Transition Metal Complexes

1
Transition Metal Complexes
2
Ligands

• Atom, ion or molecule which can donate a pair of
  e- to a metal ion
• Ligand ? Lewis base ? Nucleophile
• Halides F- Cl- Br- I-
• Hydroxide OH-
• Cyanide CN-
• Water H2O
• Ammonia NH3

monodentate (unidentate) ligands
3
ethane-1,2-diammine
(en)
bidentate ligand
ethanedioate
(ox)
4
ethylenediaminetetracetic acid
(edta4-)
hexadentate ligand
5
co-ordination number 6
Ni(edta)2-
octahedral
6
Ni(H2O) 62 Ni(NH3) 62
NiCl 42- Pale blue/green Violet
Ni(H2O) 62 XXX Violet
Cl-
H2O
NH3
Increasing stability
NiCl 42- 6H2O ?
Ni(H2O)62 4Cl-
7
Ni(ox) 34- Ni(edta)2-
Ni(H2O) 62 Blue / green Deep blue
Ni(ox) 34- XXX Deep blue
H2O
ox2-
edta4-
Increasing stability
Ni(H2O)62 3ox ?
Ni(ox)34- 6H2O
Ni(H2O)62 edta4- ?
Ni(edta)2- 6H2O
Ni(ox)34- edta4- ?
Ni(edta)2- 3ox
8
H2O
ox2-
edta4-
Increasing stability of complex
Ni(H2O)62 3ox ?
Ni(ox)34- 6H2O
Ni(H2O)62 edta4- ?
Ni(edta)2- 6H2O
Ni(ox)34- edta4- ?
Ni(edta)2- 3ox
Increase in ENTROPY
9
Ni(edta)2-
edta chelating ligand
Chelate crab-like complex
Chelates are more stable as their formation
results in a more ve entropy change
10

• unidentate

bidentate
multidentate
chelate