Chemistry

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  • Topic: Ligand, Ion, Coordination chemistry
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CHEM 301 LECTURE

Unit 1 0 . COORDINATION CHEMISTRY
Factors t hat affect solubility:
Common ion: decrease in solubility
Complex ion: increase in solubility
How does complex ion formation increase solubility?
Consider the complex ion formation between silver and ammonia: +

Ag + 2NH3

A g(NH3 )2

+

Kf = 1 .5 x 10

7

where Kf i s the formation constant (always >1 , formation of the complex is highly favorable) Complex ion formation increases the solubility of sol ids in water.

Example:

Calculate the solubility of AgCl (1.6 x 10
+

-10

) in 1.0 M NH3 .

AgCl

A g + Cl

-

Ksp = 1.6 x 10

Ag + 2NH3

A g(NH3 )2

+

Kf = 1 .5 x 10

+

+

AgCl + 2NH3

Ag(NH3 )2 + Cl

-

K = 2 .4 x 10

-10

7

-3

then:

Complex Ion
• a c harged species in which a central metal (transition) ion is bonded to molecules or ions called ligands • type of bond: Lewis acid -base
• examples:

metal: acid; base: ligand

+
32

Ag(NH )

Cu(NH3)2+2
Fe(CN)6-4
Coordination Compounds
• c ontains a complex ion
[Co(NH3)6 ]Cl3
Fe4 [Fe(CN)6]3

[Co(H2 O)6 ][Co(CN)6 ]
Ca[Cu(OH)3 (Br)(NH3 )2 ]
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CHEM 301 LECTURE

coordination number
• number of atoms bonded to the central atom
donor atom
• a tom in the ligand that is directly bonded to the central atom t ype of ligands
• monodentate
• bidentate
• polydentate

Formula Writing
1 . The formula of a complex should be enclosed in square brackets [ ], charged or not. 2 . The symbol of the metal is written first, followed by anionic ligands, and finally by neutral ligands. Example: Ca[Cu(OH)3 (Br)(NH3 )2 ]

N omenclature
1 . The cation is named before the anion.
Ca[Cu(OH)3 (Br)(NH3 )2 ]
calcium _________________________
2 . Within a complex, the ligands are named first, in alphabetical order, the metal ion last. calcium ___ammine___bromo___hydroxocopper____
3 . The number of ligands of the same kind i n a complex is indicated by Greek prefixes di -, tri -, tetra -… Note: prefixes are not regarded in alphabetical arrangement. calcium diamminebromotrihydroxocopper____

4 . The oxidation number of the metal is indicated by Roman numerals. calcium diamminebromotrihydroxocopper____ (II)
5 . If the complex is an anion, end in –ate.
calcium diamminebromotrihydroxocupr ate (II)

Example: W rite the names of the following:
Ag(NH3)2+
Fe(CN)6-4
[Co(NH3)6]Cl 3
Fe4[Fe(CN)6]3
[Co(H2O)6][Co(CN)6]

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CHEM 301 LECTURE

W rite the formula for sodium tetracyanodithiocyanatomanganate(II). ________________________________________

Some common ligands:

NH3
H2O
Cl Br IO HO -2
CO 3-2
C2O 4-2
CNSCNNO 2NO 3EDTA

a mmine
a quo or aqua
c hloro
bromo
i odo
hydroxo
oxo
carbonato
oxalato
c yano
thiocyanato
nitrito
nitro
ethylenediamimetetraacetic acid

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