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Questions and Answers
What type of bond does a metal-ligand bond represent?
What type of bond does a metal-ligand bond represent?
- Coordinate covalent bond (correct)
- Hydrogen bond
- Ionic bond
- Van der Waals bond
Which term describes a ligand that forms only one bond to a metal ion?
Which term describes a ligand that forms only one bond to a metal ion?
- Chelating
- Monodentate (correct)
- Bidentate
- Polydentate
How many bonds can a bidentate ligand form with a metal ion?
How many bonds can a bidentate ligand form with a metal ion?
- At least three bonds
- More than two bonds
- Two bonds (correct)
- One bond
What are coordination compounds containing polydentate ligands called?
What are coordination compounds containing polydentate ligands called?
According to Werner's theory, what are the two types of valencies that metals possess?
According to Werner's theory, what are the two types of valencies that metals possess?
What do ligands that satisfy the secondary valencies in coordination compounds do?
What do ligands that satisfy the secondary valencies in coordination compounds do?
Which of the following is an example of a polydentate ligand?
Which of the following is an example of a polydentate ligand?
What role do phosphates play in hard water treatment?
What role do phosphates play in hard water treatment?
What does the η value of a ligand indicate about its bonding mode with a metal center?
What does the η value of a ligand indicate about its bonding mode with a metal center?
In the context of hapticity, what is true for odd η values of carbon ligands?
In the context of hapticity, what is true for odd η values of carbon ligands?
Which of the following statements correctly describes σ-bonded organometallic compounds?
Which of the following statements correctly describes σ-bonded organometallic compounds?
What is the typical electron donation by a neutral ligand with an even η value?
What is the typical electron donation by a neutral ligand with an even η value?
Which class of organometallic compounds possesses both σ and π bonding?
Which class of organometallic compounds possesses both σ and π bonding?
How are the stability and reactivity of organometallic compounds influenced?
How are the stability and reactivity of organometallic compounds influenced?
What characterizes pi (π) bonded organometallic compounds?
What characterizes pi (π) bonded organometallic compounds?
Which ligands typically utilize the ionic method of electron counting?
Which ligands typically utilize the ionic method of electron counting?
What does crystal field theory primarily suggest about bonding in metal-ligand complexes?
What does crystal field theory primarily suggest about bonding in metal-ligand complexes?
Which factor primarily determines the splitting of d-orbitals in crystal field theory?
Which factor primarily determines the splitting of d-orbitals in crystal field theory?
In which scenario would you expect to see a smaller degree of crystal field splitting in d-orbitals?
In which scenario would you expect to see a smaller degree of crystal field splitting in d-orbitals?
What does the term 'crystal field splitting energy' refer to?
What does the term 'crystal field splitting energy' refer to?
Which type of ligand typically causes a larger splitting of the d-orbitals in complexes?
Which type of ligand typically causes a larger splitting of the d-orbitals in complexes?
What is the primary type of interaction between the ligands and the metal ion in crystal field theory?
What is the primary type of interaction between the ligands and the metal ion in crystal field theory?
Which of the following best describes a high-spin configuration in d4 to d7 metal ions?
Which of the following best describes a high-spin configuration in d4 to d7 metal ions?
What can be inferred about the stability of organometallic compounds in relation to ligands?
What can be inferred about the stability of organometallic compounds in relation to ligands?
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Study Notes
Hapticity and Ligand Bonding
- Hapticity refers to the mode of bonding between a ligand and a metal center.
- For η5-cyclopentadienyl (Cp) ligand, all five carbons engage in bonding with the transition metal.
- Odd ηx values for carbon ligands generally indicate anionic forms (e.g., η5-Cp, η1-CH3, η1-allyl).
- Electron donation from ligands is often calculated as x + 1 for odd ηx values.
- Even ηx values characterize neutral carbon π-system ligands (e.g., η6-C6H6, η2-CH2=CH2).
- In neutral cases, electron donation equals x for even ηx values.
Classification of Organometallic Compounds
- Sigma (σ) bonded compounds involve a direct sigma bond between metal and carbon (e.g., Grignard reagents, zinc compounds).
- Dimeric compound Al2(CH3)6 resembles diborane (B2H6) and is electron deficient.
- Pi (π) bonded compounds involve bonding with π-electrons from alkenes, alkynes, and aromatic compounds (e.g., Zeise’s salt, ferrocene, dibenzene chromium).
- Sigma and π-bonded organometallic compounds, such as metal carbonyls, involve both types of bonding.
Chelating Agents
- Chelates are coordination compounds with polydentate ligands form multiple bonds to a metal without excessive strain.
- Ethylenediamine is an example of a polydentate ligand forming chelates.
- Biomolecules like heme and chlorophyll are porphyrins, showcasing important chelating functions.
- Phosphates complex with Ca²⁺ and Mg²⁺ in hard water to enhance detergent effectiveness.
Werner Coordination Theory
- Proposed by Alfred Werner in 1892 to explain formation of complex compounds.
- Metals have primary (ionizable) and secondary (non-ionizable) valencies.
- Coordination involves satisfying both valencies; secondary valencies bond directionally, imparting specific geometry.
Crystal Field Theory (CFT)
- CFT describes the electronic structure through an ionic model, treating ligands as point charges.
- Bonding occurs purely through electrostatic interactions without orbital hybridization.
- Ligand attachment causes splitting of d-orbitals; different energies arise, grouping into sets (e.g., e_g and t_2g).
- In octahedral complexes, two key electrostatic interactions exist: attraction between the positive metal ion and negative ligands, and repulsion between lone pairs in ligands and d-orbital electrons.
High- and Low-Spin Complexes
- High-spin complexes often result from weak-field ligands leading to lesser splitting of d-orbitals.
- Low-spin complexes arise from strong-field ligands which cause significant d-orbital energy splitting.
- The energy difference due to crystal field splitting can be quantified through UV-Vis spectroscopy.
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