Experiment

Topics: Ammonia, Coordination complex, Ligand Pages: 11 (1723 words) Published: February 10, 2015
Experiment : 1
Tittle : Preparation of bis(acetylacetonato)copper(II) complex Objective : To synthesis the bis(acetylacetonato)copper(II) complex Introduction :
A complex ion is usually form with high charge density metal ion as a central and formation of coordinate covalent bond (dative bond) with high electron molecules or ions. These molecules or ions are functioning as ligands (electrophile in organic compounds). They are easily attracted by electrophile (electron deficiency atoms or ions ). Ligands are species that have at least one lone pair of electrons that are readily donated to a metal or an ion to form a coordinate bond. According to lewis acid- base theory, all ligands are lewis base as they act as donor. In the contrary, the metal, central atom act as an lewis acid as it receives lone pair electrons from the ligands when forming the complex ions. The properties of lewis acid is to have high electron deficiency. For transition metals in this experiment, the high charge density, positive charge and their vacant bonding orbitals leads to tendency to attract lone pair electron by filling up their vacant orbitals. Metal acetylacetonates, formed by a metal and multiple acetylacetonate anions, are prime examples of coordination complexes. In this experiment, the metal use is copper (II) ion which is crystal blue in colour when it is copper(II)nitrate. All metal ions in solution can react well with water. The water molecules can also be weakly bonded or more strongly as a ligand to form a complex ion, and these can also present in solid ‘hydrated’ salts of crystallization. For example, copper (II) nitrate (Cu(NO3)2∙3H2O) The metal complexes that contain at least one ammonia (NH3) ligand are called metal ammine complexes. Metal acetylacetonates are coordination complexes derived from the acetylacetonate anion(acac) and metal ions. The coordination number of a complex ion is the number of coordinate bonds being formed by the metal ions at its central.

Apparatus: beaker, glass rod, measuring cylinder, suction filtration set

Materials: copper(II)nitrate Cu(NO3)2.H2O , ammonia, acetyl acetone, distilled water

Methodology:
First, 6g of copper(II) nitrate (Cu(NO3)2∙3H2O) was dissolved in 60cm3 of water and the solution of 1:1 Ammonia was added slowly with stirring until the precipitate first formed has just redissolved. The solution was continued to be stirred, then 6cm3 of acetyl acetone was added drop by drop into the solution. The crude product was filtered off by using suction filtration and was washed well with water. After drying it thoroughly, the percentage (%) yield was then calculated.

Results:
Molar mass of Cu(NO3)2.3H2O = 241 g mol-1
Molar mass of (C5H7O2)2Cu = 261 g mol-1
Colour of precipitate = Blue colour
Mass of copper (II)nitrate = 6.0 g
Mass of beaker = 134.28g
Mass of beaker + crude product = 144.13g
Mass of crude product = 9.85g

Chemical equation :
Equation 1 : (Cu(NO3)2∙3H2O) → Cu(H2O)62+ + 2NO3-
Equation 2 : [Cu(H2O)6]2+ + 4NH3 →[Cu(NH3)4(H2O)2]2+ + 4H2O Equation 3 : Cu(NH3)4(H2O)6]2+ + C5H8O2 → C10H16CuO4 + 4NH3 + 4OH-

Calculations:
a Theoretical yield
Cu(NO3)2.3H2O + 2 C5H8O2 (C5H7O2)2Cu + 2 HNO3 +3H20
Mass of Cu(NO3)2.3H2O used = 6.0g
Molar mass of Cu(NO3)2.3H2O = 241 g mol-1
Molar mass of (C5H7O2)2Cu = 261 g mol-1
Mole of Cu(NO3)2.3H2O=
=
= 0.024896 mole
From equation, 1 mole of Cu(NO3)2.3H2O produce 1 mole of (C5H7O2)2Cu. Mole of Cu(NO3)2.3H2O= Mole of (C5H7O2)2Cu
= 0.025 mole
Mass of (C5H7O2)2Cu= Mole of (C5H7O2)2Cu X Molar mass of (C5H7O2)2Cu
= 0.025 mol X 261 g mol-1
= 6.525 g
b Percentage yield
Percentage (%) yield=
=
= 150%

Discussion:
The metal use in this experiment is copper(II), which is a transition element in the D-block of the periodic table. To define transition element, they are d-block...
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