Synthesis of some ruthenium(II)–Schiff base complexes bearing sulfonamide fragment: New catalysts for transfer hydrogenation of ketones

Journal of Organometallic Chemistry 770 (2014) 21e28

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Synthesis of some ruthenium(II)eSchiff base complexes bearing sulfonamide fragment: New catalysts for transfer hydrogenation of ketones b € Serkan Dayan a, Nilgun Kalaycioglu Ozpozan a, *, Namık Ozdemir , Osman Dayan c a b c

Department of Chemistry, Faculty of Science, Erciyes University, 38039 Kayseri, Turkey Department of Physics, Faculty of Art and Sciences, Ondokuz Mayıs University, 55139 Samsun, Turkey Laboratory of Inorganic Synthesis and Molecular Catalysis, Çanakkale Onsekiz Mart University, 17020 Çanakkale, Turkey

a r t i c l e i n f o

a b s t r a c t

Article history: Received 18 February 2014 Received in revised form 25 July 2014 Accepted 1 August 2014 Available online 10 August 2014

Four new ruthenium(II) complexes [RuCl(1e4)(p-cymene)] (1e4 ¼ N-(3-(2-hydroxybenzylideneamino) phenyl) benzenesulfonamides) were synthesized from [RuCl2(p-cymene)]2 with Schiff base ligands containing aromatic sulfonamide fragment, and characterized by spectroscopic techniques including 1 H and 13C NMR, FT-IR, single crystal X-ray diffraction and by elemental analysis. Additionally, all the synthesized Ru(II) complexes were tested as catalysts for the reactions in the transfer hydrogenation (TH) of acetophenone derivatives. The results showed that these facile synthesized Ru(II) complexes are efficient catalysts in this reaction (turnover frequency: 1260 h1 for 6). © 2014 Published by Elsevier B.V.

Keywords: Transfer hydrogenation Sulfonamide Ruthenium Bidentate ligand

Introduction In recent times, there has been an increase in studies regarding sulfonamides and their transition metal complexes because of their potential applications such as for drugs, catalysts, and as a luminescent substance [1e10]. Likewise, Schiff base derivatives have attracted considerable interest in recent decades because of their numerous applications, such as in coordination chemistry, medicinal chemistry, catalysis, etc. [11e24]. Nevertheless, the syntheses of compounds containing both Schiff base and sulfonamide fragments have been rarely studied in the literature [25e31]. Concurrently, complexes bearing sulfonamide or Schiff base ligands are recognized as homogeneous or heterogeneous catalysts in various organic reactions [32e37]. Furthermore, such complexes have recently attracted much attention for reactions in the transfer hydrogenation (TH) of aromatic ketones to secondary alcohols [38e40]. In particular, notable works were conducted in TH catalyzed by various metal complexes containing sulfonamide ligands [41e46]. The critical points of these works showed that the efficiencies of catalysts were directly affected by the steric and electronic properties of the ligands. Therefore, the efforts in the

* Corresponding author. Tel.: þ90 505 644 11 70; fax: þ90 352 437 49 33. E-mail address: [email protected] (N.K. Ozpozan). http://dx.doi.org/10.1016/j.jorganchem.2014.08.002 0022-328X/© 2014 Published by Elsevier B.V.

synthesis of new catalysts and investigation of their activity in the reaction of TH are an ongoing interest for the catalysis community [47e49]. Herein, we report the facile preparation and evaluation of new Schiff baseeRu(II) complexes containing sulfonamide fragment. The catalytic experiments showed that all complexes are efficient catalysts for the reaction in the TH of ketones.

Experimental Materials and methods All chemicals (reagents and solvents) were purchased from chemical companies (SigmaeAldrich, Merck and Alfa Aesar) and used as received unless otherwise stated. The 400 MHz 1H NMR and 100.56 MHz 13C NMR spectra were recorded at ambient temperature on a Bruker 400 NMR spectrometer in CDCl3 as solvent. NMR signals are given in parts per million (ppm) as d downfield from tetramethylsilane (TMS) (d 0.00) as an internal standard. Coupling constants are given in hertz. The multiplicity of NMR peaks is abbreviated as follows: br ¼ broad, d ¼ doublet, m ¼ multiplet, s ¼ singlet, t ¼ triplet. The elemental analyses were carried out using a Truspec MICRO (LECO) instrument. A PerkineElmer Spectrum 400 FTIR system with universal ATR sampling accessory was

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used to obtain the FT-IR spectra. For melting point determination, an Electrothermal 9100 instrument was used with open capillary tubes. A Younglin Acme 6100 GC instrument (FID detector and Optima 5MS capillary column) was used for the catalytic experiments. General procedure for the synthesis of ligands 1e4 Methanolic solutions (10 ml) of N-(3-aminophenyl)benzenesulfonamide (5 mmol) [27] and aromatic aldehydes (5 mmol) were stirred at ambient temperature in a Schlenk tube for 12 h. After this period of time, the volatiles were removed under reduced pressure. The residue was dissolved in ethyl alcohol (5 ml) and left in the refrigerator for crystallization. The crystalline products were filtered and dried (Fig. 1). Data for the ligands 1e4 For 1 Color: Yellow. Yield: 84%. M.P.: 149  C. 1H NMR (CDCl3, d ppm): 12.98 (1H, br., eOH), 8.53 (1H, s, eH5), 7.82e7.86 (2H, m, eH8,9), 7.57 (1H, t, J ¼ 8.0 Hz, eHc), 7.47 (1H, d, J ¼ 8.0 Hz, eH4), 7.40 (2H, t, J ¼ 8.0 Hz, eHb), 7.28 (1H, t, J ¼ 16.0, 8.0 Hz, eH3), 6.93e7.04 (5H, m, eH6, eH2, eHa, eH1). 13C NMR (CDCl3, ppm): 163.5 (eN]CH), 149.5 (eCi5), 138.9 (eCi3), 137.6 (eCi2), 137.0 (eCi1), 133.7 (eC7), 133.3 (eCc), 132.6 (eC9), 130.3 (eC3), 129.2 (eC8), 129.1 (eCb), 127.3 (eCa), 119.6 (eCi4), 119.3 (eC6), 118.5 (eC4), 117.4 (eC2), 113.9 (eC1). IR (cm1): 3258 (NH), 3066, 3008, 2919, 2845, 2786, 2722, 2660, 1621 (eN]Ce), 1594, 1574, 1569, 1484, 1456, 1445, 1397, 1371, 1330 (nasSO2), 1312, 1283, 1271, 1248, 1239, 1214, 1206, 1164 (ns-SO2), 1151, 1117, 1091, 1080, 1071, 1033, 1004, 992, 972, 944, 917, 894, 873, 844, 811, 786, 768, 757, 724, 689, 669, 644, 607, 585(D-SO2), 544, 534, 511, 488, 470, 454. Anal. Calcd. For: [C19H16N2O3S] C: 64.76, H: 4.58, N: 7.95, S: 9.10. Found: C: 64.55, H: 4.69, N: 7.77, S: 8.97. For 2 Color: Orange. Yield: 85%. M.P.: 185  C. 1H NMR (CDCl3, d ppm): 8.25 (1H, s, eH5), 7.83 (1H, d, J ¼ 4.0 Hz, eH9), 7.85 (1H, d, J ¼ 4.0 Hz, eH8), 7.52 (1H, t, J ¼ 8.0 Hz, eHc), 7.43 (2H, t, J ¼ 8.0 Hz, eHb), 7.19 (1H, t, J ¼ 16.0, 8.0 Hz, eH3), 7.13 (1H, d, J ¼ 8.0 Hz, eH4), 7.02 (1H, s, eH1), 6.99 (2H, d, J ¼ 8.0 Hz, eHa), 6.93 (1H, d, J ¼ 8.0 Hz, eH2), 6.22 (1H, s, eH6), 3.38 (4H, q, J ¼ 8.0 Hz, eNCH2CH3), 1.19 (6H, t, J ¼ 8.0 Hz, eNCH2CH3). 13C NMR (CDCl3, ppm): 164.9 (eN]CH), 159.5 (eCi5), 152.8 (eCi3), 147.9 (eC7), 139.1 (eCi2), 137.8 (eCi1), 134.7 (eC9), 133.0 (eCc), 130.1 (eC3), 129.1 (eCb), 127.3 (eCa), 118.4 (eC4), 117.6 (eC2), 113.0 (eC1), 108.5 (eCi4), 104.5 (eC8), 97.8 (eC6), 44.8 (eNCH2CH3), 12.7 (eNCH2CH3). IR (cm1): 3310 (NH), 3062, 2972, 2930, 2897, 2870, 1622 (eN]Ce), 1585, 1558, 1515, 1506, 1487, 1481, 1446, 1435, 1417, 1407, 1377, 1337 (nas-SO2), 1297, 1269, 1235, 1194, 1165, 1136 (ns-SO2), 1092, 1075, 1025, 1009, 969, 945, 899, 870, 839, 775, 751, 715, 684, 626, 587 (D-SO2), 568, 553, 530,

499, 489, 457. Anal. Calcd. For: [C23H25N3O3S], C: 65.23, H: 5.95, N: 9.92, S: 7.57. Found: C: 65.49, H: 5.72, N: 9.88, S: 7.63.

For 3 Color: Yellow. Yield: 87%. M.P.:151  C. 1H NMR (CDCl3, d ppm): 13.52 (1H, br., eOH), 8.43 (1H, s, eH5), 7.84 (1H, d, J ¼ 4.0 Hz, eH9), 7.86 (1H, d, J ¼ 4.0 Hz, eH8), 7.57 (1H,t, J ¼ 8.0 Hz, eHc), 7.55 (2H, t, J ¼ 8.0 Hz, eHb), 7.47 (1H, t, J ¼ 16.0, 8.0 Hz, eH3), 7.24 (1H, d, J ¼ 8.0 Hz, eH4), 7.17 (1H, br., eNH), 7.01 (1H, s, eH1), 6.97 (2H, d, J ¼ 8 Hz, eHa), 6.96 (1H, d, J ¼ 8.0 Hz, eH2), 6.51 (1H, s, eH6), 3.85 (3H, s, eOCH3). 13C NMR (CDCl3, ppm): 164.4 (eN]CH), 161.3 (eCi5), 149.4 (eCi3), 138.9 (eCi2), 137.5 (eCi1), 133.8 (eCc), 133.2 (eC9), 130.2 (eC3), 129.2 (eCb), 127.3 (eCa), 119.1 (eC4), 118.3 (eC2), 113.8 (eC1), 112.9 (eCi4), 107.4 (eC8), 101.1 (eC6), 55.62 (eOCH3). IR (cm1): 3258 (eNH), 3089, 3009, 2940, 2862, 2841, 1616 (eN]Ce), 1588, 1515, 1485, 1450, 1441, 1393 (nas-SO2), 1324, 1289, 1240, 1220, 1208, 1161, 1140 (ns-SO2), 1110, 1088, 1030, 992, 964, 909, 879, 831, 791, 761, 716, 688, 647, 620, 586 (D-SO2), 551, 525, 508, 487, 469, 421. Anal. Calcd. For: [C20H18N2O4S], C: 62.81, H: 4.74, N: 7.33, S: 8.38. Found: C: 62.97, H: 4.58, N: 7.44, S: 8.21.

For 4 Color: Orange Yield: 95%. M.P.: 187  C. 1H NMR (CDCl3, d ppm): 14.08 (1H, br., eOH), 8.64 (1H, s, eH5), 8.40 (1H, s, eH9), 8.30 (1H, d, J ¼ 8.0 Hz, eH7), 7.59 (1H, t, J ¼ 8.0 Hz, eHc), 7.50 (2H, t, J ¼ 8.0 Hz, eHb), 7.34 (1H, t, J ¼ 16.0, 8.0 Hz, eH3), 7.85 (1H, d, J ¼ 8.0 Hz, eH4), 7.15 (2H, d, J ¼ 8.0 Hz, eHa), 7.12 (1H, s, eH1), 7.07 (1H, d, J ¼ 8.0 Hz, eH2), 7.09 (1H, s, eH6). 13C NMR (CDCl3, ppm): 166.6 (eN]CH), 161.7 (eCi5), 147.9 (eCi3), 140.1 (eCi2), 138.8 (eC8), 137.9 (eCi1), 133.9 (eCc), 130.6 (eC3), 129.3 (eCb), 127.2 (eCa), 125.0 (eC7), 123.7 (eC9), 120.4 (eCi4), 118.5 (eC4), 118.4 (eC6), 118.0 (eC2), 113.9 (eC1). IR (cm1): 3254 (eNH), 3064, 2987, 2892, 2825, 1621 (eN]Ce), 1592, 1524, 1481, 1446, 1410, 1331 (nas-SO2), 1299, 1236, 1164, 1147 (ns-SO2), 1089, 1025, 991, 963, 945, 906, 856, 834, 799, 761, 753, 717, 688, 637, 582 (D-SO2), 554, 469, 439, 412. Anal. Calcd. For: [C19H15N3O5S], C: 57.42, H: 3.80, N: 10.57, S: 8.07. Found: C: 57.64, H: 3.89, N: 10.29, S: 8.32.

General procedure for the synthesis of complexes 5e8 A methanolic solution (10 ml) of ligands 1e4 (0.50 mmol) and [RuCl2(p-cymene)]2 (0.25 mmol) was stirred at 50  C for 12 h in a Schlenk tube. After this period of time, the volatiles were removed under reduced pressure. The residue was recrystallized in MeOH/ diethyl ether (1:3) and the crystalline product was collected by filtration, washed with a large quantity of diethyl ether, and dried in vacuum (Fig. 2).

Fig. 1. Synthesis of the ligands 1e4 together with NMR numbering scheme.

S. Dayan et al. / Journal of Organometallic Chemistry 770 (2014) 21e28

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Fig. 2. Synthesis of the complexes 5e8 together with NMR numbering scheme.

Data for complexes 5e8 For 5 Color: Red. Yield: 82%. M.P.: 109  C. 1H NMR (CDCl3, d ppm): 8.54 (1H, s, eH5), 6.81e7.97 (13H, m, AreH), 5.49 (2H, d, J ¼ 8.0 Hz, eHx), 5.36 (2H, d, J ¼ 8.0 Hz, eHy), 2.92 (1H, m, eHl), 2.16 (3H, s, eHk), 1.28 (6H, d, J ¼ 8.0 Hz, eHm). 13C NMR (CDCl3, ppm): 163.7 (eN]CH), 147.1 (eCi5), 137.0 (eCi3), 136.9 (eCi2), 133.8 (eCi1), 130.3 (eC7), 129.2 (eCc), 129.0 (eC9), 127.5 (eC3), 127.3 (eC8), 127.2 (eCb), 127.0 (eCa), 121.5 (eCi4), 119.9 (eC6), 117.4 (eC4), 113.3 (eC2), 111.1 (eC1), 101.3, 96.8, 81.3, 80.6, 30.7 (eCH(CH3)2), 22.2 (eCH(CH3)2), 18.9 (eCH3). IR (cm1): 3319 (NH), 3023, 2961, 2933, 2832, 1600 (eN] Ce), 1532, 1489, 1471, 1446, 1387, 1361, 1328 (nas-SO2), 1292, 1279, 1200, 1152 (ns-SO2), 1091, 1061, 1031, 1002, 977, 872, 804, 755, 721, 688, 667, 637, 583 (D-SO2), 550, 486, 472, 465. Anal. Calcd. For: [C29H29ClN2O3RuS], C: 55.99, H: 4.70, N: 4.50, S: 5.15. Found: C: 55.78, H: 4.59, N: 4.72, S: 5.01. For 6 Color: Brown. Yield: 84%. M.P.: 152  C. 1H NMR (CDCl3, d ppm): 8.18 (1H, s, eH5), 6.64e7.53 (12H, m, AreH), 5.48 (2H, d, J ¼ 8.0 Hz, eHx), 5.35 (2H, d, J ¼ 8.0 Hz, eHy), 3.42 (4H, q, J ¼ 8.0 Hz, eNCH2CH3), 2.93 (1H, m, eHl), 2.16 (3H, s, eHk), 1.28 (6H, d, J ¼ 8.0 Hz, eHm), 1.22 (6H, t, J ¼ 8.0 Hz, eNCH2CH3). 13C NMR (CDCl3, ppm): 166.5 (eN]CH), 158.6 (eCi5), 152.0 (eCi3), 147.9 (eC7), 143.2 (eCi2), 141.3 (eCi1), 139.5 (eC9), 133.9 (eCc), 132.9 (eC3), 129.1 (eCb), 128.2 (eCa), 118.1 (eC4), 117.0 (eC2), 114.1 (eC1), 109.6 (eCi4), 105.8 (eC8), 102.6 (eC6), 101.3, 96.8, 81.3, 80.6, 47.2 (eNCH2CH3), 30.6 (eCH(CH3)2), 22.2 (eCH(CH3)2), 18.9 (eCH3), 14.4 (eNCH2CH3). IR (cm1): 3372 (NH), 3057, 2963, 2932, 2830, 1615 (eN]Ce), 1587, 1558, 1527, 1505, 1488, 1446, 1428, 1377, 1334 (nas-SO2), 1297, 1242, 1223, 1154 (ns-SO2), 1121, 1092, 1075, 1031, 1001, 982, 964, 872, 789, 758, 720, 688, 667, 629, 582 (D-SO2), 550, 521, 500, 486, 466, 458. Anal. Calcd. For: [C33H38ClN3O3RuS], C: 57.17, H: 5.52, N: 6.06, S: 4.63. Found: C: 57.32, H: 5.39, N: 6.19, S: 4.51. For 7 Color: Light Brown. Yield: 82%. M.P.: 148  C. 1H NMR (CDCl3, d ppm): 9.73 (1H, s, eH5), 6.41e7.98 (12H, m, AreH), 5.49 (2H, d, J ¼ 8.0 Hz, eHx), 5.36 (2H, d, J ¼ 8.0 Hz, eHy), 3.70 (3H, s, eOCH3), 2.93 (1H, m, eHl), 2.16 (3H, s, eHk), 1.28 (6H, d, J ¼ 8.0 Hz, eHm). 13C NMR (CDCl3, ppm): 170.9 (eN]CH), 160.4 (eCeOCH3), 159.2 (eCi5), 144.9 (eCi3), 137.3 (eCi2), 136.6 (eCi1), 135.3 (eCc), 133.2 (eC9), 129.7 (eC3), 129.2 (eCb), 127.5 (eCa), 121.5 (eC4), 119.8 (eC2), 116.9 (eC1), 112.5 (eCi4), 108.4 (eC8), 103.0 (eC6), 101.3, 96.8, 81.3, 80.6, 55.2 (eOCH3), 30.6 (eCH(CH3)2), 22.2 (eCH(CH3)2), 18.9 (eCH3). IR (cm1): 3239 (eNH), 3054, 2962, 2933, 2872, 2837, 1607 (eN]Ce), 1588, 1520, 1488, 1471, 1445, 1417, 1374, 1330 (nas-SO2), 1297, 1259, 1216, 1150 (ns-SO2), 1120, 1090, 1057, 1023, 1002, 977, 871, 838, 789, 755, 719, 688, 637, 615, 581 (D-SO2), 548, 524, 514, 487, 471, 460.

Anal. Calcd. For: [C30H31ClN2O4RuS], C: 55.25, H: 4.79, N: 4.30, S: 4.92. Found: C: 55.31, H: 4.91, N: 4.41, S: 4.81. For 8 Color: Dark Brown. Yield: 84%. M.P.: 179  C. 1H NMR (CDCl3, d ppm): 8.59 (1H, s, eH5), 6.85e7.98 (12H, m, AreH), 5.50 (2H, d, J ¼ 8.0 Hz, eHx), 5.37 (2H, d, J ¼ 8.0 Hz, eHy), 2.92 (1H, m, eHl), 2.15 (3H, s, eHk), 1.29 (6H, d, J ¼ 8.0 Hz, eHm), 2.15 (s, 3H, eHk), 2.92 (m, 1H, eHl), 5.37 (d, 2H, J ¼ 8 Hz, eHy), 5.50 (d, 2H, J ¼ 8 Hz, eHx), 6.85e7.98 (12H, AreH), 8.59 (s, 1H, eH5). 13C NMR (CDCl3, ppm): 164.3 (eN]CH), 158.2 (eCi5), 146.0 (eCi3), 139.2 (eCi2), 137.7 (eC8), 135.9 (eCi1), 133.3 (eCc), 130.0 (eC3), 129.7 (eCb), 129.4 (eCa), 127.6 (eC7), 123.2 (eC9), 119.2 (eCi4), 117.4 (eC4), 115.9 (eC6), 102.1 (eC2), 101.3 (eC1), 99.5, 96.8, 81.3, 80.6, 30.7 (eCH(CH3)2), 22.2 (eCH(CH3)2), 18.7 (eCH3). IR (cm1): 3237 (eNH), 3061, 2962, 2922, 2855, 1594 (eN]Ce), 1544, 1471, 1446, 1387, 1308 (nas-SO2), 1238, 1150 (ns-SO2), 1089, 1024, 1001, 975, 953, 895, 871, 831, 791, 753, 719, 686, 653, 636, 613, 580 (D-SO2), 546, 505, 490, 482, 471, 463. Anal. Calcd. For: [C29H28ClN3O5RuS], C: 52.21, H: 4.23, N: 6.30, S: 4.81. Found: C: 52.32, H: 4.45, N: 6.19, S: 4.90. Catalytic experiments Distilled 2-propanol was stored under argon prior to use. All of the transfer hydrogenation reactions were performed with Schlenk techniques under argon at 82  C. In a typical run, the Ru(II) complexes (5e8) (0.01 mmol) and acetophenone (5 mmol) were stirred in the presence of 2-propanol (6 ml) in a Schlenk flask for a period 15 min at ambient temperature. After the period of time specified, the base (1 mmol) was added to the reaction mixture and heated at 82  C for the desired time period. At the end of this time, the sample was diluted with diethyl ether (5 ml) and filtered from a mini-column filled with silica gel. The purity of the products was determined by Gas Chromatography. The yields were calculated based on the residual acetophenone (Fig. 3). Single-crystal structure determination Intensity data for complex 6 were collected on an STOE IPDS II diffractometer at 296 K using graphite-monochromated Mo Ka radiation (l ¼ 0.71073 Å) by applying the u-scan method. The structure of complex 6 was determined by direct methods using

Fig. 3. Transfer hydrogenation of ketones with catalysts [RuCl(p-cymene)L].

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SHELXS-2013 [50] and refined with full-matrix least-squares calculations on F2 using SHELXL-2013 [50] implemented in the WinGX [51] program suite. All H atoms were placed geometrically and treated using a riding model, fixing the bond lengths at 0.86, 0.93, 0.98, 0.97 and 0.96 Å for NH, aromatic CH, methine CH, CH2 and CH3 atoms, respectively. The displacement parameters of the H atoms were fixed at Uiso (H) ¼ 1.2Ueq (1.5Ueq for methyl) of their parent atoms. Data collection: X-AREA [52], cell refinement: X-AREA, data reduction: X-RED32 [52]. The crystal data, data collection and structure refinement details are summarized in Table 1. The general-purpose crystallographic tool PLATON [53] was used for the structure analysis and presentation of the results. Molecular graphics were generated by using ORTEP-3 [54]. Results and discussion Synthesis of [RuCl(L)(p-cymene)] complexes (5e8) The Schiff base ligands (1e4) bearing sulfonamide fragment were readily synthesized by the reaction of N-(3-aminophenyl) benzenesulfonamide [27] and commercially available aromatic aldehydes (Fig. 1). In the 1H NMR spectra for the synthesized ligands (1e4), the eH1 was located around 7.01e7.12 ppm as a singlet. Likewise, the resonances of the eHa and eHb protons could be assigned as a doublet and triplet around d ¼ 6.97e7.15 ppm and 7.40e7.55 ppm, respectively. Additionally, eN]CHe proton peaks appeared between d 8.25e8.64 ppm. The eNCH2CH3 protons were observed as quartet and triplet in a 2:3 ratio around d 3.38 and 1.19 ppm for 2. On the other hand, eOCH3 protons were shown as a singlet at d 3.85 ppm for 3. In the 13C NMR spectra for 2, the eNCH2CH3 carbons were assigned at 44.8 (eCH2e) and 12.7 (eCH3) ppm. For 3, the eOCH3 carbon was shown at 55.6 ppm. The carbon peaks belonging to eN]CH for 1e4 were observed between d 163.5e166.6 ppm. The peaks in the region 1622 cm1 to

Table 1 Crystal data and structure refinement parameters for complex 6. CCDC deposition no. Color/shape Chemical formula Formula weight Temperature (K) Wavelength (Å) Crystal system Space group Unit cell parameters a, b, c (Å) a, b, g ( ) Volume (Å3) Z Dcalc (g/cm3) m (mm1) Absorption correction Tmin, Tmax F000 Crystal size (mm3) Diffractometer/measurement method Index ranges q Range for data collection ( ) Reflections collected Independent/observed reflections Rint Refinement method Data/restraints/parameters Goodness-of-fit on F2 Final R indices [I > 2s(I)] R Indices (all data) Drmax, Drmin (e/Å3)

967927 Clear red/prism [RuCl(C10H14)(C23H24N3O3S)] 693.24 296 0.71073 Mo Ka Monoclinic P21/c (No. 14) 15.9267(5), 22.7679(6), 22.1135(7) 90, 126.363(2), 90 6457.3(4) 8 1.426 0.670 Integration 0.8997, 0.9698 2864 0.25  0.15  0.07 STOE IPDS II/rotation (u scan) 19  h  19, 27  k  27, 25  l  27 1.45  q  25.87 51,217 12,043/5349 0.106 Full-matrix least-squares on F2 12,043/23/759 0.946 R1 ¼ 0.0561, wR2 ¼ 0.0817 R1 ¼ 0.1466, wR2 ¼ 0.0949 0.428, 0.357

1616 cm1 were assigned to >C]Ne stretching vibrations in FT-IR for ligands. The Ru(II) complexes (5e8) were successfully synthesized by the reaction of [RuCl2(p-cymene)]2 dimer and bidentate imine ligands bearing sulfonamide fragment in high yields. The structures of all the complexes were confirmed with FT-IR, 1 H and 13C NMR and elemental analysis. Also, the solid state structure of complex 6 was confirmed by single crystal X-ray analysis. When examining the 1H NMR spectra of the complexes, the eHk, eHx, eHy, eHl and eHm protons belonging to the p-cymene ligand were observed as singlet at between d ¼ 2.15e2.16 ppm, as doublet at around d ¼ 5.48e5.50 ppm, as doublet at around d ¼ 5.35e5.37 ppm, as multiplet at between d ¼ 2.92e2.93 ppm and as doublet at around d ¼ 1.28e1.29 ppm, respectively. Likewise, the eN]CHe protons were located as singlet at between d ¼ 8.18e9.73 ppm. In the 13C NMR spectra for 6 and 7, the carbon peaks belonging to eNCH2CH3 and eOCH3 groups were occurred at 47.2 (eNCH2CH3), 14.4 (eNCH2CH3), and 55.2 (eOCH3) ppm. In the FT-IR spectra of Ru(II) complexes (5e8), the stretching vibrations of the eN]Ce group were revealed at around 1594e1615 cm1. In the light of these data, it is evident that all chemical shifts and integrations of signals for NMR spectra and the peaks of FT-IR spectra were consistent with the proposed structure. Structural description of the complex 6 An ORTEP-3 diagram of complex 6 including the atomic numbering scheme is depicted in Fig. 4, and the remarkable bond lengths and angles in the structure are given in Table 2. The complex crystallizes in the monoclinic space group P21/c with eight molecules in the unit cell. There are two diastereoisomeric molecules in the asymmetric unit of complex 6, labeled as A and B. For the sake of clarity, only one (diastereomer A) of the two molecules is plotted in Fig. 4. In a following part of this paper, parameters B are quoted in square brackets. The complex consists of a Ru(II) ion, one bidentate Schiff Base (2) ligand, one p-cymene ligand and one Cl ligand. The two diastereomers in a 1:1 molar ratio have a (RRu) and (SRu) configuration for diastereomers A and B (the priority sequence: h6-pcymene > Cl > O > N), respectively [55e58]. Complex 6 exhibits a classical three legged piano stool structure with Ru(II) coordinated by the nitrogen and oxygen atoms of 2 and chloride as the legs and the h6 p-bound p-cymene ligand as the seat of the piano stool. The rotational orientation of the p-cymene ring is such that atoms Cl1, O3 and N2 are staggered towards the p-cymene ring C atoms, i.e. when viewed along the p-cymene ring centroideRu bond axis, the atoms eclipse the p-cymene ring CeC bonds rather than the C atoms.

Fig. 4. A view of complex 6 showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 10% probability level. Hydrogen atoms have been omitted for the sake of clarity.

S. Dayan et al. / Journal of Organometallic Chemistry 770 (2014) 21e28 Table 2 Selected geometric parameters for complex 6. Parameter

Molecule A Molecule B Parameter

Molecule A Molecule B

Bond lengths (Å) Ru1eCl1 2.4257(17) 2.4353(18) S1eN1 Ru1eO3 2.086(3) 2.052(4) S1eC6 Ru1eN2 2.075(5) 2.069(4) O3eC15 Ru1eC25 2.187(6) 2.196(6) N1eC7 Ru1eC26 2.151(6) 2.158(6) N2eC11 Ru1eC27 2.160(6) 2.133(8) N2eC13 Ru1eC28 2.156(6) 2.148(7) N3eC17 Ru1eC29 2.178(6) 2.140(6) N3eC20 Ru1eC30 2.182(6) 2.152(6) N3eC22 S1eO1 1.435(4) 1.417(5) C13eC14 S1eO2 1.438(5) 1.428(4)

1.626(5) 1.768(7) 1.292(6) 1.409(7) 1.446(7) 1.260(6) 1.383(8) 1.496(9) 1.642(10) 1.432(7)

1.622(5) 1.774(9) 1.303(6) 1.425(6) 1.449(6) 1.289(6) 1.389(7) 1.535(10) 1.642(11) 1.427(7)

Bond angles ( ) Cl1eRu1eO3 84.10(11) Cl1eRu1eN2 84.78(13) Cl1eRu1eC25 90.7(2) Cl1eRu1eC26 114.7(2) Cl1eRu1eC27 151.89(19) Cl1eRu1eC28 159.8(2) Cl1eRu1eC29 122.2(2) Cl1eRu1eC30 94.82(18) O3eRu1eN2 89.12(16) O3eRu1eC25 147.4(3) O3eRu1eC26 161.0(2) O3eRu1eC27 123.8(2) O3eRu1eC28 92.43(19) O3eRu1eC29 88.36(19) O3eRu1eC30 110.6(2) N2eRu1eC25 122.5(3)

95.2(3) 91.5(2) 115.2(3) 152.4(3) 160.2(2) 118.7(3) 125.4(5) 117.6(5) 104.8(3) 124.2(4) 116.7(5) 129.1(6) 121.4(7) 119.6(7) 117.1(6)

94.3(2) 92.2(2) 116.6(2) 154.5(3) 158.6(2) 119.7(3) 123.7(5) 118.1(5) 105.6(3) 118.4(4) 116.0(4) 128.3(5) 119.7(6) 120.4(7) 116.0(7)

83.23(13) 86.76(13) 92.6(2) 118.6(2) 156.9(2) 155.8(2) 118.1(2) 91.9(2) 88.10(16) 151.0(2) 158.1(2) 119.8(2) 90.8(2) 89.2(2) 113.0(2) 120.4(2)

N2eRu1eC26 N2eRu1eC27 N2eRu1eC28 N2eRu1eC29 N2eRu1eC30 O1eS1eO2 O3eC15eC14 O3eC15eC16 N1eS1eC6 S1eN1eC7 C11eN2eC13 N2eC13eC14 C17eN3eC20 C17eN3eC22 C20eN3eC22

The Ru (II) centre has a pseudo-octahedral coordination geometry in which p-cymene occupied three facial coordination sites. Nonetheless, the coordination geometry of the Ru (II) ion can be accepted as a tetrahedron with considerable trigonal distortion, taking into account the center of the h6-p-cymene aromatic ring as the fourth ligand position. If X is determined as the centroid of the p-cymene ring, the RueX distance is found to be 1.6599(5) Å [1.6452(6) Å], and the Cl1eRu1eX, O3eRu1eX and N2eRu1eX angles are 128.52(5), 126.20(10) and 129.48(14) [128.43(5), 126.17(13) and 129.29(13) ], respectively. The Cl1eRu1eO3, Cl1eRu1eN2 and O3eRu1eN2 angles [mean 86 for diastereomer A and 86.03 for diastereomer B] are smaller than the ideal tetrahedral angle (109.47 ), which is counter balanced by the expanding of the XeRueL (L is Cl1, O3 or N2) angles [mean 128.07 for diastereomer A and 127.96 for diastereomer B]. There are substantial differences in the CeC [1.368(8)e 1.423(8) Å for diastereomer A and 1.366(8)e1.425(8) Å for diastereomer B] and RueC [2.151(6)e2.187(6) Å for diastereomer A and 2.133(8)e2.196(6) Å for diastereomer B] distances for the p-cymene ring. In the complex, the p-cymene ring is planar with anr.m.s deviation from the plane of 0.0126 Å [0.0118 Å]. Ligand 2 is bent at the sulfur atom with the CeSO2eNHeC torsion angle of 48.0(5) [54.8(6) ], and the sulfur atom has a distorted tetrahedral geometry with a maximum deviation of 118.7(3) [119.7(3) ]. The O- and N-donor atoms of the bidentate ligand 2 form a sixmembered metallacycle (containing atoms O3/C15/C14/C13/N2/ Ru1) with anr.m.s deviation from the plane of 0.0027 Å [0.0921 Å]. The bond distances of RueCl1, Ru1eO3 and Ru1eN2 are found to be 2.4257(17), 2.086(3) and 2.075(5) Å [2.4353(18), 2.052(4) and 2.069(4) Å], respectively. Many Ru(II)earene complexes with the same coordination environment have been reported crystallographically [59e70]. According to the bond lengths in these structures, the RueX, RueC, RueCl, RueO and RueN bond lengths vary from 1.633 to 1.710 Å, from 2.102 to 2.267 Å, from 2.388 to 2.467 Å, from 1.728 to 2.153 Å and from 2.068 to 2.185 Å, respectively.

25

Therefore, it can be said that the coordination bond distances are in good agreement accordance with the literature values. In the molecular structure of complex 6, intramolecular C10BeH10B/Cl1B and C8AeH8A/O1A contacts lead to the formation of six-membered rings with graph-set descriptor S(6) [71]. The two diastereoisomeric molecules in the asymmetric unit are connected to each other by means of two intermolecular interactions of types CeH/Cl and NeH/O, together forming an R22 ð9Þ ring [71]. Atoms C1B and C12B in the molecule at (x, y, z) act as a hydrogen-bond donor, via atoms H1B1 and H12B, to the chloride atom Cl1A in the molecule at (x, y þ 1/2, z þ 1/2), while atom N1B forms an NeH/O contact, via atom H1B, with atom O3A. In addition, the p-cymene atom C29A in the molecule at (x, y, z) acts as a hydrogen-bond donor, via atom H29A, to the oxygen atom O2B in the molecule at (x, y þ 1/2, z  1/2). Extension of these intermolecular hydrogen-bonding interactions generates a chain of molecules running along the [001] direction. Finally, the chains are connected to each other via C24BeH24D/O2B hydrogen bonds (Fig. 5). The full geometry of the intra- and intermolecular interactions is given in Table 3. Catalytic properties It is known that Ruthenium complexes having similar structure are good catalysts in transfer hydrogenation reactions. In this study, facile synthesized [RuCl(1e4)(p-cymene)] complexes (5e8) were used as catalysts in the TH of acetophenone derivatives in the presences of 2-propanol as hydrogen donor and inorganic base (Fig. 6). For the optimization of reaction conditions, the influence of base type was investigated. For this purpose, all complexes (5e8) were studied in the model reaction using acetophenone (S/C ¼ 500/ 1 molar ratio). Concurrently, the optimization reactions were also performed without inorganic base but no reaction was observed even after 3 h. When the use of an inorganic bases (1 mmol), were used the conversion rate generally occurred as K2CO3 < KOtBu < NaOH < KOH (Table 4 and Fig. 7(a)). Likewise, the reaction was also tested with 0.1 mmol of KOH and catalyst 5 but the conversion could not obtain high values 28%. Because of this, KOH was selected as base in this system. The behavior of all complexes in the TH of acetophenone derivatives (acetophenone, 4-chloroacetophenone, 4-methoxyaceto phenone) in the presence of 2-propanol and KOH was studied

Fig. 5. Part of the crystal structure of complex 6 showing the intermolecular interactions. For clarity, only H atoms involved in hydrogen bonding have been included.

26

S. Dayan et al. / Journal of Organometallic Chemistry 770 (2014) 21e28

Table 3 Hydrogen bonding geometry for complex 6. D-H/A

D-H (Å)

H/A (Å)

D/A (Å)

D-H/A ( )

C10BeH10B/Cl1B C8AeH8A/O1A C1AeH1A1/Cl1B C12BeH12B/Cl1Aa N1AeH1A/O3B N1BeH1B/O3Aa C24BeH24D/O2Bb C1BeH1B1/Cl1Aa C29AeH29A/O2Bc

0.93 0.93 0.93 0.93 0.86 0.86 0.96 0.93 0.93

2.65 2.50 2.65 2.77 2.08 2.28 2.44 2.77 2.45

3.440(5) 3.143(9) 3.579(7) 3.690(6) 2.921(6) 3.030(6) 3.245(7) 3.533(11) 3.137(9)

143 127 173 172 164 146 141 139 130

a b c

Symmetry code: x, y þ 1/2, z þ 1/2. Symmetry code: x, y  1/2, z þ 3/2. Symmetry code: x, y þ 1/2, z  1/2.

using S/C/B: 5/0.01/1 and 10/0.01/1 molar ratios (Figs. 6 and 7). According to results, the [RuCl(1e4)(p-cymene)] complexes (5e8) were found to have good catalytic activities for the TH of ketones. The best yield was observed with 4-chloroacetophenone as substrate. The introduction of eCl substituent at the para-position of the acetophenone has a positive effect. The highest value of TOF as 1260 h1 was achieved with complex 6 for the TH of 4-chloroacetophenone for 10 min (S/C ¼ 1000/1 molar ratio). For acetophenone, it was found that the catalytic activity of the complexes for the transfer hydrogenation of acetophenone follow the order 5 > 6 > 7 > 8, respectively. Furthermore, the catalytic efficiency of the catalyst 6 was also tested in the TH of benzophenone (diaryl) and cyclohexanone (aliphatic ketones). In the presence of benzophenone 55% and cyclohexanone 73% conversion were achieved in 3 h with the catalyst 6 (Fig. 8).

Conclusions Herein, we reported the synthesis of a series of Ru(II)eSchiff base complexes bearing sulfonamide fragment and characterized them by NMR, IR, elemental analysis, and single-crystal X-ray diffraction. Moreover, catalytic tests demonstrated that these facile synthesized complexes (5e8) were highly active catalysts in the TH of acetophenone derivatives. Also, the complex 6 was tested and founded as effective catalyst in the TH of benzophenone and cyclohexanone. The catalytic yield increased in the presence of the eCl substituent at the para-position of the acetophenone according to other eH and eCH3 substituents. That is, if an electron donating group was introduced into the para-position of the acetophenone, the catalytic conversions were decreased. But the surprisingly, the presence of electron-donating groups on the imine bond ring has beneficial effect. In this context, the maximum conversions were carried out with complexes 5 and 6 bearing electron-donating group and the highest TOFs were observed at 1140 and 1260 h1

Table 4 Catalytic activity for transfer hydrogenation of acetophenone catalyzed by Ru(II) complexes (5e8) with different base. Entry Ru(II) complex 1 2 3 4 5 6 7 8 9 10 11 12 19 20 21

Fig. 6. Catalytic activity as shown by the % conversion vs. time for the transfer hydrogenation of (a) acetophenone, (b) 4-methyl-acetophenone, (c) 4-chloro-acetophenone catalyzed by compounds 5e8 in 2-propanol. Conditions: substrate/Ru/KOH, 5:0.01:1; T ¼ 82  C.

Base

5 NaOH 6 7 8 5 K2CO3 6 7 8 5 KOtBu 6 7 8 Absence of KOH (1 mmol) catalyst 5 Absence of base 5 KOH (0.1 mmol)

Yield (%)a

TOF (h1)b

10c, 20d, 29e, 39f, 47g, 55h, 60i 12c, 23d, 37e, 45f, 49g, 54h, 59i 12c, 26d, 38e, 49f, 57g, 62h, 65i 9c, 20d, 32e, 39f, 43g, 48h, 50i 5c, 9d, 13e, 15f, 19g, 23h, 27i 5c, 10d, 13e, 16f, 19g, 23h, 26i 6c, 10d, 14e, 17f, 21g, 26h, 32i 4c, 8d, 13e, 16f, 21g, 25h, 31i 8c, 13d, 19e, 25f, 31g, 38h, 42i 8c, 13d, 18e, 24f, 30g, 37h, 40i 10c, 14d, 21e, 27f, 33g, 39h, 45i 11c, 17d, 22e, 28f, 33g, 38h, 43i 5e, 9g

300c 360c 360c 270c 150c 150c 180c 120c 240c 240c 300c 330c n.c.

<5i (3 h) 28i (3 h)

n.c. 47i

Reaction conditions: 5.0 mmol of acetophenone, 1.0 mmol of base, 0.01 mmol Ru(II) complexes, 2-propanol (6 ml); all reactions were monitored by TLC and GC; temperature 82  C. a GC yields, yields are based on phenylethanol. b TOF ¼ moles of product/(moles of the catalyst)  (hour). c 15 min. d 30 min. e 60 min. f 90 min. g 120 min. h 150 min. i 180 min.

S. Dayan et al. / Journal of Organometallic Chemistry 770 (2014) 21e28

27

for 5 and 6, respectively. These results clearly show that the new Ru(II)eSchiff base complexes containing sulfonamide fragment both readily synthesized and may be as good as catalysts according to costly Ru(II) complexes [72e77]. Acknowledgments We would like to thank the financial support granted by Erciyes University (ERUBAP), (FBA-11-3547, ID: 3547). We acknowledge the Faculty of Arts and Sciences, Ondokuz Mayıs University, Turkey, for the use of the STOE IPDS II diffractometer (purchased under grant No. F-279 of the University Research Fund). Appendix A. Supplementary material CCDC 967927 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/ data_request/cif. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] Fig. 7. Catalytic activity as shown by the % conversion vs. time for the transfer hydrogenation of (a) acetophenone, (b) 4-methyl-acetophenone, (c) 4-chloro-acetophenone catalyzed by compounds 5e8 in 2-propanol. Conditions: substrate/Ru/KOH, 10:0.01:1; T ¼ 82  C.

[17] [18] [19] [20] [21]

[22] [23] [24] [25] [26] [27]

[28] Fig. 8. Catalytic activity as shown by the % conversion vs. time for the transfer hydrogenation of benzophenone and cyclohexanone catalyzed by compound 6 in 2propanol. Conditions: substrate/Ru/KOH, 5:0.01:1; T ¼ 82  C.

[29] [30]

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