Download Chapter 9. Coordination Chemistry 1

Chapter 9. Coordination Chemistry 1: Structures and Isomers
▪ coordination compd.: compds. w/ a metal atom/ion + ligand(s)
(acceptor)
(donor)
: organometallic compds. are Included
metal-carbon bonds
: name comes from coordinate covalent bond
(= covalent bond)
: = acid-base adducts
: also called complexes or complex ions
Inorganic Chemistry 2
2011 Fall
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9.1 History
▪ according to Werner’s theory - two types of bonding in the compound
1) positive charge of the central metal ion is
balanced by negative ions
2) ligand attached directly to the TM ion
( = complex ion, = coordination sphere)
▪ Metals can have 1 - 16 atom(s) attached (4 - 6 most common)
▪ Werner’s isomers w/ four or six ligands
1) able to synthesized only two isomers of [Co(NH3)4Cl2]+ ion
Fig 9 3
Fig.9.3
possible structure of hexacoordinated complexes
only octahedral has two isomers
∴ structure is octahedral!!
Fig.9.3
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2011 Fall
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9.1 History
▪ [Pt(NH3)2Cl2] – only two isomers were synthesized
- possible structures
- since two isomers were observed
∴ square-planar
q
p
str. !!!
∴ any acceptable theory needed to account for bonds b/w ligands and metals.
# bonds was more than that commonly accepted at that time.
simple Lewis theory
can not fit for TM w/ six ligands
e.g.) [Fe(CN)6]4- (w/ 18 e-)
expanding shell to 10 or 12 eInorganic Chemistry 2
2011 Fall
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9.1 History
▪ There have been,,,
- Pauling’s valence bond approach
- Griffith and Orgel’s ligand field theory
- Bethe and Van Vleck’s crystal field theory
▪ In this chapter,,,
- different shapes of coordination compds.
can be difficult to predict shapes, but
can relate some str. to the cause.
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2011 Fall
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9.2 Nomenclature
▪ older trivial names vs. International Union of Pure and Applied Chemistry (IUPAC)
still commonly used
more generally accepted
▪ chelating ligands: ligands w/ two or more points to attachment to metal atoms
: compds. → chelates (- the “claw of a crab”)
: ex) monodentate – one point of attachment (ammonia)
bidentate - two points of attachment (ethylenediamine, NH2CH2CH2NH2)
tri-, tetra-, penta-, hexa▪ chelate rings: have any # of atoms
: most common → 5~6
: smaller ring → strain due to angles & distances
larger ring → crowding
: more than one ring is possible → ethylenediaminetetraacetate (EDTA)
5 rings (using 4 carboxylate & 2 amine)
Inorganic Chemistry 2
2011 Fall
T.-S.You
9.2 Nomenclature
Inorganic Chemistry 2
2011 Fall
T.-S.You
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9.2 Nomenclature
Inorganic Chemistry 2
2011 Fall
T.-S.You
9.2 Nomenclature
Inorganic Chemistry 2
2011 Fall
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9.2 Nomenclature
▪ Nomenclature Rules
1. positive ion (cation) first, then negative ion (anion)
ex) diammine silver(Ⅱ) chloride [Ag(NH3)2]Cl
potassium hexacyanoferrate(Ⅲ), K3[Fe(CN)6]
2. inner coordination sphere → in square bracket in the formula
within the coordination sphere → in name: ligands first, metals second
→ in formula: metal first
ex) tetraamminecopper(Ⅱ) sulfide, [Cu(NH3)4]SO4
hexaamminecobalt(Ⅲ) chloride,
chloride [Co(NH3)6]Cl3
3. prefixes → use one kind
if the ligand name includes these prefixes or is complicated → parentheses
→ use 2nd set of prefixes
(ending in –s)
Inorganic Chemistry 2
2011 Fall
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9.2 Nomenclature
▪ Nomenclature Rules
3. 2 – di bis
3 - tri tris
4 - tetra tetrakis
5 - penta pentakis
6 - hexa hexakis
7 - hepta heptakis
8 - octa octakis
9 - nona nonakis
10 - deca decakis
ex) dichlorobis(ethylenediamine)cobalt(Ⅲ)
[Co(NH2CH2CH2NH2)2Cl2]+
tris(bipyridine)iron(Ⅱ)
[Fe(NH4C5-C5H4N)3]2+
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9.2 Nomenclature
▪ Nomenclature Rules
4. ligand name – alphabetical order of the name of ligand (not the prefix)
ex) tetra/amine/dichloro/cobalt(Ⅲ)
[Co(NH3)4Cl2]+
ammine/bromo/chloro/methylamine/platinum(Ⅱ)
Pt(NH3)BrCl(CH3NH2)
5.
anionic ligand → o suffix
chloro, Cl-; bromo, Br-; sulfato, SO42-
neutral ligand → usual name
methyl amine
amine, CH3NH2
coordinated water → aqua
H 2O
coordinated ammonia → ammine
NH3 (double m; alkyl amine (single m))
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