Aim:- Synthesize a metal acetylacetonate complex .

Aim:-

The aim of this experiment is to synthesize a metal acetylacetonate complex .

Theory:-

Acetylacetone (2,4-pentanedione) is an organic compound, a β-diketone, that exists as an equilibrium mixture of tautomeric keto and enol forms. In basic solution, it is deprotonated to form the acetylacetonate anion (acac).

Keto-enol equilibrium of acetylacetone and formation of acetylacetonate anion.

The acac anion can act as a ligand towards metal ions, typically forming a bidentate complex where the metal is bound to the two oxygen atoms, thus forming a 6-membered ring. Metal acac compounds are typically isolated as crystalline solids that are neutral, hence an Mn+ metal forms a complex with n acac ligands .

Acetylacetonate forms neutral complexes with most metals.

Preparation Method of Al(acac)3:-

1. To a conical flask, add 3 mL acetylacetone and 40 mL distilled water followed by 8 mL of dilute (5 mol L-1) ammonia solution.
2. Dissolve aluminium sulfate [Al(SO4)3.16 H2O] in 30 mL distilled water. To this solution, add the ammoniacal acetylacetone solution gradually with stirring.
3. After complete addition of acetyl acetone, check that the solution is neutral.
4. If the solution is still acidic, add further small portions of ammonia solution.
5. Place the flask in an ice bath until a cream colored precipitate forms.
6. Filter the product using Buchner filtration, wash with small amounts of cold distilled water and dry the product in a desiccator.
7. Determine the percentage yield of this dry product.
8. Recrystallise a small sample from warm petroleum ether.
9. The resulting needles should be filtered using Buchner filtration, rinsed with small portions of cold petroleum ether and dried in a vacuum desiccator.

Preparation Method Of Mn(acac)3:-

1. Dissolve 2.6 g of manganese chloride (MnCl2 •4 H2O) and 6.8 g of sodium acetate in 100 mL of distilled water and add 10 mL acetylacetone.
2. Dissolve 0.52 g of potassium permanganate (KMnO4) in 25 mL of distilled water and 
3. add to the acetylacetonate solution, with stirring, over a period of about 10 minutes.
4.  After stirring for 10 minutes, add a solution of sodium acetate (6.3 g) in 25 mL 
5. distilled water, with stirring, over a period of about 10 minutes.
6. Continue stirring and heat the flask on a hot plate to 60-70°C for 15 minutes, 
7. followed by cooling to room temperature and finally placed in an ice bath.
8. Using Buchner filtration, filter the dark precipitate using small portions of cold 
9. distilled water for washing, followed by drying in a vacuum desiccator.
10. Determine the percentage yield of this dry product.
11. Recrystallise a small sample from warm petroleum ether.
12. The resulting black needles should be filtered using Buchner filtration, rinsed with small portions of cold petroleum ether and dried in a vacuum desiccator.

Al(acac)3:- 

Melting point : 188-191 degree C

Aluminum is the lightest element to form trivalent ions which have a coordination number of six. Three anionic ketoenolate ligands chelate the ion forming the neutral, water-insoluble, organic solvent soluble complex. After forming the complex The IR spectrum of the tris-complex exhibits several signals in the IR region (400 cm-1 - 4000 cm-1) indicating the presence of the organic ligand. The anhydrous nature of the complex is evident from the absence of O-H vibration as no signals are observed beyond 3000 cm-1. The signals observed at 410, 484 cm-1 may be assigned to the bending mode of Al-O vibration.

Mn(acac)3:-

The band at ~1250-1650cm-1 indicate the acetylacetone ligand. The two bands of the 

stretching vibration C=C and C-CH3 group have been detected 1253 cm-1. The bending 

vibration stretch of C=CH is observed at 1185 cm-1 . The bands at 928 cm-1 and 1020 

cm-1 show that the Mn(III) is bonded to three acetylacetone ligands. The bending vibration 

of CH3 is observed at 1350cm-1 & 1388cm-1 and ν(C=C), at 1512cm-1. 

ν(C-CH3) 928 cm-1 (strong)

ν(C=C), ν(C-CH3) 1253 cm-1 (strong)

ν(C=C), δ(C=CH) 1512 cm-1 (strong)

ν(C=C), δ(C=CH) 1567 cm-1 (strong)

ν(C-H) 2920 cm-1 (weak)

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