Download Coordination Chemistry

Coordination Chemistry
Contents
I Introduction
1 History
2 Definition
3 Nomenclature
II Bonding
1 VBT & Crystal Field Theory
2 MOT & Ligand Field Theory
3 Electronic Spectroscopy
4 Magnetic Properties
III Structure of Coordination Compounds
IV Reactivity & Reaction Mechanisms
V Descriptive Chemistry
I
Introduction
1 History
1827 Discovery of Zeise’s Salt (KPtCl3C2H4)
The war between Alfred Werner & Sophus Jørgensen
— an experimentalist versus an experimentalist seeking for insight
Complex
Color old name
IUPAC name
CoCl3·6NH3
yellow Luteo complex
hexaamminecobalt(III)
chloride
CoCl3·5NH3
purple Purpureo complex
pentaamminechlorocobalt(III)
chloride
CoCl3·4NH3
green Praseo complex trans-tetraamminedichlorocobalt(III)
chloride
CoCl3·4NH3
violet Violeo complex
cis-tetraamminedichlorocobalt(III)
chloride
Jørgensen
Stick on the idea of “valence”
Co(NH3NH3Cl)3
Cl2Co(NH3NH3NH3NH3NH3Cl)
ClCo(NH3NH3Cl)2
Cl2Co(NH3NH3NH3NH3Cl)
By considering both precipitation of AgCl and conductivity (Table
11.1): Werner proposed:
[Co(NH3)6]Cl3
[Co(NH3)5Cl]Cl2
[Co(NH3)4Cl2]Cl
[Co(NH3)4Cl2]Cl
primary valence (formal oxidation state)
secondary valence (coordination number)
Werner’s experiments for the conductivity of some coordination
complexes
2 Definition
 A “coordination compound” is consisted of two components:
the metal ion (atom) and the ligand(s).
 A “ligand” is an ion, a molecule, or a group that is associated
with the metal ion as a Lewis acid-base adduct.
 The “donor atom” is the atom in the ligand, that attaches to
the metal ion.
 A ligand has only one donor atom is a “monodentate”; with
two donor atoms will be “bidentate”; “tridentate” for three;
“tetradentate” for four…..etc.
 A ligand that has more than one donor atom is of
“multi-dentate”.
 The association mold of a multidentate is called “chelation”.
 A “bridging ligand” attaches to more than one metal ion.
Isomerism and Structural insight
Structural Isomers
Hydrate Isomers
[Co(NH3)4(H2O)Cl]Cl2 and [Co(NH3)4(Cl2)]Cl·H2O
Ionization Isomers
[Co(NH3)5(SO4)](NO3) and [Co(NH3)4(NO3)](SO4)
Coordination Isomers
[Co(en)3][Cr(CN)6] and [Co(CN)6][Cr(en)3]
Linkage Isomers
Pd(AsPh3)2(SCN)2 and Pd(AsPh3)2(NCS)2
[Co(NH3)5(NO2)]2+ and [Co(NH3)5(ONO)]2+
Stereoisomers
Four-Coordinate
Tetrahedral
TiCl4, CoCl42-, CuCl42-, Pt(PPh3)4,
Geometrical Isomers
Optical Isomers
Lacking two perpendicular C2 symmetry
Six-Coordinate
Geometrical Isomers
Trans and cis - forms
mer and fac - forms
For an octahedral complex that has six different ligands
Two optical isomers
Structure versus number of isomers
Questions remained: Are isomers always synthesizable?
Optical Isomers with Bidentate Chelation


nl - nr
nl and nr are the refractive index of the left and
right circularly polarized light respectively


[], the specific rotation is defined as left; wherein c' is
the concentration and d' is the thickness of the sample
c'd'
MWxis molar rotation
l - r
kl - kr
c
kl and kr are the absorption coefficients of the left
and right circularly polarized light respectively
Asymmetric bidentate ligands
chiral without carbon
Tridentate
Tetradentate