Chapter 21

The formation of the complex ion \(\left[\mathrm{Cu}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}\) is described as a Lewis acid-base reaction. Explain. (a) What are the formulas of the Lewis acid and the Lewis base in this reaction? (b) What is the formula of the ligand? (c) What is the name of the species that provides the donor atom? (d) What atom is the donor atom, and why is it so designated? (e) What is the name of the species that is the acceptor?

Give two examples of a charged ligand and two examples of an uncharged ligand.

Why are substances that contain complex ions often called coordination compounds?

What must be true about the structure of a ligand classified as bidentate?

How many donor atoms does EDTA \(^{4-}\) have?

The cobalt(III) ion, \(\mathrm{Co}^{3+},\) forms a 1: 1 complex with \(\mathrm{EDTA}^{4-}\). What is the net charge, if any, on this complex, and what would be a suitable formula for it (using the symbol EDTA)?

What is the chelate effect? How does the dissociation of a ligand influence the chelate effect? What role does entropy have in the chelate effect?

How are the names of anionic ligands changed when they are part of the name of a coordination complex?

In a formula, what is the order of the metal and ligands?

How are the oxidation states of a metal indicated in coordination complexes?

What is a coordination number? What structures are generally observed for complexes in which the central metal ion has a coordination number of \(4 ?\) What is the most common structure observed for coordination number 6 ?

Sketch the structure of an octahedral complex that contains only identical monodentate ligands. Use \(M\) for the metal and \(L\) for the ligand.

Sketch the structure of the octahedral [Co(EDTA)] ^{-} ion. Remember that adjacent donor atoms in a polydentate ligand span adjacent positions in the octahedron.

Give the geometry or geometries for coordination number (a) \(2,\) (b) 4 , and (c) 6 .

Draw (a) a tetrahedral structure, (b) a square planar structure, (c) a tetrahedral structure, and (d) an octahedral structure.

Define stereoisomerism, geometric isomerism, chiral isomers, and enantiomers.

What condition must be fulfilled in order for a molecule or ion to be chiral?

What are the differences between optical and geometric isomers?

Which \(d\) orbitals point between the \(x, y,\) and \(z\) axes? Which point along the coordinate axes?

Explain why an electron in a \(d_{z^{2}}\) or \(d_{x^{2}-y^{2}}\) orbital in an octahedral complex will experience greater repulsions because of the presence of the ligands than an electron in a \(d_{x y}, d_{x z}\), or \(d_{y z}\) orbital.

Sketch the \(d\) -orbital energy level diagram for a typical octahedral complex.

Explain the role of (a) the ligand, (b) the oxidation state of the metal, (c) and the position of the metal in the periodic table on the crystal field splitting of the \(d\) orbitals in a metal complex.

Explain how the same metal in the same oxidation state is able to form complexes of different colors.

What does the term spectrochemical series mean? How can the order of the ligands in the series be determined?

What do the terms low-spin complex and high-spin complex mean?

If a metal ion is held in the center of a porphyrin ring structure, what is its coordination number? (Assume the porphyrin is the only ligand.)

What function does heme serve in hemoglobin? What does it do in myoglobin?

What are some of the roles played by calcium ion in the body?

The iron(III) ion forms a complex with six cyanide ions that is often called the ferricyanide ion. What is the net charge on this complex ion, and what is its formula? What is the IUPAC name for the complex?

Write the formula, including its correct charge, for a complex that contains \(\mathrm{Co}^{3+}\), two \(\mathrm{Cl}^{-}\), and two ethylenediamine ligands.

How would the following molecules or ions be named as ligands when writing the name of a complex ion? (a) \(\mathrm{NH}_{3}\) (b) \(\mathrm{N}_{3}^{-}\) (c) \(\mathrm{SO}_{4}^{2-}\) (d) \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-}\)

How would the following molecules or ions be named as ligands when writing the name of a complex ion? (a) \(\mathrm{C}_{2} \mathrm{O}_{4}^{-}\) (c) \(S^{2-}\) (b) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}\) (dimethylamine) (d) \(\mathrm{Cl}^{-}\)

Give IUPAC names for each of the following: (a) \(\left[\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6}\right] \mathrm{Cl}_{2}\) (d) \(\left[\mathrm{Mn}(\mathrm{CN})_{4}\left(\mathrm{NH}_{3}\right)_{2}\right]^{2-}\) (b) \(\left[\mathrm{CrCl}_{3}\left(\mathrm{NH}_{3}\right)_{3}\right]^{-}\) (e) \(\mathrm{K}_{3}\left[\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]\) (c) \(\left[\mathrm{Co}\left(\mathrm{NO}_{2}\right)_{6}\right]^{3-}\)

Give IUPAC names for each of the following: (a) \(\left[\mathrm{AgI}_{2}\right]^{-}\) (d) \(\left[\mathrm{Cr} \mathrm{Cl}\left(\mathrm{NH}_{3}\right)_{5}\right] \mathrm{SO}_{4}\) (b) \(\left[\mathrm{SnS}_{3}\right]^{2-}\) (e) \(\mathrm{K}_{3}\left[\mathrm{Co}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]\) (c) \(\left[\mathrm{Co}(\mathrm{en})_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\right] \mathrm{SO}_{4}\)

Write chemical formulas for each of the following: (a) tetraaquadicyanoiron(III) ion (b) tetraammineoxalatonickel(II) (c) pentaaquahydroxoaluminum(III) chloride (d) potassium hexathiocyanatomanganate(III) (e) tetrachlorocuprate(II) ion

Write chemical formulas for each of the following: (a) tetrachloroaurate(III) ion (b) bis(ethylenediamine) dinitroiron(III) ion (c) sodium tetraamminedicarbonatocobalt(III) (d) ethylenediaminetetraacetatoferrate(II) ion (e) diamminedichloroplatinum(II)

What is the coordination number of nickel in \(\left[\mathrm{Ni}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2}\left(\mathrm{NO}_{2}\right)_{2}\right]^{4-} ?\)

What is the coordination number of Fe in \(\left.\mathrm{FeCl}_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}(\mathrm{en})\right] ?\) What is the oxidation number of iron in this complex?

Draw a reasonable structure for (a) \(\left[\mathrm{Zn}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+}\) and (b) trioxalatochromate(III) ion.

Draw a reasonable structure for (a) \(\left[\operatorname{CoBr}\left(\mathrm{NH}_{3}\right)_{3}\right]^{2+}\) and (b) dichloroethylenediamineplatinum(II).

Sketch the chiral isomers of \(\left[\mathrm{CrCl}_{2}(\mathrm{en})_{2}\right]^{+}\). Is there a non-chiral isomer of this complex?

Sketch the chiral isomers of \(\left[\mathrm{Co}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]^{3-}\).

In which complex do we expect to find the larger \(\Delta\) ? (a) \(\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}\) or \(\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\) (b) \(\left[\mathrm{Cr}(\mathrm{en})_{3}\right]^{3+}\) or \(\left[\mathrm{CrCl}_{6}\right]^{3-}\)

Arrange the following complexes in order of increasing wavelength of the light absorbed by them: \(\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\) \(\left[\mathrm{CrCl}_{6}\right]^{3-},\left[\mathrm{Cr}(\mathrm{en})_{3}\right]^{3+},\left[\mathrm{Cr}(\mathrm{CN})_{6}\right]^{3-},\left[\mathrm{Cr}\left(\mathrm{NO}_{2}\right)_{6}\right]^{3-},\) \(\left[\mathrm{CrF}_{6}\right]^{3-},\) and \(\left[\mathrm{Cr}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}.\)

Which complex should absorb light at the longer wavelength? (a) \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}\) or \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}\) (b) \(\left[\mathrm{Mn}(\mathrm{CN})_{6}\right]^{3-}\) or \(\left[\mathrm{Mn}(\mathrm{CN})_{6}\right]^{4-}\)

Would the complex \(\left[\mathrm{Cr}(\mathrm{CN})_{6}\right]^{4-}\) more likely be low spin or high spin? Could it be diamagnetic?

\(\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right]^{+}\) and \(\left[\mathrm{Ag}(\mathrm{CN})_{2}\right]^{-}\) are both linear complexes. Draw the crystal field energy level diagram for the \(d\) orbitals for a linear complex, if the ligands lie along the \(z\) -axis.

Sketch all of the isomers of \(\left[\mathrm{CoCl}_{2}(\mathrm{en})\left(\mathrm{NH}_{3}\right)_{2}\right]^{+} .\) Label the cis chloro and trans chloro isomers.