Metal Complexes OF Dimethyl Sulphoxide PDF

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DEPARTMENT OF CHEMISTRY CHE 323 EXPERIMENT: 8 EXPERIMENT TITLE: METAL COMPLEX OF DIMETHYL SULPHOXIDE: THE PREPARATION OF Cu (DMSO)2Cl2 SURNAME: MPHINYANE INITIALS: S STUDENT ID: 201700690 LAB GROUP: FRIDAY DATE: 11/10/19

AIM OF THE EXPERIMENT The purpose of this experiment was to synthesize complexes [Cu(DMSO)2Cl2], and to test the bonding mode of DMSO with Cu 2+ through IR spectroscopy ABSTRACT

This experiment was performed in order to synthesize: [Cu(DMSO)2Cl2]. The IR spectra of [Cu(DMSO)2Cl2] complex showed a successfully synthesis was performed. The IR spectra for the [Cu(DMSO)2Cl2] complex signified that a metal was bonded to oxygen. The percent yield for [Cu(DMSO)2Cl2 ] was 71.9% with 0.3349g recovered. The melting range between [Cu(DMSO)2Cl2] was 110.2-121.5 °C.

INTRODUCTION The nature of dimethyl sulfoxide (DMSO, (CH3)2SO) as a monodentate ligand is explored in this set of experiments. DMSO can ligate metal atoms by bonding in one of two possible ways: through the oxygen atom or through the sulfur atom (Figure 1). The method of bonding in the complex can be determined with the use of infrared spectroscopy, and the nature of the ligand and its complexes can be explored using molecular modeling software from CAChe Scientific (Reynolds, 1970)

Figure 1: showing resonance structures of DMSO Metals can bond to DMSO either through its oxygen or its sulfur. If the bonding is to the sulfur, the metal donates electrons from its pi orbitals into an empty pi orbital on the DMSO ligand, thereby increasing the S=O bond order. Thus, if the metal is bonded to the DMSO at the sulfur, the frequency of the absorption increases. If the bonding is to the oxygen of the DMSO, the metal forms a bond with one of the lone pairs on the oxygen, and thereby withdraws electron density from the oxygen. This favors the second resonance form, since the oxygen will "seek" to gain electrons to compensate for the electrons donated to the metal. The net effect is that the S=O bond order declines and the S=O absorption appears at lower frequency.

REAGENTS AND MATERIALS    

Copper (II) Chloride .2H2O 2 mL ethanol 0.5 mL DMSO Erlenmeyer flask

     

Magnetic stirring bar Dropper Hirsch funnel Watch glass Filter paper Beaker

ACTION PLAN 0.3g of copper (II) chloride was placed in a 25 ml Erlenmeyer flask equipped with a magnetic stirring bar. 2 ml of ethanol was added to the flask using a calibrated Pasteur (dropper). The mixture was stirred until all of the copper (II) chloride dissolved. After the copper (II) chloride dissolved, 0.5ml of DMSO was slowly added using a dropper. The product was collected by suction filtration. The crystals was washed with about two 1ml portion of cold ethanol and was air dried.

EXPERIMENTAL PROCEDURE 0.3161g of copper (II) chloride was placed in a 25 ml Erlenmeyer flask equipped with a magnetic stirring bar. 2 ml of ethanol was added to the flask using a calibrated Pasteur (dropper). The mixture was stirred until all of the copper (II) chloride dissolved. After the copper (II) chloride dissolved, 0.5ml of DMSO was slowly added using a dropper. A light green precipitate was formed immediately and the mixture was stirred for 5 minutes. The product was collected by suction filtration using a Hirsch funnel. The crystals was washed with about two 1ml portion of cold ethanol and was air dried placed on watch glass. The product was weighed and the melting point was determined. The infrared spectrum of the product and that of DMSO were obtained. The absorption frequency of the S-O band was also determined.

RESULTS AND ANALYSIS Table 1: Showing mass of the copper (II) chloride used in the preparation Mass of weighing boat + CuCl2

Mass(g) 1.4067

Mass of empty boat Mass of CuCl2

1.0906 0.3161

OBSERVATIONS  Green solution was formed when ethanol was added to blue copper (II) chloride  Light green precipitate formed when DMSO was added to the mixture. Table 2: showing the mass of the product obtained Mass of watch glass+ filter paper Mass of watch glass + filter paper + product Mass of product Appearance of product Melting point

Mass (g) 41.3171 41.6520 0.3349 Light green, shiny crystals 110.2 – 121.5°C

The reaction equation for the synthesis of [Cu(DMSO)2Cl2]. CuCl2(s) + (CH3)2SO(aq) → CuCl2.(CH3)2SO(aq) Molar of CuCl2 = 134.452g/mol Mass of CuCl2 = 0.3161g n ( CuCl 2 )=

CuCl2 1

m 0.3161 g =0.002351024=0.002351 mol = MM 134.452 gmol−1

: CuCl2. (CH3)2SO :

1

0.002351mol: X X = 0.002351 mol

Molar mass of CuCl2. (CH3)2SO = 197.9980gmol-1 Theoretical mass=n × MM=0.002351mol × 197.9980 gmol−1=0.465493298=0.4655 g Percentage yield=

actual mass 0.3349 g ×100= 71.94414608=71.9 % ×100= 0.4655 g theoretical mass

DISCUSSION The complex was stable at room temperature. The IR spectrum of DMSO display strong S=O absorption band at 1050 cm-1, which in the complex is observed at lower frequency. This implies that the DMSO binds with copper through oxygen (Nakamoto, 1986). The amount of [Cu(DMSO)2Cl2] obtained was enough which shows that the method used was found to be suitable for the preparation of the product. The best IR spectrum of the product was determined when the product was dry.

CONCLUSION The light green solid of 0.3349g [Cu (DMSO)2Cl2] was obtained. The percentage yield was calculated to be 71.9%. IR spectroscopy will show a higher absorption level for sulfur and a lower absorption level for oxygen.

REFERENCES 1) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination Compounds, 4th ed., John Wiley: New York, 1986, pp. 269-272. 2) Reynolds, W. R. "Dimethyl Sulfoxide in Inorganic Chemistry", Progress in Inorganic Chemistry, S. J. Lippard, Ed., Interscience: New York, 1970, volume 12, 1....