Michael Thomson & James Papatzimas
October 17, 2013
Synthesis of a Coordination Compound
Purpose: The purpose of this lab was to illustrate some of the chemistry of the elements
of the first transition series. The reactions were carried out on a test tube scale,
examining the relative stabilities of the various oxidation states for a given element.
The elements studied in this experiment were cobalt, copper, vanadium and
chromium.
Procedure: Refer to Chem 341 lab manual, for the procedures for the reactions of cobalt,
copper, vanadium and chromium.
Observations:
Reactions of Cobalt:
 Initial solution of cobalt (II) chloride was made by adding 0.991 g of the pink,
crystalline CoCl2 to a beaker, and dissolved in 25 mL of triply deionized water.
1. Upon addition of a concentrated solution of NaOH (~50%), a bright blue/purple
precipitate was initially formed. As more was added, the solution became more
brown/blue with a precipitate.
Reaction: 2NaOH + CoCl2 2NaCl + Co(OH)2
2. When excess 4 M NaOH was added to the light pink cobalt solution, a bright blue
precipitate was former, like in part 1. As the NaOH shifted towards being in
excess, the mixture became pink/grey cloudy mixture; less dark than part 1.
Reaction: 2NaOH + CoCl2 2NaCl + Co(OH)2
3. When excess NaCO3 is added to the pink cobalt solution, a bright pink/violet
precipitate was formed. Compared to reaction number one, the reaction of the
cobalt did not proceed as far due to the carbonate being a weaker base.
Reaction: Na2CO3 + CoCl2 CoCO3 + 2NaCl
4. When excess aqueous NH3 was added to the pink cobalt solution, the color
change only formed a bright royal blue solution. Adding 4 drops of H2O2 (6%), a
green solution was obtained. Adding excess 4 M NaOH, a dark black/green
solution was obtained. The mixture was placed on the heat for 22 minutes,
which yielded a black precipitate formation.
Reaction: CoCl2 +6NH3  [Co(NH3)6]Cl2
[Co(NH3)6]Cl2 + H2O2 [Co(NH3)6]Cl3 + 2OH-(aq)
5. Adding 2 drops of 2 M HCl, 4 drops of thioacetamide, and 5 drops of 4 M NH3(aq),
a bright blue precipitate was formed.
*****Reaction: HCl + CoCl2 + 2CH3CH2SNH2 + NH3 H2O + C2CoN2S2 + HCl +
2NH3
6. When 1 mL of 2 M ammonium thiocyanate was added to 1 mL of cobalt solution,
the solution changed color to a purple/red grape juice color. Upon addition of 1
mL of pyridine, a milky, pink solution was formed, with a white precipitate.
Adding 1mL of 2 M ammonium thiocyanate (clear, colorless) to 1 mL of saturated
zinc sulfate (clear, colorless), then adding 1 mL of pyridine, a milky solution with
a white precipitate was obtained.
Michael Thomson & James Papatzimas
October 17, 2013
To a light pink mixture of 1 mL of cobalt(II) solution and 1 mL of saturated zinc
sulfate solution, 1 mL of 2 M ammonium thiocyanate solution was added, forming
a darker pink mixture, then 1 mL of pyridine was added, forming a pink/blue
solution.
7. When a concentrated solution of potassium thiocyanate was added to ~2 mL of
the cobalt (II) solution, a deep fuscia color was obtained. Adding ~2 mL of diethyl
ether, there was a clear, colorless upper layer (diethyl ether). Acidifying the
solution caused the extraction of light blue compound into the upper light blue,
clear ether layer.
8. Acidifying ~1 mL of the cobalt (II) solution with clear, colorless acetic acid, no
change was observed. Adding a little solid potassium nitrate resulted in a yellow
precipitate being formed.
*****Compounds/oxidation states of cobalt.
Reactions of Copper:
 Initial solution of a light aqua blue copper (II) sulfate was made by adding 1.011 g
of the blue, crystalline CuSO4 to a beaker, and dissolved in 25 mL of triply
deionized water.
1. Upon addition of excess sodium hydroxide, the color darkened to a royal blue.
Upon heating, the color changed to a darker grey/black color.
2. Slowly added excess NaOH (~50%) to ~1 mL of copper (II) solution, a slightly
brighter royal blue color appeared than in part 1, with some white crystals
forming at the bottom of the test tube.
3. Adding a little tartaric acid to ~1 mL of copper (II) sulfate solution, it settled to the
bottom. Excess 4 M NaOH caused the solution to be dark blue/black color. A
yellow/green color changed to an orange solution after heating.
4. Slowly adding excess 4 M aqueous ammonia to ~1 mL of copper (II) sulfate
solution, a light blue solution with a white precipitate was formed. The reaction
did not proceed as far since the ammonia as a weak base did not cause the
black precipitate to form, as in the addition of the strong base, hydroxide in
reaction 1.
5. Adding excess sodium carbonate to the copper (II) solution, a milky blue solution
was formed. Upon boiling, the solution formed a darker black precipitate, similar
to reaction 1. The heat likely shifted the acid/base equilibrium of the carbonate,
causing the reaction to proceed further.
*****Compounds/oxidation states of copper.
Calculations:
Results:
Product:
Zinc Acetylacetonate Monohydrate
Sulfatobis(ethylendiamine)copper(II)
Mn3(Hedta)2.10H2O
Questions:
Mass of Product:
1.313 g
2.258 g
2.482 g
Percent Yield:
23.7%
133.3%
52.3%
Michael Thomson & James Papatzimas
October 17, 2013
𝑎𝑐𝑡𝑢𝑎𝑙 𝑦𝑖𝑒𝑙𝑑
18.0𝑔
a. eld: 𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑦𝑖𝑒𝑙𝑑 ∗ 100% = 21.1 𝑔 ∗ 100% = 85.3% 𝑦𝑖𝑒𝑙𝑑
Discussion:
References: