5.3.3: Transition metals and complex ions Flashcards
What is a complex ion?
A transition metal ion bound to one or more ligands by coordinate bonds (dative covalent bonds).
What are ligands?
A ligand is a molecule or ion that can donate a pair of electrons to the transition metal ion to form a coordinate bond.
What is the coordination number?
The total number of coordinate bonds formed between a central metal ion and its ligands
What is a coordinate bond?
- A bond in which one of the atoms provides both electrons for the covalent bond.
- The transition metal ion accepts the pair of electrons from the ligand in forming the coordinate bond.
How are ligands Lewis bases?
They are electron donors.
How is [Cu(H2O)6]2+ an example of a complex ion?
- The central metal ion is Cu2+
- The ligands are molecules of water, H2O.
- Each water molecule donates a lone pair of electrons from its oxygen atom to the Cu2+ ion to form a coordinate bond.
- Coordinate number=6
What is the overall charge of a complex ion?
The sum of the individual charges of the transition metal ion and those of the ligands present in the complex.
When is a ligand monodendate?
In a monodendate ligand, the ligand donates just one pair of electrons to the central metal ion to form one coordinate bond.
When is a ligand bidendate?
- Bindendate ligands have two pairs of electrons from different atoms to donate to the central metal.
- This means two coordinate bonds can be formed.
What is The most common bidendate ligand?
ethane-1,2-diamine (NH2CH2CH2NH2) ‘en’.
-Each nitrogen atom donates its lone pair to the metal ion.
Name of ligand:
Water
What is the formula and charge?
:OH2
none-neutral ligand
Name of ligand:
Ammonia
What is the formula and charge?
:NH3
none-neutral charge
Name of ligand:
Thiocyanate
What is the formula and charge?
:SCN-
-1 charge
Name of ligand:
Cyanide
What is the formula and charge?
:CN-
-1 charge
Name of ligand:
Chloride
What is the formula and charge?
:Cl-
-1 charge
Name of ligand:
hydroxide
What is the formula and charge?
:OH-
-1 charge
What is a hexadentate ligand?
A ligand that has 6 lone pairs of electrons available to form coordinate bonds.
What is one example of a hexadentate ligand?
Ethylenediaminetetraacetic acid (EDTA) -Exists in complexes as the ion EDTA4-
What is EDTA used for and what is it?
- To bind metal ions.
- It is known as a chelating agent.
- This means that EDTA decreases the conc. of metal ions in solutions by binding them into a complex.
How is EDTA used in detergents?
-It binds to calcium and magnesium ions to reduce hardness in water.
How is EDTA used in foods?
-As a stabiliser to remove metal ions that might catalyse the oxidation of the product.
How is EDTA used in medical applications?
-It is added to blood samples to prevent clotting and used to treat patients suffering from lead and mercury poisoning.
Describe the features of an octahedral complex.
- No. of coordinate bonds
- shape
- bond angles
- Six-coordinate bonds attached to the central ion.
- The outer face of the shape is an eight-sided octahedron.
- Four of the ligands are in the same plane, one ligand is above the plane and the remaining ligand is below the plane.
- All bond angles are 90 or 180.
What shape do chloride complexes form and why?
- Tetrahedral shape
- Chloride ligands are so large that only four can fit around a transition metal ion.
What is another rare four ligand structure?
- A square planar complex.
- This is when the for monodentate ligands arrange themselves in the same plane as the metal ion.
- e.g. Cis-platain.
