Synthesis and Characterization of Unsymmetrical

D.r/ R. M. El-Mehdawi, and etat.,

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Synthesis and Characterization of Unsymmetrical Tridentate Schiff Base Complex of Nickel (II) Acetate Dr. R. M. El-Mehdawi1, Dr. A. N. Eldewik2, K. M. Kreddan3, F. A. Treish1, A. M. Naghmush4 Hend ben Hussien3, M. E. Ben-Younes1 and S. H. Abu-Agrab1 1

Chemistry Department- Faculty of science- Al-Fateh University. Chemistry Department- Faculty of science- seventh April University. 3 Libyan Petroleum Institute, PO. Box 6431 Tripoli-Libya 4 The Advanced Lab. of chemical analysis PO. Box 13439 Tripoli-Libya 2

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‫ ﺤﻴﺙ‬،1:1 ‫ ﺒﻨﺴﺒﺔ‬L ‫ﺍﻝﺘﻜﺎﻓﺅ ﻓﻲ ﻤﺤﻠﻭل ﺍﻻﻴﺜﺎﻨﻭل ﺍﻝﻤﺤﻤﺽ ﺘﻤﺜل ﻗﺎﻋﺩﺓ ﺸﻴﻑ ﺜﻡ‬ ‫[ ﺃﻋﻁﻰ ﻤﻌﻘﺩ ﻜـﺎﺘﻴﻭﻨﻲ ﺒـﺼﻴﻐﺔ ﻜﻴﻤﻴﺎﺌﻴـﺔ ﺘـﻡ‬Ni(L)(AC)(EtOH)2]+ Univirsity Bulletin – lssue No.10-2008

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Synthesis and Characterization ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬

‫ ﻭﺒﺘﻐﻴﻴﺭ ﺍﻻﻴـﻭﻥ ﺍﻝـﺴﺎﻝﺏ‬.‫ﺃﻤﻴﻥ ﺍﻨﺘﻴﺒﻴﺭﻴﻥ ﻤﻊ ﺴﻠﺴﻴﻠﺩﻫﺎﻴﺩ‬-4 ‫ﺘﺤﻀﻴﺭﻫﺎ ﺒﺘﻜﺘﻴﻑ‬ [Ni (L)(AC)(EtOH)2]BPh4 ‫ﺒﺭﺍﺒﻊ ﻓﻴﻨﻴل ﺍﻝﺒﻭﺭﺍﺕ ﺃﺩﻱ ﺇﻝﻲ ﺇﻨﺘـﺎﺝ ﻤﻌﻘـﺩ‬

‫ ﺘﻡ ﻭﺼﻑ ﺍﻝﻤﻌﻘﺩ ﺒﻭﺍﺴﻁﺔ ﺍﻝﺘﺤﻠﻴل ﺍﻝﻌﻨﺼﺭﻱ‬.‫ﺍﻝﺫﻱ ﻴﺫﻭﺏ ﻓﻲ ﺍﻝﻤﺫﻴﺒﺎﺕ ﺍﻝﻌﻀﻭﻴﺔ‬ ‫ ﻭﻤﻁﻴﺎﻓﻴﺔ ﻜﻼ ﻤﻥ ﺍﻷﺸـﻌﺔ ﺘﺤـﺕ ﺍﻝﺤﻤـﺭﺍﺀ ﻭﻓـﻭﻕ‬FT-IR, UV-Vis, 1H

‫ ﻭﻤﻥ ﻜﺎﻓﺔ‬.13 ‫ﺍﻝﺒﻨﻔﺴﺠﻴﺔ ﻭﺍﻝﺭﻨﻴﻥ ﺍﻝﻨﻭﻭﻱ ﺍﻝﻤﻐﻨﺎﻁﻴﺴﻲ ﻝﻠﺒﺭﻭﺘﻭﻥ ﻭﻨﻅﻴﺭ ﺍﻝﻜﺭﺒﻭﻥ‬ .‫ﺘﻠﻙ ﺍﻝﺘﺤﺎﻝﻴل ﺘﻡ ﺍﻝﺘﻭﺼل ﺇﻝﻰ ﺼﻴﻐﺔ ﺍﻝﻤﺭﻜﺏ ﺍﻝﻤﻌﻨﻭﻥ ﻝﻬﺫﺍ ﺍﻝﺒﺤﺙ‬ Abstract: Reaction of unsymmetrical tridentate Schiff base with nickel (II) acetate in ethanolic solution gives 1:1 [M:L] cationic complex of chemical formula [Ni(L)(AC)(EtOH)2]+, where L represent the Schiff base prepared by condensing 4aminoantipyrine with salicylaldehyde. Changing the counter ion by tetra phenyl borate gives [Ni (L)(AC)(EtOH)2]BPh4 complex which is soluble in organic solvents. The complex was characterized by elemental analysis, FT-IR, UV-Vis, 1H and 13C NMR spectroscopy. From all of these analysis the title compound was established. Introduction: Transition metal complexes that contain Schiff base ligands such as salen and salphen attracted much attention for the last decades [1, 2]. These types of ligands act as tetradentate ligands in their complexation with nickel (II) and gives a neutral square planer compounds as a result of deprotonations of phenolic protons in absence of base. Our interest is to investigate the reaction of unsymmetrical tridentate Schiff base with nickel acetate in order to get a different structure that may have cationic character with large anion containing organic groups as a counter ion. These kinds of complexes have a high solubility in organic solvents [3, 4]

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which makes their study by 1H and 13C NMR spectroscopy possible. Also, our interest in future is to study the biological activity of this cationic complex and to develop it to act as a catalyst for polymerization processes [5]. It was known that cations of early transition elements can perform better than latter transition elements in polymerization processes in the presence of various additives. Exception to this generalization is organo nickel (II) catalysis in polymerize of ethylene under mild conditions without using additives [6]. Experimental: All chemicals used were pure reagent grade of BDH or Aldrich. All manipulations were carried out under atmospheric pressure. Microanalysis (C, H, N) were performed on Vario EL (III) elemental analyzer. IR spectra were recorded at room temperature with a Bruker IFS-25 OPUS/IR spectrometer over wave number range from 400 to 4000 cm-1 with a resolution of about 4 cm-1. The electronic absorption spectra were carried out by using Perkin-Elmer Lambda 4B spectrometer. 1H and 13C NMR were performed on a Bruker Avance-300 MHz spectrometer, equipped with a Bruker 5mm ΦNP probe with resonance frequency of 75.47 MHz for 13C nuclei and 300.13 MHz for 1H nuclei. The 1H and 13C chemical shifts were internally referenced to tetramethyl silane (TMS) in ppm. Preparation of Schiff base (4-salicylaldiminato) antipyrine-EtOH (L). Yellow nice crystals were prepared using previous method [4, 5]. The Schiff base (scheme 1) was characterized by elemental analysis. Anal. Calc. for C20H23N3O3: C, 68.18; H, 6.25; N, 11.93; Found: C, 67.95; H, 6.20; N, 11.70.

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Carbon No. CHn Chem. Shift (ppm) 4 CH3 10.26 18 CH3 35.63 16 CH 116.24 12 C 116.72 15 CH 119.09 6 CH 120 7 CH 120 2 C 124.64 10 CH 128.96 8 CH 129.31 9 CH 129.31 13 CH 131.85 17 CH 131.97 1 C 134.34 5 C 149.85 11 CH 160.26 14 C 160.46 3 C 160.64 13 Scheme 1.Ligand structure (L) and its C NMR chemical shifts Preparation of [Ni(L)(OAC)(EtOH)2]BPh4 complex A solution of Schiff base (2.0 mmol, 0.60g) and nickel acetate (2.0 mmol, 0.50g) in ethanol (50.0 ml) were refluxed Univirsity Bulletin – lssue No.10 -2008

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for 2.3 hr’s. The green solution formed was reduced to the half by evaporation of the solvent, then an appropriate amount of NaBPh4 in ethanol was added. The resulting green solid was separated by filtration, washed with ethanol and recrystallized from dichloromethane-ether. The nickel complex was characterized by elemental analysis. Anal. Calc. for C48H52N3O6BNi: C, 68.9; H, 6.02; N, 5.22; Found: C, 70.3; H, 5.3; N, 5.4, FT-IR, UV-Vis, 1H, and 13C NMR. Results and Discussion: The title complex (scheme 2) was prepared using nickel acetate and Schiff base (L) in ethanolic solution in the absence of base. A green solid of nickel complex was precipitated after the addition of an ethanolic solution of NaBPh4 to the green solution. N N N H O O Ni O

HO O O

H

Scheme 2. Structure of [Ni(L)(OAC)(EtOH)2]+ complex. The uv-vis spectrum of [Ni(L)(OAC)(EtOH)2]BPh4 complex was obtained in chloroform solution. The spectrum shows intense bands at higher energy at 269 nm and 335 nm which are related to the metal-to-ligand and ligand-to-metal charge transfer bands respectively [7]. The bands at 376 nm, 400 nm give indication that the geometry around nickel ion in the title complex is distorted octahedral. Univirsity Bulletin – lssue No.10-2008

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IR spectrum of the nickel complex shows peaks ranging from 1420 cm-1 to 1500 cm-1 assigned to the stretching vibration of C=C for aromatic ring. The region from 3000 cm-1 to 3050 cm-1 indicates the fingerprint peak of the counter ion. Bands in the region 690 cm-1 to 780 cm-1 are assigned to out of plane bending vibration of the aromatic ring. The symmetric and asymmetric stretching vibration of the acetate group coordinated to the nickel as bidentate ligand occurs at 1491 and 1443 cm-1 respectively [7], are consistent with symmetrical bidentate chelate arrangement of the carboxylate group [8, 9]. Also, an important IR stretching vibrations at 1627 cm-1 and 1600 cm-1 are related to νC=O (Free ligand at 1667 cm-1) and νC=N for the coordinated ligand respectively [10]. The 1H and 13C NMR spectra of this complex are shown in figures 1 and 2. The 1H NMR spectrum of Ni (II) complex shows the phenolic proton does not coordinate to the metal which gave a signal at δ 13.5 ppm. The resonance at δ 9.8 ppm (s) was assigned for N=C-H proton. Also, a new resonance at δ 9.9 ppm (s) assigned to the hydroxyl proton of the ethanol group.

7.3 9.90

9.85

9.80

*

EtOH

EtOH

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

-1

ppm Figure 1: 1H NMR spectrum of the [Ni (L)(AC)(EtOH)2]Bph4 complex (* CDCl3 solvent)


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13

C NMR spectrum for Ni(II) complex in figure 2 shows that there are two resonances for the methyl carbon of acetate group and carbonyl carbon at δ 161.7 ppm and δ 196.6 ppm respectively compared with one resonance at δ 160.3 ppm for the carbonyl carbon of the Schiff base. Also, new resonances at δ 119.86, 124.67, 132.02 ppm and δ 160.35 ppm for phenyl carbons of the counter ion BPh4 of the nickel (II) complex. The peak at δ 160.5 ppm was assigned to N=CH. The chemical shifts at 18.4 and 58.4 ppm are related to the coordinated ethanol molecule to nickel ion.

*

140

130

120

155

EtOH

EtOH

200 190 180 170 160 150 140 130 120 110 100

90

80

70

60

50

40

30

20

10

0

ppm

13

Figure 2: C NMR spectrum of [Ni (L)(AC)(EtOH)2]BPh4 complex .(* CDCl3 solvent)

Previous study by addition of ammonium hydroxide solution to the nickel (II) complex in ethanolic solution ends up with the formation of a red complex which is characterized by elemental analysis, IR, UV-Vis, 1H and 13C NMR as a square planar cis-(C7H6NO)2 Ni complex [11].

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Conclusion: By comparing cis-(C7H6NO)2Ni complex results with the title complex characterization we conclude that the complex may have distorted octahedral geometry around nickel ion. Acknowledgment The help from the advanced laboratory of chemical analysis for their C, H, N; IR and UV-VIS and the Libyan petroleum institute for their 1H and 13C NMR analyses are greatly appreciated. References: 1) G. W. Everett, Jr, and R. H. Holm, Inorg. Chem. 7, 776 (1968). 2) M. L. Wicholas and R. S. Drago. J. Amer. Chem. Soc., 91, 5963 (1969). 3) Nishinago, A., Tajo, Ti, Matsuuro, T., J. chem. Soc. Chem.. comm.., 896 (1974). 4) Lioret, F.; Julue, M., Mollar, M. Castro, I. Latorre, J., J. chem.. soc. Dalton Trans., 729 (1989). 5) G. T. P. Britorsck, V. C. Gibson, D. F. Wasss, Angew. Chem. Int. Ed. Engl., 38, 428 (1999). 6) Eric N. Jacobson and Rolf Breinabauer Science vol 287, 437 (2000). 7) J. I. Zink and R. S. Drago, J. Amer. Chem. Soc., 42, 5339 (1979). 8) T. A. Stephenson, S. M. Moerhouse, A. R. Powell, J. P. Heffer and G. Wilkinson, J. chem. soc. 3632 (1965). 9) C. A. Agambar and K. G. Orrell, J. chem.. soc. (A), 897 (1969). 10) D. M. Boghaei and Lashanizadegan, J. Sci. I. R. Iran vol II. No.4, 302 (2000). 11) R. M. El-Mehdawi, A. N. Eldewik, K. M. Kreddan, A. A. Maihub, M. M. El-Ajaily, M. A. Abuzwida; 5th International Conference on Inorganic Materials, Ljubljana, Slovenia, (2006).


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