Inorganic Chemistry 2

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2/9/2015
Inorganic Chemistry 2
An introduction to
Coordination Chemistry
Alireza Gorji
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Department of Chemistry, Yazd University
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Coordination Chemistry
Alfred Werner
1866-1919
Nobel prize 1913
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‫فلزات واسطه‬
Transition Metals
20_432
d-block transition elements
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
La*
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Ac† Unq Unp Unh Uns Uno Une Uun Uuu
f-block t ransition elemen ts
*Lanthanides
Ce
Pr
Nd
Pm Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
† Actinides
Th
Pa
U
Np
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr
Pu
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Coordination compounds
Complexes
A neutral molecule or ion having a lone electron
pair (Lewis base B) that can be used to form a
bond to a metal ion (Lewis acid A).
A + :B  A-B
A
B
Metal atom or Metal ion
Ligand (nutral molecule or ion)
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Terminology for Complexes
A complex consists of a central atom, which is
usually a metal atom or ion, and attached groups
called ligands
The coordination
number is the total
number of points at
which a central atom
or ion attaches
ligands
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Terminology for Complexes
The region surrounding the central atom or ion and
containing the ligands is called the coordination sphere
A substance
consisting of one or
more complexes is
called a
coordination
compound
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Terminology for Complexes
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Terminology for Complexes
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Constitution and Isomerism ‫ساختار و ایزومری‬
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Linear Complexes
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Tetrahedral Complexes
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Square Planar Complexes
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Coordination Number: 5
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N
NH
NH
N
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Myoglobin, a protein that stores O2 in cells
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Coordination Environment of Fe2+ in Oxymyoglobin and
Oxyhemoglobin
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Trigonal-Prismatic Complexes
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Distortion from Octahedral Geometry
Tetragonal distortion
Elongation
Compression
Trigonal
distortion
Rhombic
distortion
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Nomenclature of Coordination Complexes
– Ligands
• Ligands are often organic molecules with IUPAC names
• Common names are most often used for the ligands in
coordination compounds
• Chelate = Greek for Claw = a ligand that can bind a metal ion
by more than one point of attachment.
– Bidentate = “two teeth” = NH2CH2CH2NH2 = ethylenediamene = en
– Tridentate = NH2CH2CH2NHCH2CH2NH2 = diethylenetriamine = trien
– Tetradentate = cyclam
• lists common ligands, names, structures, and abbreviations
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Polydentate refers to multiple points of attachment by one ligand
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Transition Name if in Cationic
Metal
Complex
Sc
scandium
Ti
titanium
V
vanadium
Cr
chromium
Mn
manganese
Fe
iron
Co
cobalt
Ni
nickel
Cu
copper
Zn
zinc
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Name if in Anionic
Complex
scandate
titanate
vanadate
chromate
manganate
ferrate
cobaltate
nickelate
cuprate
zincate
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Nomenclature of Coordination Complexes
1. The cation comes first, then the anion(s)
–
–
diamminesilver(I) chloride [Ag(NH3)2]Cl
potassium hexacyanoferrate(III) K3[Fe(CN)6]
2. Inner Sphere Complex Ion is enclosed in brackets
–
–
–
–
Ligands are named before the metal
Metal is written first in the formula
A space only between cation and anion
No capitalization is needed
» tetraamminecopper(II) sulfate [Cu(NH3)4]SO4
» hexaamminecobalt(III) chloride [Co(NH3)6]Cl3
3. Prefixes denote the number of each ligand type. Special
prefixes and parentheses are used if the ligand already contains
a prefix.
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3
4
5
di
Tri
tetra
penta
bis
tris
tetrakis
pentakis
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7
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9
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hexa
hepta
octa
nona
deca
hexakis
heptakis
octakis
nonakis
decakis
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– dichlorobis(ethylenediamine)cobalt(III) fluoride [Co(en)2Cl2]F
– tris(bipyridine)iron(II) chloride [Fe(bipy)3]Cl2
4)Ligands are named in alphabetical order not counting prefixes.
– tetraamminedichlorocobalt(III) ion [Co(NH3)4Cl2]+
– amminebromochloromethylamineplatinum(II) [Pt(NH3)BrCl(CH3NH2)]
5)Ligand name alterations:
– Anionic ligands are given an -o suffix: chloro, flouro, oxo, sulfato
- Neutral ligands keep their name: methylamine, bipyridine
– Water becomes aqua
– NH3 becomes ammine to keep separate from alkylamines
6)Two systems for showing charge or oxidation state of metal ion
– Stock system: oxidation state in Roman Numerals in parenthesis after the metal
ion name. This is the most common method.
– Ewing-Basset system: charge of the total complex ion is placed in parenthesis
after the name of the metal ion.
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Both systems add –ate to the metal name if the complex ion has an overall (-)
charge
[Pt(NH3)4]2+ = tetraammineplatinum(II) ion or (2+)
[PtCl4]2- = tetrachloroplatinate(II) ion
or (2-)
[PtCl6]2- = hexachloroplatinate(IV) ion
or (2-)
7)Isomer designations come before the rest of the name and in italics
– cis-diamminedichloroplatinum(II)
– trans-diamminedichloroplatinum(II)
8)
Bridging ligands have the prefix m
[(NH3)4Co(OH)(NH2)Co(NH3)4]4+ =
-amido--hydroxobis(tetraamminecobalt(III)) ion
9)Negatively charged complexes of certain metals use their Latin
names:
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K2[Co(NH3)2Cl4]
potassium diamminetetrachlorocobaltate(II)
[Co(NH3)4Cl2]Cl
tetraamminedichlorocobalt(III) chloride
[Co(NH3)4Cl2]+
tetraamminedichlorocobalt(III) ion
[Ru(NH3)4(HSO3)2]
tetraaminebis(bisulfito)ruthenium(II)
[Ti(H2O)6][CoCl6]
hexaaquatitanium(III)hexachlorocobaltate(III)
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K3[Fe(CN)6]
potassium hexacyanoferrate(III)
[Fe(CN)6]3hexacyanoferrate(III) ion
3+
[Co(NH3)6]
[Fe(SCN)6]3[Co(en)3]3+
[Cr(C2O4)3]3[Fe(NH3)4(o-phen)]3+
[Fe(EDTA)]-1
[Co(EDTA)]-1
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Isomerism
20_441
‫ایزومری‬
Isomers
(same formula but different properties)
Structural
isomers
(different bonds)
Coordination
isomerism
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Linkage
isomerism
Stereoisomers
(same bonds, different
spatial arrangements)
Geometric
(cis-trans)
isomerism
Optical
isomerism
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Coordination Isomerism
‫ایزومری کوئوردیناسیون‬
[Co(NH3)6][Cr(CN)6]
hexaaminecobalt(III) hexacyanochromate(III)
[Cr(NH3)6][Co(CN)6]
hexaaminechromium(III) hexacyanocobaltate(III)
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Ionization Isomerism
‫ایزومری یونش‬
[CrSO4(NH3)5]Cl
pentaaminsulfatochromium(III) chloride
[CrCl(NH3)5]SO4
pentaaminchlorochromium(III) sulfate
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Hydrated Isomerism
‫ایزومری آب پوشی‬
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Linkage Isomerism
‫ایزومری اتصال‬
[Co(NH3)4(NO2)Cl]Cl & [Co(NH3)4(ONO)Cl]Cl
[Co(SCN)(NH3)5]+
& [Co(NCS)(NH3)5]+
Ambidentate Ligands
NCS-
‫لیگاندهای دوسردندانه‬
NO2- R-CONH2
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Linkage Isomerism
[Co(NH3)5(NO2)]Cl2
Pentaamminenitrocobalt(III) chloride
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‫ایزومری اتصال‬
[Co(NH3)5(ONO)]Cl2
Pentaamminenitritocobalt(III) chloride
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Isomerism
20_441
‫ایزومری‬
Isomers
(same formula but different properties)
Structural
isomers
(different bonds)
Coordination
isomerism
Linkage
isomerism
Stereoisomers
(same bonds, different
spatial arrangements)
Geometric
(cis-trans)
isomerism
Optical
isomerism
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Stereoisomerism
‫استریوایزومری‬
1- Geometric isomerism
1. Geometric isomerism (cis-trans):
Pt(NH3)2Cl2
2. Geometric isomerism (fac-mer):
IrH3(PR3)3
– Atoms or groups arranged differently spatially
relative to metal ion
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Geometric Isomerism
cis-trans
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‫ایزومری هندسی‬
‫سیس – ترانس‬
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Geometric Isomerism ‫ایزومری هندسی‬
fac-mer
‫وجهی – کمربندی‬
ML3X3
•fac (facial) ‫وجهی‬
three identical ligands occupying the
corners of a common triangular
•mer (meridional) ‫کمربندی‬
three identical ligands occupying three
consecutive corners of a square plane
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IrH3(PMe3) 3
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‫تحمیل ایزومری به وسیله لیگاند‬
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fac ‫فقط‬
mer ‫فقط‬
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Stereoisomerism
‫استریوایزومری‬
2- Stereoisomerism
2- Optical isomerism ‫ایزومری نوری‬
Cn Dn
S S = S =i
n
1
2
Each of the two
molecules or ions of
an optical isomer is
called an
enantiomer and each
enantiomer rotates
the plane-polarized
light in opposite
directions
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Optical Activity
‫فعالیت نوری‬
Optical isomers are isomers that differ in their
ability to rotate the plane of polarized light
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Chiral Complexes Cn Dn
Sn
•
•
•
•
•
•
•
S1= S2=i
Different all ligands
Tris bidentate chelate
cis bis bidentate chelate
Chiral organic ligand
…
…
…
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Optical Isomerism
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‫ایزومری نوری‬
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Optical Isomerism
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‫ایزومری نوری‬
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Presentation of [M(en)3]
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Enantiomer
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Diasteriomer
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Complex-Ion Equilibria
Zn2+(aq) + 4 NH3(aq)  [Zn(NH3)4]2+(aq)
[[Zn(NH3)4]2+]
Kf =
= 4.1*108
[Zn2+][NH3]4
Displacement is stepwise from the hydrated ion:
Step 1:
[Zn(H2O)4]2+(aq) + NH3(aq)  [Zn(H2O)3(NH3)]2+(aq) + H2O(aq)
[[Zn(H2O)3(NH3)]2+]
2
K1 =
[[Zn(H2O)4]2+][NH3]= 1 = 3.9*10
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Step 2:
[Zn(H2O)3(NH3)]2+(aq) + NH3(aq)  [Zn(H2O)2(NH3)2]2+(aq) + H2O(aq)
K2 =
[[Zn(H2O)2(NH3)2]2+]
[[Zn(H2O)3(NH3)]2+][NH3]
= 2.1*102
Combining steps 1 and 2:
[Zn(H2O)4]2+(aq) + 2 NH3(aq)  [Zn(H2O)2(NH3)2]2+(aq) + 2 H2O(aq)
K = 2 =
[[Zn(H2O)2(NH3)2]2+]
[[Zn(H2O)4]2+][NH3]2
= K1 * K2 = 8.2*104
4 = K1 * K2 * K3 *K4 = Kf
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‫ شد نشان دهنده تغییرات ساختاری یا تغییرات اسپینی است‬Kn+1 > Kn ‫اگر‬
[Fe(OH2)6]2+ + bipy  [Fe(OH2)4 (bipy)]2+
[Fe(OH2)4 (bipy)]2+ + bipy  [Fe(OH2)2 (bipy) 2]2+
[Fe(OH2)2 (bipy) 2]2+ + bipy  [Fe (bipy) 3]2+
K3 > K2
eg
eg
K2
eg


t2g
K3
K1
K2
K3
t2g
t2g
‫ شد نشان دهنده تغییرات ساختاری یا اسپینی است‬Kn+1 > Kn ‫اگر‬
[Cd(OH2)6]2+ + Br-  [Cd(OH2)5 Br] +
K1
[Cd(OH2)5 Br] + + Br-  [Cd(OH2)4 Br2]
K2
[Cd(OH2)4 Br2] + Br-  [Cd(OH2)3 Br3]K3
2[Cd(OH2)3 Br3] + Br  [CdBr4]
K4
logK1=1.56 > logK2=0.54 > logK3=0.06 <logK4=0.37

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Irving Williams Seies
Fig is obtained when log Kf is plotted for comps. of the M2+ ions
of the first series. This variation is summarized by the IrvingWilliams series for the order of formation constants. For M2+:
Ba2+ < Sr2+ < Ca2+ < Mg2+ < Mn2+ < Fe2+ < Co2+ < Ni2+ < Cu2+ > Zn2+
The order is relatively insensitive to the choise of ligands
The series reflects electrostatic effects.
However, beyond Mn2+ there is a sharp
increase in the value of Kf for Fe(II),
d6, Co(II), d7, Ni(II) d8,and Cu(II) d9.
These ions experince an additional
stabilization proportional to the LFSE.
Tetragoanally distorted Cu(II) enhances
the stabilization of comp.
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Chelate Effect
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Macrocyclic Ligands
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Acid-Base Reactions of Complex Ions
[Fe(H2O)6]3+(aq) + H2O(aq)  [Fe(H2O)5(OH)]2+(aq) + H3O+(aq)
Ka1 = 9*10-4
[Fe(H2O)5(OH)]2+ (aq) + H2O(aq)  [Fe(H2O)4(OH)2]2+(aq) + H3O+(aq)
Ka2 = 5*10-4
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