SYNTHESIS OF PALLADIUM(II) COMPLEXES FROM SULFONYLDIANILINE AMINOPHENYLSULFONYLACETIMIDIC ACID AND SULFAMOYLTHIADIAZOLACETAMIDE AS LIGANDS.
The reaction of 44'-sulfonyldianiline N-((4-aminophenyl)sulfonyl)acetimidic acid and N-(5- sulfamoyl-134-thiadiazol-2-yl)acetamide with Na2PdCl4 in suitable solvents resulted complexes 1-3. All the complexes were recrystalized and collected in a suitable yield. Each of the complex was characterized by FT-IR 1H 13C NMR specroscopic techniques.
Key words: acetamindes thiazoles palladium complexes.
Palladium has significant role in the industrial processes specifically its complexes are frequently used as catalysts for
a number of synthetic processes [1-5]. When palladium is finely divided for example palladium on carbon palladium
becomes a versatile catalyst and finally boosts up hydrogenation and dehydrogenation reactions. A number of carbon-carbon bond forming reactions in organic
chemistry such as the Heck reaction and Suzuki coupling are facilitated by catalysis using palladium compounds. In addition when palladium is dispersed on conductive
materials becomes an excellent electrocatalyst for oxidation of primary alcohols in alkaline media. In 2010 palladium- catalysed organic reactions were acknowledged by the Nobel
Prize in Chemistry. Palladium is also an adaptable metal for homogeneous catalysis. It is now conventional to use palladium in combination with a broad variety of ligands for
highly selective chemical transformations.
In addition recently a number of palladium complexes have been tested for possible biological applications [6-9]. For example Palladium complexes have been recently explored as potential anti microbial and anticancer agents [10-13]. Palladium is also used in electronic devices hydrogen
storage and photography. In the current study we synthesized some palladium complexes to further explore the reactivity and geometrical parameters of palladium
2.1 Reagents and general procedures
Synthetic procedures and sample preparation were performed under aerobic conditions. Solvents such as acetone and ethanol were used without further purification.
1H and 13C NMR spectra were recorded on a 500 MHz BRUKER-TT-AVANCE spectrometer and was referenced to solvent used (DMSO-d6). The samples were prepared in
deuterated dimethyl sulfoxide. FT-IR spectra were recorded by 2000 PERKIN ELMER in KBr disk containing 1.21.7 mg of the sample and 100 mg KBr. The melting point
measurment was by using GALLEN KAMP apparatus.
2.3.1. Synthesis of palladium complex 1.
The reaction of 44'-sulfonyldianiline (0.22 g 0.886 mmol) with Na2PdCl4 (0.135 g 0.44 mmol) was carried out in ethanol by stirring the mixture at room temperature for 24 h see scheme 1A. The product (1) was obtained as a crystalline yellow precipitates after filteration and solvent evaporation. The complex so obtained was found to be in soluble in water but soluble in organic solvents DMF and DMSO. (0.5 g yield 57%). FT-IR (KBr max cm-1): 3504 (NH stretch)
3143 3046 (aromatic C-H stretch) 1595 (aromatic C=C stretch). 1H NMR (500 MHz DMSO-d6): d ppm 7.4 (d J = 8.0 Hz) 6.6 (d J = 8.5 Hz). 13C NMR (125.7 MHz DMSO- d6): d ppm 152.5 128.4 127.8 113.2.
2.3.2. Synthesis of complex 2.
The reaction of N-((4-aminophenyl)sulfonyl)acetimidic acid (0.22 g 1.026 mmol) with Na2PdCl4 (0.151 g 512 mmol) was carried out in hot acetone by stirring the mixture at reflux for 24 h scheme 1B. The product (2) was obtained as a crystalline orange material after filteration and solvent evaporation. The comlex so obtained was found to be insoluble in chlororform water ethanol and soluble in solvents like DMF and DMSO (0.34 g yield 81%). FT-IR (KBr max cm-1): 3380 (NH stretch) 3095 3049 (aromatic
C-H stretch) 1595 1552 (aromatic C=C stretch). 1H NMR (500 MHz DMSO-d6): d ppm 7.41 (d J = 9.0 Ar-CH) 6.49 (d J = 9.0 Hz Ar-CH) 1.66 (s -CH3). 13C NMR (125.7 MHz DMSO-d6): d ppm 175.1 150.5 132.1 130.5 127.9 111.9 26.5.
2.3.3. Synthesis of complex 3.
The reaction of N-(5-sulfamoyl-134-thiadiazol-2- yl)acetamide (0.20 g 0.899 mmol) with Na2PdCl4 (0.135 g 0.45 mmol) was carried out in hot acetone by stirring the mixture at reflux for 24 h scheme 1C. The product (3) was obtained as yellowish brown precipitates after filteration and solvent evaporation. The comlex so obtained was found to be insoluble in chlororform water ethanol and soluble in organic solvents like dichloromethane DMF and DMSO (0.25 g yield 87%). FT-IR (KBr max cm-1): 3301 (NH stretch) 3091 3049 (aromatic C-H stretch) 2950 (alkyl C- H stretch) 1679 (C=O stretch) 1541 (aromatic C=C stretch). 1H NMR (500 MHz DMSO-d6): d ppm 13.01 (s azole N-H) 8.31 (s N-H 2.24 (s -CH3). 13C NMR (125.7 MHz DMSO-d6): d ppm 169.4 164.2 161.0 22.3.
3. RESULTS AND DISCUSSION
3.1. Characterization by FT-IR
3.1.1. Complex 1
FT-IR spectra of complex 1 exhibits unilateral behavior that is associated to the nitrogen atom in one of the two groups (NH2). The loss of a proton in the complex 1 after reacting with the palladium atom was diagnosed by the appearance of a strong bilateral vibrational band at the site 383cm-1 back to (Pd-Cl) and refers to the arrangement trans while the emergence of two packages to indicate the order size. While the (Pd-N) at the site 561cm-1 and appearance of vibrational bands for (NH) at the site 3143cm-1 which is less than its location in the ligand 3170cm-1 suggested that one of the two NH2 groups has coordinated to the Pd metal ion. The vibrational bands for Ar-CH stretch appeared in the complex at the site 3064cm-1 which is comparable to its location in the ligand 3060cm-1. Furthermore the vibrational bands for SO2 sy or asy in the complex appeared at sites 1269cm-1 1145cm-1 respectively as compared to their positions in the free ligand 1290cm-1 1140cm-1.
Similarly the vibrational bands for the CS stretching appeared at 1012cm-1 in the complex which is identical to its location in the free ligand 1012cm-1. Based on this preliminary information the structure of complex 1 was proposed.
3.1.2. Complex 2
The FT-IR spectral features of free ligand (N-((4- aminophenyl)sulfonyl)acetimidic acid) were compared with that of synthesized complex 2. The FT-IR spectrum of 2 showed a medium peak at 322cm-1 for Pd-Cl which refers to the trans arrangement. Also featured package (C = N) at the site 1552cm-1 and the dislocation of a package (CO) in a favorable location 1685cm-1 suggested a link of ligand through oxygen atom of the carbonyl group. While the vibrational bands for SO2 sy and asy appeared at 1271cm-1 1145cm-1 respectively. In the respective ligand these vibrations appeared at 1270cm-1 1143cm-1 respectively also showed formation of new chemical moiety. While observing the vibrational bands of NH2 in the complex at 3380cm-1 which is close to its location in the free ligand 3384cm-1 indicated that NH2 remained unreacted in this reaction. Based on the FT-IR data the structure of the complex has been proposed in scheme 1B.
3.1.3. Complex 3
FT-IR spectrum of complex 3 showed a reasonable vibrational band at 462 cm-1 for Pd-N coordination. Furthermore the appearance of a vibrational band at 356cm-
1 indicated the presence of tran Pd-Cl group. Also the carbonyl FT-IR band moved toward a higher frequency 1679cm-1 compared with that of free ligand 1660cm-1. Importantly the vibrational bands at 3186cm-1 for NH remained at comparable location in ligand and respective complex indicating no coordination through this specific site. Based on the above information the structure has been proposed in scheme 1C.
3.2. Characterization by NMR
3.2.1. Complex 1
1H NMR spectrum of complex 1 showed two distinct chemical shifts in the aromatic region. First at d H = 6.6ppm and second dH = 7.4ppm as two doublets for the para substituted benzene ring. Furthermore 13C NMR spectrum showed four signals for four atoms of carbons in chemically different environment. This is consistent with the similar ligands. For example such ligands show mono signal at the site d13C = 113.2ppm representing aromatic carbon atoms which is close to the theoretical value given by the spectrum measured theoretically d13C = 117.3ppm practically mono signal at the site d13C = 128.4ppm; theoretically d13C =
131.4ppm practical mono signal at the site d13C = 152.4ppm; theoretically d13C = 151.7ppm and practically d13C = 127.8ppm; theoretically d13C = 129.1ppm. The above discussion supports the formation of complex 1 as shown in scheme 1A.
3.2.2. Complex 2
1H NMR spectrum of complex 2 showed a chemical shift at dH = 1.66ppm for the only methyl group and two visible doublets dH = 6.4ppm and dH = 7.4ppm for the aromatic ring protons. Similarly 13C NMR spectrum showed a chemical shift at d 26.5 ppm for the only methyl group. Also a signal at 111.9 indicated the carbon attached to the coordinated oxygen atom. The aromatic carbons appeared as following mono signal at the site d13C = 127.9ppm which is identical to the value given in the theoretical spectrum d13C
= 127.3ppm the signal at the site d13C = 150.5ppm which is close to its position in the spectrum of theoretical d13C = 153.4ppm. The chemical shift at d 175.1ppm appeared for
the carbonyl carbon coordinated to the palladium metal ion.
3.2.2. Complex 3
1H NMR spectrum of complex 3 remained very simple since the complex does not have any aromatic ring and very few protons. The complex showed a very downfield chemical shift d13.01ppm which might be for SNH and a comparatively upfield signal at d8.31ppm for NH. The signal for only methyl group appeared at d2.20ppm. 13C NMR showed four signals. For the methyl group carbon the signal appeared at d22.32ppm. For the carbonyl carbon the signal appeared at d169.40ppm. For the azole ring carbons thes signals appeared at d161.40ppm and d164.2ppm.
The current study describes the synthesis and characterization of three new palladium complexes derived from different types of ligands. The complexes are stable at roo temperature and remained soluble in organic solvents like DMSO and DMF. All the compounds were characterized by FT-IR 1H and 13C NMR spectroscopic techniques. Further work on the synthsis of respective platinum complexes is in progress and will be reported in due course.
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