
bering scheme. Displacement ellipsoids are drawn at the 30% probability level.
The disordered methanol molecule and H atoms have been omitted for clarity.
compensated for by the opening of the X–Ru–L (L is Cl1, Cl2
or N1) angles [mean 129.66(3)° for 4, 129.49(3)° for 5 and
129.49(3)° for 6].
The average Ru–C bond distance is 2.174(3) Å for 4, 2.181(2)
Å for 5 and 2.178(3) Å for 6. Note that the two longest Ru–C
bonds (Ru1–C2 and Ru1–C5; see Table 2) are trans with respect
to Cl atoms as a result of the strong trans influence of these
atoms. For all compounds, the p-cymene rings are planar with
mean deviation from the planes of 0.0047, 0.0080 and
0.0124 Å for 4, 5 and 6, respectively. The C–C bond lengths in
the p-cymene ring are almost equal in all complexes, and there
are no alternate short and long bond lengths. This indicates
that there is no localization and shows no trends associated
with non-planarity of the arene ring. The N-(3-aminophenyl)-
benzenesulfonamide ligand is bent at the S atom with the
C–SO2–NH–C torsion angle of 56.19(19)° for 4, 69.9(3)° for 5
and 57.6(2)° for 6, and the S atom has a distorted tetrahedral
geometry [maximum deviation being 119.10(10)° for 4,
120.54(14)° for 5 and 119.61(13)° for 6].
Fig. 6 Perspective view of the asymmetric unit of 5 showing the atom-num-
bering scheme. Displacement ellipsoids are drawn at the 30% probability level
and H atoms have been omitted for clarity.
The Ru atoms adopt a pseudo-octahedral coordination geo-
metry, with the arene formally occupying three facial coordi-
nation sites. However, the geometry around the metal atoms
may be regarded as a tetrahedron with considerable trigonal
distortion, considering the center of the η6-p-cymene aromatic
ring as the fourth ligand position. Defining X as the centroid
of the aromatic ring, the Ru–X distances are 1.6570(2), 1.6637(2)
The bond lengths of Ru–Cl1, Ru1–Cl2 and Ru1–N1 are
found to be 2.4107(7), 2.4124(7) and 2.186(2) Å for 4, 2.4273(6),
2.4104(6) and 2.1971(17) Å for 5, 2.4249(7), 2.4116(7) and
2.192(2) Å for 6, respectively. Many Ru(II)–arene complexes
with the same coordination sphere have been characterized
crystallographically.57–67 Inspection of the bond lengths in
these examples shows that the Ru–X, Ru–C, Ru–Cl and Ru–N
bond lengths vary from 1.637 to 1.689 Å, from 2.098 to
2.273 Å, from 2.399 to 2.470 Å and from 2.118 to 2.213 Å,
respectively. As can be seen from these values, the coordi-
nation bond lengths in the complexes are well in accordance
with the literature values.
and 1.6581(2)
Å for 4, 5 and 6, respectively, and the
Cl1–Ru1–X, Cl2–Ru1–X and N1–Ru1–X angles are 128.06(3),
128.26(2) and 132.65(5)° for 4, 129.10(2), 129.02(2) and 130.36(5)°
for (5) and 128.84(2), 128.46(2) and 131.16(6)° for 6. The
Cl1–Ru1–Cl2, Cl1–Ru1–N1 and Cl2–Ru1–N1 bond angles
[mean 83.66(5)° for 4, 83.84(4)° for 5 and 83.86(5)° for 6] are
smaller than the ideal tetrahedral angle (109.47°), which is
The structures are stabilized by intra- and intermolecular
hydrogen bonds of types C–H⋯X [X = O, Cg(π-ring), Cl],
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Table 2 Selected geometric parameters for complexes (4), (5) and (6)
Parameters
(4)
(5)
(6)
Parameters
(4)
(5)
(6)
Bond lengths (Å)
Ru1–Cl1
Ru1–Cl2
Ru1–N1
Ru1–C2
Ru1–C3
Ru1–C4
Ru1–C5
Ru1–C6
2.4107(7)
2.4124(7)
2.186(2)
2.187(3)
2.161(3)
2.164(2)
2.201(2)
2.170(3)
2.158(3)
2.4273(6)
2.4104(6)
2.1971(17)
2.210(2)
2.174(2)
2.138(2)
2.200(2)
2.175(2)
2.190(2)
2.4249(7)
2.4116(7)
2.192(2)
2.201(3)
2.175(3)
2.143(3)
2.206(3)
2.164(3)
2.176(3)
S1–O1
S1–O2
S1–N2
S1–C17
O3–C20
O3–C23
O3–C27
N1–C11
N2–C13
1.4191(16)
1.4398(15)
1.6225(19)
1.759(2)
—
1.421(2)
1.432(2)
1.617(2)
1.758(3)
—
—
—
1.439(3)
1.407(3)
1.419(2)
1.435(2)
1.615(2)
1.752(3)
1.344(3)
1.409(4)
—
—
1.47(3)
1.433(3)
1.426(2)
1.444(3)
1.419(3)
Ru1–C7
Bond angles (°)
Cl1–Ru1–Cl2
Cl1–Ru1–N1
Cl1–Ru1–C2
Cl1–Ru1–C3
Cl1–Ru1–C4
Cl1–Ru1–C5
Cl1–Ru1–C6
Cl1–Ru1–C7
Cl2–Ru1–N1
Cl2–Ru1–C2
Cl2–Ru1–C3
Cl2–Ru1–C4
Torsion angles (°)
Ru1–N1–C11–C12
Ru1–N1–C11–C16
Cl1–Ru1–N1–C11
86.96(3)
81.33(5)
86.03(2)
80.57(5)
89.28(7)
99.36(7)
131.68(7)
168.41(7)
142.80(7)
107.68(7)
84.91(5)
133.42(7)
168.63(7)
140.53(7)
85.51(3)
80.37(6)
89.02(8)
98.06(8)
129.28(8)
166.74(8)
144.81(9)
108.78(9)
85.69(6)
129.58(10)
166.21(9)
143.93(8)
Cl2–Ru1–C5
Cl2–Ru1–C6
Cl2–Ru1–C7
Ru1–N1–C11
S1–N2–C13
O1–S1–O2
O1–S1–N2
O2–S1–N2
O1–S1–C17
O2–S1–C17
N2–S1–C17
C20–O3–C23
90.69(8)
93.02(8)
105.30(7)
89.21(7)
107.63(8)
88.79(8)
98.33(9)
91.74(10)
118.70(9)
156.86(8)
154.88(7)
117.11(8)
91.55(10)
82.70(6)
158.37(10)
153.78(9)
115.90(8)
120.46(10)
117.79(13)
124.93(14)
119.10(10)
109.95(10)
103.55(9)
108.09(10)
108.26(10)
107.32(10)
—
101.48(7)
118.95(14)
129.17(17)
120.54(14)
108.79(12)
103.80(12)
107.77(13)
108.35(14)
106.85(12)
—
122.15(15)
126.78(18)
119.61(13)
110.17(13)
103.85(13)
106.87(13)
109.88(13)
105.67(13)
118.0(2)
−93.7(2)
85.4(2)
−174.08(16)
−98.9(2)
78.4(2)
−173.03(16)
−109.7(2)
70.1(3)
−170.03(19)
Cl2–Ru1–N1–C11
C13–N2–S1–C17
−86.06(16)
56.19(19)
−86.22(15)
69.9(3)
−83.86(18)
57.6(2)
N–H⋯X [X = O, Cl] and O–H⋯X [X = Cl]. The detailed geome- the results are summarized in Table 4. The BET isotherms
tries of these interactions are given in Table S1 in the ESI.†
(Fig. 10) of SiO2 and 7–9 were found to be of type-III adsorp-
tion isotherm according to IUPAC, which is related to the for-
mation of multilayer adsorption. When the results were
investigated, the surface areas of 7–9 were lower compared to
SiO2. A lower surface area shows us that the [(p-cymene)-
RuLCl2] complexes (4–6) were embedded in amorphous SiO2.
SEM-EDX analysis
The SEM images of 4–9 and amorphous SiO2 are depicted in
Fig. 8. From the SEM image, it can be concluded that the
[(p-cymene)RuLCl2] complexes (4–6) were embedded in the
amorphous SiO2 in powder form and it is impossible to see
Thermal behavior
them from
a low resolution SEM image. However, the
[(p-cymene)RuLCl2]–SiO2 (7–9) prepared with the impregnation The thermograms of the synthesized catalysts are given in
method is apparent as a different form from 4–6 and amor- Fig. 11. The results of TGA are also summarized in Table 5.
phous SiO2 in the SEM images. The average sizes of the com- According to the obtained TG curves, 4 and 7–9 decompose in
pounds were found to be between 40 nm and 1.25 µm for 4–6, three steps while 5–6 decompose in two steps between 50 and
and between 70 nm and 4.50 µm for 7–9, and between 50 nm 950 °C. Table 5 indicates that 4 and 6 have the highest onset
and 1.10 µm for SiO2. In addition to SEM images the ele- temperature (Ton). However, catalyst 5 and also 7–9 have a
mental composition of 7–9 was determined by EDX elemental similar thermal degradation onset temperature. On the other
analysis.
hand, the supported catalysts (7–9) and the non-supported
The EDX analysis image belonging to [(p-cymene)RuLCl2] ones showed similar thermal behaviors. Also, the crystal struc-
and [(p-cymene)RuLCl2]–SiO2 compounds are shown in Fig. 9. tures of 4 and 6 described by single-crystal X-ray diffraction
The data supported the structure of the compounds. In indicated absorbed solvents (CH4O and H2O, respectively).
addition, the analytic data of Ru and Si are shown in Table 3.
The EDX spectra given in Fig. 9(d–f) reveals that [(p-cymene)
RuLCl2]–SiO2 supported on SiO2 consists of Ru, S, C, N, O, Cl
and Si as expected. Similarly, Fig. 9(a–c) and 9g reveals that
[(p-cymene)RuLCl2] and SiO2 consist of Ru, S, C, N, O, Cl and
Si, O as expected, respectively.
Catalytic studies
Recently, the TH of ketones to alcohols has been extensively
investigated. At the same time, studies are continuously
aiming at obtaining better catalysts. Herein, we defined the
synthesis of a series of novel ruthenium complexes (4–6) and
[(p-cymene)RuLCl2]–SiO2 materials (7–9) employed as catalysts
for the TH of acetophenone.
BET analysis
Surface area, pore volume and pore width were calculated
Catalytic studies with 4–9 were performed for the TH of
using the nitrogen adsorption–desorption (BET) isotherm and acetophenone in the presence of KOH by 2-propanol
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Fig. 8 SEM image of (a) 4, (b) 5, (c) 6, (d) 7, (e) 8, (f) 9, (g) amorphous SiO2.
Fig. 9 EDX analysis of (a) 4, (b) 5, (c) 6, (d) 7, (e) 8, (f) 9, (g) amorphous SiO2.
Table 4 Adsorption–desorption characteristics of amorphous SiO2 and 7–9
Table 3 EDX analysis data for [(p-cymene)RuLCl2] and [(p-cymene)RuLCl2]–
SiO2 compounds
Ru wt%
calculated found
Ru wt% Si wt%
Si wt%
Compounds
calculated found
C26H34Cl2N2O2RuS: (4)
C22H26Cl2N2O2RuS: (5)
C23H28Cl2N2O3RuS: (6)
SiO2
[(p-cymene)RuLCl2]–SiO2: (7) 2.48
[(p-cymene)RuLCl2]–SiO2: (8) 2.73
[(p-cymene)RuLCl2]–SiO2: (9) 2.59
16.55
18.23
17.29
—
16.75
17.65
17.54
—
2.33
2.65
2.67
—
—
—
46.74
39.72
39.72
39.72
—
—
—
46.61
40.24
39.50
39.59
BET surface area
Compound (m2 g−1
BJH pore volume
(cm3 g−1
BJH pore
width (nm)
)
)
SiO2
7.1984
4.0619
5.3866
2.8031
0.031258
0.024639
0.026201
0.021703
19.5425
24.5455
17.2406
26.3826
7
8
9
(Scheme 1). The reaction conditions for this important process RuLCl2] or [(p-cymene)RuLCl2]–SiO2, 1 mmol of acetophenone
are economic, relatively mild and environmentally friendly. and 1 mmol or 10 mmol of KOH were refluxed at 80 °C in
The volatile acetone product can also be easily removed to 2-propanol as a hydrogen source. After the mixture was cooled
shift an unfavorable equilibrium. Reactions were performed to room temperature, the volatiles were removed under
under identical conditions to allow comparison of results reduced pressure. The residues were diluted with diethyl ether
(Fig. 12). In a typical experiment, 0.01 mmol of [(p-cymene)- (5 ml) and filtered from a mini-column. The purity of the
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Fig. 10 BET isotherms of amorphous SiO2, and 7–9 with corresponding BJH cumulative pore volume curves of amorphous SiO2, and 7–9.
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Fig. 11 DTA/TG curves of (a) 4, (b) 5, (c) 6 and TG curves of (d) 7–9.
Table 5 TGA data of the synthesized compounds (Ton – thermal degradation onset temperature, Tmax – maximum weight loss temperature, Tend – final thermal
degradation temperature)
First degradation temp. °C
Second degradation temp. °C
Third degradation temp. °C
Loss of
Percentage of
Comp. Ton Tmax Tend weight loss
Percentage of
Ton Tmax Tend weight loss
Percentage of
Ton Tmax Tend weight loss
Char at
950 °C % solvent %
absorbed
4
5
6
7
8
9
201 224
189 228
201 225
196 221
191 221
180 217
271 25
273 29
277 29
271 287
273 331
277 318
271 330
274 326
274 323
300
950 45
950 39.5
471
469
482
6.5
300 335
950 39
27
26
30
80.5
79.5
79.5
2.5
—
1.5
1
—
—
—
—
—
—
—
950
—
—
7
271
274
274
5
5
5
6.5
5
6.5
471 541
469 541
482 535
950 10.5
950 7.5
1.5
obtained in high yield and in a short period when 10 mmol
KOH was used. For 2 hours, the catalytic activity of [(p-cymene)-
RuLCl2] increased in the order 6 (70%) < 4 (71%) < 5 (85%)
and for [(p-cymene)RuLCl2]–SiO2 it increased in the order
9 (73%) < 7 (75%) < 8 (78%) for 10 mmol of KOH, respectively.
When the amount of KOH decreased, we observed that the
slowing of the catalytic conversion depends on the amount of
KOH. According to the results, [(p-cymene)RuLCl2] (4–7) and
[(p-cymene)RuLCl2]–SiO2 (7–9) are efficient catalysts for the TH
of acetophenone. In particular, when electron-donating (4)
and electron-neutral (5) groups were used, the catalytic activity
increased. On the other hand, when the same reaction con-
ditions were carried out with catalysts 7 and 9, the yield of the
products was found to be lower than that obtained using 8
(Fig. 12). This result may be related with the BET surface area
Scheme 1 General reaction schema for the Ru(II)-catalyzed hydrogen transfer
from 2-propanol to acetophenone.
compounds was checked by GC. The yields obtained were
related to the residual unreacted acetophenone.
On the basis of the results in Fig. 12, when 1 mmol of KOH
and 4–9 were used, for a 24 hour period, the catalytic activity
of [(p-cymene)RuLCl2] increased in the order 4 (75%) < 6
(78%) < 5 (87%). Similarly, the catalytic activity of [(p-cymene)-
RuLCl2]–SiO2 increased in the order 9 (68%) < 7 (78%) < 8
(80%) for 1 mmol of KOH. Similar activity ranking was
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Table 7 Transfer hydrogenation of acetophenone in the presence of KOH
(10 mmol) by 2-propanol using 5 and 8 over multiple runs
Entry
Catalyst
Conversion (%)
1
2
3
4
5
6
7
8
9
10
5
8
5
8
5
8
5
8
5
8
85a
75a
67b
72b
60c
76c
51d
74d
90e
98e
a Acetophenone–Ru–KOH, 1 : 0.01 : 10, 2 h. b Acetophenone–Ru–KOH,
2 : 0.01 : 10. At the end of 2 h, an additional 1 mmol acetophenone was
added and the reaction was finished at 4 h. c Acetophenone–Ru–KOH,
3 : 0.01 : 10. At the end of
2 and 4 h, an additional 1 mmol
acetophenone was added and the reaction was finished at 6 h.
d Acetophenone–Ru–KOH, 4 : 0.01 : 10. At the end of 2, 4 and 6 h, an
additional 1 mmol acetophenone was added and the reaction was
finished at 8 h. e Acetophenone–Ru–KOH, 4 : 0.01 : 10, 8 h.
(m2 g−1). The yield of the TH of acetophenone decreased with
low surface area for the supported catalysts. The results are
summarized in Table 6.
A catalyst lifetime experiment was performed with 5 and 8
in the presence of KOH (10 mmol) with 2-propanol as a hydro-
gen source. Multiple runs are shown in Table 7. Herein,
although catalytic conversion decreased in each catalytic run
performed with 5, the catalytic conversion was stabilized in
each catalytic run performed with 8. The catalytic conversions
were observed as 75% for the first run and 74% for the fourth
run. After the fourth run, the volatiles were concentrated
under reduced pressure and washed with pure water (5 ml)
◆
Fig. 12 Catalytic activity for the transfer hydrogenation of acetophenone of
●
■
◆
for (4) appear as green, for (5) appear as red, for (6) appear as blue, for
●
■
(4)–SiO2 appear as green, for (5)–SiO2 appear as red, for (6)–SiO2 appear as
blue. (a) In the presence of 2-propanol at 80 °C with [(p-cymene)RuLCl2]; aceto-
phenone–Ru–KOH, 1 : 0.01 : 1. (b) In the presence of 2-propanol at 80 °C with and methyl alcohol–diethyl ether (10 ml 2 : 8, v/v), respectively,
[(p-cymene)RuLCl2]–SiO2; acetophenone–Ru–KOH, 1 : 0.01 : 1. (c) In the pres-
and the products were extracted with diethyl ether (10 ml).
After leaching, catalyst 8 was still stabilized. When the TH of
acetophenone was performed with 5 and 8 at the substrate/cat-
ence of 2-propanol at 80 °C with [(p-cymene)-RuLCl2]; acetophenone–Ru–KOH,
1 : 0.01 : 10. (d) In the presence of 2-propanol at 80 °C with [(p-cymene)
RuLCl2]–SiO2; acetophenone–Ru–KOH 1 : 0.01 : 10.
alyst ratio: 400 : 1, 8 showed a better conversion than 5, and so
the silica-supported catalysts were found to be more advan-
tageous than the non-supported analogues.
Finally, we investigated the catalytic efficiency of amor-
phous SiO2 on TH of acetophenone for the control of catalytic
reactions. Surprisingly, we found that SiO2 was an active cata-
Table 6 The activity of the catalysts 4–9, comparison in terms of the TON and lyst in the TH of acetophenone, leading to the formation of
TOF values
sec-alcohol with moderate to good conversions (32–68%)
(Table 8). These results may be related to the lifetime of
[(p-cymene)RuLCl2]–SiO2 being longer than the lifetime of
[(p-cymene)RuLCl2].
Conversion
(%)
TOFb
(h−1
Entry
Catalyst
26H34Cl2N2O2RuS: (4)
C22H26Cl2N2O2RuS: (5)
C23H28Cl2N2O3RuS: (6)
[(p-cymene)RuLCl2]–SiO2: (7)
[(p-cymene)RuLCl2]–SiO2: (8)
[(p-cymene)RuLCl2]–SiO2: (9)
TONa
)
1
2
3
4
5
6
C
71
85
70
75
78
73
71a
85a
70a
75a
78a
73a
35.5b
42.5b
35b
37.5b
39b
36.5b
Conclusion
In this work, we reported the preparation and characterization
of sulfonamide ligands (1–3), neutral sulfonamide–Ru(II) com-
plexes (4–6), SiO2 supported sulfonamide–Ru(II) complexes
(7–9) and their catalytic activities for the hydrogen transfer
Reaction condition: 1.0 mmol of acetophenone, 10 mmol KOH and
0.01 mmol 4–9 in the presence of 2-propanol for 2 h at 80 °C. a TON =
moles of product/moles of the catalyst. b TOF = moles of product/
(moles of the catalyst) × (hour).
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Table 8 Catalytic activity for the transfer hydrogenation of acetophenone cata-
lyzed by SiO2
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E. J. Ellena and M. H. Torre, J. Inorg. Biochem., 2006, 100,
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Entry
Catalyst
SiO2
Conversion (%)
Reaction time
0.5 h
1
2
3
4
5
6
7
8
9
10
39a
32b
48a
42b
52a
46b
68a
52b
<3c
<3d
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1.0 h
1.5 h
2.0 h
2.0 h
2.0 h
a In the presence of 2-propanol at 80 °C with SiO2; acetophenone–Si–
KOH, 1:0.5:10. b In the presence of 2-propanol at 80 °C with SiO2;
acetophenone–Si–KOH, 1:0.05:10. c In the presence of 2-propanol at
80 °C with SiO2; acetophenone–Si–KOH, 1:0.05:0. d In the presence of
2-propanol at 80 °C with SiO2; acetophenone–Si–KOH, 1:0.5:0.
reaction of acetophenone with the use of 2-propanol in the
presence of KOH. The synthesized catalysts (4–9) have a simple
chemical structure, are easy to synthesize and do not require
an inert atmosphere. In addition, the support material (SiO2)
has the advantage of being inexpensive. The catalytic reactions
show that because of their long lifetime, silica-supported cata-
lysts (7–9) are more advantageous than non-supported ana-
logues (4–6). The efficiency of the silica-supported catalysts
seems to depend on the ligands of the complexes and the BET
surface area of the materials. Also, to our knowledge, this is
the first report of the hydrogenation of acetophenone using
amorphous silica as a catalyst under TH conditions.
17 (a) S. Dayan and N. Özpozan Kalaycıoğlu, Appl. Organomet.
Chem., 2013, 27, 52–58; (b) N. Özdemir, S. Dayan, O. Dayan,
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Acknowledgements
We acknowledge the financial support granted by Erciyes
University (ERUBAP) (FBA-11-3547, ID: 3547). We further
acknowledge the Faculty of Arts and Sciences, Ondokuz Mayıs
University, Turkey, for the use of the STOE IPDS II diffract-
ometer (purchased under grant No. F-279 of the University
Research Fund).
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