Ch 23_Transition Elements and Coordination Compounds.pdf

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Chapter 23 Transition Elements

and Coordination

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Electron Configurations

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Properties of Transition Elements

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Properties of Transition Elements

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Properties of Transition Elements

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Properties of Transition Elements

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Properties of Transition Elements

Ionization Energies and Oxidation Potentials

All but copper are positive.

M2+₍_aq_{) + H}

2(g)

M(s) + 2 H+₍_aq₎ _E° _{> 0 V}

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Practice

What is the electron configuration of Mo?

What is the electron configuration of V3+_?

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Oxidation States of Transition Elements

For group 8B, the loss or sharing of all the valence electrons is energetically prohibitive because of the increasing value of Z_eff. Consequently, only lower oxidation states are accessible. Also, they can sometimes be reduced to even lower oxidation

states:

4 Co2+₍_aq_{) + O}

2(g) + 4 H+(aq)

4 Co3+₍_aq_{) + 2 H}

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Chemistry of Selected Transition Elements

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Chemistry of Selected Transition Elements

Chromium

Cr(OH)₄−(aq) Cr(OH)₃(s) + OH−(aq)

Cr3+₍_aq_{) + 6 H}

2O(l)

Cr(OH)₃(s) + 3 H₃O+₍_l₎

• In basic solution, Cr3+ _{precipitates as Cr(OH)}

3, a pale

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Chemistry of Selected Transition Elements

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Chemistry of Selected Transition Elements

Chromium

Cr₂O₇2−(aq) + H₂O(l) 2 CrO₄2−(aq) + 2 H+₍_aq₎

• The orange dichromate ion is a powerful oxidizing agent in acidic solution and is widely used as an oxidant in

analytical chemistry:

orange yellow

• In the +6 oxidation state, the most important solution species are yellow chromate ion and the orange

dichromate ion:

2 Cr3+₍_aq_{) + 7 H}

2O(l)

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Chemistry of Selected Transition Elements

Iron

• In the presence of air, Fe2+ _{is slowly oxidized:}

4 Fe3+₍_aq_{) + 2 H}

2O(l)

4 Fe2+₍_aq_{) + O}

2(g) + 4 H+(aq)

Fe3+₍_aq_{) + e}−

Fe2+₍_aq₎

Fe2+₍_aq_{) + H}

2(g)

Fe(s) + 2 H+₍_aq₎

spontaneous

nonspontaneous

• In the absence of air, iron metal will react with acids:

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Chemistry of Selected Transition Elements

Iron

Fe(OH)₃(s) Fe3+₍_aq_{) + 3 OH}−₍_aq₎

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Chemistry of Selected Transition Elements

Copper

Cu₂(OH)₂SO₄(s) + CO₂(g) + H₂O(l) Cu₂(OH)₂CO₃(s) + H₂SO₄(aq)

• Over time, copper turns green due to oxidation: 2 Cu(l) + SO₂(g) Cu₂S(l) + O₂(g)

• Copper sulfides are separated from ores, and then hot air is blown through molten copper(I) sulfide (Cu₂S):

Cu₂(OH)₂CO₃(s) 2 Cu(s) + O₂(g) + CO₂(g) + H₂O(g)

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Chemistry of Selected Transition Elements

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Coordination Compounds

Coordination Compound: A compound in which a central metal ion or atom is attached to a group of surrounding

molecules or ions by coordinate covalent bonds.

Ligands: The ions or molecules that surround the central metal ion.

Ligand Donor Atom: The atoms in the ligand that attach directly to the metal.

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Ligands

Monodentate: Ligand using a single donor atom that bonds to the metal ion.

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Ligands

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Naming Coordination Compounds

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Naming Coordination Compounds

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Naming Coordination Compounds

3. If the complex contains more than one ligand of a

particular type, indicate the number with the appropriate Greek prefix. The ligands are listed in alphabetical order, and the prefixes are ignored in determining the order.

4. If the name of a ligand itself contains a Greek prefix, then put the ligand name in parentheses and use one of the following alternative prefixes to specify the number of ligands: bis− (2), tris− (3), tetrakis− (4), and so forth.

5. Use a Roman numeral in parentheses immediately

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Naming Coordination Compounds

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Practice

[Cr(NH₃)₃(H₂O)₃]Cl₃

triamminetriaquachromium(III) chloride

[Pt(NH₃)₅Cl]Br₃

pentaamminechloroplatinum(IV) bromide

[Pt(H₂NCH₂CH₂NH₂)₂Cl₂]Cl₂

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Isomers

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Isomers

Constitutional Isomers—Ionization Isomers

A free bromide ion. [Co(NH₃)₅SO₄]Br

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Isomers

Stereoisomers—Diastereoisomers

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Isomers

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Enantiomers and Molecular Handedness

Chiral: Objects that have a handedness to them. Nonidentical mirror images.

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Practice

Which one of the following complexes can exhibit geometrical isomerism?

(a) [Pt(NH₃)₂Cl₂] (square planar) (b) [Zn(NH₃)₂Cl₂] (tetrahedral) (c) [Cu(NH₃)₄]2+ _{(square planar)}

(d) [Co(NH₃)₅Cl]2+ _(octahedral)

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Color of Transition Metal Complexes

or

∆E hc λ =

∆E = E₂ − E₁ = hν =

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Low spin High spin

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Crystal Field Theory

Crystal Field Theory: A model that views the

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Crystal Field Theory

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Crystal Field Theory

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Crystal Field Theory

[Ni(X)₆]2+ _{X = H}

2O, NH3, and ethylenediamine (en) Octahedral Complexes

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Crystal Field Theory

Octahedral Complexes

The crystal field splitting changes according to the spectrochemical series.

[Ni(X)₆]2+ _{X = H}

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Crystal Field Theory

Octahedral Complexes

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Crystal Field Theory

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