Formation of the Piano Stool Type Compound : Mesitylene Tricarbonylmolybdenum(0) from Molybdenum Hexacarbonyl and Mesitylene

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  • Topic: Ligand, Molybdenum, Solvent
  • Pages : 2 (697 words )
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  • Published : December 19, 2011
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There are many different binding modes of ligands to transition metal atoms. In past experiments with Co(II) and Co(III), you observed that a ligand such as Chloride or amine can coordinate in a monodentate fashion. You also observed that carbonate occupies two sites of a transition metal and is known as a bidentate ligand. In this experiment, you will observe the reaction of a -bond in an olefin with a molybdenum metal center to form a piano-stool shaped molecule. The molybdenum metal retains its octahedral shape with three carbonyl’s serving as the “legs” of the stool and the mesitylene is the “seat” of the stool and is position on one face of the octahedral.

This form of coordination is relatively common with olefins and metal atoms, the most famous being ferrocene, (cyclopentadiene)2Fe. It is composed of two 5-membered rings situated directly above and below the metal center. It looks like an iron sandwich.

The reaction of molybdenum hexacarbonyl and mesitylene is unstable with respect to air. Because inorganic chemists desire to work with compound that have some component that is air sensitive, they have devised a couple of ways to manipulate air-sensitive materials. We will focus our efforts on the use of a Schlenk line in this laboratory. A Schlenk line is a piece of equipment that is designed with the purpose of conducting experimental operations and techniques under an inert air environment. You will be shown how to use a Schlenk line during lab. Experimental

Metal carbonyls can be very toxic and should be handled carefully and weighed in a hood. Metal carbonyls composed of light metals, such as Ni(CO)4 can have high volatilities (43 °C). Fortunately, we are working with Mo(CO)6, which has a higher sublimation point. In addition, the reaction will produce a bit of CO(g) which, at high levels can be fatal. Since your reaction vessels will be vented into a hood, you will not need to be concerned about asphyxiation. Week 1 – synthesis and...
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