WARNING NOTICE: The e perimcats described in these materials are potentialy harzardous and require a high lovel ofafcty training special facilities and t, and supervision by appropriate individual. You bear the sole responsiblity, liability, and risk for the implementation of such safty procedures and measures. MIT shall have no responsibility, Hability, or risk for the content or implemcatation of amy of the material presented. Legal Notices 2.2. Expert Experimentalist Rating: " The Single-Crystal Shakedown Overview X-Ray diffraction is an important and powerful tool for determining the solid structure of compounds. Modern advances have made data collection and structure solution almost routine for many small molecules. To use this technique, however, good quality single crystals are still needed. In this exercise, you will experiment with the art of growing single crystals. Techniques Checklist: Manipulation of milligram quantities of materi Syringe use Crystallization techniques for growing good quality single crystals Pre-Lab discussion: Use of different recrystallization techniques: vapor diffusion, solvent layering temperature variation Synthesize Cr(acac)3, then perform several slow recrystallizations to obtain a single crystal of satisfactory quality Magnetic stir plate tle and variac 50-mL Round-bottomed flask ·2- mL Glass syringe Stir bar Glass frit D) Chromium Acetylacetonate Cr(acac) 250-mL Filter flask and rubber filter adaptor 3 Large vials(white cap) 4 Small vials(black cap) 2 Glass jars 2Adapted from Szafran, Z; Pike, R M; Sing, M. M. Microscale Inorganic Chemistry: A Comprehensive Laboratory Experience: Wiley: New York, 1991: "Synthesis of Metal Acetylacetonates"p 224-229 21
2.2. Expert Experimentalist Rating: “The Single-Crystal Shakedown” Overview: X-Ray diffraction is an important and powerful tool for determining the solid state structure of compounds. Modern advances have made data collection and structure solution almost routine for many small molecules. To use this technique, however, good quality single crystals are still needed. In this exercise, you will experiment with the art of growing single crystals. Techniques Checklist: • Manipulation of milligram quantities of material ❑ • Syringe use ❑ • Crystallization techniques for growing good quality single crystals ❑ Pre-Lab Discussion: • Use of different recrystallization techniques: vapor diffusion, solvent layering, temperature variation Goal: Synthesize Cr(acac)3, 2 then perform several slow recrystallizations to obtain a single crystal of satisfactory quality. Equipment: Me • Magnetic stir plate • Heating mantle and Variac Cr O O O O O O Me Me • 50-mL Round-bottomed flask • 2-mL Glass syringe Me • Condenser Me • Stir bar Me • Glass frit (D) Chromium Acetylacetonate Cr(acac)3 • 250-mL Filter flask and rubber filter adaptor • 3 Large vials (white cap) • 4 Small vials (black cap) • 2 Glass jars 2Adapted from Szafran, Z.; Pike, R. M.; Sing, M. M. Microscale Inorganic Chemistry: A Comprehensive Laboratory Experience; Wiley: New York, 1991; “Synthesis of Metal Acetylacetonates” p. 224-229. 21 WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. 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WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. WARNING NOTICE: The experiments described in these materials are potentially hazardous and require a high level ofsafety 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. 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Experiment Outline: Before coming to the lab, perform the necessary calculations to fill in the H2N 2. 4-Pentanedione rea Reagent ource W Density Mass or mmols Volume CrCl3 6H2O 100 mmol entanedione Cr(acac)3 Product Dissolve CrCl3 6H2O in 2 mL of distilled water in a 50-mL round-bottomed flask, equipped with a stir bar H20(out) Add the urea in one portion to the flask, and stir until completely dissolved. Add the 2, 4-pentanedione dropwise via syringe H+ HO(in Attach the condenser to the flask and heat the mixture to vigorous reflux(this is important!), with stirring, for about I hour. Cool the reaction flask to room temperature, and Heat Stir collect the product by vacuum filtration on a size D glass frit funnel, washing the product with cold water Reaction Setup Dry the product in your desiccator overnight, and ain a y1 Set up multiple recrystallizations to grow X-ray qualitysingle crystals-see Growing a Single Crystal guide Note: Urea slowly hydrolyzes under the reaction conditions, liberating ammonia(NH3), which controls the ph of the reaction. As more N3 is generated, the solution becomes more basic, making it easier to remove the proton from the acetylacetonate(acac), also known as 2, 4-pentanedione. It is the anion of the acetylacetonate that coordinates to the
Experiment Outline: • Before coming to the lab, perform the necessary calculations to fill in the following table. O O O Me Me H2N NH2 2,4-Pentanedione Urea Reagent Source F.W. Density Mass or Volume mmols Equiv CrCl3·6H2O 1.00 mmol 1 Urea 17 2,4-Pentanedione 8 Cr(acac)3 Product • Dissolve CrCl3·6H2O in 2 mL of distilled water in a 50-mL round-bottomed flask, equipped with a stir bar. • Add the urea in one portion to the flask, and stir until completely dissolved. • Add the 2,4-pentanedione dropwise via syringe. • Attach the condenser to the flask, and heat the mixture to vigorous reflux (this is important!), with stirring, for about 1 hour. • Cool the reaction flask to room temperature, and collect the product by vacuum filtration on a size D glass frit funnel, washing the product with cold water. H2 H2 Heat & Stir O (in) O (out) Reaction Setup • Dry the product in your desiccator overnight, and obtain a yield. • Set up multiple recrystallizations to grow X-ray qualitysingle crystals - see Growing a Single Crystal Guide. Note: • Urea slowly hydrolyzes under the reaction conditions, liberating ammonia (NH3), which controls the pH of the reaction. As more NH3 is generated, the solution becomes more basic, making it easier to remove the proton from the acetylacetonate (acac), also known as 2,4-pentanedione. It is the anion of the acetylacetonate that coordinates to the 22
metal to form the desired cr(acac), complex. What is the limiting reagent? Calculate your percent yield H2o NH (hydrolysis) H2N H2N NH (deprotonation) Helpful Hints When using a saturated solution to grow crystals, it is important that you filter the solution through a plug of glass wool in a pipet before setting up the crystallization esults. To obtain your EE Rating, you must obtain 50%o yield of Cr(acac)3, and you must produce at least one single crystal that is suitable for X-ray analysis
metal to form the desired Cr(acac)3 complex. What is the limiting reagent? Calculate your percent yield. H2N NH2 O H2N OH O H2O NH3 (hydrolysis) O O O O NH3 NH4 (deprotonation) Me Me Me Me Helpful Hints: • When using a saturated solution to grow crystals, it is important that you filter the solution through a plug of glass wool in a pipet before setting up the crystallization. Results: • To obtain your "EE Rating," you must obtain ≥ 50% yield of Cr(acac)3, and you must produce at least one single crystal that is suitable for X-ray analysis. 23
