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Questions and Answers

What is the primary role of a ligand in coordination chemistry?

To provide charge balance to the complex

To stabilize metal ions through ionic bonds

To donate an electron pair to a metal ion (correct)

To increase the solubility of metal ions

Which of the following ligands is classified as bidentate?

Chloride (Cl-)

Ethylenediamine (en) (correct)

Ammonia (NH3)

Cyanide (CN-)

How does the denticity of a ligand affect the stability of coordination complexes?

Denticity has no effect on the stability of the complex

Lower denticity increases stability by limiting binding sites

Higher denticity leads to weaker complexes due to steric hindrance

Higher denticity generally increases the stability of the complex (correct)

Which of the following statements about ligands is false?

Only neutral ligands can act as Lewis bases Signup and view all the answers

Which of the following ligands is a Lewis base?

Water (H2O) Signup and view all the answers

What type of interactions typically occur between a ligand and a metal ion?

Coordination or coordinate covalent interactions Signup and view all the answers

Which term describes ligands that are able to bind to a metal ion through multiple donor atoms?

Polydentate Signup and view all the answers

What distinguishes a tridentate ligand from other types of ligands?

It can donate three electron pairs to a metal ion Signup and view all the answers

What characterizes a chelating ligand in coordination chemistry?

It forms a stable compound by wrapping around the metal ion with multiple donor atoms. Signup and view all the answers

Which of the following statements correctly reflects the relationship between enthalpy and entropy changes in reaction favorability?

High positive ΔS can counteract a negative ΔH in determining reaction feasibility. Signup and view all the answers

In the context of the chelate effect, how do chelate complexes compare to non-chelate complexes?

The chelate effect explains why chelate complexes are typically more stable. Signup and view all the answers

Which of the following reactions would likely demonstrate the largest increase in entropy (ΔS)?

Formation of [Pt(trien)]2+ involving three different ligands. Signup and view all the answers

Which of the following statements accurately describes the trend of stability among the given complexes?

[Pt(trien)]2+ is more stable than [Pt(en)2]2+, which is in turn more stable than [Pt(NH3)4]2+. Signup and view all the answers

Which formula correctly indicates the donor atom in the thiocyanate complex [Cu(SCN)4]2-?

[Cu(SCN)4]2- indicates sulfur as the donor atom. Signup and view all the answers

How is a ligand denoted when specifying which donor atom is coordinating in ligands with multiple potential donor atoms?

By using the Greek symbol κ. Signup and view all the answers

What suffix is added to the name of a metal complex when it has an overall negative charge?

-ate Signup and view all the answers

Which of the following names corresponds to the complex [ZnCl4]2-?

tetrachloridozincate Signup and view all the answers

In the naming convention, what term is used for complexes where copper is involved when it is anionic?

Cuprate Signup and view all the answers

Which ligand is identified by the formula [Cu(NCS)4]2- when N is the donor atom?

N-thiocyanato Signup and view all the answers

Why is the term 'cuprate' utilized in complex naming conventions?

It is the Latin root of the element's name. Signup and view all the answers

What does the 'κ' symbol indicate in coordination chemistry?

The specific donor atom of a ligand. Signup and view all the answers

In coordination chemistry, what is the significance of writing the donor atom first in the formula of a ligand?

It clarifies which atom is coordinating without ambiguity. Signup and view all the answers

Which type of ligand has the ability to coordinate to a metal ion through only one donor atom at a time?

Monodentate ligand Signup and view all the answers

What type of chelate ring is formed by bidentate ligands when bonding with metal ions?

Five-membered ring Signup and view all the answers

Which of the following ligands is an example of a tridentate ligand?

Diethylenetriamine Signup and view all the answers

In coordination chemistry, which term is used to describe ligands with multiple donor atoms?

Polydentate Signup and view all the answers

Which factor contributes to chelating ligands forming more stable complexes compared to monodentate ligands?

Increased entropy Signup and view all the answers

What characteristic allows bidentate ligands to be symmetrical or asymmetrical?

Presence of donor atoms Signup and view all the answers

Which of the following ligands is particularly noted for its application in the extraction of metals?

EDTA Signup and view all the answers

Which ligands can not always act as chelating agents even though they are capable of doing so?

Bidentate ligands Signup and view all the answers

Which statement best describes polydentate ligands?

They contain multiple donor atoms that can coordinate simultaneously. Signup and view all the answers

What does the term 'chelate' refer to in relation to bidentate ligands?

Cycle formation of donor atoms and metal Signup and view all the answers

What is a key characteristic of EDTA as a ligand?

It can fill the coordination sphere of an octahedral metal on its own. Signup and view all the answers

Which of the following is an example of a macrocyclic ligand?

18-crown-6 Signup and view all the answers

How do bridging ligands function in coordination chemistry?

They simultaneously coordinate to multiple metals. Signup and view all the answers

What role do derivatives of porphyrins play in biological systems?

They transport O2 in mammals and assist in photosynthesis. Signup and view all the answers

Which of the following statements about aqua complexes is true?

They involve water molecules coordinating with metal ions. Signup and view all the answers

What is the primary feature of the ligand field theory?

It explains the spatial arrangement of ligands around a metal. Signup and view all the answers

What type of ligands are hydroxide and cyanide considered in coordination complexes?

They are both classified as bridging ligands. Signup and view all the answers

What distinguishes a hexadentate ligand from other ligands?

It has six donor atoms capable of chelating. Signup and view all the answers

What is a common characteristic of strong Lewis acids in coordination chemistry?

They strongly attract electron pairs towards themselves. Signup and view all the answers

Which of the following statements best describes the significance of ligands in coordination chemistry?

They play an active role in stabilizing metal ions. Signup and view all the answers

Study Notes

Introduction to Ligands

Ligands are molecules or ions that act as Lewis bases (electron pair donors)
Ligands contain donor atoms with lone pairs of electrons
Examples of ligands include:
- neutral molecules like water (H2O) or ammonia (NH3)
- anionic ligands like chloride (Cl-) or cyanide (CN-)
Ligands are classified by their denticity - the number of donor atoms that attach to a metal center
Monodentate ligands have one donor atom
Bidentate ligands have two donor atoms
Tridentate ligands have three donor atoms
Polydentate ligands have many donor atoms
Ethylenediaminetetraacetate (EDTA) is a common polydentate ligand used for metal extraction

Ligands with Multiple Potential Donor Atoms

Ligands can coordinate through different donor atoms
Thiocyanate (SCN-) can coordinate through sulfur or nitrogen
The donor atom is written first in the formula (e.g, [Cu(SCN)4]2- vs [Cu(NCS)4]2- )
Kappa notation (κ) denotes the donor atom in full names

Naming Anionic Complexes

Anionic metal complexes have the suffix "-ate"
[ZnCl4]2- is called tetrachloridozincate
Some elements use Latin roots in anionic complex names (e.g., cuprate)

Ligands and Coordination Complexes

First-row transition metals dissolve in water forming aqua complexes with water or hydroxide ligands
For example, NiCl2 + 6H2O → [Ni(OH2)6]2+ + 2Cl-
All metal ions are Lewis acids, but their strength varies
Strong Lewis acids (e.g., Fe3+, Ti3+) pull electron pairs strongly

Additional Information on Chelating Ligands

A multidentate ligand coordinating to a metal ion through more than one donor atom is called a chelating ligand
The resulting compound is a chelate complex
Chelate complexes are more stable than non-chelate complexes, this is known as the chelate effect
The chelate effect is due to favorable entropy changes (increase in disorder) during chelate complex formation

Activity 1: Coordination Complex

The workbook includes an activity regarding a simple coordination complex

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Description

This quiz covers the fundamentals of ligands, including their definitions, examples, and classifications by denticity. You will learn about monodentate, bidentate, tridentate, and polydentate ligands, along with their coordination mechanisms. Test your understanding of how ligands interact with metal centers and their significance in various chemical processes.