• Coordination compounds are derived from simpler compounds that are joined together, or coordinated.

Coordination Chemistry

• The two compounds have very similar formulas but are very different in appearance because of the different chemical structures.

• A complex consists of a central atom, which is usually a metal atom or ion, and attached groups called ligands.

• The region surrounding the central atom or ion and containing the ligands is called the coordination sphere.

• The coordination number is the total number of points at which a central atom or ion has ligands attached.

• A complex that carries a net electric charge is called a complex ion.

• A substance consisting of one or more complexes is called a coordination compound.

Some Terminologyfor Complexes

Nomenclature

Rules for Coordination Compounds: • neutral compound• ionic cation before anion

LigandsNeutral Molecules• water → aqua• ammonia → amine• ethylenediamine (en)• pyridine (py)• 1,10-phenanthroline (phen)• 2,2'-bipyridine (bipy)• 4,4'-bipyridine• triphenylphosphine

Ligands

Anions:• F-→ fluoro• Cl- → chloro• Br- → bromo• I-→ iodo• O-2 → oxo• OH- → hydroxo• CN- → cyano

Ligands

Anions• HSO3

- => bisulfito• H- => hydrido• C6H5

- => phenyl (ph)• C5H5

- => cyclopentadienyl• CO3

-2 => carbonato

Multiplicity

monodentate• mono → 1• di → 2• tri → 3• tetra → 4• penta → 5• hexa → 6

Multiplicity

bi- or tri- dentate• bis → 2• tris → 3• tetrakis → 4

Special Bonding Conditions

• Bridging units → μ• Delocalized bonding → η

Coordination Sphere Nomenclature

Cationic coordination sphere– -ium ending

Anionic coordination sphere– -ate ending

Nomenclature

Neutral molecule[Ru(NH3)4(HSO3)2]

bis(bisulfite)tetraamineruthenium(II)

Nomenclature

Anionic coordination sphereK3[Fe(CN)6]

potassium hexacyanoferrate(III)

Nomenclature

Cationic coordination sphere[Cu(NH3)4]SO4

tetraaminecopper(II) sulfate

Nomenclature

Cationic coordination sphere & Anionic coordination sphere[Ti(H2O)6][CoCl6]hexaaquatitanium(III) hexachlorocobaltate(III)

Position Numbering

1

5-----2M

4-----3

6

Isomerism

Geometric Isomerism

• cis → 2 adjacent ligands• trans → 2 ligands across the center of

coordination sphere

cis and transGeometric Isomerism

[PtCl2(NH3)2]

Linkage Isomerism

Ionizational Isomerism

[CoIII(NH3)5Br]SO4

[CoIII(NH3)5SO4] Br

Coordination Isomerism

[CrIII(H2O)6][CoIIICl6]

[CoIII(H2O)6][CrIIICl6]

Optical Isomerism

3 Theories :

VBT, CFT, MOT