chemistry of coordination compounds · chemistry of coordination compounds ... the molecules or...

Nov. 2006 Shanghai Jiao Tong University

Chemistry of Coordination Chemistry of Coordination CompoundsCompounds

Chapter 24


The Position of the Transition Elements on The Position of the Transition Elements on the Periodic Tablethe Periodic Table

Ca

Sr

Ba

Ra

s1

s2

d3 d10d4 d5

d10s1

d10s2

s2p1·············s2p6

ds

sd


Electron Configurations and other properties of the first row transition Metals

Oxidation States of the 1st Row Transition Metals(most stable oxidation numbers are shown in red)


3d3 3d4 3d5 3d6 3d7 3d8 3d9 3 d10 3d104s1

+2

Ca

-1

Os+8

Zn

+2

d0+4

Scandium Titanium Vanadium

Chromium Manganese Iron

Nov. 2006 Shanghai Jiao Tong University Cobalt Nickel Copper 22.2

cation

coor

Metal at

dinate compou moleculesligan

omcomplex io

tsions

a A

a counter ion

dn

n

⎧⎨⎩⎧

⎧ ⎧⎪⎪⎨⎪

⎪⎪⎪

⎪⎨

⎨⎩⎩

⎪⎪⎪⎩

Coordination CompoundsCoordination Compounds

[Cr(H2O)4Cl2] Cl

[Co(NH3)4Cl2] SO4

K4 [Fe(NCS)6]

The molecules or ions that surround the metal in a complex ion are called ligands.




A ligand has at least one unshared pair of valence electrons

• •

H

N

HHH

O

H

• • ••

• •••Cl• •

••

- ••C O••

The atom in a ligand that is bound directly to the metal atom is the donor atomdonor atom.

Ligands with:one donor atom monodentate H2O, NH3, Cl-

two donor atoms bidentate ethylenediamine

three or more donor atoms polydentate EDTA



H2N CH2 CH2 NH2• • • •

bidentate ligand



polydentate ligand(EDTA)

CH2 CH2 NN

H2C

H2CCH2

CH2

COOH

COOH

HOOC

HOOC

Bidentate and polydentate ligands are called chelating agents


Naming Coordination Compounds

• The cation is named before the anion.

• Within a complex ion, the ligands are named first in alphabetical order and the metal atom (or ion) is named last.

• The names of anionic ligands end with the letter o. Neutral ligands are usually called by the name of the molecule.(The exceptions are H2O (aquo), CO (carbonyl), and NH3(ammine)).



• When several ligands of a particular kind are present, the Greek prefixes di-, tri-, tetra-, penta-, and hexa- are used to indicate the number. If the ligand contains a Greek prefix, use the prefixes bis, tris, and tetrakis to indicate the number.

• The oxidation number of the metal is written in Roman numerals following the name of the metal.

• If the complex is an anion, its name ends in –ate.



4 6cation anion

K [Fe(CN) ] Potassium hexacyanoferrate(II)cation anion

3 6 3[Co(NH ) ]Clcation anion

Hexaamminecobalt(III) chlorideanioncation

- Fe anion6 oxidationCN number

hexa cyano ferrate (II) ion4-3 6[Fe(NH ) ]

anion

6 Coligand name oxidation number

tris (ethylenediamine) cobalt (III) chloride3 3[Co(en) ]Clcation anion


Naming Coordination CompoundsEnglish Name Anion NameCopper CuprateGold AurateIron FerrateLead PlumbateSilver ArgentateTin Stannate

Write the structural formula corresponding to each of the following IUPAC names:

a. hexaaquairon(II) chloride; b. tetraamminedichloroplatinum chloridec. Potassium hexachloroplatinate(IV)


Structure of Coordination CompoundsStructure of Coordination Compounds

lewis blew aseis aci

2+ - 4-

d6Fe + CN [Fe(CN) ]⎯⎯→

Three important properties of complexes: Three important properties of complexes: a.a. IsomerismIsomerismb.b. ColorColorc.c. ParamegnetismParamegnetism


Isomerism of Coordination CompoundsIsomerism of Coordination Compounds

Constitutional isomerismIsomerism

Steroisomerism⎧⎨⎩

Constitutional isomerismConstitutional isomerism: : are isomers that differ in how the atoms are joined together.

StereoisomerismStereoisomerism: : are isomers in which the atoms are bonded to each other in the same order, but differ in the precise arrangement of the atoms in the space.



Constitutional isomerismConstitutional isomerism::

4 43 5 3 5[Co(NH ) ] and [Co(NHBr BrO ) ]S SO

3 4 4 3 4 4[ (NH ) ][ Cl ] andP [ (NH )Cu Cu][Pt Clt ]

doner doner ato

3 4 2 3 4 2

m ato

2

m

[Co(NH ) ( NO)]Cl and [Co(NH ) N( O )]ClO


Constitutional isomerismConstitutional isomerism::

doner atom

done

3 5 2 2

3 5 2r

atom

[Co(NH ) ( O )]Cl

[Co(NH ) ( NO O)]Cl

N


Isomerism of Coordination CompoundsIsomerism of Coordination CompoundsConstitutional isomerism

IsomerismSteroisomeris

Geometric isomerismOptical isomer

mism

⎧⎪

⎧⎨⎨⎪⎩⎩

Geometric isomersGeometric isomers: : are isomers in which the atoms are bonded to each other in the same way, but differ because some atoms occupy different relative position in space.

cis-[Pt(NH3)2Cl2] trans-[Pt(NH3)2Cl2]



cis

trans

trans-[Co(NH3)4Cl2]cis-[Co(NH3)4Cl2]





mism

⎧⎪

⎧⎨⎨⎪⎩⎩

Optical isomers (enantiomers)Optical isomers (enantiomers): : are isomers that are non-superimposable mirror images of one another.





mism

⎧⎪

⎧⎨⎨⎪⎩⎩

Isomers of Co(en)33+



trans-[Co(en)2Cl2]cis-[Co(en)2Cl2]

optical isomers not optical isomers

achiralachiralchiralchiral


The Optical Isomers of Co(en)2CI2+


Un-polarized Light Consists of Waves Vibrating in Many Different Planes


Color of Coordination CompoundsColor of Coordination Compounds

The color of the different coordination compounds of CoThe color of the different coordination compounds of Co3+3+

3 2 3 23 6 3 5 3 5 2 3 5 3 4 2[Co(NH ) ] ,[Co(NH ) ] ,[Co(NH ) ] ,[Co(NH ) ] , [Co(NH ) ]NCS H O Cl trans Cl+ + + + +−


Color of Coordination CompoundsColor of Coordination Compounds

510

(green and yellow)absorption nmλ =

The absorption spectrum of [Ti(H2O)6]3+ at 510 nm (green and yellow), the complex transmits all light except green and yellow. The complex is purple


Magnetism of Coordination compoundsMagnetism of Coordination compounds

• Many transition metal complexes are paramagneticparamagnetic (have unpaired electrons)

• An interesting observations ( a dd66 metal ion):– [Co(NH3)6]3+ has no unpaired electrons, – [CoF6]3- has four unpaired electrons.

• A bonding theory to account for both color and magnetism in transition metal complexes.

???


Crystal-Field Theory

provide

donor

Metal ionLigands

empty orbitalselectrons pa ir s

⎯⎯⎯→

⎯⎯⎯→


Structure of Coordination CompoundsStructure of Coordination Compounds

The Ligand Arrangements for Coordination Numbers 2, 4, and 6


The Hybrid Orbitals Requiredfor OctahedralOctahedral and LinearLinear Complex Ions

Octahedral ligand arrangement for Co3+


The Hybrid Orbitals Requiredfor TetrahedralTetrahedral and Square planerSquare planer

Complex Ions


An Octahedral Arrangement of Point-Charge Ligands and the Orientation of the 3d Orbitals


Bonding in Coordination CompoundsBonding in Coordination Compounds

Isolatedtransition metal

atomBonded

transition metalatom

Crystal field Splitting of

outer d orbital in octahedral field

Crystal field splitting ( ∆): the energy difference between two sets of d orbitals in a metal atom when ligands are present


Bonding in Coordination Compounds

Ti3+: a d1 ion

∆ = hν

The absorbance spectrum of Ti(H2O)63+, the maximum

absorption peak at 498nm



Spectrochemical SeriesI- < Br- < Cl- < OH- < F- < H2O < NH3 < en < CN- < CO

Weak field ligandsSmall Small ∆∆

Strong field ligandsLarge Large ∆∆


CrystalCrystal--Field TheoryField Theory

I- < Br- < Cl- < OH- < F- < H2O < NH3 < en < CN- < CO



High-spin High-spinLow-spin Low-spin

Orbital Diagrams for high-spin and low-spin octahedral complex


Crystal field splitting between d orbitals in Crystal field splitting between d orbitals in a tetrahedral complexa tetrahedral complex


Crystal field splitting between d orbitals in Crystal field splitting between d orbitals in a a tetrahedraltetrahedral complexcomplex


The Crystal Field Diagrams for Octahedral Octahedral and TetrahedralTetrahedral

Complexes


The d Energy Diagrams for SquareSquare--Planar Planar and LinearLinear

Complexes


Chemistry In Action: Coordination Compounds in Living Systems

The Heme Complex



Chemistry In Action: Cisplatin – The Anticancer Drug


Chlorophyll


HomeworkChapter 24:24.02 a to f and K[MnO4]**24.04 a to f and [Cr(C6H6)2]**24.06 a, e and tetraammincopper(II)sulfate24.08 a, b and d24.10 a and b24.12**24.14 a and c** optional, for extra credits 24.18, 24.28, 24.30, 24.46

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