Experiment 12: The Paramagnetic Complex- Mn(acac)3

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Experiment 12: The Paramagnetic Complex- Mn(acac)3

Kimberlee London

Department of Chemistry, Saint John’s University

Lab Date: February 1, 2011.

Report Due:  February 8, 2011.


Abstract:

The manganese complex [Mn(acac)3] is an octahedral complex containing three bidentate ligands.  Because each metal ion carries a +3 charge, and each ligand carries a –1 charge, the complex is electrically neutral. Tris(acetylacetonato)manganese(III) was prepared and used for magnetic susceptibility.  The number of unpaired of electrons were determined through this process to assign the geometry and to gain information on the bonding between the ligand and metal.  The Tris(acetylacetonato)manganese(III) complex had four unpaired electrons.  The ligand was a weak field strength thus concluding in a high spin.  

Introduction:

Magnetic susceptibility is the magnetic moment of an atom or ion due solely on its spin of N unpaired electrons.  A substance has the ability to apply its own field within the magnetic balance, which will add (paramagnetic) or subtract (diamagnetic) to the applied field. [4] It is predictable that paramagnetic compounds will have unpaired electrons because they contribute by adding to the magnetic field of the balance by the electron’s angular momentum (characterized as high spin). Therefore, diamagnetic compounds will have no unpaired electrons because the entrance to the higher sub-shells is too large for the electrons to overcome (characterized as low spin). This experiment involves the preparation of a Mn(III) complex of acetyl acetone, which is Tris(acetylacetonato)manganese(III).  The high or low spin of the complex was determined by using magnetic susceptibility.

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Experimental Details:

First and foremost, the safety precautions should be noted.  Potassium permanganate is a strong oxidant.  If the chemical is spilled on the skin, immediately wash off with water.  All glassware must be cleaned properly.  The first step is to make the Tris(acetylacetonato)manganese(III).  In a 250 mL beaker, 3.75 grams of potassium permanganate was measured.  75 mL of distilled water was added to the beaker.  The solution was stirred and heated to 80°C.  The temperature should be monitored by using a thermometer and by checking the temperature every few minutes.  Once the solution reached the desired temperature, cool the ...

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