Transition Metals Flashcards
What colour is the [Cu(H2O)6]2+ complex?
Blue
What happens if you add a small amount of methylamine solution to the [Cu(H2O6]2+ complex?
- Pale blue precipitate
- Amine acts as a Bronsted-Lowry base and removes two H+ ions from the complex
- this forms copper hydroxide, [Cu(H20)4(OH)2], which is insoluble
What happens if you add more methylamine solution to the [Cu(H2O)4(OH)2] complex?
- Deep blue solution
- Ligands are replaced by methylamine molecules which donate their lone pairs to form dative covalent bonds with the Cu2+ ion
- this forms [Cu(CH3NH2)4(H2O)2]2+ complex which is soluble
What is a complex ion?
A species containing a central metal ion surrounded by ligands bonded to it by dative bonds
The ethanedioate ion, C2O42-, can act as a ligand. With the help of a displayed formula, explain why the ethanedioate ion is a bidentate ligand
-OOCCOO-
The ethanedioate ion has two pairs of lone electrons to donate to form two dative covalent bonds
Explain why EDTA4- may be described as a multidentate ligand
-Six lone pairs of electrons able to form dative covalent bonds
The complex, cis-platin, is used in cancer treatment. Explain why it is supplied as a single isomer and not as a mixture in the trans form?
- Trans is less effective at treating cancer than cis
- Trans is more toxic than cis
- This reduces the chances of side effects
What is it called when electrons change from one energy level to another?
Electron transition
Explain why the hexaaquacopper(II) complex ion, [Cu(H2O)6]2+, is blue
- Water ligands split the d-orbitals energies
- d-d electron transitions absorb all light except blue light
What happens in terms of electrons when a ligand bonds with a transition metal ion?
- Electrons in the ligand and metal d-orbitals repel each other
- This causes the energy levels of the d-orbitals to increase and form slightly different energy levels
Octahedral complexes’ d-orbitals split to produce…
Two d-orbitals at a higher energy level
Tetrahedral complexes’ d-orbitals split to produce…
-Three d-orbitals at a higher energy level
What affects the colour of complex ions?
- The amount of splitting of d-orbitals energy levels by ligands
- The energy level difference between d-orbitals
How can carbon monoxide damage health?
- CO can act as a ligand
- It binds to haemoglobin more strongly than oxygen does
- It is a non-reversible reaction
- Haemoglobin can no longer transport oxygen
What is the ligand exchange when oxyhaemoglobin reacts with CO?
Oxyhaemoglobin + CO –> Carboxyhemoglobin
\+O2
Suggest why the [Cr(H2O)6]2+ ion is sky blue but the [Cr(H2O)6]3+ ion is violet
- Central metal ion have different oxidation numbers
- So different levels of the d-orbitals are split by different amounts
Suggest why Carboxyhemoglobin and oxyhaemoglobin are different colours
- Different ligands
- So energy levels of d-orbitals are split by different amounts
What are transition elements?
- d-block elements that can form stable ion with incompletely filled d-orbitals
Explain why the methane molecule cannot act as a ligand
- No lone pairs of electrons
- Ligands need a lone pair
State why solutions containing Al3+(aq) ions are colourless
-No electrons in 3d orbitals that could absorb light from the EM spectrum
A complex forms between nickel (II) ions and chloride ions. Predict it’s shape, name and formula
- Tetrahedral (Cl- ions bigger than most ligands)
- Tetrachloronickelate (II)
- [Ni(Cl)4]2-
Problem with trans-platin for treating cancer
- Less effective than cis
- More toxic than cis
Name the ‘en’ ligand
1,2-diaminoethane
What is the structural formula for the ‘en’ ligand?
H2NCH2CH2NH2
What does it mean when a complex is ‘stable’?
It does not decompose readily
The water molecule contains three atoms and has two lone pairs of electrons. Explain why it can only act as a monodentate ligand and not as a bidentate
- Two lone pairs are on the same atom of oxygen
- Hydrogen atoms have no lone pairs
