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Ch.21 - Transition Elements and Coordination Chemistry
Chapter 21, Problem 21.114

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-

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1
Identify the oxidation state of the metal in each complex.
Determine the electron configuration of the metal ion in each complex.
Assess the ligand field strength: CN^- is a strong field ligand, NH_3 is a moderate field ligand, and F^- is a weak field ligand.
Apply crystal field theory to determine the electron distribution in the d-orbitals for each complex.
Identify if there are unpaired electrons in the d-orbitals, which would indicate paramagnetism.

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Key Concepts

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

Paramagnetism

Paramagnetism is a property of materials that have unpaired electrons, which causes them to be attracted to magnetic fields. In transition metal complexes, the presence of unpaired electrons in d-orbitals is a key factor in determining whether a complex is paramagnetic. The number of unpaired electrons can be influenced by the metal's oxidation state and the nature of the ligands surrounding it.
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Crystal Field Theory

Crystal Field Theory (CFT) explains how the arrangement of ligands around a central metal ion affects its electronic structure and properties. According to CFT, the interaction between the metal ion and the ligands leads to the splitting of d-orbitals into different energy levels. The extent of this splitting, influenced by the ligand's strength (strong field vs. weak field), determines the number of unpaired electrons and thus the magnetic properties of the complex.
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The study of ligand-metal interactions helped to form Ligand Field Theory which combines CFT with MO Theory.

Oxidation States of Transition Metals

The oxidation state of a transition metal in a complex is crucial for determining its electronic configuration and magnetic properties. Different oxidation states can lead to varying numbers of d-electrons, which directly affect the number of unpaired electrons. Understanding the oxidation states of the metals in the given complexes is essential for predicting whether they will exhibit paramagnetism or not.
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