WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level of safety training, special facilities and equipment, and supervision by appropriate individuals. You bear the sole responsibility, liability, and risk for the implementation of such safety procedures and measures. MIT shall have no responsibility, liability, or risk for the content or implementation of any of the material presented. Legal Notice Experiment #4: The Preparation of Ferrocene & AcetylferroceneMASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Chemistry 5.311 Introductory Chemical Experimentation EXPERIMENT #4 THE PREPARATION OF FERROCENE & ACETYLFERROCENES1 I. Purpose The principal aims of this experiment are to provide background information about and experience in: · the synthesis and electronic structure of ferrocene (1), (h5-C5H5)2Fe [bis(pentahaptocyclopentadienyl) iron]2 · the synthesis of an ionic liquid, as environment for the acetylation of ferrocene · the use of inert atmospheres (including glove box techniques) · recrystallization or sublimation · the use of GC/MS and thin-layer chromatography as analytical tools and column chromatography as a purification technique • the concepts of Green Chemistry such as Atom Economy3 and alternative non-polluting solvents Ferrocene is a historically important molecule. The initial recognition of the structure of C10H10Fe in 19514 spawned a vast area of chemistry, viz., transition metal organometallic chemistry. This field is still developing and has produced a huge number of compounds in which saturated, unsaturated, and aromatic organic fragments are bonded directly to metals. All carbon atoms in the two cyclopentadienyl rings are equally bonded to the central ion by p electrons in the rings. The sandwich structure proposed by Wilkinson and Fischer5,6 (Nobel prize in 1973) in early 1 Mircea D. Gheorghiu designed the experiment to include the acetylation of ferrocene in ionic liquid. 2 The word hapto means in Greek to fasten. Pentahapto therefore, is to be taken as “fastened in five places.” The greek letter h followed by a superscript indicates how many atoms of the ligand are attached to the metal. 3 Atom economy means to maximize the incorporation of all starting materials into the final product. For example, the synthesis of the ionic liquid precursor from 1-methylimidazole and iodoethane to yield 1-ethyl-3-methyl imidazolium iodide is 100% atom efficient. Visit: http://www.chemistry.org/portal/a/c/s/1/acsdisplay.html?DOC=education%5Cgreenchem%5Cindex.html 4 Kealy, T. J.; Pauson, P. L., Nature, 1951, 168, 1039. 5 Wilkenson, Geoffry; Rosenblum, M.; Whiting, M. C. and Woodward, R. B. “The Structure of Iron Bis-Cyclopentadienyl” Journal of the American Chemical Society. 1952, 74, 2123. 6 Fischer, Von E. O. and Pfab, W. “Cyclopentadien-Metallkomplexe, ein neuer typ metallorganischer Verbindungen” Zeitschrift fur Naturforschung. 7b 1952, 377. Exp. 4-1Experiment #4: The Preparation of Ferrocene & Acetylferrocene1952 has been supported by X-ray diffraction (solid state)7 and electron diffraction data (gas phase)8. Ferrocene exhibits the properties of a typical aromatic molecule. This compound is stable to more than 500 °C. It does not react readily with acids or bases; however, it is sensitive toward oxidizing agents. Ferrocene does not undergo addition reactions typical of cyclopentadiene, but readily undergoes electrophilic aromatic substitution. Depending upon the catalyst and the reaction conditions, the major acetylation product is either the monosubstituted product 2 or the disubstituted product 3. For a particular set of reaction conditions, the student will determine whether the major product is the orange acetylferrocene (2) or the red 1,1-diacetylferrocene (3). II. Safety NOTE: The organic liquids to be used in quantity in this experiment: · dimethylsulfoxide · dimethoxyethane · cyclopentadiene · dicyclopentadiene · 1-methylimidazole · iodoethane are all volatile and possess noxious vapors. Avoid inhalation. Carry out all designated operations in the hood. All of the chemicals described in this section are designated with an asterisk (*) in the text the first time they appear. This is so you will be aware of their properties. 1. Dicyclopentadiene (C10H12): This is a noxious liquid. It should be handled with the usual caution: do not ingest. If it is spilled on skin, rinse well with water. 7 Dunitz, J. D.; Orgel, L. E.; Rich, R. A., Acta Crystallogr., 1956, 9, 373. 8 Bohn, R. K. and Haaland, A. J. Organomet. Chem. 1966 5, 470. Haaland, A. and Nilsson, J.E. Acta Chem. Scand. 1968 22 2653. Exp. 4-2 FeFeFeCOCH3COCH3H3COC(CH3CO)2OAlCl3/ionic liquid+123Experiment #4: The Preparation of Ferrocene & Acetylferrocene2. Potassium Hydroxide (KOH): Potassium hydroxide is extremely corrosive and hydroscopic. It should be handled with caution and kept away from skin and clothing. If it spills, wash with plenty of water. Keep containers tightly closed. Powdered KOH must be handled in the hood. 3. Iron(II) Chloride Tetrahydrate (FeCl2•4H2O): Ferrous salts can be toxic. This chemical should be handled with the usual cautions. 4. Dimethyl Sulfoxide (DMSO): DMSO has the ability to render the skin permeable to many chemical compounds. Substances ordinarily regarded as harmless on the skin become dangerous toxic substances when the nonpermeability of the skin has been altered by the application of dimethylsulfoxide. Consequently, keep dimethylsulfoxide off the hands; if it is accidently spilled on the skin, the area should be washed promptly with a strong soap or detergent and plenty of water. 5. Hydrochloric Acid (HCl): Conc. HCl (12 N) is a strong acid. Contact with the skin will cause burns. If any gets on you or your clothing, rinse immediately with water. Dilute HCl (3N or less) is less hazardous but will still burn the skin and produce holes in clothing. 6. Acetone (CH3COCH3): Acetone is an organic solvent and should be treated with normal caution: keep away from flames, dispose in the organic waste. It also has the ability to increase the permeability of skin and should therefore not be spilled over hands, etc. 7. Aluminum Chloride (AlCl3): Anhydrous aluminum chloride releases HCl when it comes in contact with water. It should therefore be treated with the same precautions as for HCl. 8. Acetic anhydride