Coordination Chemistry

ligands bonding to metals

Donor-Acceptor Complexes

DefinitionsLewis 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 LigandsMonodentate Ligands:

Halides: F-, Cl-, Br-, I-

O2-, S2-, OH-, CN-

NH3, H2O, CO

Bidentate Ligands: Polydentate Ligands:

heme, salen

Monodentate complexes

Monodentate complexes

Bidentate ligand complexes

Ni(DMG)2Co(en)2Cl2

Bidentate complexes

Co(en)32+

Fe(phen)32+

Polydentate complexes

Co(salen)+

chlorophyll

Fe-heme

Polydentate complexes

Fe-hemeO2-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) Stereo

linkage ionization hydration geometric optical

[Co(NH3)5Cl]NO2

[Co(NH3)5NO2]Cl [Co(NH3)4Cl(H2O)]Cl2

[Co(NH3)4Cl2]ClH2O[Co(NH3)5SCN]2+

[Co(NH3)5NCS]2+

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 = metala, b, c, etc. are different ligands

Example 1: Co(NH3)4Cl2

Example 2: Co(NH3)3BrCl2

Example 3: Co(NH3)3enBr2+