Textbook Question
Predict the crystal field energy-level diagram for a linear ML2 complex that has two ligands along the :
Ch.21 - Transition Elements and Coordination Chemistry
McMurry8th EditionChemistryISBN: 9781292336145
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Table of contents
- Ch.1 - Chemical Tools: Experimentation & Measurement170
- Ch.2 - Atoms, Molecules & Ions160
- Ch.3 - Mass Relationships in Chemical Reactions169
- Ch.4 - Reactions in Aqueous Solution199
- Ch.5 - Periodicity & Electronic Structure of Atoms102
- Ch.6 - Ionic Compounds: Periodic Trends and Bonding Theory92
- Ch.7 - Covalent Bonding and Electron-Dot Structures61
- Ch.8 - Covalent Compounds: Bonding Theories and Molecular Structure59
- Ch.9 - Thermochemistry: Chemical Energy122
- Ch.10 - Gases: Their Properties & Behavior155
- Ch.11 - Liquids & Phase Changes54
- Ch.12 - Solids and Solid-State Materials73
- Ch.13 - Solutions & Their Properties120
- Ch.14 - Chemical Kinetics98
- Ch.15 - Chemical Equilibrium125
- Ch.16 - Aqueous Equilibria: Acids & Bases110
- Ch.17 - Applications of Aqueous Equilibria147
- Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium86
- Ch.19 - Electrochemistry154
- Ch.20 - Nuclear Chemistry96
- Ch.21 - Transition Elements and Coordination Chemistry156
- Ch.22 - The Main Group Elements187
- Ch.23 - Organic and Biological Chemistry51
Chapter 21, Problem 21.9
What is the crystal field energy level diagram for the complex [Fe(NH3)6]3+?
(a)
(b)
(c)
(d)
Verified step by step guidance1
Identify the oxidation state and electron configuration of the metal ion. In this case, Fe in [Fe(NH3)6]3+ is in the +3 oxidation state. The electron configuration of Fe3+ is 3d5.
Determine the geometry of the complex. Ammonia (NH3) is a neutral ligand and typically forms octahedral complexes with transition metals. Thus, [Fe(NH3)6]3+ is an octahedral complex.
Understand the splitting of d-orbitals in an octahedral field. In an octahedral complex, the d-orbitals split into two groups due to the ligand field: t2g (lower energy) and eg (higher energy).
Distribute the electrons of Fe3+ in the split d-orbitals. Since Fe3+ has 5 electrons, these will occupy the t2g orbitals first (according to Hund's rule and the Pauli exclusion principle), resulting in three electrons in t2g and two remaining in t2g.
Sketch the crystal field energy level diagram based on the above information. The diagram should show the t2g orbitals fully occupied by five electrons and the eg orbitals empty, reflecting the electron configuration and energy levels in an octahedral field.
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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 the electronic structure of transition metal complexes by considering the effect of surrounding ligands on the d-orbitals of the metal ion. It describes how the degeneracy of d-orbitals is lifted due to the electrostatic interactions between the metal ion and the ligands, leading to different energy levels for the d-electrons.
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01:18
The study of ligand-metal interactions helped to form Ligand Field Theory which combines CFT with MO Theory.
Ligand Field Splitting
In a complex like [Fe(NH3)6]3+, the arrangement of ligands around the metal ion causes the d-orbitals to split into different energy levels. For octahedral complexes, the d-orbitals split into two sets: the lower-energy t2g orbitals and the higher-energy eg orbitals. The extent of this splitting is influenced by the nature of the ligands and the oxidation state of the metal.
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02:40Strong-Field Ligands result in a large Δ and Weak-Field Ligands result in a small Δ.
High Spin vs. Low Spin Complexes
High spin and low spin configurations refer to the arrangement of electrons in the d-orbitals of transition metal complexes. High spin complexes have unpaired electrons in higher energy orbitals, resulting from weak field ligands, while low spin complexes have paired electrons in lower energy orbitals due to strong field ligands. The spin state affects the magnetic properties and stability of the complex.
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01:28For octahedral complexes, Weak-Field Ligands create High-spin complexes and Strong-Field Ligands create Low-spin complexes.
Related Practice
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-
Textbook Question
Predict the number of unpaired electrons for each of the following.
(c) Zn2+
(d) Cr3+
Textbook Question
Based on the wavelength of maximum absorption of the cobalt complexes, arrange the following ligands in a spectrochemical series from weakest-field to strongest-field ligand.
(a) Cl- < NCS- < H2O < NH3
(b) Cl- < NCS- < H2O < NH3
(c) H2O < Cl- < NH3 < NCS-
(d) Cl- < H2O < NCS- < NH3
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.
(a) [CrF6]3-
(b) [V(H2O)6]3+
(c) [Fe(CN)6]3-
Textbook Question
What is the general trend in standard potentials for the oxidation of first-series transition metals from Sc to Zn? What is the reason for the trend?