Name: air-free solvent transfer on a schlenk line
Uploaded: 2023-04-30T07:01:26.000Z
Duration: 6 min 50 s
Channel: JoVE

1. Setup of the Schlenk Line
For a more detailed procedure, please review the &#34;Schlenk Lines Transfer of Solvent&#34; video in the Essentials of Organic Chemistry series. Schlenk line safety should be reviewed prior to conducting this experiment. Glassware should be inspected for star cracks before use. Care should be taken to ensure that O2 is not condensed in the Schlenk line trap if using liquid N2. At liquid N2 temperature, O2 condenses and is explosive in the presence of organic solvents. If it is suspected that O2 has been condensed or a blue liquid is observed in the cold trap, leave the trap cold under dynamic vacuum. Do NOT remove the liquid N2 trap or turn off the vacuum pump. Over time the liquid O2 will sublime into the pump - it is only safe to remove the liquid N2 trap once all of the O2 has sublimed.
<ol>
	<li>Close the pressure release valve.</li>
	<li>Turn on the N2 gas and the vacuum pump.</li>
	<li>As the Schlenk line vacuum reaches its minimum pressure, prepare the cold trap with either liquid N2 or dry ice/acetone.</li>
	<li>Assemble the cold trap.</li>
</ol>
2. Preparation of the Solid Reactants
<ol>
	<li>Weigh 100 mg (0.40 mmol) of solid dicyclopentadienyltitanium(IV) dichloride (compound 1, Figure 1) and 78 mg (1.2 mmol) zinc dust into a Schlenk flask (Schlenk flask A).</li>
	<li>Fit Schlenk flask A with a greased glass stopper and attach the Schlenk flask side arm to the Schlenk line with Tygon tubing.</li>
	<li>Open the stopcock of the Schlenk line tube attached to Schlenk flask A to vacuum. Slowly open the stopcock on Schlenk flask A. Evacuate Schlenk flask A for 5 min.</li>
	<li>Repressurize Schlenk flask A with N2 by first closing the stopcock on the Schlenk flask. Slowly repressurize the Schlenk line tubing with N2 by turning the Schlenk line stopcock to N2. Make several (at least 5) quick 180 &#176; turns on the Schlenk flask stopcock, making sure the stopcock is closed after each turn. Slowly open the stopcock to finish filling Schlenk flask A with N2.</li>
	<li>Close the Schlenk flask A stopcock.</li>
	<li>Repeat steps 2.3-2.5 two more times. On the last cycle, leave the stopcock to the Schlenk flask A open.</li>
</ol>
3. Preparation of the Solvent
NOTE: Since the reaction is not water sensitive, glassware and solvents do not need to be dried. However, if the preparation is for use in the glovebox, all glassware and solvents should be appropriately dried.
<ol>
	<li>Measure 15 mL of acetonitrile and transfer the solvent to a new Schlenk flask (Schlenk flask B). Fit Schlenk flask B with a septum.</li>
	<li>Connect Schlenk flask B to the Schlenk line using Tygon tubing. Evacuate the tubing for 5 min and refill the tubing with N2 (the stopcock to the Schlenk flask should remain closed). Repeat the evacuation/refill cycles two more times. Leave the tubing under N2.</li>
	<li>Purge one of the unused Tygon tubes on the Schlenk line with N2, fitted with a long needle.</li>
	<li>Insert the needle into the septum of Schlenk flask B and lower the needle into the acetonitrile.</li>
	<li>Insert a second needle (not attached to the Schlenk line) into the septum of Schlenk flask B. This is the vent needle. Upon insertion of the vent needle, N2 should start bubbling through the acetonitrile.</li>
	<li>Allow the acetonitrile to degas for 15 min.</li>
	<li>Open the stopcock to Schlenk flask B.</li>
	<li>Remove the vent needle, followed by the needle connected to the Schlenk line. Close the stopcock on the Schlenk line that is connected to the long needle.</li>
</ol>
4. Addition of Solvent via Cannula (Figure 3)
<ol>
	<li>Make sure that the stopcocks to both of the Schlenk flasks (A &#38; B) are open to N2.</li>
	<li>Replace the glass stopper on Schlenk flask A with a rubber septum.</li>
	<li>Insert one end of the cannula through the septum on Schlenk flask B (the donor flask). Do NOT put the needle into the acetonitrile.</li>
	<li>Ensure N2 is flowing through the cannula by putting the opposite end of the cannula close to the skin of the arm.</li>
	<li>Insert the other end of the cannula into Schlenk flask A (the receiving flask).</li>
	<li>Close the stopcock to Schlenk flask A.</li>
	<li>Lower the cannula in Schlenk flask B so that the tip reaches the bottom of the acetonitrile.</li>
	<li>Insert a vent needle in the septum of Schlenk flask A. Solvent should begin to flow. If no solvent is flowing, try increasing the N2 flow or raising the solvent flask above the height of the receiving flask.</li>
	<li>Transfer all 15 mL of the acetonitrile from Schlenk flask B to A. If only a portion of the solvent is desired, simply remove the cannula tip from the solvent in Schlenk flask B to stop the flow of liquid.</li>
	<li>Remove the vent needle from the septum and open the stopcock to Schlenk flask A.</li>
	<li>Remove the cannula from Schlenk flask A.</li>
	<li>Remove the cannula from Schlenk flask B.</li>
</ol>
5. Synthesis of Ti(III) Metallocene (Compound 3)
<ol>
	<li>Vigorously stir the solution for 15 min (or until the reaction mixture turns blue).</li>
	<li>If a green color persists, add more zinc dust (1-2 additional equivalents). To add more zinc dust to the system without introducing O2, make sure that the Schlenk flask stopcock is open to positive N2 pressure. Remove the rubber septum and add the solid to the flask. Re-attach the rubber septum. If the addition of excess zinc dust does not effect the desired color change to blue, O2 was likely introduced into the system.</li>
</ol>
6. Addition of Solvent via Syringe
<ol>
	<li>Degas 10 mL of acetonitrile as described in step 3 in Schlenk flask B.</li>
	<li>Make sure that both Schlenk flask A &#38; B stopcocks are open to N2 and are fitted with rubber septa.</li>
	<li>Insert the syringe needle into either flask and pull N2 gas into the syringe.</li>
	<li>Remove the needle and eject the N2 into the hood.</li>
	<li>Repeat steps 6.3-6.4 two more times.</li>
	<li>Insert the syringe needle fitted to a 10 mL syringe into Schlenk flask B and pull up the desired volume of solvent (5 mL).</li>
	<li>Remove the needle from the solvent but leave the needle in the Schlenk flask. Bend the needle so that the syringe is pointing up (the needle should form an arch) and pull ~1 mL of N2 gas into the needle. There should be a gas &#34;bubble&#34; at the top of the syringe.</li>
	<li>While keeping the needle arched, remove the needle from Schlenk flask B. The syringe should still be pointed up with the bubble of N2 at the tip of the syringe where the needle is attached. The N2 bubble will prevent acetonitrile from leaking out of the syringe.</li>
	<li>With the needle still arched and the syringe pointing up, insert the needle into the septum of Schlenk flask A.</li>
	<li>Slowly add acetonitrile to Schlenk flask A. At this point, the position of the syringe is irrelevant.</li>
	<li>When solvent addition is complete, remove the syringe needle from Schlenk flask A.</li>
</ol>

Here, we demonstrated standard Schlenk line technique to synthesize an air-sensitive Ti(III) metallocene complex. The solvent was degassed by bubbling N2 through the liquid in a Schlenk flask. We also demonstrated how to set up a reaction under anaerobic conditions on the Schlenk line and transfer solvent anaerobically by cannula transfer as well as by syringe.
Inorganic chemists use Schlenk line technique in the synthesis of air- and water-sensitive compounds. The solvent used in t...

synthesis of a ti(iii) metallocene using schlenk line technique

Synthesis Of A Ti(III) Metallocene Using Schlenk Line Technique

Source: Tamara M. Powers, Department of Chemistry, Texas A&amp;M University 
Inorganic chemists often work with highly air- and water-sensitive compounds. The two most common and practical methods for air-free synthesis utilize either Schlenk lines or gloveboxes. This experiment will demonstrate how to perform simple manipulations on a Schlenk line with a focus on solvent preparation and transfer. Through the synthesis of a reactive Ti(III) metallocene complex, we will demonstrate a new, simple method to degas solvent as well as how to transfer solvent by cannula and by syringe on a Schlenk line.
The synthesis of a Ti(III) metallocene compound 3 is shown in Figure 1.1 Compound 3 is highly reactive with O2, (see oxidation of compound 3 to Ti(IV) metallocene 4 shown in Figure 1). Therefore, it is important to run the synthesis under anaerobic conditions. The synthesis of target compound 3 can be monitored visually and progresses through one additional color change before arriving at the desired product, which is blue in color. If during the experiment there is an observed color change from blue to yellow (or green = blue + yellow), this is an indication that O2 entered the flask and that undesired oxidation of compound 3 to the Ti(IV) analog (compound 4) has occurred.
<img alt="Chloride substitution reaction scheme with Cp2TiCl2, Zn dust, and acetonitrile; diagram shows intermediates." src="/files/ftp_upload/10428/10428fig1v2.jpg" data-altupdatedat="1761830439000" data-alt="Figure 1"> 
Figure 1. Synthesis of Ti(III) metallocene compound 3 and it's reaction with O2.

Upon addition of the acetonitrile in step 4, the solution should change color from orange, to green, to blue (Figure 4). Failure to obtain the blue color indicates a leak in the system. Addition of acetonitrile by syringe in step 6 should result in no color change if anaerobic conditions are maintained. If oxygen is present, the solution will turn from blue, to green, to orange.
<img alt="Chemistry ...

Source: Tamara M. Powers, Department of Chemistry, Texas A&#38;M University&#160;
Inorganic chemists often work with highly air- and water-sensitive ...

Chemists frequently encounter air-sensitive chemical reagents and reactions, and thus have to apply special techniques when working with them.The slightest trace of air in a chemical reaction would likely result in unwanted side products. To avoid this, first traces of oxygen are removed by purging equipment and reagents.Then, in order to maintain an oxygen-free atmosphere, reagents are handled in a glovebox, or transferred from one closed system to another by cannulation using a Schlenk line.This video will illustrate a procedure for purging oxygen from a reaction mixture and maintaining an air-free atmosphere in the synthesis of a Ti(III) metallocene. This will be followed by a few examples demonstrating the application of this technique.Inorganic chemical reactions, such as the conversion of titanocene dichloride to its dimeric form and the final Ti(III) metallocene, are highly sensitive to oxygen, and therefore must be carried out in air-free conditions.To start, in a fume hood equipped with a Schlenk line, also known as a double manifold, weigh Cp2(Ti4+)Cl2 and zinc dust into a 200 mL Schlenk flask equipped with a stir bar, labeled as "A". Seal the flask with a greased glass stopper and secure with a rubber band. Attach Tygon tubing from the Schlenk line to flask sidearm.Open the stopcock to vacuum and evacuate for 5 min, then close the stopcock to the flask, switch to N2, and make at least five rapid 180 ? turns before slowly opening to fill the flask with N2.In a separate Schlenk flask labeled "B", measure 15 mL of acetonitrile and seal with a rubber septum. Attach Tygon tubing from the Schlenk line to the flask sidearm, then evacuate the tubing for 5 min. Refill the tubing with N2.Attach a long needle to a second Tygon tube on the Schlenk line, and purge with N2 for several minutes. Insert the purged needle into the Schlenk flask containing acetonitrile, followed by the venting needle. Bubble N2 into the solvent for 15 min, then open the flask stopcock to N2 and remove the needles.With Schlenk flask A under N2, remove the glass stopper and replace it with a rubber septum. With the two Schlenk flasks open to N2, insert one end of the cannula into the donor flask, above the level of the solvent, and determine whether N2 is flowing through the other end. Then insert the other end of the cannula into the receiving flask containing the reagents, close the receiving flask's stopcock, and attach a venting needle.Lower the cannula into the solvent, and allow all of the acetonitrile to drip or slowly flow along the sides of the receiving flask. Once the addition is complete, reopen the receiving flask stopcock to N2, and remove the cannula and venting needle.After the solvent is added, vigorously stir the reaction mixture of acetonitrile, zinc dust, and Cp2(Ti4+)Cl2 until it turns blue, indicating formation of Ti(III) metallocene complex.If the reaction mixture remains green after 15 min, keep the stopcock open to positive N2 pressure, remove the septum and add 1-2 equivalents of zinc dust. If the mixture is still green or has turned yellow, it is likely that oxygen has entered the system, which results in further oxidation to the Ti(IV) metallocene complex.Now you know how to use a cannula transfer, but in case this is not possible, the solvent can be added via a syringe. First, make sure both the receiving and donor flasks are open to N2.Insert the needle fitted to a 12 mL syringe into either flask and pull only N2 into it. Remove the needle and eject the N2 into the hood.Once the needle and syringe are purged, insert the needle into the donor flask and pull up the desired volume of solvent. Then, raise the needle slightly, bend it to an arch and pull up 1 mL of N2. Keep the needle arched and syringe pointing up and remove it from the donor flask.Insert the arched needle into the receiving flask. Slowly add the solvent, and remove the syringe needle from receiving flask when finished.Now that we have discussed a procedure for an air-free synthesis, let's look at a few applications.Cadmium selenide quantum dots are semiconductor nanocrystals composed of a cadmium selenide core and a ligand shell. These multicomponent structures are capable of manipulating electrons at the nanoscale.The synthesis of these nanocrystals requires precise reaction conditions, especially an oxygen-free atmosphere.Titanocene dichloride, the reagent used in this video, is an organotitanium compound commonly used in organic and organometallic synthesis. The compound itself is synthesized by reacting 2 equivalents of sodium cyclopentadiene (NaCp)?with TiCl4?in anhydrous, oxygen-free THF. Titanocene dichloride is also used for the production of the Petasis reagent, which is a useful reagent applied in the conversion of esters to vinyl ethers.Another titanocene dichloride reagent, called the Tebbe reagent, is applied to convert various carbonyl functional groups to alkenes, or also known as methylenation.You've just watched JoVE's introduction to Synthesis of a Ti(III) metallocene using the Schlenk Line Technique. You should now understand how to perform degassing as well as cannula transfer, and some of its applications. Thanks for watching!

synthesis-of-a-tiiii-metallocene-using-schlenk-line-technique

Education

JoVE Science Education

Chemistry

Inorganic Chemistry

air-free solvent transfer on a schlenk line

Schlenk line technique is a useful way to handle air- and water-sensitive chemicals. In inorganic chemistry, it is often used when compounds must be kept away from oxygen and moisture. This experiment focuses on simple Schlenk line steps, especially solvent preparation and solvent transfer.

The procedure shows a new, simple method for degassing solvent, which means removing dissolved gas before use. It also demonstrates how to move solvent by cannula and by syringe on a Schlenk line. These air-free methods help students see how careful handling supports reactions with reactive compounds.

A Ti(III) metallocene complex is used as the example reaction. This compound is highly reactive with O2, so the synthesis must be done under anaerobic conditions, which means without oxygen. The product can be tracked by color changes during the reaction and is blue when the target compound is formed.

If the solution changes from blue to yellow, or to green as blue and yellow mix, that is a sign that O2 entered the flask. That means the Ti(III) metallocene has been oxidized to the Ti(IV) analog instead of giving the desired product. The reaction therefore shows both how to work air-free and how to spot oxygen contamination during synthesis.

Air-Free Solvent Transfer on a Schlenk Line

air-free-solvent-transfer-on-a-schlenk-line

Schlenk line technique is a useful way to handle air- and water-sensitive chemicals. In inorganic chemistry, it is often used when compounds must be kept away from oxygen and moisture. This experiment focuses on simple Schlenk line steps, especially solvent preparation and solvent transfer. The procedure shows a new, simple method for degassing solvent, which means removing dissolved gas before use. It also demonstrates how to move solvent by cannula and by syringe on a Schlenk line. These...

glovebox and impurity sensors

Handling Air-Sensitive Samples in a Glovebox

A glovebox lets chemists handle air- and moisture-sensitive solids and liquids inside an inert atmosphere. It is a sealed box with gloves attached to one or more sides. Those gloves let the user work inside the chamber without exposing the sample to air. For inert-atmosphere work, chemists may choose a glovebox, a Schlenk setup, or high-vacuum techniques. Schlenk and especially high-vacuum methods give tighter control over the atmosphere. That makes them useful for reactions that are very...

purification of ferrocene by sublimation

Ferrocene Purification Using Sublimation

Sublimation can be used to purify ferrocene, a solid that turns directly from a solid into a gas. This phase change happens without first becoming a liquid. It occurs at temperatures and pressures lower than the compound's triple point. During sublimation, the solid is heated into the gas phase. Non-volatile impurities stay behind in the sample. The vaporized compound then cools and deposits as a solid on a cold surface. This method works for both organic and inorganic solids. In this...

the evans method

Magnetic Susceptibility in Transition Metal Complexes

Magnetic susceptibility helps reveal whether a transition metal complex has unpaired electrons. Many organic molecules are diamagnetic, which means all of their electrons are paired in bonds. In contrast, many transition metal complexes are paramagnetic and have unpaired electrons in their ground state. Hund's rule says that electrons fill orbitals of similar energy to maximize the number of unpaired electrons before they pair up. Transition metals have partially filled d-orbitals, and ligand...

single crystal and powder x-ray diffraction

single-crystal-and-powder-x-ray-diffraction

X-ray Diffraction for Crystal Structure

X-ray diffraction is used to study the structure of molecules with X-rays. In chemistry, this method is called X-ray crystallography. It is commonly done with either a single crystal or a powdered sample. Single-crystal X-ray diffraction can show the absolute structure of a compound. It reveals the exact positions of atoms, so bond lengths and bond angles can be measured. This method gives the structure inside one crystal, which may not match the bulk of the material. For that reason, other...

electron paramagnetic resonance (epr) spectroscopy

electron-paramagnetic-resonance-epr-spectroscopy

EPR for Studying Antioxidant Behavior

Electron Paramagnetic Resonance (EPR) helps students study unpaired electrons in chemical systems. EPR spectroscopy is used here to examine how dibutylhydroxy toluene, or BHT, acts as an antioxidant during the autoxidation of aliphatic aldehydes. The lesson focuses on the basic principles behind EPR and shows how this method can track radical behavior in a reaction. It also connects the technique to a real chemical example, where BHT is studied for its role in slowing autoxidation. This makes...

m&#246;ssbauer spectroscopy

Ferrocene Analysis by Mössbauer Spectroscopy

Mössbauer spectroscopy is a bulk characterization technique used to study atoms in the solid state. It examines the nuclear excitation of an atom by gamma rays. The method gives a spectrum that can reveal the oxidation state, spin state, and electronic environment around the target atom. These spectral features help build evidence about a molecule’s electronic structure and ligand arrangement, or geometry. The video explains the basic principles behind Mössbauer spectroscopy. It also shows how...

lewis acid-base interaction in ph3p-bh3

Ph3P-BH3 Adduct and Lewis Acids

Chemistry uses models to explain patterns in reactivity, and acid-base definitions have changed over time. Substances have been grouped as acids and bases since ancient Greece. Early descriptions were based on taste. Acids were sour, like lemon juice and vinegar. Bases were used to neutralize acids. The word acid comes from the Latin term for sour-tasting. The word alkaline comes from an Arabic word for roasting, linked to early ash-based bases used to make soap. A later model came from Svante...

structure of ferrocene

Ferrocene Synthesis and Electron Count

Ferrocene synthesis and electron count are the focus of this high school chemistry experiment. Ferrocene is an organometallic compound, which means it contains a metal bonded to carbon-based groups. It was first reported in 1951 by Kealy and Pauson in Nature. The early structure for ferrocene placed the iron atom in a simple sigma bond to one carbon atom on each cyclopentadiene ligand. A later model from Wilkinson and Woodward described a sandwich shape, with iron between two cyclopentadiene...

application of group theory to ir spectroscopy

application-of-group-theory-to-ir-spectroscopy

IR Spectroscopy of Metal Carbonyl Isomers

Infrared spectroscopy of metal carbonyl isomers shows how symmetry can help identify a complex. Metal carbonyl complexes are useful metal precursors for making organometallic complexes and catalysts. IR spectroscopy is one of the most useful ways to study compounds that contain CO groups. Group theory is the use of mathematics to describe molecular symmetry. It can be used to predict how many IR-active C-O vibrational modes a molecule should have. The number of C-O stretches seen in an IR...

molecular orbital (mo) theory

Geometry of Ni and Pd dppf Complexes

Nickel and palladium dppf complexes are the focus of this chemistry protocol. It guides the synthesis of two metal complexes that contain the ligand 1,1'-bis(diphenylphosphino)ferrocene, or dppf. The compounds are M(dppf)Cl2, where M is Ni or Pd. Both metal complexes are four-coordinate, meaning each metal center is bonded to four groups. Even so, they do not share the same geometry at the metal center. Molecular orbital, or MO, theory is used together with 1H NMR and the Evans method to...

quadruply metal-metal bonded paddlewheels

quadruply-metal-metal-bonded-paddlewheels

Synthesizing a Mo2 Quadruple-Bond Complex

Paddlewheel complexes are coordination compounds made from two transition metal ions held close together by four bridging ligands. The metals can come from the 1st, 2nd, or 3rd row of transition metals. The bridging ligands are most often formamidinates or carboxylates. Changing the metal ion or the bridging ligand gives many different paddlewheel complexes. Their close structure allows metal-metal bonding, and that bonding strongly affects how the complexes look and react. Because of this,...

dye-sensitized solar cells

Dye-Sensitized Solar Cells and Light Capture

Dye-sensitized solar cells use a dye to capture sunlight and turn it into electrical current. They are a type of solar cell, which is an electrical device that uses light to create current. This approach is modeled on nature, where colored molecules absorb light energy and help drive chemical reactions. The idea connects to photosynthesis in plants. In leaves, chlorophyll pigments give plants their green color and absorb sunlight to power the conversion of water and carbon dioxide into...

synthesis of an oxygen-carrying cobalt(ii) complex

synthesis-of-an-oxygen-carrying-cobaltii-complex

Cobalt Complex Model for Oxygen Binding

Bioinorganic chemistry studies how metals help living systems work. Many proteins contain metals, and some depend on metal-containing active sites to function. Proteins with metals are called metalloproteins. They help carry out important cell functions needed for life. One major role of metalloproteins is oxygen transport. These proteins bind oxygen, move it, and then release it for processes such as respiration. Synthetic inorganic chemists study coordination compounds to model these...

photochemical initiation of radical polymerization reactions

photochemical-initiation-of-radical-polymerization-reactions

Photopolymerizing Styrene Into Polystyrene

Photopolymerizing styrene with light produces polystyrene, a common commodity plastic. This experiment uses simple photochemistry to start a radical polymerization reaction. A radical is a highly reactive particle with an unpaired electron that can help build long polymer chains. The module focuses on benzoyl peroxide as a photo-initiator for styrene polymerization. Benzoyl peroxide absorbs light and helps trigger the reaction. The process also shows how photochemistry can be used to control...

inorganic chemistry

This collection covers a range of inorganic chemistry protocols and concepts including air-free techniques, syntheses of transition metal based compounds, core inorganic chemistry concepts like Lewis Acid and Bases, and advanced analysis techniques including EPR spectroscopy.

Learn how Schlenk line technique is used for air-free solvent preparation and transfer, and how oxygen-sensitive Ti(III) metallocene synthesis is monitored by color change.

Air-Free Solvent Transfer on a Schlenk Line

Description

Transcript

Tags