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Coordination Chemistry
ligands bonding to metals
Donor-Acceptor Complexes
Definitions
Lewis Acid = acceptor = usually a transition metal cation
Lewis Base = donor = ligand = usually something with a lone electron pair
Coordination number = # of metal-ligand attachments
Denticity = # of attachments a ligand makes
Common Ligands
Monodentate Ligands:
Bidentate Ligands:
Polydentate Ligands:
Halides: F-, Cl-, Br-, IO2-, S2-, OH-, CNNH3, H2O, CO
heme, salen
Monodentate complexes
Monodentate complexes
Bidentate ligand complexes
Ni(DMG)2
Co(en)2Cl2
Bidentate complexes
Co(en)32+
Fe(phen)32+
Polydentate complexes
Co(salen)+
chlorophyll
Fe-heme
Polydentate complexes
Fe-heme
O2-Fe-heme
Determining Metal Oxidation States
[Ag(NH3)2]NO3
K2[NiCl4]
[Co(en)2Cl2]Cl
[Cr(H2O)4CO3]Br
Isomerization in Coordination
Compounds
Do for octahedral Complexes
Inner and Outer Spheres
[Co(NH3)4Cl2]Cl H2O
[Co(NH3)4(H2O)Cl]Cl2
All compounds
Structural (constitutional)
linkage
ionization
[Co(NH3)5Cl]NO2
[Co(NH3)5NO2]Cl
[Co(NH3)5SCN]2+
[Co(NH3)5NCS]2+
hydration
Stereo
geometric
[Co(NH3)4Cl(H2O)]Cl2
[Co(NH3)4Cl2]ClH2O
optical
Linkage Isomers
Ionization Isomers
Hydration Isomers
Optical Isomers: enantiomers (mirror images)
key to recognizing: no mirror planes of symmetry
Type 1. arrangement of monodentate ligands
Type 2. arrangement of bidentate ligands
Geometric isomerism: like cis-trans
Geometric isomerism
Fac- isomer
Mer- isomer
Geometric Isomers: predicting numbers
Use shorthand:
M = metal
a, b, c, etc. are different ligands
Example 1: Co(NH3)4Cl2
Example 2: Co(NH3)3BrCl2
Example 3: Co(NH3)3enBr2+