Coordination Compounds and Ligands Quiz

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Questions and Answers

What is the term for additional bonding species that bond with a metal cation?

  • Covalents
  • Coordination bodies
  • Ligands (correct)
  • Anions

Which type of ligands typically results in the most stable coordination complexes?

  • Anionic or molecular ligands (correct)
  • Hydrophobic molecules
  • Metal cations
  • Neutral atoms

What characteristic of ligands allows them to form coordinate covalent bonds with metal ions?

  • Possession of at least one nonbonded pair of electrons (correct)
  • Presence of a positive charge
  • Formation of ionic bonds
  • Low electronegativity

When polydentate ligands form a complex with a metal ion, what do the resulting structures commonly refer to?

<p>Chelates (A)</p> Signup and view all the answers

What is the most common range of total atoms that makes chelates more stable?

<p>Five to seven (B)</p> Signup and view all the answers

What purpose do sequestering agents serve in chemical applications?

<p>To stabilize metal ions through chelation (D)</p> Signup and view all the answers

Which of the following types of ligands only has one position capable of coordinating with a metal?

<p>Monodentate ligands (D)</p> Signup and view all the answers

What is NOT a property of ligands as mentioned?

<p>They are always charged species (B)</p> Signup and view all the answers

Which heavy metal poisoning is primarily treated with calcium disodium edetate?

<p>Lead (D)</p> Signup and view all the answers

What is the pH range of an aqueous solution of calcium disodium edetate?

<p>6.5 to 8.0 (B)</p> Signup and view all the answers

What is a significant side effect of the disodium calcium form of edetate?

<p>Hypocalcemia (A)</p> Signup and view all the answers

What route of administration is typically used for calcium disodium edetate?

<p>Intravenous (A)</p> Signup and view all the answers

Which of the following metals is not treated by calcium disodium edetate?

<p>Mercury (D)</p> Signup and view all the answers

What is the main use for disodium edetate?

<p>Condition related to hypercalcemia (C)</p> Signup and view all the answers

What characteristic does the compound dimercaprol (BAL) possess?

<p>Colorless with a disagreeable odor (A)</p> Signup and view all the answers

Which of the following statements about chelating agents is true?

<p>They can treat poisoning from various heavy metals. (D)</p> Signup and view all the answers

What type of hybridization occurs when Cr(III) complexes with six CN- ligands in the formation of [Cr(CN)6]-3?

<p>d2sp3 hybridization (B)</p> Signup and view all the answers

Which orbital remains empty when a d3 Cr(III) ion complexes with six cyanato groups?

<p>d x2-y2 and d z2 (D)</p> Signup and view all the answers

What characteristic of the magnetic moment (MM) indicates the number of unpaired electrons in a complex?

<p>It reflects the unpairedness of electrons in the d orbitals. (C)</p> Signup and view all the answers

How does the replacement of water with cyanato anions affect the magnetic moment of an Fe(III) complex?

<p>It decreases the magnetic moment to about 2. (D)</p> Signup and view all the answers

What role do chelating agents play in analytical chemistry?

<p>They stabilize the oxidation state of metals and enhance titration accuracy. (D)</p> Signup and view all the answers

Which chelating agent is found in Benedict's solution for the identification of reducing substances?

<p>Citric acid (B)</p> Signup and view all the answers

In drug therapy, chelating agents are primarily used for which purpose?

<p>To remove trace quantities of undesirable metals. (D)</p> Signup and view all the answers

What change in electronic configuration occurs in metal ions with four or more d electrons when complexing?

<p>They undergo hybridization to facilitate bonding. (A)</p> Signup and view all the answers

What is the usual route of administration for Dimercaprol?

<p>Intramuscular (B)</p> Signup and view all the answers

Which heavy metals are contraindicated for treatment with Dimercaprol?

<p>Iron and cadmium (C)</p> Signup and view all the answers

What is the primary medical use of Penicillamine?

<p>Increasing copper excretion in Wilson’s disease (C)</p> Signup and view all the answers

Which statement accurately describes Penicillamine?

<p>It is a chelating agent that forms complexes with several metals. (B)</p> Signup and view all the answers

What is the solubility characteristic of Deferoxamine Mesylate?

<p>Freely soluble in water (B)</p> Signup and view all the answers

Why is urine alkalinization recommended during treatment with Dimercaprol?

<p>To prevent dissociation of metal chelates in acid media (B)</p> Signup and view all the answers

What distinguishes Penicillamine from other chelating agents discussed?

<p>It lacks a hydrogen on the beta-carbon atom. (C)</p> Signup and view all the answers

The effective neutralizing mechanism of Dimercaprol primarily involves:

<p>Competing with enzymes for metal binding. (D)</p> Signup and view all the answers

Flashcards

Coordination Compound

A compound formed when a metal cation bonds with additional anions or neutral molecules beyond its normal valence requirements.

Ligand

The additional anions or neutral molecules that bond to the metal cation in a coordination compound.

Maximum Coordination Number

The maximum number of ligands a metal ion can accommodate in a coordination compound.

Chelate

A ring structure formed when a polydentate ligand complexes a metal ion.

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Polydentate Ligand

A ligand having multiple bonding sites to coordinate with a metal ion.

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Chelating Agent

A polydentate ligand used to form a chelate.

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Sequestering Agent

A polydentate ligand used to improve solubility and stabilize a metal ion by chelation.

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Coordinate Covalent Bond

A bond where both electrons in the shared pair come from the same atom.

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Monodentate

A ligand with one binding site.

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Bidentate

A ligand with two binding sites.

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EDTA (Calcium Disodium Edetate)

A chelating agent used to treat heavy metal poisoning by forming insoluble complexes excreted by the kidneys, particularly effective against lead poisoning.

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EDTA (Calcium Disodium Edetate) - Disodium Form

A chelating agent used primarily for hypercalcemia (high calcium) treatment, used in high calcium blood conditions. Also used to treat other related conditions, but not for mercury, arsenic, or gold poisoning.

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Lead Poisoning Treatment

EDTA is a crucial chelating agent for lead poisoning treatment, aiding lead excretion.

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Chelating Agent

A specific type of molecule that binds to metal ions, often used for treating metal poisoning.

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Dimercaprol (BAL)

A chelating agent, primarily used for treating mercury poisoning. It is given in solution form.

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Metal Poisoning Diagnosis

Increased metal excretion measurement (in the urine) can indicate an existing heavy metal poisoning.

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Intravenous Injection

A method of administering a substance directly into a vein.

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d2sp3 hybridization

Six bonding orbitals directed along axes occupied by ligands, formed by combining (n-1)d, ns, and np orbitals in a complex.

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Cr(III) complex [Cr(CN)6]-3

Chromium(III) ion (d3 configuration) complexes with six cyanide ions, using empty d, s, and p orbitals for bonding.

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Magnetic Moment (MM)

A measure of unpaired electrons in a complex, useful to understand its ground state configuration.

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Fe(III) complex with water

Iron(III) complex with water ligands (d5 configuration) has a magnetic moment (MM) of 6, indicative of 5 unpaired electrons.

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Fe(III) complex with CN-

Iron(III) complex with cyanide ligands has a different magnetic moment (MM of ~2) due to electron pairing caused by the ligands' strong repelling effect.

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Outer orbital hybridization

Electrons are promoted to empty d orbitals using higher energy orbitals in certain complex ions (e.g., d orbitals in Fe3+ complex using 4s and 4p).

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Chelating agents

Molecules that bond to metal ions at multiple points, forming stable complexes and influencing metal ions' behavior.

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Analytical Chemistry (complexes)

Complexation is used to determine metal concentrations via titration with complexing agents.

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Chelating agents (Preservation)

Preserve substances by preventing metal-catalyzed decomposition reactions. Examples: Stabilizing or solubilizing metals.

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Chelating agents (drug therapy)

Chelating agents play a significant role in drug therapy for various applications.

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DIMERCAPROL, use

A chelating agent used to treat arsenic, mercury, and gold poisoning.

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DIMERCAPROL, contraindication

Should not be used for iron, cadmium, or selenium poisoning due to increased renal toxicity.

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DIMERCAPROL, administration

Administered intramuscularly.

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PENICILLAMINE, use

Used for copper excretion in Wilson's disease and gold dermatitis.

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PENICILLAMINE, solubility

Freely soluble in water; slightly soluble in alcohol.

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PENICILLAMINE, administration

Administered orally.

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DEFEROXAMINE MESYLATE, form

Lyophilized (freeze-dried) white crystalline powder.

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DEFEROXAMINE MESYLATE, solubility

Soluble in water and stable in aqueous solution for 2 weeks.

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Chelating Agents

Substances that form complexes with metals.

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Renal Toxicity

Harmful effects on the kidneys.

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Study Notes

Coordination Compounds and Complexation

  • Cations can bond with additional anions or neutral molecules after fulfilling their initial valence requirements
  • These additional bonding species are called ligands
  • Ligands bond directly to the metal cation, following a maximum coordination number
  • The maximum coordination number represents the maximum number of ligands a metal ion can accommodate; it's a property of the metal and its charge.
  • Coordination numbers for various metal ions are presented in a table.

Properties of Ligands

  • Ligands are typically anions or neutral molecules, not neutral atoms
  • Ligands possess at least one nonbonded electron pair, used to form a coordinate covalent bond with the metal ion
  • More stable complexes form with anionic or molecular ligands from Groups VA, VIA, or VIIA
  • The stability order of ligands often parallels their basicity (Lewis base)
  • Ligands can be classified based on the number of positions they can coordinate with a metal (e.g., monodentate, bidentate).

Some Common Polydentate Ligands

  • Tables list several examples of polydentate ligands (e.g. Ethylenediamine, Glycinate, Oxalate).

Chelate Formation

  • Polydentate ligands form ring structures called chelates when complexing a metal ion
  • More stable chelates generally contain 5, 6, or 7 atoms in the ring
  • Four and eight-membered rings are typically unstable

Complexes and Chelating Agents

  • Complexation is used in analytical chemistry, enabling metal ion concentration determination by titration with complexing agents
  • Chelating agents can solubilize metals, stabilizing their oxidation state
  • Examples include Benedict's and Fehling's solutions (containing chelated copper(II) ions)
  • Chelating agents are used as preservatives for preparations that might decompose due to trace metal contaminants (especially those containing hydrogen peroxide).

Bonding in Complexes

  • (n-1)d, ns, and np orbitals often hybridize into six bonding orbitals, oriented along the ligand axes.
  • This hybridization, often d2sp3, is equivalent when six ligands are equivalent.
  • If a metal ion has four or more d electrons, the configuration changes during complexation, as can be measured by magnetic moment (MM).

Specific Chelating Agents

  • Calcium Disodium Edetate (EDTA): Used to treat lead poisoning and other heavy metal poisonings; poorly absorbed from the gastrointestinal tract, administered intravenously. It has an affinity for calcium, and it forms stable water-soluble octahedral complexes with ferric ions.
  • Dimercaprol (BAL): Used in arsenic, mercury, or gold poisoning. Poorly absorbed from the gastrointestinal tract and administered intramuscularly. Requires alkalinization of urine
  • Penicillamine: Used in the treatment of Wilson's disease (copper buildup) and gold dermatitis. Administrated orally.
  • Deferoxamine Mesylate: Used to treat acute iron toxicity. Administered intravenously; poorly absorbed from gastrointestinal tract

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Coordination Compounds & Complexation (Lecture Notes) PDF

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