Alfred Werner and Coordination Chemistry
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Questions and Answers

What revolutionary theory did Alfred Werner develop?

The theory of coordination compounds.

In what years did Werner formulate his theory of coordination compounds?

From 1890 to 1893.

What is a coordination entity?

A coordination entity consists of a central metal atom or ion bonded to a fixed number of ions or molecules.

Who was the first Swiss chemist to win the Nobel Prize, and for what work?

<p>Alfred Werner won the Nobel Prize for his work on the linkage of atoms and coordination theory.</p> Signup and view all the answers

What is referred to as the central atom or ion in a coordination entity?

<p>The central atom or ion is the one to which a fixed number of ions/groups are bound.</p> Signup and view all the answers

Give an example of a coordination entity.

<p>[Ni(CO)4] is an example of a coordination entity.</p> Signup and view all the answers

What are ligands in the context of coordination compounds?

<p>Ligands are the ions or molecules bound to the central atom or ion in a coordination entity.</p> Signup and view all the answers

What role do central atoms/ions play in coordination compounds?

<p>Central atoms/ions act as Lewis acids in coordination compounds.</p> Signup and view all the answers

How is the position of an abbreviated ligand determined in the alphabetical order?

<p>The first letter of the abbreviation is used to determine its position in the alphabetical order.</p> Signup and view all the answers

What is the proper way to write the formula for a coordination entity?

<p>The entire formula is enclosed in square brackets and ligands are enclosed in parentheses.</p> Signup and view all the answers

What should you ensure when writing the formula of a charged coordination entity?

<p>The charge is indicated outside the square brackets as a right superscript.</p> Signup and view all the answers

In what order are ligands named when creating the names of coordination compounds?

<p>Ligands are named in alphabetical order before the name of the central atom/ion.</p> Signup and view all the answers

What is the naming convention for anionic ligands in coordination compounds?

<p>Anionic ligands end in '–o'.</p> Signup and view all the answers

Which ligands have special names instead of the usual naming conventions?

<p>Neutral and cationic ligands that are called aqua, ammine, carbonyl, and nitrosyl have special names.</p> Signup and view all the answers

What ensures there is no space between the ligands and the metal in a coordination sphere?

<p>There should be no space between the ligands and the metal within a coordination sphere.</p> Signup and view all the answers

How do you determine the charge balance in coordination entities?

<p>The charge of the cation(s) is balanced by the charge of the anion(s).</p> Signup and view all the answers

What type of hybridisation occurs in a tetrahedral complex with four coordination numbers?

<p>sp3</p> Signup and view all the answers

Which hybridisation leads to a square planar geometry?

<p>dsp</p> Signup and view all the answers

Identify the hybridisation associated with a trigonal bipyramidal arrangement.

<p>sp3d</p> Signup and view all the answers

What hybridisation corresponds to octahedral complexes?

<p>sp3d2 or dsp2</p> Signup and view all the answers

How can the geometry of a complex be predicted?

<p>By knowing its magnetic behaviour and applying valence bond theory.</p> Signup and view all the answers

What is the oxidation state of cobalt in the diamagnetic complex [Co(NH3)6]?

<p>+3</p> Signup and view all the answers

What electron configuration does cobalt have in the complex [Co(NH3)6]3+?

<p>3d6</p> Signup and view all the answers

Why is it significant for hybridised orbitals to overlap with ligand orbitals?

<p>It allows for the formation of sigma bonds through the donation of electron pairs.</p> Signup and view all the answers

Why is geometrical isomerism not possible in tetrahedral complexes?

<p>Geometrical isomerism is not possible in tetrahedral complexes because the relative positions of the unidentate ligands coordinated with the central metal atom remain the same with respect to each other.</p> Signup and view all the answers

What are optical isomers?

<p>Optical isomers are molecules or ions that are mirror images of each other and cannot be superimposed, known as enantiomers.</p> Signup and view all the answers

What distinguishes dextro and laevo optical isomers?

<p>Dextro (d) optical isomers rotate plane-polarized light to the right, while laevo (l) optical isomers rotate it to the left.</p> Signup and view all the answers

In which type of complexes is optical isomerism more common?

<p>Optical isomerism is more common in octahedral complexes involving didentate ligands.</p> Signup and view all the answers

What type of isomerism does the coordination entity [PtCl2(en)2] exhibit?

<p>The coordination entity [PtCl2(en)2] exhibits optical activity only in its cis-isomer.</p> Signup and view all the answers

How are chiral molecules related to optical isomerism?

<p>Chiral molecules cannot be superimposed on their mirror images, leading to the formation of optical isomers.</p> Signup and view all the answers

Can tetrahedral complexes have optical isomers?

<p>No, tetrahedral complexes typically do not have optical isomers due to their symmetrical arrangement.</p> Signup and view all the answers

What are the two forms of optical isomers based on their optical activity?

<p>The two forms of optical isomers are called dextro (d) and laevo (l).</p> Signup and view all the answers

What is the molar ratio of ethane-1,2-diamine to nickel(II) that produces the complex [Ni(H2O)4(en)]?

<p>1:1</p> Signup and view all the answers

What color change occurs when [Ni(H2O)6]2+ reacts with ethane-1,2-diamine?

<p>The color changes from green to pale blue.</p> Signup and view all the answers

What is the final complex formed when excess ethane-1,2-diamine is added to [Ni(H2O)2(en)2]?

<p>[Ni(en)3]2+</p> Signup and view all the answers

What is the apparent color of the complex [Ni(H2O)2(en)2]?

<p>Blue/purple</p> Signup and view all the answers

Which transition metal ion is responsible for the red color of ruby?

<p>Chromium (Cr3+)</p> Signup and view all the answers

What characteristic does chromium(III) have in relation to its position in the alumina lattice of ruby?

<p>Cr3+ ions occupy positions normally occupied by Al.</p> Signup and view all the answers

What mineral do chromium(III) ions occupy to form emerald?

<p>Beryl (Be3Al2Si6O18)</p> Signup and view all the answers

What type of transitions give rise to the colors observed in transition metal complexes?

<p>d–d transitions.</p> Signup and view all the answers

Study Notes

Alfred Werner and Coordination Chemistry

  • Alfred Werner developed the coordination theory in 1890-1893.
  • Werner was the first Swiss chemist to win the Nobel Prize (1913) for his work.

Key Terms in Coordination Chemistry

  • A coordination entity consists of a central metal atom or ion bonded to a fixed number of atoms, ions, or molecules.
    • Example: [CoCl3(NH3)3]
  • The central atom/ion is the atom/ion to which ligands are bound.
    • Examples: Ni in [NiCl2(H2O)4], Co in [CoCl(NH3)5], Fe in [Fe(CN)6]
  • Ligands are the ions or molecules bound to the central atom/ion.
    • Examples: Cl-, H2O, NH3, H2NCH2CH2NH2, N(CH2CH2NH2)3, proteins
  • The entire coordination entity's formula is enclosed in square brackets.

Naming Coordination Compounds

  • Cation is named first.
  • Ligands are named alphabetically, followed by the central atom/ion.
  • Anionic ligands end in -o, while neutral and cationic ligands have the same name except for:
    • aqua (H2O)
    • ammine (NH3)
    • carbonyl (CO)
    • nitrosyl (NO)

Geometric Isomerism

  • Tetrahedral complexes do not show geometric isomerism.
  • The relative positions of the unidentate ligands are the same.

Optical Isomerism

  • Optical isomers are non-superimposable mirror images, also called enantiomers.
  • Chiral molecules or ions cannot be superimposed.
  • Dextro (d) and laevo (l) forms rotate the plane of polarized light in a polarimeter.
    • d rotates to the right.
    • l rotates to the left.
  • Optical isomerism is common in octahedral complexes with didentate ligands.
    • Example: [Co(en)3]3+, where en = ethane-1,2-diamine

Valence Bond Theory and Hybridization

  • Hybridization allows for the overlap of metal orbitals with ligand orbitals that can donate electron pairs.
  • Coordination number and hybridization type determine the geometry:
    • 4: sp3 (tetrahedral), dsp2 (square planar)
    • 5: sp3d (trigonal bipyramidal)
    • 6: sp3d2 (octahedral), d2sp3 (octahedral)

Examples of Coordination Compounds and their Properties

  • [Co(NH3)6]3+:
    • Octahedral geometry
    • Diamagnetic
    • Cobalt(III) ion has a 3d6 configuration.
  • [Ni(H2O)6]2+, [Ni(H2O)4(en)]2+, [Ni(H2O)2(en)2]2+, [Ni(en)3]2+:
    • Show a series of color changes as the number of ethane-1,2-diamine (en) ligands increases.
    • Illustrate the effect of ligand exchange on color.

Color in Coordination Complexes

  • The color of coordination complexes is due to electronic transitions within the d orbitals of the transition metal ion.
  • Gemstones like ruby and emerald get their colors from the presence of transition metal ions in their crystal structures.
    • Ruby: Al2O3 with Cr3+ ions.
    • Emerald: Be3Al2Si6O18 with Cr3+ ions.

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Description

Explore the pioneering work of Alfred Werner in coordination chemistry. This quiz covers key terms, naming conventions, and the structural aspects of coordination entities. Test your understanding of ligands, central atoms, and the overall chemistry involved.

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