Ligand Substitutions & Kstab

Ligand Subsitution & K_stab

Complex metal ions have ligands which can be substituted. K_stab is defined as the equilibrium constant for the formation of the complex ion in a solvent from its constituent ions or molecules.

The reaction

The complex ion [ Cu(H₂O)₆ ]²⁺ undergoes a ligand substitution reaction where H₂O is replaced by Cl^-.
The reaction is reversible.
- [ Cu(H₂O)₆ ]²⁺ + 4Cl⁻ $\:\leftrightharpoons\:$ [ CuCl₄ ]^2- + 6H₂O
The equilibrium can be pushed to the right using concentrated hydrochloric acid (HCl).
The reaction can be reversed by adding water. This will push the equilibrium to the left.

Illustrative background for [ Cu(H<sub>2</sub>O)<sub>6</sub> ]<sup>2+</sup> vs. [ CuCl<sub>4</sub> ]<sup>2-</sup>

Illustrative background for [ Cu(H<sub>2</sub>O)<sub>6</sub> ]<sup>2+</sup> vs. [ CuCl<sub>4</sub> ]<sup>2-</sup> ?? "content

[ Cu(H₂O)₆ ]²⁺ vs. [ CuCl₄ ]^2-

In the reaction, the copper goes from having six water ligands to having four chloride ligands.
- The co-ordination number changes from six to four in the reaction.
- This is because the chloride ions are larger than the water molecules.
- There is only space for four chloride ions around the copper.

Reversible reaction

As this reaction is reversible, we can form an equilibrium expression. This is known as K_stab, or the stability constant.
For the below reaction:
- [ Cu(H₂O)₆ ]²⁺ + 4Cl⁻ $\:\leftrightharpoons\:$ [ CuCl₄ ]^2- + 6H₂O
- K_stab = $\Large\frac {[CuCl_4]}{[Cu(H_2O)_6][Cl^-]^4}$
Looking at the expression, we can see a large K_stab results in the formation of a stable complex ion.

Colour change

The colour change observed should be from blue to yellow.
- However, there is normally a mixture of [ Cu(H₂O)₆ ]²⁺ and [ CuCl₄ ]^2- ions.
- This means the observed colour change is from blue to green (blue + yellow = green).

Substituting Water for Chlorine in a Complex Cobalt Ion

Let's go through another example. The chemistry in this reaction with a complex cobalt ion is exactly the same as the reaction with the with a complex copper ion.

The reaction

The complex ion [ Co(H₂O)₆ ]²⁺ undergoes a ligand substitution reaction where H₂O is replaced by Cl^-.
The reaction is reversible.
- [ Co(H₂O)₆ ]²⁺ + 4Cl⁻ $\:\leftrightharpoons\:$ [ CoCl₄ ]^2- + 6H₂O
The equilibrium can be pushed to the right using concentrated hydrochloric acid (HCl).
The reaction can be reversed by adding water. This will push the equilibrium to the left.

Illustrative background for [ Co(H<sub>2</sub>O)<sub>6</sub> ]<sup>2+</sup> vs. [ CoCl<sub>4</sub> ]<sup>2-</sup>

Illustrative background for [ Co(H<sub>2</sub>O)<sub>6</sub> ]<sup>2+</sup> vs. [ CoCl<sub>4</sub> ]<sup>2-</sup> ?? "content

[ Co(H₂O)₆ ]²⁺ vs. [ CoCl₄ ]^2-

In the reaction, the cobalt goes from having six water ligands it to having four chloride ligands.
- The co-ordination number changes from six to four in the reaction.
- This is because the chloride ions are larger than the water molecules.
- There is only space for four chloride ions around the cobalt.

Reversible reaction

As this reaction is reversible, we can form an equilibrium expression. This is known as K_stab, or the stability constant.
For the below reaction:
- [ Co(H₂O)₆ ]²⁺ + 4Cl⁻ $\:\leftrightharpoons\:$ [ CoCl₄ ]^2- + 6H₂O
- K_stab = $\Large\frac {[CoCl_4]}{[Co(H_2O)_6][Cl^-]^4}$
Looking at the expression, we can see a large K_stab results in the formation of a stable complex ion.

Colour change

The colour change observed should be from pink [ Co(H₂O)₆ ]²⁺ ions to blue [ CoCl₄ ]^2- ions.

1Physical Chemistry

1.1Atoms, Molecules & Stoichiometry

1.1.1Relative Masses

1.1.2The Mole

1.1.3Mass Spectrometry

1.1.4Empirical & Molecular Formulae

1.1.5Balanced Equations

1.1.6Molar Volume

1.1.7End of Topic Test - Amount of Substance

1.2Atomic Structure

1.2.1Fundamental Particles

1.2.2Isotopes & Mass Number

1.2.3Electron Shells, Sub-Shells & Orbitals

1.2.4Electron Configuration

1.2.5Ionisation Energy

1.2.6Factors Affecting Ionisation Energies

1.2.7Trends of Ionisation

1.2.8Specific Impacts on Ionisation Energies

1.2.9Electron Affinity

1.2.10End of Topic Test - Atomic Structure

1.2.11A-A* (AO2/3) - Atomic Structure

1.3Chemical Bonding

1.3.1Ionic Bonding

1.3.2Covalent & Dative Bonding

1.3.3Shapes of Molecules

1.3.4Intermolecular Forces

1.3.5Intermolecular Forces 2

1.3.6Electronegativity

1.3.7Bond Length, Bond Energy, & Bond Polarity

1.3.8Metallic Bonding

1.3.9Physical Properties

1.3.10End of Topic Test - Bonding

1.3.11A-A* (AO2/3) - Bonding

1.4States of Matter

1.4.1Simple Covalent Molecules

1.4.2The Ideal Gas Equation

1.4.3States of Matter

1.4.4Particle Diagrams

1.4.5The Liquid State

1.4.6Giant Ionic Lattices

1.4.7Giant Metallic Lattices

1.4.8Giant Covalent Structures

1.4.9Graphene & Fullerene

1.4.10Recycling

1.5Chemical Energetics

1.5.1Calorimetry

1.5.2Bond Enthalpies

1.5.3Enthalpy Changes

1.5.4Hess' Law

1.5.5Born-Haber Cycles

1.5.6Born-Haber Cycle Calculations

1.5.7Entropy

1.5.8Free Energy

1.5.9End of Topic Test - Energetics

1.6Electrochemistry

1.6.1Electrochemical Cells

1.6.2Electrochemical Series

1.6.3Commercial Application

1.6.4Nernst Equation

1.6.5Redox

1.7Equilibria

1.7.1Dynamic Equilibrium & Le Chatelier

1.7.2Kc

1.7.3Kp

1.7.4pH

1.7.5The Ionic Product of Water

1.7.6Weak Acids & Bases

1.7.7Introduction to Solubility Equilibria

1.7.8Solubility Equilibria Calculations

1.7.9Free Energy of Dissolution

1.7.10pH and Solubility

1.7.11Common-Ion Effect

1.7.12End of Topic Test - Kp & Electrochemistry

1.7.13A-A* (AO2/3) - Electrochemical Cells

1.8Partition Coefficient

1.8.1Kpc

1.9Reaction Kinetics

1.9.1Collision Theory

1.9.2Orders, Rate Constants & Equations

1.9.3Rate Graphs

1.9.4Rate Determining Step

1.9.5Maxwell-Boltzmann Distribution

1.9.6Catalysts

1.9.7Homogeneous Catalysts

1.9.8Heterogeneous Catalysts

1.9.9End of Topic Test - Kinetics

1.9.10End of Topic Test - Rate Equations

1.9.11A-A* (AO2/3) - Rate Equations

2Inorganic Chemistry

2.1The Periodic Table

2.1.1The Periodic Table

2.1.2Trends in the Periodic Table

2.1.3End of Topic Test - Periodicity & Trends

2.1.4Ceramics

2.1.5Period 3 Elements & Oxides

2.1.6Period 3 Oxides

2.1.7End of Topic Test - Period 3

2.2Group 2

2.2.1Group 2 Chemistry

2.3Group 17

2.3.1Introduction to Halogens

2.3.2Reactions of Halogens

2.3.3Chlorine & Chlorate(I)

2.3.4End of Topic Test - Group 17

2.3.5A-A* (AO2/3) - Periodicity, Group 2 & 17

2.4Transition Metals

2.4.1General Properties

2.4.2Titrations

2.4.3Shapes of Complex Ions

2.4.4Variable Oxidation States

2.4.5Ligands

2.4.6Colours of Ions

2.4.7Stereoisomerism of Complex Ions

2.4.8Cisplatin

2.4.9Ligand Substitutions & Kstab

2.4.10End of Topic Test - Transition Metals

2.4.11A-A* (AO2/3) - Transition Metals

2.5Nitrogen & Sulfur

2.5.1Nitrogen & Ammonia

2.5.2Formulated vs Manure Fertilisers

2.5.3Nitrogen Containing Fertilisers

2.5.4Fertilizers & Eutrophication

2.5.5Common Atmospheric Pollutants & Their Properties

2.5.6Catalytic Converters

2.5.7Atmospheric Oxides

3Organic Chemistry & Analysis

3.1Introduction to Organic Chemistry

3.1.1Naming Conventions

3.1.2Mechanism

3.1.3Isomerism

3.1.4End of Topic Test - Introduction to Organic Chem

3.2Hydrocarbons

3.2.1Fractional Distillation

3.2.2Cracking

3.2.3Combustion

3.2.4Chlorination

3.2.5End of Topic Test - Alkanes

3.2.6Introduction to Alkenes

3.2.7Reactions of Alkenes

3.2.8Polymerisation Reactions

3.2.9End of Topic Test - Alkenes

3.2.10Arenes

3.2.11Evidence for Structure of Arenes

3.2.12Reactions of Benzene

3.2.13End of Topic Test -Arenes

3.3Halogen Derivatives

3.3.1Properties of Haloalkanes

3.3.2Substitution Reactions of Haloalkanes

3.3.3Environmental Impacts of Haloalkanes

3.3.4End of Topic Test - Halogenoalkanes

3.4Hydroxy Compounds

3.4.1Types of Alcohol

3.4.2Oxidation 1

3.4.3Oxidation 2

3.4.4Elimination

3.4.5Acids & Esters

3.4.6Acyl Chlorides & Acylation

3.4.7Phenols & Their Reactions

3.4.8End of Topic Test - Alcohols

3.5Carbonyl Compounds

3.5.1Carbonyls

3.5.2Hydrogen Bonding & Carbonyls

3.5.3Aldehydes & Ketones

3.5.4Tri-Iodomethane Reaction

3.5.5End of Topic Test -Carbonyls

3.6Carboxylic Acids & Derivatives

3.6.1Properties of Carboxylic Acids

3.6.2Esters

3.6.3Acyl Chlorides

3.6.4End of Topic Test - Carboxylic Acids

3.7Nitrogen Compounds

3.7.1Nature & Preparation of Amines

3.7.2Basicity & Nucleophilicity

3.7.3Amides

3.7.4Reactions of Amino Acids

3.7.5Amino Acids

3.8Polymerisation

3.8.1Properties of Addition Polymers

3.8.2Condensation Polymerisation

3.8.3Effects of Side-Chains on Polymers

3.8.4Hydrolysis of Ester & Amide Groups

3.8.5Proteins

3.8.6DNA

3.8.7Adhesive & Conducting Polymers

3.8.8End of Topic Test - Amines & Proteins

3.9Analytical Techniques

3.9.1Chromatography

3.9.2High-Performance Liquid Chromatography

3.9.3Gas Chromatography

3.9.4IR Spectroscopy

3.9.5Uses of IR Spectroscopy

3.9.6Mass Spectrometry

3.9.7Mass Spectrometry Analysis

3.9.8Nuclear Magnetic Resonance

3.9.9Carbon-13 NMR

3.9.10Proton NMR I

3.9.11Proton NMR II

3.9.12End of Topic Test - Analytical Techniques

3.9.13A-A* (AO2/3) - Analytical Techniques

3.10Organic Synthesis

3.10.1Chirality & Drug Synthesis

3.10.2Organic Synthesis

3.10.3Examples of Synthetic Routes

3.10.4End of Topic Test - Organic Synthesis

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