1. Acid and Base Theories Continuation and
Introduction to Coordination Chemistry

2. Review of the Previous Lecture
Solubility principles
Like dissolves like
Solvent overcome solute interactions
Simple dissolution vs dissolution with dissociation
Acid and Base Theories
Defined by taste
Arrhenius: Defined for aqueous solutions
Brønsted-Lowry: Defined for all solvents

3. 1. Lewis Acids and Bases Ag+ + 2 :NH3 H3N-Ag- NH3 Definition
Acid: e- pair acceptor
Base: e- pair donor
Encompasses the Brønsted-Lowry definition:
H+ accepts an e- pair from a Brønsted base
Includes reactions involving metal adduct formation
Dative Bond: e- pair comes from
Lewis Base
Ag :NH H3N-Ag- NH3
Lewis acid-base adducts involving metal ions are called coordination compounds.

4. 1. Lewis Acids and Bases H+ + :NH3 H4N+ + Point Group: C3v Td
Adduct formation and frontier orbitals
Consider the following reaction:
Involves a change in geometry
Involves the interaction of frontier orbitals
H :NH H4N+ +
Point Group: C3v Td

5. Driving force: stabilization of the e- in the donor HOMOX y
Orbitals that will interact are those of comparable energy and symmetry
a1 LUMO of H+ and
a1 HOMO of NH3
New set of orbitals,
New LUMO and HOMO
Driving force: stabilization of the e- in the donor HOMO

6. Orbitals that will interact are those of comparable energy and symmetry
a1 LUMO of H+ and
a1 HOMO of NH3
New set of orbitals,
New LUMO and HOMO
Driving force: stabilization of the e- in the donor HOMO

7. y x N N N N

8. 1. Lewis Acids and Bases :B + A BA [BA] KBA =
C. Thermodynamics of binding
Consider the following reaction:
Use affinity scales to measure relative strengths:
Compare strength of Lewis acids or bases to a standard
For instance, compare the strength of different Lewis Bases to Boron-based Lewis Acids
:B A BA
[BA]
KBA =
KBA , the stronger the interaction
[B]
[A]
KLB-BF3 or
-∆H⁰ = BF3 Affinity
BF LB LB-BF3
Set
Constant
Vary
Affinity , Stronger Lewis Basicity

9. 2. Hard and Soft Acids and Bases
A. Expands the Lewis Acid-Base concept by identifying the “why” behind the affinity
Pearson (1968) and Chatt recognized that the polarizability of species was correlated with the preference of species to interact with other species.
Consider a random base:
KH+
H :B HB+
Affinity Scales
KCH3Hg+
CH3Hg :B CH3HgB+

10. 2. Hard and Soft Acids and Bases
For a given base:
KH+
H :B HB+
KCH3Hg+
CH3Hg :B CH3HgB+
if KH+ >> KCH3Hg+ B is “Hard”, Nonpolarizable, High charge/size ratio
if KH+ << KCH3Hg+ B is “Soft”, Polarizable, Low charge/size ratio
if KH+ ~ KCH3Hg+ B is “Intermediate”

11. 2. Hard and Soft Acids and Bases
B. Locating Hard and Soft Acids on the Periodic Table
Hard acids
Alkali metals
Alkaline earth metals
1st row transition metals in high oxidation states
Soft acids
2nd row or lower transition metals in low oxidation states
Note:
As you go down the periodic table of the main group elements, the elements are less Hard
The Hard- or Softness of a metal can depend on oxidation state
Oxidation State, Hardness
Fe3+ vs Fe2+
Hard
Intermediate

12. 2. Hard and Soft Acids and Bases
C. Binding preferences
Hard acids prefer Hard bases
Soft acids prefer Soft bases
These interactions are stronger than those between Hard-Soft species.
LiF CsI LiI CsF

13. 2. Hard and Soft Acids and Bases
C. Binding preferences
Hard acids prefer Hard bases
Soft acids prefer Soft bases
These interactions are stronger than those between Hard-Soft species.
LiF CsI LiI CsF
∆Gformation = kJ/mol
∆Gformation = Σ ∆Gf (products) Σ ∆Gf (reactants)
∆Gformation = kJ/mol Not favorable

14. 2. Hard and Soft Acids and Bases
Hard-Hard/Soft-Soft matching of acids and bases represents a stabilization that is additional to other factors that contribute to the strength of donor and acceptor bonds:
Orbital overlap
∆ Electronegativities
In solution competition with solvent binding

15. 2. Hard and Soft Acids and Bases
Hard-Hard/Soft-Soft matching of acids and bases represents a stabilization that is additional to other factors that contribute to the strength of donor and acceptor bonds:
Orbital overlap
∆ Electronegativities
In solution competition with solvent binding

16. Coordination Chemistry:
History, Introduction to Structure, and Nomenclature
Chapter 7 and 19

17. 1. Coordination Compounds
Composed of:
Metal atoms or ions
One or more ligands (atoms, ions, or molecules) that donate e- to the metal
Chemistry of the metal d-orbitals
Consist of the formation of coordinate covalent (dative) bonds:
Acid base concept is what underlines the main interactions of M-L
Adduct: a product of a direct addition of two or more distinct molecules
Lewis Acid-Base Adduct
Metal is the Lewis Acid
Ligand is the Lewis Base

18. 2. History Complimentary Color Wheel Absorb See Compound
A tale as old as time (Prehistoric)
Formally introduced by Alfred Werner (late 19th Century)
Introduced new bonding concepts
The famous Werner Cobalt Compounds
Absorb
See
Why does compound C have 2 colors?
Compound
Elemental Formula
Color A
CoN6H18Cl3
Yellow B
CoN5H15Cl3
Red C
CoN4H12Cl3
Green or Purple D
CoN3H9Cl3

19. C. Werner Compounds Compound Elemental Formula Color A CoN6H18Cl3
Yellow B
CoN5H15Cl3
Red C
CoN4H12Cl3
Green or Purple D
CoN3H9Cl3
Early bonding theories allowed only three atoms to be attached to cobalt
because of its valence of 3 (Co3+) for charge balance.
Jørgensen proposed that for the above compounds
N could form chains because of its valence of 5
Chloride (Cl-) could be bound to N or to Co3+
Werner proposed something very radical for the time
As many as 6 N (as NH3) could bond directly to Co3+
Cl- could bond to Co3+ or associate loosely; two kinds of Cl-

20. D. The Werner Titrations
Complex + AgNO3
n AgCl + Complexn+
Compound
Jørgensen
AgCl equivs
Werner A 3 B 2
Note: 2 Isomers C 1
Note: 0 Cl-? D

21. Remember these are older theories
E. Werner’s Theory
[Co(NH3)6]Cl3
Primary Bonding
The positive charge of the metal ion is balanced by negative ions.
Does not have to involve direct bonding to the metal ion.
Today when direct bonding is not involved, we refer to it
as the secondary coordination sphere.
B. Secondary Bonding
Ligands (molecules or ions) directly attached to the metal ion.
This interaction constitutes the coordination sphere; the complex ion.
Today we refer to it as the primary coordination sphere.
Defines the coordination number.
Defines a specific geometry; “directed in space”.
Remember these are older theories
Primary Sphere
Secondary Sphere

22. F. Determining the coordination geometry
Which coordination mode would give 2 isomers for complex C? a b d c

26. cis
trans
Yes!

27. Cis and Trans Isomers Ethylenediamine (en)
You can have optical isomers.
Ethylenediamine (en)

28. 3. Nomenclature Rules
For charged molecules, the cation comes first followed by the anion.
The following rules apply to both neutral and charged molecules:
B. The elemental formulation has the inner coordination sphere in brackets.
[Pt(NH3)4]Cl2
When writing the name, the ligands within the coordination sphere are written before the metal and are listed in alphabetical order.
tetrakisammineplatinum(II) chloride
C. Ligand names (handout page 1).
Monodentate: Ligands with one point of attachment
Chelates (Bidentate…multidentate): Ligands with two or more points of attachment

29. Tris(ethylenediamine)rhodium(III)
3. Nomenclature Rules
D. The number of ligands of each kind is indicated by prefixes using the following table.
Use prefixes in column A for simple cases.
Use prefixes in column B for ligands with names that already use prefixes from column A.
[Co(en)2Cl2]+
Dichlorobis(ethylenediamine)cobalt(III)
Always use prefixes in column B when the name of a ligand begins with a vowel.
[Rh(en)3]3+
Tris(ethylenediamine)rhodium(III) A B

30. 3. Nomenclature Rules
E. Ligands are written in alphabetical order-according to the ligand name, not the prefix.
F. Special:
Anionic ligands are given an o suffix.
Neutral ligands retain their usual name
Coordinated water is called aqua
Coordinated ammonia is called ammine

31. 3. Nomenclature Rules
G. Designate the metal oxidation state after the metal.
[PtClBr(NH3)(H2O)]
Ammine
aqua
bromo
chloro
platinum(II)
[Pt(NH3)4]2+
Tetrakisammineplatinum(II)
If the molecule is negatively charged, the suffix –ate is added to the name
[Pt(NH3)Cl3]-
Amminetrichloroplatinate(II)
Ammineaquabromochloroplatinum(II)

32. 3. Nomenclature Rules
Special names for metals when in a negatively charged molecule:
Copper (Cu): Cuprate
Iron (Fe): ferrate
Silver (Ag): argentate
Lead (Pb): Plumbate
Tin(Sn): Stannate
Gold(Au): Aurate

33. 3. Nomenclature Rules
H. Prefixes designate adjacent (cis-) and opposite (trans-) geometric locations
cis-bisamminedichloroplatinum(II) is an anticancer agent.
The trans isomer is not.

34. 3. Nomenclature Rules
I. Bridging ligands between two metal ions have the prefix μ
μ-amido-μ-hydroxobis(tetrakisaminecobalt)(IV)
miu