1. Make one table of reagents and one table of products for the experiment. (inc
ID: 899343 • Letter: 1
Question
1. Make one table of reagents and one table of products for the experiment. (including molecular weights, weight/volume needed, melting points, boiling points, hazards for each chemicals)
2. Write a flowchart of the experiments process. e.g. 1. put 0.105g (0.3mmol) of xxxx all in a flask..... ---> 2. ......
* week 1 and week 2 pleaes do them separately please.
CHM 231
VASKA’S COMPLEX TRANS-IrCl(CO)(PPH3)2: SYNTHESIS AND REACTION WITH OXYGEN
INTRODUCTION
This experiment introduces you to a variety of new concepts and experimental techniques. For example, most transition metals you have worked so far belong to the 1st row of transition metals (Sc, Ti, V, Cr, Mn, Fe...). Now, this experiment introduces you to a 3rd row metal: iridium. With the exceptions of molybdenum and tungsten, the metals of the 2nd and 3rd row are much less common on the earths crust compared to 1st row metals. Iridium is a precious metal, and while iridium is currently „only half as expensive as gold, it is still 26 times more expensive than silver. Despite its price, iridium compounds (and, similarly, rhodium compounds) are used extensively as catalysts. You will work with iridium compounds on a small scale, a common and important practice in working with precious metals. Vaskas compound contains a phosphine (PR3) ligand, which is related to the NR3 (amine) ligands you are familiar with. Vaskas compound contains a metal-bonded carbon monoxide. A metal complex containing a CO functionality is also called a “metal carbonyl”. Compounds of this type, where a carbon is directly bonded to a metal center, are called “organometallic” compounds, and you might study these compounds in more detail in advanced classes. The synthesis you will do is very elegant: unlike most syntheses of metal carbonyls it avoids the use of gaseous CO. The solvent dimethylformamide acts as a precursor to CO, instead. Vaskas complex is very famous: it was the first artificial metal complex that reversibly binds O2. In some sense, it is mimicking the behavior of hemoglobin. In addition, Vaskas complex is a catalyst for various organic reactions. In this experiment, you will synthesize Vaskas complex and observe its reaction with O2, by UV-Vis spectroscopy.
EXPERIMENTAL PROCEDURE
Week 1: Trans-IrCl(CO)(PPh3)2: Synthesis and Reaction with Oxygen
Transfer 0.105 g (0.3 mmol) of IrCl3·3H2O, 0.393g (1.5 mmol) of triphenylphosphine, 10 mL of dimethylformamide and five drops of aniline into a two-neck round bottom flask. Add a stir bar and attach a reflux condenser to one neck. To purge
the system with nitrogen place a gas adaptor on the
other neck of the flask and connect it to the nitrogen
line. Attach a gas adaptor to the top of the
condenser and connect it to the oil bubbler. The
flask will be placed into a sand bath set on a
magnetic stir plate. Purge the system with nitrogen
to remove the air from the system (rapid bubbling
of nitrogen through the oil without loss of oil).
After 3 minutes reduce the nitrogen flow (a bubble
every few seconds), turn on the stirring and heat the
flask to a gentle reflux. Once a constant, slow reflux
is obtained, wait for 5 minutes and turn off the
nitrogen flow and clamp the tubing. Reflux the
solution for 2 hours and then turn off the heat. While the system is cooling down, purge gently with nitrogen to avoid oil from the bubbler being sucked into the reaction flask.
Once the system has been cooled to 50°C or less, add 30 mL of ethanol. The solution is cooled in an ice bath for 10 minutes. Yellow, air stable microcrystals will form. Collect the crystals by vacuum filtration (use two pieces of filter paper) and wash with a few mL of methanol and then ethyl ether. Weigh and label the sample vial provided by the technician before transferring the product to the sample vial. Place the sample vial in the desiccator for storage.
Week 2: Yield and Melting Point
Weigh your dry compound. Measure the melting point. You will need both yield and melting point for your lab report.
UV-Vis Spectroscopy and Oxygenation of IrCl(CO)(PPh3)2
Weigh about 7 mg of Vaskas complex. Transfer the product into a 25 mL volumetric flask and fill it with toluene to the 25 mL mark. Stopper the flask and shake the solution until the crystals are completely dissolved. Use a Pasteur pipette to transfer the sample to a quartz cuvette. Record the UV-Vis spectrum of Vaskas complex in the 300 -500 nm spectral range. Three absorption bands should be visible in the spectrum.
The solution from the cuvette is returned into the volumetric flask. Place a long tip
Pasteur pipette, connected to an oxygen cylinder, in the flask. A stream of oxygen is bubbled through the solution for 90 minutes. Care must be taken not to spill any solution. The volume of the solution might decrease during oxygenation due to the evaporation of toluene. If that is the case bring the volume to 25 mL by adding more toluene. A sample of this solution is transferred to a quartz cuvette and another UV-Vis spectrum is recorded.
Explanation / Answer
reagents
Melting or boiling points
Molecular weights
Weight/volume
needed
hazards
IrCl3·3H2O
(iridium chloride hydrate)
763
352.6218 g/mol
0.15 g
Contact with eyes, skin causes irritation
Triphenylphosphine
BP-377
262.28 g/mol
0.393 g
Contact with eyes, skin causes irritation
dimethylformamide
Bp-153
73.09 g/mol
10 mL
It causes birth defects to humans. It is very hazardous.
aniline
Bp-184.1
93.13 g/mol
5 drops
Aniline is very toxic by inhalation of vapors
Ethanol
Bp-78.37
46 g/mol
30 mL
Methanol
Bp-64.7
32.04 g/mol
Few mL
Flammable and toxic
Toluene
Bp-110
92.14 g/mol
25 mL
Highly flammable
Inhalation causes headache and dullness
Products
Melting or boiling points
Molecular weights
IrCl(CO)(PPh3)2
Bp-360
780.25 g/mol
step-1:
take two necked round bottmed flask, now transfer 0.105 g of IrCl3·3H2O, 0.393g of triphenylphosphine, 10 mL of dimethylformamide and five drops of aniline.
Now connect the one neck of flask with nitrogen line and other with adaptor.
the adaptor is attached with condensor and connect it to the oil bubler.
step 3:
The
flask will be placed into a sand bath set on a magnetic stir plate. Purge the system with nitrogen
to remove the air from the system.
After 3 minutes reduce the nitrogen flow (a bubble
every few seconds), turn on the stirring and heat the
flask to a gentle reflux
step:4
Once the system has been cooled to 50°C or less, add 30 mL of ethanol.
The solution is cooled in an ice bath for 10 minutes. Yellow, air stable microcrystals will form. Collect the crystals by vacuum filtration (use two pieces of filter paper) and wash with a few mL of methanol and then ethyl ether.
step 5:
Weigh your dry compound. Measure the melting point. You will need both yield and melting point for your lab report.
step 6:
UV-Vis Spectroscopy and Oxygenation of IrCl(CO)(PPh3)2
7 mg of Vaska?s complex. Transfer the product into a 25 mL volumetric flask and fill it with toluene to the 25 mL mark. Stopper the flask and shake the solution until the crystals are completely dissolved. Use a Pasteur pipette to transfer the sample to a quartz cuvette.
Record the UV-Vis spectrum of Vaska?s complex in the 300 -500 nm spectral range. Three absorption bands should be visible in the spectrum.
reagents
Melting or boiling points
Molecular weights
Weight/volume
needed
hazards
IrCl3·3H2O
(iridium chloride hydrate)
763
352.6218 g/mol
0.15 g
Contact with eyes, skin causes irritation
Triphenylphosphine
BP-377
262.28 g/mol
0.393 g
Contact with eyes, skin causes irritation
dimethylformamide
Bp-153
73.09 g/mol
10 mL
It causes birth defects to humans. It is very hazardous.
aniline
Bp-184.1
93.13 g/mol
5 drops
Aniline is very toxic by inhalation of vapors
Ethanol
Bp-78.37
46 g/mol
30 mL
Methanol
Bp-64.7
32.04 g/mol
Few mL
Flammable and toxic
Toluene
Bp-110
92.14 g/mol
25 mL
Highly flammable
Inhalation causes headache and dullness
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