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Ch.21 - Transition Elements and Coordination Chemistry
McMurry - Chemistry 8th Edition
McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook
All textbooksMcMurry 8th EditionCh.21 - Transition Elements and Coordination ChemistryProblem 21.102
Chapter 21, Problem 21.102

Draw a crystal field energy-level diagram for the 3d orbitals of titanium in [Ti(H2O)6]3+]. Indicate the crystal field splitting, and explain why is [Ti(H2O)6]3+] colored.

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Identify the oxidation state of titanium in [Ti(H_2O)_6]^{3+}. Since the complex has a 3+ charge and water is a neutral ligand, titanium must be in the +3 oxidation state.
Determine the electron configuration of the Ti^{3+} ion. Titanium in its elemental form has the electron configuration [Ar] 3d^2 4s^2. When it loses three electrons to form Ti^{3+}, the configuration becomes [Ar] 3d^1.
Draw the crystal field energy-level diagram for the 3d orbitals. In an octahedral field, the 3d orbitals split into two sets: the lower-energy t_{2g} set (d_{xy}, d_{xz}, d_{yz}) and the higher-energy e_g set (d_{x^2-y^2}, d_{z^2}).
Place the single 3d electron of Ti^{3+} in one of the t_{2g} orbitals, as these are lower in energy compared to the e_g orbitals.
Explain the color of [Ti(H_2O)_6]^{3+}. The complex is colored because the electron in the t_{2g} level can absorb visible light to be promoted to the e_g level, resulting in a d-d transition. The specific wavelength of light absorbed corresponds to the energy difference between these levels, which is perceived as color.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Crystal Field Theory

Crystal Field Theory (CFT) explains how the arrangement of ligands around a central metal ion affects the energy levels of its d orbitals. In an octahedral complex like [Ti(H2O)6]3+, the d orbitals split into two sets: the lower-energy t2g and the higher-energy eg orbitals. This splitting occurs due to the electrostatic interactions between the negatively charged ligands and the positively charged metal ion.
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The study of ligand-metal interactions helped to form Ligand Field Theory which combines CFT with MO Theory.

Crystal Field Splitting Energy (Δ)

Crystal Field Splitting Energy (Δ) is the energy difference between the split d orbital sets in a coordination complex. The magnitude of Δ influences the electronic transitions of the metal ion, which in turn affects the color observed in the complex. A larger Δ typically results in different colors due to the specific wavelengths of light absorbed during these transitions.
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The crystal field splitting pattern for octahedral complexes has the d orbitals on or along the axes as having the higher energy.

Color in Transition Metal Complexes

The color of transition metal complexes, such as [Ti(H2O)6]3+, arises from the absorption of specific wavelengths of light that promote electrons from the lower-energy t2g orbitals to the higher-energy eg orbitals. The color observed is complementary to the color of light absorbed. For example, if the complex absorbs light in the red region, it will appear green, as green is the complementary color to red.
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Transition Metals
Related Practice
Textbook Question

Which of the following complexes are paramagnetic?

(a) [Mn(CN)6]3-

(b) [Zn(NH3)4]2+ (tetrahedral)

(c) [Fe(CN)6]4-

(d) [FeF6]4-

101
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Textbook Question

The glycinate anion, gly-= NH2CH2CO2 -, bonds to metal ions through the N atom and one of the O atoms. Using to represent gly-, sketch the structures of the four stereoisomers of Co(gly)3.

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Textbook Question

What is the oxidation state of the metal in each of the complexes?

a. [Ni(CN)5]3–

b. Ni(CO)4

c. [Co(en)2(H2O)Br]2+

d. [Cu(H2O)2(C2O4)2]2–

e. Co(NH3)3(NO2)3

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Textbook Question

Draw the three possible diastereoisomers of the triethylenetetramine complex [Co(trend)Cl2]+. Abbreviate the flexible tetradentate trien ligand H2NCH2CH2NHCH2CH2NHCH2CH2NH2 as . Which of the isomers can exist as a pair of enantiomers?

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Textbook Question

Draw all possible diastereoisomers of [Cr(C2O4)2(H2O)2]-. Which can exist as a pair of enantiomers?

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Textbook Question

Which of the following complexes can exist as diastereoisomers?

 

(a) [Cr(NH3)2Cl4]-

(b) [Co(NH3)5Br]2+

(c) [MnCl2Br2]2- (tetrahedral)

(d) [Pt(NH3)2Br2]2-

89
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