Textbook Question
For each of the following complexes, draw a crystal field energy-level diagram, assign the electrons to orbitals, and predict the number of unpaired electrons.
(c) [Co(NCS)4]2- (tetrahedral)
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Ch.21 - Transition Elements and Coordination Chemistry
McMurry8th EditionChemistryISBN: 9781292336145
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Table of contents
- Ch.1 - Chemical Tools: Experimentation & Measurement143
- Ch.2 - Atoms, Molecules & Ions134
- Ch.3 - Mass Relationships in Chemical Reactions149
- Ch.4 - Reactions in Aqueous Solution157
- Ch.5 - Periodicity & Electronic Structure of Atoms92
- Ch.6 - Ionic Compounds: Periodic Trends and Bonding Theory73
- Ch.7 - Covalent Bonding and Electron-Dot Structures47
- Ch.8 - Covalent Compounds: Bonding Theories and Molecular Structure51
- Ch.9 - Thermochemistry: Chemical Energy104
- Ch.10 - Gases: Their Properties & Behavior138
- Ch.11 - Liquids & Phase Changes43
- Ch.12 - Solids and Solid-State Materials56
- Ch.13 - Solutions & Their Properties98
- Ch.14 - Chemical Kinetics79
- Ch.15 - Chemical Equilibrium107
- Ch.16 - Aqueous Equilibria: Acids & Bases94
- Ch.17 - Applications of Aqueous Equilibria125
- Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium66
- Ch.19 - Electrochemistry130
- Ch.20 - Nuclear Chemistry73
- Ch.21 - Transition Elements and Coordination Chemistry122
- Ch.22 - The Main Group Elements155
- Ch.23 - Organic and Biological Chemistry43
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McMurry 8th EditionCh.21 - Transition Elements and Coordination ChemistryProblem 21-113b
McMurry 8th EditionCh.21 - Transition Elements and Coordination ChemistryProblem 21-113bChapter 21, Problem 21-113b
For each of the following complexes, draw a crystal field energy-level diagram, assign the electrons to orbitals, and predict the number of unpaired electrons.
(b) [MnCl4]2- (tetrahedral)
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Identify the oxidation state and electron configuration of the metal ion. For Mn in [MnCl4]2-, the oxidation state of Mn is +2. The electron configuration of Mn2+ is [Ar] 3d5.
Understand the crystal field splitting in a tetrahedral complex. In tetrahedral complexes, the d orbitals split into two sets due to the approach of ligands along the axes between the x, y, and z axes. The lower energy set is the e orbitals (dxy, dxz, dyz), and the higher energy set is the t2 orbitals (dx^2-y^2, dz^2).
Distribute the electrons among the split d orbitals. Start filling the lower energy e orbitals first, following Hund's rule (maximize the number of unpaired electrons with parallel spins in degenerate orbitals).
Count the number of unpaired electrons. Since each of the three e orbitals will contain one electron and the two t2 orbitals will contain one electron each, all five electrons remain unpaired.
Predict the magnetic properties based on the number of unpaired electrons. A complex with five unpaired electrons, like [MnCl4]2-, is expected to be paramagnetic.
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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 a tetrahedral complex like [MnCl4]2-, the d-orbitals split into two sets: the lower energy e orbitals and the higher energy t2 orbitals. This splitting is crucial for determining the electronic configuration and magnetic properties of the complex.
Tetrahedral Coordination
In tetrahedral coordination, a central metal ion is surrounded by four ligands positioned at the corners of a tetrahedron. This geometry leads to a specific pattern of d-orbital splitting, where the t2 orbitals are lower in energy than the e orbitals. Understanding this geometry is essential for predicting the electron distribution and the resulting magnetic behavior of the complex.
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Unpaired Electrons and Magnetism
The presence of unpaired electrons in a complex determines its magnetic properties. In the case of [MnCl4]2-, after filling the d-orbitals according to Hund's rule and the Aufbau principle, the number of unpaired electrons can be counted. A higher number of unpaired electrons typically indicates a paramagnetic nature, while a complete pairing results in a diamagnetic complex.
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Related Practice
Textbook Question
For each of the following complexes, describe the bonding using valence bond theory. Include orbital diagrams for the free metal ion and the metal ion in the complex. Indicate which hybrid orbitals the metal ion uses for bonding, and specify the number of unpaired electrons.
(b) [Ag(NH3)2]+
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Textbook Question
Spinach contains a lot of iron but is not a good source of dietary iron because nearly all the iron is tied up in the oxalate complex [Fe(C2O4)3]3-.
(c) Draw a crystal field energy-level diagram for [Fe(C2O4)3]3-, and predict the number of unpaired electrons. (C2O42- is a weak-field bidentate ligand.)
107
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Textbook Question
Predict the number of unpaired electrons for each of the following.
(c) Mn3+
(d) Cr2+
98
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Textbook Question
Tell how many diastereoisomers are possible for each of the following complexes, and draw their structures.
(c) [Cu(H2O)4Cl2]+
(d) Ru(NH3)3I3
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Textbook Question
Give a valence bond description of the bonding in each of the following complexes. Include orbital diagrams for the free metal ion and the metal ion in the complex. Indicate which hybrid orbitals the metal ion uses for bonding, and specify the number of unpaired electrons.
(b) [NiBr4]2- (tetrahedral)
112
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