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Inorganic Chemistry 2
An introduction to
Coordination Chemistry
Alireza [email protected]
Department of Chemistry, Yazd University
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Coordination Chemistry
Alfred Werner1866-1919
Nobel prize 1913
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Transition Metals فلزات واسطه
20_432
Sc
Y
La*
Ac†
Ti
Zr
Hf
Unq
V
Nb
Ta
Unp
Cr
Mo
W
Unh
Mn
Tc
Re
Fe
Ru
Os
Co
Rh
Ir
Ni
Pd
Pt
Cu
Ag
Au
Zn
Cd
Hg
Ce
Th
Pr
Pa
Nd
U
Pm
Np
Sm
Pu
Eu
Am
Gd
Cm
Tb
Bk
Dy
Cf
Ho
Es
Er
Fm
Tm
Md
Yb
No
Lu
Lr
d-block transition elements
*Lanthanides
†Actinides
f-block t ransition elemen ts
Uns Uno Une Uun Uuu
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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).
Coordination compounds
Complexes
A + :B A-BA Metal atom or Metal ion
B Ligand (nutral molecule or ion)
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A complex consists of a central atom, which is
usually a metal atom or ion, and attached groups
called ligands
Terminology for Complexes
The coordination
number is the total
number of points at
which a central atom
or ion attaches
ligands
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
Terminology for Complexes
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N
NH NH
N
Myoglobin, a protein that stores O2 in cells
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Coordination Environment of Fe2+ in Oxymyoglobin and
Oxyhemoglobin
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Distortion from Octahedral Geometry
Tetragonal distortion
Rhombic
distortion
Trigonal
distortion
Elongation
Compression
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– 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
Nomenclature of Coordination Complexes
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Polydentate refers to multiple points of attachment by one ligand
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Transition
Metal
Name if in Cationic
Complex
Name if in Anionic
Complex
Sc scandium scandate
Ti titanium titanate
V vanadium vanadate
Cr chromium chromate
Mn manganese manganate
Fe iron ferrate
Co cobalt cobaltate
Ni nickel nickelate
Cu copper cuprate
Zn zinc zincate
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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.2 di bis 6 hexa hexakis
3 Tri tris 7 hepta heptakis
4 tetra tetrakis 8 octa octakis
5 penta pentakis 9 nona nonakis
10 deca decakis
Nomenclature of Coordination Complexes
– 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]3-
hexacyanoferrate(III) ion
[Co(NH3)6]3+
[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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20_441
Isomers
(same formula but different properties)
Stereoisomers
(same bonds, different
spatial arrangements)
Structural
isomers
(different bonds)
Optical
isomerism
Geometric
(cis-trans)
isomerism
Linkage
isomerism
Coordination
isomerism
Isomerism ایزومری
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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
[CrCl(NH3)5]SO4
pentaaminsulfatochromium(III) chloride
pentaaminchlorochromium(III) sulfate
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Hydrated Isomerism ایزومری آب پوشی
[Co(NH3)4(NO2)Cl]Cl & [Co(NH3)4(ONO)Cl]Cl
[Co(SCN)(NH3)5]+ & [Co(NCS)(NH3)5]
+
Ambidentate Ligands لیگاندهای دوسردندانه
NCS- NO2- R-CONH2
Linkage Isomerism ایزومری اتصال
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[Co(NH3)5(NO2)]Cl2Pentaamminenitrocobalt(III) chloride
[Co(NH3)5(ONO)]Cl2Pentaamminenitritocobalt(III) chloride
Linkage Isomerism ایزومری اتصال
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20_441
Isomers
(same formula but different properties)
Stereoisomers
(same bonds, different
spatial arrangements)
Structural
isomers
(different bonds)
Optical
isomerism
Geometric
(cis-trans)
isomerism
Linkage
isomerism
Coordination
isomerism
Isomerism ایزومری
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 ایزومری هندسی
cis-trans ترانس–سیس
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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
Geometric Isomerism ایزومری هندسی
fac-mer کمربندی –وجهی
IrH3(PMe3) 3
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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
2- StereoisomerismStereoisomerism استریوایزومری
2- Optical isomerism نوری ایزومری
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Sn S1= S2=iCn Dn
Optical Activity فعالیت نوری
Optical isomers are isomers that differ in their
ability to rotate the plane of polarized light
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• Different all ligands
• Tris bidentate chelate
• cis bis bidentate chelate
• Chiral organic ligand
• …
• …
• …
Chiral Complexes
Sn S1= S2=i
Cn Dn
Optical Isomerism نوریایزومری
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Presentation of [M(en)3]
EnantiomerDiasteriomer
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Complex-Ion Equilibria
Kf = [[Zn(NH3)4]2+]
[Zn2+][NH3]4 = 4.1*108
Zn2+(aq) + 4 NH3(aq) [Zn(NH3)4]2+(aq)
[Zn(H2O)4]2+(aq) + NH3(aq) [Zn(H2O)3(NH3)]2+(aq) + H2O(aq)
K1= [[Zn(H2O)3(NH3)]2+]
[[Zn(H2O)4]2+][NH3]= 1 = 3.9*102
Displacement is stepwise from the hydrated ion:
Step 1:
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[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
K = 2 =[[Zn(H2O)2(NH3)2]2+]
[[Zn(H2O)4]2+][NH3]2= K1 * K2 = 8.2*104
Step 2:
[Zn(H2O)4]2+(aq) + 2 NH3(aq) [Zn(H2O)2(NH3)2]2+(aq) + 2 H2O(aq)
Combining steps 1 and 2:
4 = K1 * K2 * K3 *K4 = [email protected]
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Kn+1اگر > Knستشد نشان دهنده تغییرات ساختاری یا تغییرات اسپینی ا
[Fe(OH2)6]2+ + bipy [Fe(OH2)4 (bipy)]2+ K1
[Fe(OH2)4 (bipy)]2+ + bipy [Fe(OH2)2 (bipy) 2]2+ K2
[Fe(OH2)2 (bipy) 2]2+ + bipy [Fe (bipy) 3]
2+ K3
K3 > K2
eg
t2g
eg
t2g
eg
t2g
K3K2
Kn+1اگر > Knستشد نشان دهنده تغییرات ساختاری یا اسپینی ا
[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
[Cd(OH2)3 Br3]- + Br-
[CdBr4]2- 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 Irving-
Williams 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 [email protected]
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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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