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Identify each of the following coordination complexes as either diamagnetic or paramagnetic: (a) \(\left.\left[\mathrm{ZnBr}_{4}\right)\right]^{2-}\) (b) \(\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\) (c) \(\mathrm{OsO}_{4}\) (d) \(\left[\mathrm{PtCl}_{4}\right]^{2-}\)

Short Answer

Expert verified
The following coordination complexes can be classified as: (a) \(\left[\mathrm{ZnBr}_{4}\right]^{2-}\) is diamagnetic. (b) \(\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\) is paramagnetic. (c) \(\mathrm{OsO}_{4}\) is diamagnetic. (d) \(\left[\mathrm{PtCl}_{4}\right]^{2-}\) is diamagnetic.

Step by step solution

01

(a) Analyzing \(\left[\mathrm{ZnBr}_{4}\right]^{2-}\)

First, we'll determine the oxidation state of Zn in the complex. Since the complex has a -2 charge, and each Br ion has a -1 charge, the oxidation state of Zn must be +2. The electron configuration of Zn in its +2 oxidation state (Zn虏鈦) is: \[1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10}\] As all the d-orbitals are completely filled, there are no unpaired electrons, and therefore, the complex is diamagnetic.
02

(b) Analyzing \(\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\)

Next, we'll find the oxidation state of Mn in this complex. As each H鈧侽 ligand has a neutral charge, the oxidation state of Mn must be +3. The electron configuration of Mn in its +3 oxidation state (Mn鲁鈦) is: \[1s^2 2s^2 2p^6 3s^2 3p^6 3d^4\] There are four unpaired electrons in the 3d orbitals. Therefore, the complex is paramagnetic.
03

(c) Analyzing \(\mathrm{OsO}_{4}\)

To find the oxidation state of Os in OsO鈧, note that each O atom has a charge of -2 and the complex has a neutral charge. Thus, the oxidation state of Os must be +8. The electron configuration of Os in its +8 oxidation state (Os鈦糕伜) is: \[1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2 4p^6 4d^10 5s^2 5p^6\] As all the d-orbitals are completely filled, there are no unpaired electrons. Hence, the complex is diamagnetic.
04

(d) Analyzing \(\left[\mathrm{PtCl}_{4}\right]^{2-}\)

Finally, let's determine the oxidation state of Pt in this complex. Since each Cl ion has a -1 charge and the complex has a -2 charge, the oxidation state of Pt must be +4. The electron configuration of Pt in its +4 oxidation state (Pt鈦粹伜) is: \[1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2 4p^6 4d^10 5s^2\] As all the d-orbitals are completely filled, there are no unpaired electrons. Thus, the complex is diamagnetic. In summary: (a) \(\left[\mathrm{ZnBr}_{4}\right]^{2-}\) is diamagnetic. (b) \(\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\) is paramagnetic. (c) \(\mathrm{OsO}_{4}\) is diamagnetic. (d) \(\left[\mathrm{PtCl}_{4}\right]^{2-}\) is diamagnetic.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Diamagnetism
Diamagnetism is a property of a substance that does not have any unpaired electrons in its electron configuration. When a substance is diamagnetic, it creates an induced magnetic field in the opposite direction of an externally applied magnetic field. This causes a very weak repulsion.
In the context of coordination complexes, a complex is considered diamagnetic if all of its electrons are paired in its d-orbitals. This typically happens when the d-orbitals are completely filled. For example, in the given problem, complexes like
  • \([\mathrm{ZnBr}_{4}]^{2-}\)
  • \([\mathrm{PtCl}_{4}]^{2-}\)
  • and \(\mathrm{OsO}_{4}\)
are diamagnetic, as all their electrons are paired. Understanding diamagnetism in coordination complexes helps in predicting how these complexes will react in magnetic fields.
Paramagnetism
Paramagnetism occurs when a substance has one or more unpaired electrons in its electron configuration. Unlike diamagnetism, paramagnetic substances are attracted to an external magnetic field and as a result, align with it.
In coordination complexes, a paramagnetic complex typically contains unpaired electrons in its d-orbitals. This is caused by partially filled d-orbitals. For example, the complex \([\mathrm{Mn}(\mathrm{H}_{2} \mathrm{O})_{6}]^{3+}\) is paramagnetic because it has four unpaired electrons in its 3d orbitals.
Key characteristics of paramagnetic substances include:
  • Presence of unpaired electrons
  • Attraction to external magnetic fields
  • Production of an induced magnetic field in the same direction as the external field
Recognizing paramagnetism in coordination complexes helps predict their behavior in magnetic fields, which is essential for various applications in chemistry and materials science.
Oxidation States
An oxidation state, or oxidation number, is an indicator of the electron density or charge around an atom in a compound or complex. Determining the oxidation state is crucial for understanding the electron configuration and magnetic properties of a coordination complex.
For coordination complexes in the exercise:
  • The \(\mathrm{Zn}\) in \([\mathrm{ZnBr}_{4}]^{2-}\) has an oxidation state of +2.
  • The \(\mathrm{Mn}\) in \([\mathrm{Mn}(\mathrm{H}_{2} \mathrm{O})_{6}]^{3+}\) is in the +3 oxidation state.
  • The \(\mathrm{Os}\) in \(\mathrm{OsO}_{4}\) has an oxidation state of +8.
  • The \(\mathrm{Pt}\) in \([\mathrm{PtCl}_{4}]^{2-}\) has an oxidation state of +4.
The oxidation state provides insight into how electrons are distributed in a complex, which in turn, helps predict the geometry, reactivity, and magnetic properties of the complex. Knowing the oxidation state helps chemists in manipulating these properties for specific applications.
Electron Configuration
Electron configuration is the arrangement of electrons in an atom or ion within its atomic orbitals. This arrangement is crucial for determining the chemical behavior and magnetic properties of coordination complexes.
Each coordination complex in the exercise has different electron configurations due to varying oxidation states:
  • For \(\mathrm{Zn}^{2+}\), \[1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10}\], all d-orbitals are filled, indicating diamagnetism.
  • For \(\mathrm{Mn}^{3+}\), \[1s^2 2s^2 2p^6 3s^2 3p^6 3d^{4}\], there are unpaired electrons, leading to paramagnetism.
  • For \(\mathrm{Os}^{8+}\), \[1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6 4d^{10} 5s^2 5p^6\], filled d-orbitals indicate diamagnetism.
  • For \(\mathrm{Pt}^{4+}\), \[1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6 4d^{10} 5s^2\], completely fills the d-orbitals, also showing diamagnetism.
Understanding electron configurations helps predict the stability, reactivity, and magnetic tendencies of coordination complexes, which is paramount in advancing chemical knowledge and its applications.

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Most popular questions from this chapter

Oxyhemoglobin, with an \(\mathrm{O}_{2}\) bound to iron, is a low-spin Fe(II) complex; deoxyhemoglobin, without the \(\mathrm{O}_{2}\) molecule, is a high- spin complex. (a) Assuming that the coordination environment about the metal is octahedral, how many unpaired electrons are centered on the metal ion in each case? (b) What ligand is coordinated to the iron in place of \(\mathrm{O}_{2}\) in deoxyhemoglobin? (c) Explain in a general way why the two forms of hemoglobin have different colors (hemoglobin is red, whereas deoxyhemoglobin has a bluish cast). (d) A 15-minute exposure to air containing 400 ppm of CO causes about \(10 \%\) of the hemoglobin in the blood to be converted into the carbon monoxide complex, called carboxyhemoglobin. What does this suggest about the relative equilibrium constants for binding of carbon monoxide and \(\mathrm{O}_{2}\) to hemoglobin? (e) CO is a strong-field ligand. What color might you expect carboxyhemoglobin to be?

Write out the ground-state electron configurations of (a) \(\mathrm{Sc}^{2+}\) (b) \(\mathrm{Mo}^{2+}\) (c) \(\mathrm{Rh}^{3+}\), (d) \(\mathrm{Fe}^{3+}\).

The total concentration of \(\mathrm{Ca}^{2+}\) and \(\mathrm{Mg}^{2+}\) in a sample of hard water was determined by titrating a 0.100-L sample of the water with a solution of EDTA^{4-} \text { . The EDTA } ^ { 4 - } \text { chelates } the two cations: $$ \begin{aligned} \mathrm{Mg}^{2+}+[\mathrm{EDTA}]^{4-} & \longrightarrow[\mathrm{Mg}(\mathrm{EDTA})]^{2-} \\ \mathrm{Ca}^{2+}+[\mathrm{EDTA}]^{4-} & \longrightarrow[\mathrm{Ca}(\mathrm{EDTA})]^{2-} \end{aligned} $$ It requires \(31.5 \mathrm{~mL}\) of \(0.0104 \mathrm{M}\) [EDTA \(]^{4-}\) solution to reach the end point in the titration. A second 0.100 -L sample was then treated with sulfate ion to precipitate \(\mathrm{Ca}^{2+}\) as calcium sulfate. The \(\mathrm{Mg}^{2+}\) was then titrated with \(18.7 \mathrm{~mL}\) of 0.0104 \(M[\mathrm{EDTA}]^{4-}\). Calculate the concentrations of \(\mathrm{Mg}^{2+}\) and \(\mathrm{Ca}^{2+}\) in the hard water in \(\mathrm{mg} / \mathrm{L}\).

Metallic elements are essential components of many important enzymes operating within our bodies. Carbonic anhydrase, which contains \(\mathrm{Zn}^{2+}\) in its active site, is responsible for rapidly interconverting dissolved \(\mathrm{CO}_{2}\) and bicarbonate ion, \(\mathrm{HCO}_{3}^{-}\). The zinc in carbonic anhydrase is tetrahedrally coordinated by three neutral nitrogencontaining groups and a water molecule. The coordinated water molecule has a \(\mathrm{p} K_{a}\) of \(7.5,\) which is crucial for the enzyme's activity. (a) Draw the active site geometry for the \(\mathrm{Zn}(\mathrm{II})\) center in carbonic anhydrase, just writing "N" for the three neutral nitrogen ligands from the protein. (b) Compare the \(\mathrm{p} K_{a}\) of carbonic anhydrase's active site with that of pure water; which species is more acidic? (c) When the coordinated water to the \(\mathrm{Zn}(\mathrm{II})\) center in carbonic anhydrase is deprotonated, what ligands are bound to the \(\mathrm{Zn}(\mathrm{II})\) center? Assume the three nitrogen ligands are unaffected. \((\mathbf{d})\) The \(\mathrm{p} K_{a}\) of \(\left[\mathrm{Zn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}\) is \(10 .\) Suggest an explanation for the difference between this \(\mathrm{p} K_{a}\) and that of carbonic anhydrase. (e) Would you expect carbonic anhydrase to have a deep color, like hemoglobin and other metal-ion-containing proteins do? Explain.

(a) Sketch a diagram that shows the definition of the crystalfield splitting energy \((\Delta)\) for an octahedral crystal-field. \((\mathbf{b})\) What is the relationship between the magnitude of \(\Delta\) and the energy of the \(d-d\) transition for a \(d^{1}\) complex? (c) Calculate \(\Delta\) in \(\mathrm{kJ} / \mathrm{mol}\) if a \(d^{1}\) complex has an absorption maximum at \(545 \mathrm{nm}\).

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