The Transition Elements and Their Coordination Compounds

Why is silver used in jewellery and other decorative objects?

How is a photographic latent image different from the image you see on a piece of developed film?

Why is mercury a liquid? Why does it have a 1+ ion?

When a basic solution of $\mathit{C}\mathit{r}{\mathbf{\left(}\mathit{O}\mathit{H}\mathbf{\right)}}_{\mathbf{4}}^{\mathbf{-}}$ ion is slowly acidified, solid $\mathit{C}\mathit{r}{\mathbf{\left(}\mathbf{O}\mathbf{H}\mathbf{\right)}}_{\mathbf{5}}$ precipitates and then redissolves in excess acid. If  width="69" height="29" style="max-width: none; vertical-align: -11px;" $\mathit{C}\mathit{r}{\mathbf{\left(}\mathit{O}\mathit{H}\mathbf{\right)}}_{\mathbf{4}}^{\mathbf{-}}$ exists as $\mathit{C}\mathit{r}{{}^{\mathbf{2}}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}\mathbf{)}}_{\mathbf{2}}{\left(OH\right)}_{\mathbf{4}}^{\mathbf{-}}$, write equations that represent these two reactions.

Use the following data to determine if Cr²⁺(aq) can be prepared by the reaction of  with Cr²⁺(aq) :

$\begin{array}{rcl}\mathit{C}{\mathit{r}}^{\mathbf{3}\mathbf{+}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{+}{\mathit{e}}^{\mathbf{-}}\mathit{C}{\mathit{r}}^{\mathbf{2}\mathbf{+}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}{\mathit{E}}^{\mathbf{0}}& \mathbf{=}& \mathbf{-}\mathbf{0}\mathbf{.}\mathbf{41}\mathit{V}\\ \mathit{C}{\mathit{r}}^{\mathbf{3}\mathbf{+}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{+}\mathbf{3}{\mathit{e}}^{\mathbf{-}}\mathit{C}\mathit{r}\mathbf{\left(}\mathit{s}\mathbf{\right)}{\mathit{E}}^{\mathbf{0}}& \mathbf{=}& \mathbf{-}\mathbf{0}\mathbf{.}\mathbf{74}\mathit{V}\\ \mathit{C}{\mathit{r}}^{\mathbf{2}\mathbf{+}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{+}\mathbf{2}{\mathit{e}}^{\mathbf{-}}\mathit{C}\mathit{r}\mathbf{\left(}\mathit{s}\mathbf{\right)}{\mathit{E}}^{\mathbf{0}}& \mathbf{=}& \mathbf{-}\mathbf{0}\mathbf{.}\mathbf{91}\mathit{V}\end{array}$

When solid CrO₃ is dissolved in water, the solution is orange rather than the yellow of H₂CrO₄ - How does this observation indicate that CrO₃ is an acidic oxide?

Solutions of KMnO₄ are used in redox titrations because dark purple MnO₄^- oxidizing agent changes to the faint pink Mn²⁺ as it is reduced. The end point occurs when a slight purple remains as more KMnO₄ is added. If a sample that has reached this end point stands for a long time, the purple fades and a suspension of a small amount of brown, muddy MnO₂ appears. Use standard electrode potentials to explain this result.

Describe the makeup of a complex ion, including the nature of the ligands and their interaction with the central metal ion. Explain how a complex ion can be positive or negative and how it occurs as part of a neutral coordination compound.

What electronic feature must a donor atom of a ligand have?

What is the coordination number of a metal ion in a complex ion? How does it differ from oxidation number?

What structural feature is characteristic of a chelate?

What geometries are associated with the coordination numbers 2, 4, and 6?

What are the coordination numbers of cobalt (III), platinum (II), and platinum (VV) in complexes?

How is a complex ion a Lewis adducts?

What does the ending rue signify in a complex ion name?

In what order are the metal ion and ligands given in the name of a complex ion?

In what order are the metal ion and ligands given in the name of a complex ion?

Give the systematic names for the following formulas

1. $\mathbf{\left[}\mathbf{Ni}\left(H_2{O}_6\right)\mathbf{\right]}{\mathbf{Cl}}_{\mathbf{2}}$
2. $\mathbf{\left[}\mathbf{Cr}{\mathbf{\left(}\mathbf{en}\mathbf{\right)}}_{\mathbf{3}}\mathbf{\right]}{\mathbf{\left(}\mathbf{C}\mathbf{l}{\mathbf{O}}_{\mathbf{4}}\mathbf{\right)}}_{\mathbf{3}}$
   
3. ${\mathit{K}}_{\mathbf{4}}\mathbf{\left[}\mathbf{M}\mathbf{n}{\left(CN\right)}_{\mathbf{6}}\mathbf{\right]}$
   

Give systematic names for the following formulas:

(a) $\mathbf{\left[}\mathbf{C}\mathbf{o}{\left(N{H}_3\right)}_{\mathbf{4}}{\left(N{O}_2\right)}_{\mathbf{2}}\mathbf{\right]}\mathit{C}\mathit{l}$

(b) $\mathbf{\left[}\mathbf{C}\mathbf{r}{\left(N{H}_3\right)}_{\mathbf{6}}\mathbf{\right]}\mathbf{\left[}\mathbf{C}\mathbf{r}{\left(CN\right)}_{\mathbf{6}}\mathbf{\right]}$

(c) ${\mathit{K}}_{\mathbf{2}}\mathbf{\left[}\mathbf{C}\mathbf{u}\mathbf{C}{\mathbf{l}}_{\mathbf{4}}\mathbf{\right]}$

What are the charge and coordination number of the central metal ion(s) in each compound of Problem 23_55?

(a) What is the crystal field splitting energy $(∆)$?

 (b) How does it arise for an octahedral field of ligands?

 (c) How is it different for a tetrahedral field of ligands?

What is the distinction between a weak-field ligand and a strong-field ligand? Give an example of each.

Is a complex with the same number of unpaired electrons as the free gaseous metal ion termed high spin or low spin?

How do the relative magnitudes of E_pairing and  $(∆)$ affect the paramagnetism of a complex?

Why are there both high-spin and low-spin octahedral complexes but only high-spin tetrahedral complexes?

What are the charge and coordination number of the central metal ion(s) in each compound of Problem 23.56?

In terms of the theory of color absorption, explain two ways that a solution can be blue.

Give the number of d electrons ( n of ${\mathit{d}}^{\mathbf{n}}$ ) for the central metal ion in (a)  ${\mathbf{\left[}{\mathbf{TiCl}}_{\mathbf{6}}\mathbf{\right]}}^{\mathbf{2}\mathbf{-}}$; (b)  $\mathbf{K}\mathbf{\left[}{\mathbf{AuCl}}_{\mathbf{4}}\mathbf{\right]}$; (c)  ${\mathbf{\left[}{\mathbf{RhCl}}_{\mathbf{6}}\mathbf{\right]}}^{\mathbf{3}\mathbf{-}}$.

Give the number of d electrons (n of dⁿ) for the central metal ion in 

(a) $\left[\mathrm{Cr}{\left(H_{2}O\right)}_6\right]{\left({\mathrm{ClO}}_3\right)}_{\mathbf{2}}$; (b) ${\left[\mathrm{Mn}{\left(\mathrm{CN}\right)}_6\right]}^{\mathbf{2}\mathbf{-}}$; (c) $\left[\mathrm{Ru}\left(\mathrm{NO}\right){\left(\mathrm{en}\right)}_2\mathrm{Cl}\right]\mathbf{Br}$.

How many d electrons (n of dⁿ) are in the central metal ion in

 (a) $\mathbf{Ca}\left[{\mathrm{IrF}}_6\right]$; (b) ${\left[{\mathrm{HgI}}_4\right]}^{\mathbf{2}\mathbf{-}}$; (c) $\mathbf{\left[}\mathbf{Co}\mathbf{\right(}\mathbf{EDTA}\mathbf{)}{\mathbf{]}}^{\mathbf{2}\mathbf{-}}$?

How many d electrons (n of dⁿ) are in the central metal ion in 

(a) $\left[\mathrm{Ru}{\left({\mathrm{NH}}_3\right)}_5\mathrm{Cl}\right]{\mathbf{SO}}_{\mathbf{4}}\mathbf{;}$(b) ${\mathbf{Na}}_{\mathbf{2}}\left[\mathrm{Os}{\left(\mathrm{CN}\right)}_6\right]$; (c) $\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_4{\mathrm{CO}}_{3}I\right]$?

Sketch the orientation of the orbitals relative to the ligands in an octahedral complex to explain the splitting and the relative energies of the ${\mathit{d}}_{\mathbf{xy}}$ and the ${\mathit{d}}_{{\mathbf{x}}^{\mathbf{2}}\mathbf{-}{\mathbf{y}}^{\mathbf{2}}}$orbitals. 

${\mathit{d}}_{{\mathbf{x}}^{\mathbf{2}}\mathbf{-}{\mathbf{y}}^{\mathbf{2}}}$The two ${\mathit{e}}_{\mathbf{g}}$ orbitals are identical in energy in an octahedral complex but have different energies in a square planar complex, with the ${\mathit{d}}_{{\mathbf{z}}^{\mathbf{2}}}$ orbital being much lower in energy than the ${\mathit{d}}_{{\mathbf{x}}^{\mathbf{2}}\mathbf{-}{\mathbf{y}}^{\mathbf{2}}}$. Explain with orbital sketches.

Which of these ions cannot form both high-spin and low-spin octahedral complexes: 

(a) ${\mathbf{Ti}}^{\mathbf{3}\mathbf{+}}$; (b) ${\mathbf{Co}}^{\mathbf{2}\mathbf{+}}\mathbf{;}$(c) ${\mathbf{Fe}}^{\mathbf{2}\mathbf{+}}$; (d) ${\mathbf{Cu}}^{\mathbf{2}\mathbf{+}}\mathbf{?}$

Octahedral ${\mathbf{\left[}\mathbf{Ni}{\left({\mathrm{NH}}_3\right)}_{\mathbf{6}}\mathbf{\right]}}^{\mathbf{2}\mathbf{+}}$ is paramagnetic, whereas planar ${\mathbf{\left[}\mathbf{Pt}{\left({\mathrm{NH}}_3\right)}_{\mathbf{6}}\mathbf{\right]}}^{\mathbf{2}\mathbf{+}}$ is diamagnetic, even though both metal ions are d⁸ species. Explain.

At one time, it was common to write the formula for copper chloride as ${\mathbf{Cu}}_{\mathbf{2}}{\mathbf{Cl}}_{\mathbf{2}}$, instead of $\mathbf{CuCl}$, analogously to ${\mathbf{Hg}}_{\mathbf{2}}{\mathbf{Cl}}_{\mathbf{2}}$ for mercury(I) chloride. Use electron configurations to explain why ${\mathbf{Hg}}_{\mathbf{2}}{\mathbf{Cl}}_{\mathbf{2}}\mathbf{ }\mathbf{and}\mathbf{ }\mathbf{CuCl}$ are both correct.

Question: For the compound $\left[\mathrm{Co}{\left(\mathrm{en}\right)}_2{\mathrm{Cl}}_2\right]\mathbf{Cl}$, give:

(a) The coordination number of the metal ion

(b) The oxidation number of the central metal ion

(c) The number of individual ions per formula unit

(d) The moles of AgCl that precipitate immediately when 1 mol of compound is dissolved in water and treated with ${\mathbf{AgNO}}_{\mathbf{3}}$

Hexafluorocobaltate(III) ion is a high-spin complex. Draw the orbital-energy splitting diagram for its d orbitals.

Criticize and correct the following statement: strong-field ligands always give rise to low-spin complexes.

The following reaction is a key step in black-and-white photography (see p. 1035):

$\mathbf{AgBr}\left(s\right)\mathbf{+}\mathbf{2}{\mathbf{S}}_{\mathbf{2}}{{\mathbf{O}}_{\mathbf{3}}}^{\mathbf{2}\mathbf{-}}\left(\mathrm{aq}.\right)\mathbf{\to }\mathbf{Ag}{{\left(S_2{O}_1\right)}_{\mathbf{2}}}^{\mathbf{3}\mathbf{-}}\left(\mathrm{aq}.\right)\mathbf{+}{\mathbf{Br}}^{\mathbf{-}}\left(\mathrm{aq}.\right)$

During fixing,  $\mathbf{258}\mathbf{ }\mathbf{mL}$ of hypo (sodium thiosulfate) was used. The hypo concentration was 0.1052M before the AgBr reacted, and 0.0378M afterward. How many grams of reacted?

The metal ion in platinum(IV) complexes, like that in cobalt(III) complexes, has a coordination number of 6 and often has ${\mathbf{Cl}}^{\mathbf{-}}$ ions and ${\mathbf{NH}}_{\mathbf{3}}$ molecules as ligands. For the traditional (before the work of Werner) formulas ${\mathbf{PtCl}}_{\mathbf{4}}\mathbf{·}\mathbf{6}{\mathbf{NH}}_{\mathbf{3}}$  and ${\mathbf{PtCl}}_{\mathbf{4}}\mathbf{·}\mathbf{4}{\mathbf{NH}}_{\mathbf{3}}$, (a) give the modern formula and charge of the complex ion, and (b) predict the moles of ions per mole of compound dissolved and moles of AgCl formed with excess ${\mathbf{AgNO}}_{\mathbf{3}}\mathbf{.}$

In  , the  ion absorbs visible light in the blue-violet range, and the compound is yellow-orange. In   , the ion absorbs visible light in the red range, and the compound is blue-gray. Explain these differences in light absorbed and color of the compound.

Werner prepared two compounds by heating a solution of  ${\mathrm{PtCl}}_2$ with triethyl phosphine, $\mathrm{P}{\left({\mathrm{C}}_2{\mathrm{H}}_5\right)}_3$ which is an excellent ligand for $\mathrm{Pt}$. The two compounds gave the same analysis: $\mathrm{Pt}$,   $38.8\%$, $\mathrm{Cl},14.1\%$, $\mathrm{C},28.7\%$, $\mathrm{P},12.4\%$and $\mathrm{H},6.02\%$ . Write formulas, structures, and systematic names for the two isomers.

Mercury has a small but significant vapor pressure, and  poisoning can occur in $20.0\raisebox{1ex}{$\mathrm{mg}$}\!\left/ \!\raisebox{-1ex}{${\mathrm{m}}^3\mathrm{Hg}$}\right.$ poorly ventilated rooms where has been spilled. What is the partial pressure (in torr) of $\mathrm{Hg}$ if the maximum concentration at  $25°\mathrm{C}$is?

You know the following about a coordination compound:

(1) The partial empirical formula is $\mathit{K}\mathit{M}\mathbf{\left(}\mathbf{C}\mathbf{r}{\mathbf{O}}_{\mathbf{4}}\mathbf{\right)}\mathit{C}{\mathit{l}}_{\mathbf{2}}{\mathbf{\left(}\mathbf{N}{\mathbf{H}}_{\mathbf{3}}\mathbf{\right)}}_{\mathbf{4}}$

(2) It has A (red) and  B (blue) crystal forms.

(3) When  $\mathbf{1}\mathbf{.0}\mathbf{ }\mathbf{\text{mol}}$of A or B reacts with $\mathbf{1}\mathbf{.0}\mathbf{ }\mathbf{\text{mol}}$ of $\mathit{A}{\mathbf{\text{gNOH}}}_{\mathbf{3}}$  $\mathbf{0}\mathbf{.50}\mathbf{ }\mathbf{\text{mol}}$of a red precipitate forms immediately.

(4) After the reaction in (3),  $\mathbf{1}\mathbf{.0}\mathbf{ }\mathbf{\text{mol}}$of  A reacts very slowly with $\mathbf{1}\mathbf{.0}\mathbf{ }\mathbf{\text{mol}}$ of silver oxalate $\mathbf{\left(}{\mathbf{A}}_{{\mathbf{g}}_{\mathbf{2}}}{\mathbf{C}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{4}}\mathbf{\right)}$ to form $\mathbf{2}\mathbf{.0}\mathbf{ }\mathbf{\text{mol}}$ of a white precipitate. (Oxalate can displace other ligands.)

(5) After the reaction in $\mathbf{\left(}\mathbf{3}\mathbf{\right)}\mathbf{,}\mathbf{1}\mathbf{.0}\mathbf{ }\mathbf{\text{mol}}$ of B does not react further with I.0 mol of ${\mathbf{\text{AgNO}}}_{\mathbf{5}}$

From this information, determine the following:

(a) The coordination number of M

(b) The group(s) bonded to M ionically and covalently

(c) The stereochemistry of the red and blue formulas

Question: Some octahedral complexes have dissented shapes. In some, two metal-ligand bonds that are  apart are shorter than the other four. In , for example, two  bonds are  long, and the other four are  long. 

(a) Calculate the longest distance between two  atoms in this complex. 

(b) Calculate the shortest distance between two  atoms.