Name: ir spectroscopy of metal carbonyl isomers
Uploaded: 2023-04-30T07:02:34.000Z
Duration: 11 min 10 s
Channel: JoVE

1. Setup of the Schlenk Line (for a more detailed procedure, please review the "Schlenk Lines Transfer of Solvent" 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. Synthesis of Mo(CO)4[P(OPh)3]2 (Figure 4)1
Note: Use standard Schlenk line techniques for the synthesis of Mo(CO)4[P(OPh)3]2 (see the "Synthesis of a Ti(III) Metallocene Using Schlenk line Technique" video). Metal carbonyl complexes are a source of free CO, which is highly toxic. Carbon monoxide poisoning occurs when CO binds to hemoglobin, resulting in significant reduction of oxygen supply to the body. Therefore, it is extremely important to take appropriate safety measures when handling and working with metal carbonyl complexes. Reactions that generate free CO need to be conducted in a well-ventilated hood to prevent exposure to the toxic gas.
<ol>
	<li>Add 1.6 g (4.92 mmol) Mo(CO)4(nbd) (nbd = 2,5-Norbornadiene) and 1.6 mL (9.84 mmol) triphenyl phosphite (P(OPh)3) to a 100 mL Schlenk flask and prepare the Schlenk flask for the cannula transfer of solvent. 
	Note: Mo(CO)4(nbd) ((Bicyclo[2.2.1]hepta-2,5-diene)tetracarbonylmolybdenum(0)) can be purchased from Sigma Aldrich or synthesized using literature methods.2</li>
	<li>Add 20 mL of degassed dichloromethane to the Schlenk flask via cannula transfer.</li>
	<li>Stir the reaction mixture for 4 h at room temperature under N2.</li>
	<li>Remove the volatiles under vacuum and wash the resulting precipitate with cold hexanes (two washes each with 10 mL, −78 °C). </li>
	<li>Dry the solid product under vacuum for 15 min.</li>
	<li>Measure the IR spectrum of the product in a solution of hexanes.</li>
</ol>
<img alt="Chemical reaction formula synthesizing Mo(CO)4[P(OPh)3]2 using Mo(CO)3 and diphenyl phosphite ligand." src="/files/ftp_upload/10442/10442fig11v2.jpg" data-altupdatedat="1761830439000" data-alt="Figure 11"> 
Figure 4. Synthesis of Mo(CO)4[P(OPh)3]2.

In this video, we learned how to use group theory to predict the number of IR active vibrational modes in a molecule. We synthesized the molecule Mo(CO)4[P(OPh)3]2 and used IR to determine which isomer was isolated. We observed that the product had three C-O vibrations in its IR spectrum, which is consistent with the cis-isomer.
Group theory is a powerful tool that is used by chemists to not only predict IR active vibrational modes, but also vibrationa...

application of group theory to ir spectroscopy

Application of Group Theory to IR Spectroscopy

Source: Tamara M. Powers, Department of Chemistry, Texas A&amp;M University
Metal carbonyl complexes are used as metal precursors for the synthesis of organometallic complexes as well as catalysts. Infrared (IR) spectroscopy is one of the most utilized and informative characterization methods of CO containing compounds. Group theory, or the use of mathematics to describe the symmetry of a molecule, provides a method to predict the number of IR active C-O vibrational modes within a molecule. Experimentally observing the number of C-O stretches in the IR is a direct method to establish the geometry and structure of the metal carbonyl complex.
In this video, we will synthesize the molybdenum carbonyl complex Mo(CO)4[P(OPh)3]2, which can exist in the cis- and trans-forms (Figure 1). We will use group theory and IR spectroscopy to determine which isomer is isolated.
<img alt="Cis-trans isomer diagram of Mo(CO)4(PPh3)2 complexes, illustrating molecular geometry and ligands." src="/files/ftp_upload/10442/10442fig1.jpg" data-altupdatedat="1761830439000" data-alt="Figure 1"> 
Figure 1. The cis- and trans-isomers of Mo(CO)4[P(OPh)3]2.

<img alt="Infrared absorption spectrum graph of Mo(CO)₄(P(OPh)₃)₂; % transmittance vs. wavenumber." src="/files/ftp_upload/10442/IR.png" data-altupdatedat="1761830439000" data-alt="Figure 11">
Figure 5. IR of Mo(CO)4[P(OPh)3]2.
Solution IR in saturated hydrocarbon (cm-1): 2046 (s), 1958 (s), 1942 (vs). 
The fourth resonance can only be seen under high-resolution conditions. There...

Source: Tamara M. Powers, Department of Chemistry, Texas A&#38;M University
Metal carbonyl complexes are used as metal precursors for the synthesis of ...

Group theory is a mathematical model connecting molecular symmetry to properties such as IR-active vibrational modes.Every molecule can be classified with a point group, which describes every symmetry element present in a molecule with respect to a fixed point.Group theory provides special tables, called character tables, to predict the effect of a molecule's symmetry on its vibrational modes and other important properties.This video will discuss the underlying principles of group theory, illustrate the procedure for the synthesis and characterization of an isomer of Mo(CO)4[P(OPh)3]2, and introduce a few applications of group theory in chemistry.Molecular symmetry describes the indistinguishable configurations of a molecule. The transformations between them are called symmetry operations, which occur with respect to one or more symmetry elements.The five symmetry elements are proper and improper rotation axes, mirror planes, centers of inversion, and identity. Every molecule has the identity element, or E, in which no change occurs.A mirror plane, labeled ?, is a reflection plane with identical starting and ending configurations. Molecules may have more than one mirror plane. A ce

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

Education

JoVE Science Education

Chemistry

Inorganic Chemistry

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 spectrum can then help reveal the geometry and structure of a metal carbonyl complex.

The procedure here focuses on the molybdenum carbonyl complex Mo(CO)4[P(OPh)3]2. This compound can form cis and trans isomers, and IR data are used to determine which one is isolated. By combining group theory with IR spectroscopy, the structure of the molybdenum carbonyl product can be identified.

IR Spectroscopy of Metal Carbonyl Isomers

ir-spectroscopy-of-metal-carbonyl-isomers

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

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

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...

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.

Use group theory and IR spectroscopy to identify cis and trans metal carbonyl isomers in a molybdenum complex and link CO stretches to structure.

IR Spectroscopy of Metal Carbonyl Isomers

Description

Transcript

Tags