Transition Metals Flashcards
What are transition metals?
Elements in the d-block of the periodic table with a partially filled d-orbital.
What happens to electrons when transition metals form positive ions?
They lose electrons, with the s-orbital electrons being removed first.
List some similar physical properties of transition metals.
- Atomic radius
- High densities
- High melting points
- High boiling points
What are the special chemical properties of transition metals?
- They form complexes
- They form coloured ions
- Variable oxidation states
- Good catalysts
What are complexes in the context of transition metals?
Structures consisting of a central metal ion or atom surrounded by ligands.
Provide an example of a complex with cobalt.
[Co(H2O)6]2+
What are ligands?
Molecules or ions with a lone electron pair that can form a coordinate bond to the central metal ion.
Give examples of common ligands.
- Cl-
- H2O
- NH3
What is the coordination number?
The coordination number is equal to the number of coordinate bonds formed around the central metal ion.
What is the coordination number of silver complexes?
Silver complexes have a coordination number of 2.
What is the coordination number of platinum complexes?
Platinum complexes commonly have a coordination number of 4.
What ligands can be exchanged without a change in coordination number?
The ligands NH3 and H2O can be exchanged without a change in coordination number.
What is an example of a ligand substitution reaction?
[Co(H2O)6]2+ + 6NH3 → [Co(NH3)6]2+ + 6H2O
What happens with copper complexes and NH3 in excess?
The substitution is incomplete, resulting in a complex with a combination of water and ammonia ligands.
What is an example of a copper complex substitution?
[Cu(H2O)6]2+ + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 4H2O
This complex ion product forms as a deep blue solution.
What is the effect of substituting larger ligands like Cl-?
Substitution with larger ligands results in a change in coordination number for that complex.
What is an example of a substitution reaction with Cl-?
[Cu(H2O)6]2+ + 4Cl- → [CuCl4]2- + 6H2O
Complexes with just Cl- ligands always have a coordination number of four, producing a tetrahedral shaped complex.
What are bidentate ligands?
Bidentate ligands are able to form two coordinate bonds to the central metal ion as they have two lone electron pairs.
What are two common examples of bidentate ligands?
- Ethanedioate ions - a lone electron pair on two of the oxygen atoms.
- Ethane-1,2-diamine - a lone electron pair on each of the nitrogen atoms.
What happens when bidentate ligands replace unidentate ligands?
Bidentate ligands can replace two unidentate ligands, but the coordination number remains at six as six coordinate bonds still form.
Provide an example of a bidentate ligand coordination.
Example: Mo(CO)2 + 2 CO + Oc → Mo(CO)2(bpm)
bpm refers to a bidentate ligand in this context.
