Structural Methods in Inorganic Chemistry

In order to synthesize our metal complexes, we were able to make both Copper and Ruthenium metals. From this, we combined each metal complex with DMSO by refluxing the compound. The metal complexes were analyzed through their melting point and IR spectroscopy to determine whether the metal bonded to a Sulfur atom or an Oxygen atom of the DMSO. After analyzing the IR spectrum, it was determined that S=O shifted to a lower wavenumber in CuCl2~2DMSO and that S=O shifted to a higher wavenumber in RuCl2~4DMSO.

Introduction

Depending on the metal, it will bond to DMSO through its oxygen or sulfur atom. This will cause the frequency of the S=O bond absorption to move depending on which atom it bonds to. For oxygen bond the frequency will be low due to the weakened interaction. As for sulfur bond the frequency will be higher because the metal donates the electrons as a back donation to the pi orbital in DMSO. In the first experiment, I had to synthesized CuCl2~2DMSO to determine which DMSO atom; Sulfur or Oxygen, combined to Copper (II) Chloride. I was able to determine it base on finding the melting point and observing the Infrared Spectroscopy. Since copper is a hard metal, it will most likely bond to an oxygen atom because they are both hard. In the second experiment, I also synthesized RuCl2~4DMSO to determine which DMSO atom; Sulfur or Oxygen, combines to Ruthenium (III) to be reduced to Ruthenium (II). I was able to determine it based on finding the melting point and observing the Infrared Spectroscopy. Since ruthenium is a soft metal, it will most likely bond to Sulfur because they are both soft.

Experimental

We prepared the sample by synthesizing Copper Chloride with DMSO. 0.160 grams of CuCl2~2DMSO was added to a 10 mL Erlenmeyer flask with a magnetic stir bar. Than 1 mL of absolute ethanol was added to the flask using a Pasteur pipet until Copper chloride dissolved. 250 µl of DMSO was added slowly to the mixture using a dispensing pipet and stirred for 10 minutes. A light green product formed. The product was than collected by suction filtration using a Hirsch Funnel and washed with two portions of 500 µl of cold ethanol. IR spectroscopy was used to analyze the products and an emission spectrum was obtained. Results and Discussion

Product
Theoretical yield
Actual yield
Percent yield
Melting point °C
CuCl2~2DMSO
0.273 grams
0.179 grams
65.56 %
154.2-155.1

Frequency (cm−1)
Bond responsible
(DMSO) 1017.65
S=O stretching
(CuCl2~2DMSO) 920.20
S=O stretching

When analyzing the IR spectrum of Copper complex with DMSO, the prominent peak is presented at 920.20 cm−1. This peak indicates that S=O bonded in DMSO. For DMSO, the frequency is around 1050 cm−1. From our spectra obtained for DMSO, the S=O peak is at 1017.65 cm−1. Since the bond appears at a lower frequency, this shows that the bond is weakened by the reaction. This signifies that when the copper metal was combined with DMSO, it bonded with the oxygen atom.

20B Preparation of RuCl2~2DMSO

Experimental

For the second experiment, we synthesized Ruthenium (III) Chloride with DMSO. 0.102 grams of RuCl2~4DMSO was added to a 10 mL round bottom flask that was equipped with a magnetic stir bar. The round bottom flask was attached to a water condenser with a keck clip. The flask was placed in a sand bath in a hot plate. Than 1 mL of DMSO was added through the condenser using a calibrated pasteur pipet. While stirring the mixture the reaction refluxed for 5 minutes until the deep solution turned into an orange yellow solution. I allowed the reaction to cool. Than transferred the solution to a 10 mL beaker using a pasteur pipet to boil away the solvent reducing it to a smaller amount. Added 2 mL of acetone drop wise cooling the mixture in an ice bath for 15 minutes; yellow crystals began to form. The yellow crystals were collected through suction filtration using a Hirsch funnel and washed with one 500 µl of acetone. IR spectroscopy was used to analyze the product and an emission spectrum was obtained.

Results and Discussion

Product
Theoretical yield
Actual yield
Percent yield
Melting point °C
RuCl2~4DMSO
0.189 grams
0.082 grams
43.38 %
203.4-204.6
Frequency (cm−1)
Bond responsible
(DMSO) 1017.65
S=O stretching
(RuCl2~4DMSO) 1105.54
S=O stretching

When analyzing the IR spectrum of Ruthenium complex with DMSO, the prominent peak is presented at 1105.54 cm−1. This peak indicates that S=O bonded in DMSO. For DMSO, the frequency is around 1050 cm−1. From our spectra obtained for DMSO where the S=O peak is at 1017.65 cm−1. Since the bond appears at a higher frequency, this shows that the bond is strengthened by the reaction. This indicates that when the copper metal was combined with DMSO, it bonded with the Sulfur atom. Combining ruthenium with sulfur atom caused it to donate a pi electron as a back donation.

Conclusions

From both experiments, we were able to detect which Sulfur and Oxygen atom bonded to the metal. Copper metal was added to DMSO to bond with the oxygen by weakening the S=O therefore lowering the IR spectrum. As for Ruthenium metal, it was added to DMSO to bond with the sulfur compound, strengthening the S=O therefore increasing the IR spectrum. Based on the IR spectrums and melting points, my product for both metal were pure.

References

Boschmann, E; Wollaston, G.J. Chem. Edu. 1982, 59,57

Ebsworth, E. A. V.; Ranking, D.W.H.; Cradock, S., Structural Methods in Inorganic Chemistry, Blackwell: Oxford, 1987

Pike, M Ronald; Singh, M Mono; Szafran Zvi. Microscale Inorganic Chemistry; A Comprehensive Laboratory Experience. New York 1991, p218-222.

Reynolds, W. R, “Dimethyl Sulfoxide in Inorganic Chemistry” in Progress in Inorganic Chemistry, S. J. Lippard, Ed., Interscience: New York, 1970, Vol 12, p. 1.