Slide 1 - Introduction to Coordination Compounds

  • Definition: Coordination compounds are substances that consist of a central metal atom or ion surrounded by ligands.
  • Ligands: Ligands are molecules or ions that donate pairs of electrons to the metal atom or ion.
  • Coordination number: The number of bonds formed between the metal atom or ion and the ligands is called the coordination number.
  • Examples of coordination compounds: [Fe(CN)6]4-, [Co(NH3)6]3+, [CuCl2(H2O)4]

Slide 2 - Types of Ligands

  • Mono dentate ligand: Ligands that form only one bond with the metal atom or ion. Example: NH3, H2O
  • Bidentate ligand: Ligands that can form two bonds with the metal atom or ion. Example: ethylenediamine (en), oxalate ion (C2O4^2-)
  • Polydentate ligand: Ligands that can form multiple bonds with the metal atom or ion. Example: ethylenediaminetetraacetate (EDTA)

Slide 3 - Isomerism in Coordination Compounds

  • Stereoisomerism:
    • Geometric isomerism: Same chemical formula, but differ in spatial arrangement.
    • Optical isomerism: Non-superimposable mirror images of each other.
  • Coordination isomerism:
    • Exchange of ligands between the metal atom or ion and the counter ions.
  • Linkage isomerism:
    • Existence of different isomeric compounds due to a ligand which can bind through different atoms or through different bonds.

Slide 4 - Werner’s Theory of Coordination Compounds

  • Propounded by Alfred Werner in 1893.
  • Central atom or ion is linked to ligands by primary or secondary valencies.
  • Coordination number: Number of ligands coordinated to the central metal ion.
  • Primary valency: Indicates the oxidation state of the central atom or ion.
  • Secondary valency: Indicates the coordination number of the central atom or ion.

Slide 5 - Hybridization of Central Metal Atom with Ligands

  • Hybridization refers to the mixing of atomic orbitals to form new hybrid orbitals.
  • Hybrid orbitals determine the geometry around the central metal atom. Examples of hybridization:
  • [Fe(CN)6]4-: Fe(III) has d^2sp^3 hybridization.
  • [Co(NH3)6]3+: Co(III) has d^2sp^3 hybridization.
  • [CuCl2(H2O)4]: Cu(II) has d^2sp^3 hybridization.

Slide 6 - Shapes and Structures of Coordination Compounds

  • Square planar: Coordination number 4, d^2sp^3 hybridization.
  • Tetrahedral: Coordination number 4, sp^3 hybridization.
  • Octahedral: Coordination number 6, d^2sp^3 hybridization.
  • Linear: Coordination number 2, sp hybridization.

Slide 7 - Crystal Field Theory (CFT)

  • CFT explains the stability and color observed in coordination compounds.
  • It is based on the interaction between the d-orbitals of the central metal atom and the ligands.
  • Splitting of d-orbitals into two energy levels: eg and t2g.
  • The energy difference between eg and t2g levels corresponds to the absorbed or emitted light, giving the compound its color.

Slide 8 - Colors of Transition Metal Complexes

  • Color arises due to d-d transitions.
  • Different ligands can cause different energy levels of d-orbitals.
  • Greater energy difference between eg and t2g levels results in higher energy light absorbed, and vice versa.
  • Examples:
    • Cu(II) with Cl ligands appears blue due to high energy absorption.
    • Cu(II) with NH3 ligands appears green due to lower energy absorption.

Slide 9 - Nomenclature of Coordination Compounds

  • Cationic part is written first, followed by the anionic part.
  • Nomenclature of cationic part:
    • The name of the metal is written first, followed by the oxidation state in Roman numerals in parentheses.
    • Example: Iron(III)
  • Nomenclature of anionic part:
    • The name of the ligand is written, followed by the metal name ending in -ate.
    • Example: Chlorido, Nitrito, Aquo

Slide 10 - Isomerism in Coordination Compounds

  • Structural isomerism:
    • Linkage isomerism: Different bond formation between the central atom and ligands.
    • Ionization isomerism: Exchange of ligand with the same molecular formula but different connectivity.
    • Coordination isomerism: Exchange of ligand between the cationic and anionic parts.
  • Coordination compounds exhibit a variety of isomerism due to the different arrangements of ligands around the central metal atom or ion.

Slide 11 - Coordination Compounds: Hybridization of Central Metal Atom with Ligands

  • Hybridization refers to the mixing of atomic orbitals to form new hybrid orbitals.
  • The type of hybridization determines the geometry and shape around the central metal atom.
  • Different types of hybridization can occur depending on the coordination number and ligands involved.
  • Examples of hybridization in coordination compounds include sp, sp^2, sp^3, dsp^2, and d^2sp^3.
  • The type of hybridization influences the magnetic properties, reactivity, and bonding in coordination compounds.

Slide 12 - sp Hybridization in Coordination Compounds

  • Occurs when the central metal atom or ion has a coordination number of 2.
  • The s orbital and one p orbital from the metal atom combine to form two sp hybrid orbitals.
  • The sp hybrid orbitals are linearly oriented at an angle of 180 degrees.
  • Examples: [Ni(CO)4], [PtCl2(NH3)2]

Slide 13 - sp^2 Hybridization in Coordination Compounds

  • Occurs when the central metal atom or ion has a coordination number of 3.
  • The s orbital and two p orbitals from the metal atom combine to form three sp^2 hybrid orbitals.
  • The sp^2 hybrid orbitals are trigonally planarly oriented at an angle of 120 degrees.
  • Examples: [Cu(CN)3]2-, [Co(NH3)3]+

Slide 14 - sp^3 Hybridization in Coordination Compounds

  • Occurs when the central metal atom or ion has a coordination number of 4.
  • The s orbital and three p orbitals from the metal atom combine to form four sp^3 hybrid orbitals.
  • The sp^3 hybrid orbitals are tetrahedrally oriented at an angle of 109.5 degrees.
  • Examples: [Ni(CO)4], [Zn(NH3)4]2+

Slide 15 - dsp^2 Hybridization in Coordination Compounds

  • Occurs when the central metal atom or ion has a coordination number of 4 and there are two lone pairs of electrons.
  • The dxy, dxz, dyz, and dz^2 orbitals from the metal atom combine with one s and two p orbitals to form five dsp^2 hybrid orbitals.
  • The dsp^2 hybrid orbitals are trigonal bipyramidal in shape.
  • Examples: [Fe(CO)5], [Cu(NH3)4]2+

Slide 16 - d^2sp^3 Hybridization in Coordination Compounds

  • Occurs when the central metal atom or ion has a coordination number of 6.
  • The dxy, dxz, dyz, dz^2, and dx^2-y^2 orbitals from the metal atom combine with one s and three p orbitals to form six d^2sp^3 hybrid orbitals.
  • The d^2sp^3 hybrid orbitals are octahedrally oriented at an angle of 90 degrees.
  • Examples: [Cr(H2O)6]3+, [Co(NH3)6]3+

Slide 21 - Coordination Compounds: Hybridization of Central Metal Atom with Ligands

  • Hybridization determines the shape and geometry of coordination compounds.
  • Hybridization involves the mixing of atomic orbitals to form new hybrid orbitals.
  • Different types of hybridization can occur depending on the coordination number and ligands.
  • sp hybridization:
    • Occurs when the central metal atom or ion has a coordination number of 2.
    • One s orbital and one p orbital from the metal atom combine to form two sp hybrid orbitals.
    • Examples: [PtCl2(NH3)2], [Ag(CN)2]-
  • sp^2 hybridization:
    • Occurs when the central metal atom or ion has a coordination number of 3.
    • One s orbital and two p orbitals from the metal atom combine to form three sp^2 hybrid orbitals.
    • Examples: [Co(NH3)3]+, [Cu(CN)3]2-
  • sp^3 hybridization:
    • Occurs when the central metal atom or ion has a coordination number of 4.
    • One s orbital and three p orbitals from the metal atom combine to form four sp^3 hybrid orbitals.
    • Examples: [NiCl4]2-, [Zn(NH3)4]2+
  • dsp^2 hybridization:
    • Occurs when the central metal atom or ion has a coordination number of 4 with two lone pairs of electrons.
    • One d orbital and two p orbitals from the metal atom combine with one s orbital to form five dsp^2 hybrid orbitals.
    • Examples: [Fe(CO)5], [Cu(NH3)4]2+
  • d^2sp^3 hybridization:
    • Occurs when the central metal atom or ion has a coordination number of 6.
    • Two d orbitals and three p orbitals from the metal atom combine with one s orbital to form six d^2sp^3 hybrid orbitals.
    • Examples: [Cr(H2O)6]3+, [Co(NH3)6]3+

Slide 22 - Hybridization Examples

  • Example 1: sp hybridization in [Ag(CN)2]-
    • Coordination number = 2
    • 1s orbital and 1p orbital from Ag atom combine to form two sp hybrid orbitals.
    • Linear arrangement, bond angle = 180 degrees.
  • Example 2: sp^2 hybridization in [Cu(CN)3]2-
    • Coordination number = 3
    • 1s orbital and 2p orbitals from Cu atom combine to form three sp^2 hybrid orbitals.
    • Trigonal planar arrangement, bond angle = 120 degrees.
  • Example 3: sp^3 hybridization in [Zn(NH3)4]2+
    • Coordination number = 4
    • 1s orbital and 3p orbitals from Zn atom combine to form four sp^3 hybrid orbitals.
    • Tetrahedral arrangement, bond angle = 109.5 degrees.

Slide 23 - Hybridization Examples (Contd.)

  • Example 4: dsp^2 hybridization in [Fe(CO)5]
    • Coordination number = 5
    • 1d orbital, 2p orbitals, and 1s orbital from Fe atom combine to form five dsp^2 hybrid orbitals.
    • Trigonal bipyramidal arrangement.
  • Example 5: d^2sp^3 hybridization in [Cr(H2O)6]3+
    • Coordination number = 6
    • 2d orbitals, 3p orbitals, and 1s orbital from Cr atom combine to form six d^2sp^3 hybrid orbitals.
    • Octahedral arrangement.
  • Hybridization plays a crucial role in determining the shape, geometry, and properties of coordination compounds.

Slide 24 - Importance of Hybridization in Coordination Chemistry

Hybridization is significant in coordination chemistry for various reasons:

  • Predicting the geometry and shape of coordination compounds.
  • Understanding the reactivity and bonding in coordination compounds.
  • Explaining the magnetic properties and spectroscopic behavior of coordination compounds.
  • Determining the stability and color observed in coordination compounds.
  • Providing a basis for the naming and characterization of coordination compounds. The knowledge of hybridization helps in analyzing and explaining various properties and behaviors of coordination compounds.

Slide 25 - Summary

In summary:

  • Hybridization is based on the mixing of atomic orbitals to form new hybrid orbitals.
  • Different types of hybridization occur depending on the coordination number and ligands present.
  • Examples include sp, sp^2, sp^3, dsp^2, and d^2sp^3 hybridizations.
  • Hybridization determines the geometry, shape, and properties of coordination compounds.
  • Understanding hybridization is crucial for studying coordination chemistry and analyzing its various aspects.

Slide 26 - References

  • Textbook: Organic Chemistry by Morrison & Boyd (2011)
  • Textbook: Inorganic Chemistry by Housecroft & Sharpe (2012)
  • Journal Article: “Coordination Chemistry and Bonding in Transition Metal Complexes” by Jens Muller (Chemical Reviews, 2008)
  • Lecture Notes: Coordination Chemistry lecture series by Prof. John Smith (University of XYZ) Note: The references provided are for further reading and exploration on the topic.