d- and f-Block Elements and Coordination Compounds
This is the largest inorganic area: electronic configurations, magnetic and colour properties, and coordination compound structure, naming and isomerism.
Transition metal trends
- Cr is [Ar]3d⁵4s¹ and Cu is [Ar]3d¹⁰4s¹ (extra stability)
- variable oxidation states, catalytic activity, coloured ions, paramagnetism, alloy formation
- colour arises from d–d transitions; Sc³⁺ (d⁰) and Mn²⁺ (d⁵, high spin) are colourless or very pale
- magnetic moment μ = √(n(n+2)) BM for n unpaired electrons
Coordination chemistry
- oxidation state x = total complex charge − sum of ligand charges
- CFSE and the spectrochemical series: CO ≈ CN⁻ > en > NH3 > H2O > F⁻ > Cl⁻
- strong-field ligands give low spin; tetrahedral complexes are essentially always high spin
- isomerism: geometrical (square planar and octahedral), optical, ionisation, hydrate, linkage (NO2⁻, SCN⁻)
- chelating ligands such as en give extra stability
f-block
- lanthanoid contraction makes Zr and Hf nearly identical in size and chemistry
- actinoids show more variable oxidation states and are radioactive
Worked example
[Fe(CN)6]³⁻: Fe is +3, so d⁵. CN⁻ is strong field, so the electrons pair up giving t2g⁵ - one unpaired electron and μ = √3 = 1.73 BM. In [Fe(H2O)6]³⁺ the field is weak, giving high-spin d⁵ with five unpaired electrons and μ = √35 = 5.92 BM. Same metal, same oxidation state, different spin state.
Traps that cost marks
- Forgetting tetrahedral complexes do not show low spin.
- Miscounting the metal oxidation state in an anionic complex.
- Naming ligands without alphabetical order (e.g. bromido before chlorido).