INORGANIC CHEM - TRANSITION METALS
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What is a transition metal?
a metal that has an incomplete d subshell in atoms/ions
Why is copper a transition metal but zinc isnt?
• Cu has an incomplete d subshell as an ion (Cu^2+) • Zn has a complete d subshell as both an atom and an ion
What is a ligand?
particle with lone pair that bonds to metals by a dative covalent/coordinate bond
What is a complex?
metal atom/ion surrounded by ligands (coordinately bonded to it)
What is a coordination no.?
no. of dative covalent/coordinate bonds from ligands to metal ion
What is a unidentate ligand?
a ligand that forms 1 dative covalent/coordinate bond to a metal ion (1 lone pair donated per ligand)
Give examples of a unidentate ligand
• NH3 • Cl^- • OH^- • H2O
What is a bidentate ligand?
a ligand that forms 2 dative covalent/coordinate bonds to a metal ion (2 lone pair donated per ligand)
Give examples of a bidentate ligand
• ethylenediamine (NH2CH2CH2NH2) (en) • oxalate ion (C2O4^2-)
What is a multidentate ligand?
a ligand that forms 3+ dative covalent/coordinate bonds to a metal ion (3+ lone pair donated per ligand)
Give an example of a multidentate ligand and the number of coordinate/dative covalent bonds it can form
• EDTA^4- ion • can form 6 coordinate/dative covalent bonds
What shape are complexes with a coordination no. of 2? What is the bond angle?
• linear • 180
What shape are complexes with a coordination no. of 4? What is the bond angle?
• square planar/tetrahedral • 90/109.5
What shape are complexes with a coordination no. of 6? What is the bond angle?
• octahedral • 90
When do complexes with a coordination no. of 2 form? Give an example and its use
• with Ag^+ • [Ag(NH3)2]^+ (used in tollen’s reagent, can be reduced to silver)
When do complexes with a coordination no. of 4 that have a square planar shape form?
with Pt^2+/Ni^2+
When do complexes with a coordination no. of 4 that have a tetrahedral shape form?
with larger ligands (eg: Cl^-) (when ligands are too big for 6 to fit)
When do complexes with a coordination no. of 6 form?
with small ligands (eg: H2O/NH3) (most complexes)
What types of isomerism can occur with transition metal complexes?
• cis-trans isomerism (geometric) • optical isomerism
What would cause equilibrium to shift right in a ligand substitution reaction?
• if conc. of reactants increases • if temp changes to favour forward reaction • if incoming ligand forms stronger bonds
What is chelation?
replacing monodentate ligands with bi/multidentate ligands
Why are chelation reactions usually feasible?
• ΔH is negligible as same type and number of bonds formed • ΔS is very +ve as more molecules on RHS due to substitution of unidentate ligand with bi/multidentate ligand • so ΔG is -ve
Why are transition metal complexes coloured?
• d orbitals split in energy • electrons can be excited to a higher energy level within the d subshell • absorb some wavelengths of visible light • wavelengths not absorbed are transmitted
What factors affect the colour of a transition metal complex?
• type of metal ion • oxidation state of metal ion • coordination no. • type of ligand