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Questions and Answers
Which term refers to the charged species surrounding the central metal atom in a coordination compound?
Which term refers to the charged species surrounding the central metal atom in a coordination compound?
- Coordination entity (correct)
- Ligand
- Ion pair
- Chelate
What distinguishes coordination compounds from double salts in terms of their behavior in solution?
What distinguishes coordination compounds from double salts in terms of their behavior in solution?
- Coordination compounds are less stable than double salts.
- Coordination compounds retain their identity in solution, while double salts dissociate. (correct)
- Coordination compounds contain only neutral molecules.
- Coordination compounds dissociate in solution, while double salts do not.
What is the characteristic feature of chelating ligands?
What is the characteristic feature of chelating ligands?
- They can only bind to transition metals.
- They cause cyclisation around the metal atom. (correct)
- They form complex ions with no rings.
- They donate only one electron to the central atom.
Which of the following could be classified as a cationic complex entity?
Which of the following could be classified as a cationic complex entity?
Which type of ligand can bind to a metal atom at more than one site?
Which type of ligand can bind to a metal atom at more than one site?
How does the chelate effect contribute to the stability of coordination compounds?
How does the chelate effect contribute to the stability of coordination compounds?
What distinguishes geometrical isomers from each other?
What distinguishes geometrical isomers from each other?
Which of the following is a characteristic of ambidentate ligands?
Which of the following is a characteristic of ambidentate ligands?
Which type of complex is formed only with one kind of donor atom?
Which type of complex is formed only with one kind of donor atom?
In the formula for Effective Atomic Number (EAN), which variable represents the coordination number?
In the formula for Effective Atomic Number (EAN), which variable represents the coordination number?
What defines the central atom or ion in a coordination entity?
What defines the central atom or ion in a coordination entity?
Which formula represents an octahedral complex that can exhibit cis and trans isomerism?
Which formula represents an octahedral complex that can exhibit cis and trans isomerism?
What is defined as the number of coordinate bonds formed by the central metal atom with ligands?
What is defined as the number of coordinate bonds formed by the central metal atom with ligands?
What type of ligands can form π-bonds and accept electron density from metal atoms?
What type of ligands can form π-bonds and accept electron density from metal atoms?
What does EAN stand for in the context of coordination chemistry?
What does EAN stand for in the context of coordination chemistry?
Which d-orbitals are classified as t2g orbitals?
Which d-orbitals are classified as t2g orbitals?
Which coordination number typically does NOT show geometrical isomerism?
Which coordination number typically does NOT show geometrical isomerism?
Which of the following complexes exhibits optical isomerism?
Which of the following complexes exhibits optical isomerism?
What is called when a complex exhibits slow ligand substitution?
What is called when a complex exhibits slow ligand substitution?
What do primary valencies in metals correspond to?
What do primary valencies in metals correspond to?
In tetrahedral complexes, which set of orbitals has a higher energy level?
In tetrahedral complexes, which set of orbitals has a higher energy level?
How is the oxidation number of the central atom in a complex determined?
How is the oxidation number of the central atom in a complex determined?
What is the condition for the fourth electron to enter an eg orbital in octahedral complexes?
What is the condition for the fourth electron to enter an eg orbital in octahedral complexes?
In octahedral complexes of the formula [MA3X3], when three donor atoms occupy adjacent positions, what is this form called?
In octahedral complexes of the formula [MA3X3], when three donor atoms occupy adjacent positions, what is this form called?
What type of orbital splitting is denoted by Δ in a crystal field?
What type of orbital splitting is denoted by Δ in a crystal field?
What is the result of optical isomerism in coordination compounds?
What is the result of optical isomerism in coordination compounds?
In octahedral complexes, how does the energy of the t2g set change relative to eg orbitals?
In octahedral complexes, how does the energy of the t2g set change relative to eg orbitals?
Which of the following ligands leads to low spin complexes due to pairing electrons?
Which of the following ligands leads to low spin complexes due to pairing electrons?
How are ligands arranged in the spectrochemical series?
How are ligands arranged in the spectrochemical series?
Which of the following correctly describes the coordination sphere?
Which of the following correctly describes the coordination sphere?
In a square planar complex of the type [MABXL], how many isomers can be formed?
In a square planar complex of the type [MABXL], how many isomers can be formed?
What defines the crystal field splitting energy in octahedral complexes?
What defines the crystal field splitting energy in octahedral complexes?
What primarily causes the color of coordination compounds?
What primarily causes the color of coordination compounds?
Which statement best describes the relationship between charge on the central metal atom and the stability of coordination complexes?
Which statement best describes the relationship between charge on the central metal atom and the stability of coordination complexes?
Which theory discusses the mixing of atomic orbitals to form molecular orbitals?
Which theory discusses the mixing of atomic orbitals to form molecular orbitals?
What factor does not influence the stability of coordination compounds?
What factor does not influence the stability of coordination compounds?
What is a limitation of Crystal Field Theory (CFT)?
What is a limitation of Crystal Field Theory (CFT)?
Which of the following applications relates to coordination compounds?
Which of the following applications relates to coordination compounds?
What is the definition of the stability constant (K) for coordination complexes?
What is the definition of the stability constant (K) for coordination complexes?
In terms of ligand strength, which of the following statements is true?
In terms of ligand strength, which of the following statements is true?
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Study Notes
Coordination Compounds
- Coordination compounds maintain their identity both in solid and dissolved states.
- Central metal atom or ion is linked to surrounding ions or molecules via coordinate bonds.
- Example: Potassium ferrocyanide, K₄[Fe(CN)₆].
Double Salts
- Double salts are stable in solid form but dissociate into constituent ions when dissolved.
- Example: Mohr’s salt, [FeSO₄·(NH₄)₂SO₄·6H₂O], dissociates into Fe²⁺, NH₄⁺, and SO₄²⁻ ions.
Key Terms Related to Coordination Compounds
-
Complex Ion (Coordination Entity): Charged species with a central atom/ion surrounded by ions or molecules.
- Cationic complex: Carries a positive charge. Example: [Pt(NH₃)₄]²⁺.
- Anionic complex: Carries a negative charge. Example: [Fe(CN)₆]⁴⁻.
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Central Atom/Ion: The atom/ion bound to ligands, often a transition element, referred to as a Lewis acid. Example: Ni in [NiCl₂(H₂O)₄].
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Ligands: Electron-donating species (ions/molecules) bound to the central atom.
- Types of ligands:
- Unidentate: One donor site (e.g., H₂O, NH₃).
- Didentate: Two donor sites.
- Polydentate: Multiple donor sites (e.g., [EDTA]⁴⁻).
- Ambidentate: Monodentate with two possible binding sites (e.g., NO₂⁻, SCN⁻).
- Chelating: Ligands forming rings around the metal ion, increasing stability via chelate effect.
- Types of ligands:
-
Coordination Number: Number of coordinate bonds formed by the central metal atom with ligands.
- For monodentate ligands, CN equals number of ligands.
- For polydentate ligands, CN equals number of ligands multiplied by denticity.
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Coordination Sphere: The central ion and its attached ligands, enclosed in square brackets; counter ions are outside the brackets.
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Coordination Polyhedron: Spatial arrangement of ligands around the central atom.
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Oxidation Number: Charge of the complex if all ligands and shared electrons are removed.
Types of Complexes
- Homoleptic Complexes: Linked to one type of donor atom (e.g., [Co(NH₃)₆]³⁺).
- Heteroleptic Complexes: Linked to multiple types of donor atoms (e.g., [Co(NH₃)₄Cl₂]⁺).
- Labile Complexes: Fast ligand substitution.
- Inert Complexes: Slow ligand substitution.
Effective Atomic Number (EAN)
- Proposed by Sidgwick: EAN of a metal equals total electrons:
EAN = Z - ON + 2 × CN
- Z: Atomic number, ON: Oxidation number.
IUPAC Naming of Complex Compounds
- Name comprises cation name followed by anion name (e.g., [Co(H₂O)₆]Cl₃).
Stereoisomerism
- Different spatial arrangements with the same formula.
- Geometrical Isomerism: cis and trans isomers.
- Occurs in coordination numbers 4 and 6.
- Optical Isomerism: Chiral structures with non-superimposable mirror images (enantiomers).
Bonding in Coordination Compounds
- Werner’s Theory: Distinction between primary (oxidation number, satisfied by anions) and secondary valencies (coordinate bonds).
- Crystal Field Theory: Describes electron distribution in split d-orbitals in response to ligand approach, creates energy separation.
- Octahedral Complexes: Higher energy in eg orbitals.
- Tetrahedral Complexes: Energy of t₂g > energy of eg.
Colour in Coordination Compounds
- Colour results from d-d electron transitions due to ligand interactions.
Limitations of Crystal Field Theory
- Fails to account for π bonding in complexes.
- Insufficient explanation for ligand strength comparison.
Ligand Field Theory
- Integrates atomic orbitals to form molecular orbitals, considering multiple nuclei interactions.
Stability of Coordination Compounds
- Stability constant (K) indicates complex stability.
- Stability depends on:
- Charge of the central atom (higher charge increases stability).
- Nature of metal ion (stability order: 3d < 4d < 5d).
- Basicity of ligands (strong field ligands yield stable complexes).
Importance and Applications
- Used in qualitative and quantitative analysis.
- EDTA titrations estimate water hardness.
- Metal purification via coordination compounds.
- Essential in biological systems.
- Catalysts in industrial processes.
- Growing interest in medicinal chemistry for chelating therapy.
Organometallic Compounds
- Contain metal-carbon bonds; classified into various types.
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