Anusha Ambaselkar
Coordination Complexes - Geometrical Isomerism in Octahedral
Complexes
Anusha Ambaselkar Lab B05 A-1
Feb 11 2021
Abstract:
In this experiment, Dichlorobis(ethylenediamine)cobalt(III) Chloride was synthesized in
two forms. The trans isomer was made by mixing cobalt chloride hexahydrate, diaminoethane,
water and hydrochloric acid and then evaporated and filtered to get a solid product. This product
was heated in an oven to remove the hydrochloric acid which made the final
trans-[Co(en)2Cl2]Cl (1.455g, 60.3%). A portion of the trans isomer was evaporated in water to
create cis-[Co(en)2Cl2]Cl solution(6.47%). Both trans (green solution) and cis (purple solution)
isomers were made into diluted solutions in 50mL volumetric flask. A UV-vis spectrophotometer
measured the absorbance and maximum wavelength for both solutions. The molar absorption
coefficient (trans: 30.306 molLcm ) (cis: 31.565 molLcm ) was calculated using the absorbances and
the calculated concentrations for the cis (0.0109M)and trans (0.0108M) isomers. The maximum
wavelengths were compared to the wavelength ranges for the colors absorbed and reflected.
According to the wavelengths from the spectra, the color reflected for the trans (620.1nm)
isomer was green and for this cis (510.0nm) it was red.
Introduction:
Geometric isomerism which is also known as cis and trans isomerism is a form of
stereoisomerism. Cis and trans isomers differ in the position of the ligands for a coordination
complex. For trans molecules, two identical ligands are on the opposite side of the molecules
and for cis, the two ligands are on the same side. For the coordination complexes of
trans-[Co(en)2Cl2 ]Cl
and cis-[Co(en)2 Cl
2]Cl
synthesized in this experiment, the position of the
two Cl ligands determine whether its a trans or cis isomer.
This study source was downloaded by 100000858936669 from CourseHero.com on 02-06-2023 01:21:35 GMT -06:00
https://www.coursehero.com/file/83007473/Geometrical-Isomerismpdf/
, Anusha Ambaselkar
The purpose of this experiment was to explore the differences between cis and
trans-Dichlorobis(ethylenediamine)cobalt(III) Chloride by obtaining an absorption spectra by
using a Ultraviolet visible spectrophotometer. A UV-vis spectrophotometer refers to absorption
spectroscopy where it measures at what wavelength light is absorbed at for the sample.The
maximum wavelengths determined by the spectra for both isomers were compared to the range
of colors reflected and absorbed at different wavelengths to determine if the experiment was a
success. The absorbance was also measured and the concentrations were calculated for both
to determine the molar absorption coefficient using the Beer-Lambert equation[1].
Product Reactions:
4 CoCl2 + 8 en + 4 HCl + O2 → 4 trans-[CoCl2(en)2]Cl + 2 H2O
trans-[CoCl2(en)2]Cl + H2O + heat → cis-[CoCl2(en)2]Cl + H2O
Methods:
Part A: Preparation of trans-[Co(en)2Cl
]Cl
2
Cobalt chloride hexahydrate (8.6mmol, 2g) and distilled water (5.0mL) in a 250mL
beaker was added. Then a mixture of anhydrous 1,2-diaminoethane (1.0mL) and water (3.0mL)
was added into the chloride solution. Finally, 30% hydrogen peroxide (1.0mL) was added
dropwise to this solution. This solution was heated until the effervescence had stopped (5min)
and after, concentrated hydrochloric acid (5.0mL) was added. The solution was gently
evaporated for another 30min until a dark green thick layer was formed. The beaker was then
placed in an ice water bath (10min). Vacuum filtration was used to filter off the crystals and
washed with 3 small portions of 95% ethanol. Then the powder was placed in an oven (10 min)
to remove the HCl and leave the trans-[Co(en)2Cl
]Cl
2 roduct by itself. This product was a dark
p
green powder.
This study source was downloaded by 100000858936669 from CourseHero.com on 02-06-2023 01:21:35 GMT -06:00
https://www.coursehero.com/file/83007473/Geometrical-Isomerismpdf/
Coordination Complexes - Geometrical Isomerism in Octahedral
Complexes
Anusha Ambaselkar Lab B05 A-1
Feb 11 2021
Abstract:
In this experiment, Dichlorobis(ethylenediamine)cobalt(III) Chloride was synthesized in
two forms. The trans isomer was made by mixing cobalt chloride hexahydrate, diaminoethane,
water and hydrochloric acid and then evaporated and filtered to get a solid product. This product
was heated in an oven to remove the hydrochloric acid which made the final
trans-[Co(en)2Cl2]Cl (1.455g, 60.3%). A portion of the trans isomer was evaporated in water to
create cis-[Co(en)2Cl2]Cl solution(6.47%). Both trans (green solution) and cis (purple solution)
isomers were made into diluted solutions in 50mL volumetric flask. A UV-vis spectrophotometer
measured the absorbance and maximum wavelength for both solutions. The molar absorption
coefficient (trans: 30.306 molLcm ) (cis: 31.565 molLcm ) was calculated using the absorbances and
the calculated concentrations for the cis (0.0109M)and trans (0.0108M) isomers. The maximum
wavelengths were compared to the wavelength ranges for the colors absorbed and reflected.
According to the wavelengths from the spectra, the color reflected for the trans (620.1nm)
isomer was green and for this cis (510.0nm) it was red.
Introduction:
Geometric isomerism which is also known as cis and trans isomerism is a form of
stereoisomerism. Cis and trans isomers differ in the position of the ligands for a coordination
complex. For trans molecules, two identical ligands are on the opposite side of the molecules
and for cis, the two ligands are on the same side. For the coordination complexes of
trans-[Co(en)2Cl2 ]Cl
and cis-[Co(en)2 Cl
2]Cl
synthesized in this experiment, the position of the
two Cl ligands determine whether its a trans or cis isomer.
This study source was downloaded by 100000858936669 from CourseHero.com on 02-06-2023 01:21:35 GMT -06:00
https://www.coursehero.com/file/83007473/Geometrical-Isomerismpdf/
, Anusha Ambaselkar
The purpose of this experiment was to explore the differences between cis and
trans-Dichlorobis(ethylenediamine)cobalt(III) Chloride by obtaining an absorption spectra by
using a Ultraviolet visible spectrophotometer. A UV-vis spectrophotometer refers to absorption
spectroscopy where it measures at what wavelength light is absorbed at for the sample.The
maximum wavelengths determined by the spectra for both isomers were compared to the range
of colors reflected and absorbed at different wavelengths to determine if the experiment was a
success. The absorbance was also measured and the concentrations were calculated for both
to determine the molar absorption coefficient using the Beer-Lambert equation[1].
Product Reactions:
4 CoCl2 + 8 en + 4 HCl + O2 → 4 trans-[CoCl2(en)2]Cl + 2 H2O
trans-[CoCl2(en)2]Cl + H2O + heat → cis-[CoCl2(en)2]Cl + H2O
Methods:
Part A: Preparation of trans-[Co(en)2Cl
]Cl
2
Cobalt chloride hexahydrate (8.6mmol, 2g) and distilled water (5.0mL) in a 250mL
beaker was added. Then a mixture of anhydrous 1,2-diaminoethane (1.0mL) and water (3.0mL)
was added into the chloride solution. Finally, 30% hydrogen peroxide (1.0mL) was added
dropwise to this solution. This solution was heated until the effervescence had stopped (5min)
and after, concentrated hydrochloric acid (5.0mL) was added. The solution was gently
evaporated for another 30min until a dark green thick layer was formed. The beaker was then
placed in an ice water bath (10min). Vacuum filtration was used to filter off the crystals and
washed with 3 small portions of 95% ethanol. Then the powder was placed in an oven (10 min)
to remove the HCl and leave the trans-[Co(en)2Cl
]Cl
2 roduct by itself. This product was a dark
p
green powder.
This study source was downloaded by 100000858936669 from CourseHero.com on 02-06-2023 01:21:35 GMT -06:00
https://www.coursehero.com/file/83007473/Geometrical-Isomerismpdf/
